diora-web/static/js/app.js

/**
 * diora — radio player
 * Handles playback, SSE metadata, search, station management, and affiliate links.
 */

'use strict';

// ---------------------------------------------------------------------------
// State
// ---------------------------------------------------------------------------

// Hardcoded for now -- only creamfresh radio gets the vote buttons, since
// only its backend (the DJ) actually does anything with them.
const CREAMFRESH_RADIO_URL = 'https://diora.creamfresh.xyz/radio/creamfresh-stream/';

let currentStation = null;   // { url, name, id } | null
let currentTrack = '';
let sseSource = null;
let isPlaying = false;
let currentPlayId = null;

const audio = new Audio();

// Reconnect audio when the output device changes (e.g. Bluetooth, USB DAC)
if (navigator.mediaDevices) {
  let _deviceChangeDebounce = null;
  navigator.mediaDevices.addEventListener('devicechange', () => {
    clearTimeout(_deviceChangeDebounce);
    _deviceChangeDebounce = setTimeout(() => {
      if (!isPlaying || audio.src === '') return;
      const savedTime = audio.currentTime;
      const savedSrc  = audio.src;
      audio.src = savedSrc;
      audio.load();
      if (savedTime > 0) {
        audio.addEventListener('loadedmetadata', function onMeta() {
          audio.currentTime = savedTime;
          audio.removeEventListener('loadedmetadata', onMeta);
        });
      }
      audio.play().catch(() => {});
    }, 500);
  });
}

// ---------------------------------------------------------------------------
// DOM helpers
// ---------------------------------------------------------------------------

function $(id) { return document.getElementById(id); }

function getCsrfToken() {
  const cookie = document.cookie.split('; ').find(r => r.startsWith('csrftoken='));
  return cookie ? cookie.split('=')[1] : '';
}

function formatDateTime(iso) {
  if (!iso) return '';
  const d = new Date(iso);
  const pad = n => String(n).padStart(2, '0');
  return `${d.getFullYear()}-${pad(d.getMonth()+1)}-${pad(d.getDate())} `
       + `${pad(d.getHours())}:${pad(d.getMinutes())}`;
}

function escapeHtml(str) {
  return String(str)
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;');
}

// ---------------------------------------------------------------------------
// Modal dialogs — styled replacements for native alert()/confirm()/prompt(),
// which look jarring against the rest of the custom dark UI and can't be
// styled or (in confirm/prompt's case) awaited without blocking the thread.
// All three return a Promise; callers must be async and `await` them.
// ---------------------------------------------------------------------------

function _showModal({ message, showInput = false, inputValue = '', showCancel = false, okLabel = 'OK', danger = false }) {
  return new Promise((resolve) => {
    const overlay  = $('modal-overlay');
    const dialog   = $('modal-dialog');
    const msgEl    = $('modal-message');
    const inputEl  = $('modal-input');
    const okBtn    = $('modal-ok-btn');
    const cancelBtn = $('modal-cancel-btn');
    if (!overlay || !dialog) { resolve(null); return; }

    msgEl.textContent = message;
    inputEl.style.display = showInput ? '' : 'none';
    inputEl.value = inputValue;
    cancelBtn.style.display = showCancel ? '' : 'none';
    okBtn.textContent = okLabel;
    okBtn.className = danger ? 'btn btn-danger' : 'btn btn-primary';

    overlay.style.display = '';
    dialog.style.display = '';
    (showInput ? inputEl : okBtn).focus();
    if (showInput) inputEl.select();

    function cleanup(result) {
      overlay.style.display = 'none';
      dialog.style.display = 'none';
      overlay.removeEventListener('click', onCancel);
      okBtn.removeEventListener('click', onOk);
      cancelBtn.removeEventListener('click', onCancel);
      document.removeEventListener('keydown', onKeydown);
      resolve(result);
    }
    function onOk()     { cleanup(showInput ? inputEl.value : true); }
    function onCancel() { cleanup(showInput ? null : false); }
    function onKeydown(e) {
      if (e.key === 'Escape') onCancel();
      if (e.key === 'Enter' && showInput) onOk();
    }

    okBtn.addEventListener('click', onOk);
    cancelBtn.addEventListener('click', onCancel);
    overlay.addEventListener('click', onCancel);
    document.addEventListener('keydown', onKeydown);
  });
}

function customAlert(message) {
  return _showModal({ message });
}

function customConfirm(message, { danger = false } = {}) {
  return _showModal({ message, showCancel: true, danger });
}

// The server answers with short English error codes (an API contract, tests and
// other clients rely on them); what the page shows of them is German.
const _GERMAN_ERRORS = {
  'no stations found in file': 'In der Datei wurden keine Sender gefunden.',
  'file must be .m3u or .m3u8': 'Die Datei muss eine .m3u- oder .m3u8-Datei sein.',
  'no file uploaded': 'Keine Datei hochgeladen.',
  'only jpeg, png, or webp allowed': 'Nur JPEG, PNG oder WebP erlaubt.',
  'file too large (max 50 MB)': 'Datei zu groß (höchstens 50 MB).',
  'file too large (max 5 MB)': 'Datei zu groß (höchstens 5 MB).',
  'authentication required': 'Bitte anmelden.',
  'not found': 'Nicht gefunden.',
  'invalid JSON': 'Ungültige Anfrage.',
  'upstream unreachable': 'Der Server dahinter ist nicht erreichbar.',
};
function _germanError(code) {
  return _GERMAN_ERRORS[code] || code;
}

function customPrompt(message, defaultValue = '') {
  return _showModal({ message, showInput: true, inputValue: defaultValue, showCancel: true });
}

// ---------------------------------------------------------------------------
// Play / Stop
// ---------------------------------------------------------------------------

function playStation(url, name, stationId) {
  stopPlayback(false);
  if (window.__dioraAmbientStop) window.__dioraAmbientStop();

  // A secure page can't load plain-http streams (mixed content). Native shells
  // that play the stream themselves set window.DIORA_PLAYS_HTTP_STREAMS.
  if (location.protocol === 'https:' && url.startsWith('http://') && !window.DIORA_PLAYS_HTTP_STREAMS) {
    window.open(url, '_blank');
    return;
  }

  currentStation = { url, name, id: stationId || null };
  isPlaying = true;

  audio.src = url;
  const volSlider = document.getElementById('volume');
  if (volSlider) audio.volume = volSlider.value / 255;
  audio.play().catch(() => {
    // Browser may block autoplay; the user needs to interact first
    console.warn('Audio play blocked by browser policy.');
  });

  $('now-playing-station').textContent = name;
  $('now-playing-track').textContent = '';
  $('play-stop-btn').style.display = '';
  $('play-stop-btn').textContent = '⏹ Stopp';
  $('play-stop-btn').classList.add('playing');
  $('save-station-btn').style.display = '';

  const isCreamfresh = url === CREAMFRESH_RADIO_URL;
  $('creamfresh-vote-up-btn').style.display = isCreamfresh ? '' : 'none';
  $('creamfresh-vote-down-btn').style.display = isCreamfresh ? '' : 'none';
  $('creamfresh-vote-up-btn').classList.remove('active');
  $('creamfresh-vote-down-btn').classList.remove('active');

  startMetadataSSE(url);
  startPlaySession(name, url);
  maybeShowDonationHint(url, name);

  if ('mediaSession' in navigator) {
    navigator.mediaSession.metadata = new MediaMetadata({title: name, artist: 'Radio'});
    navigator.mediaSession.setActionHandler('play',  () => { audio.play(); isPlaying = true; });
    navigator.mediaSession.setActionHandler('pause', () => { audio.pause(); isPlaying = false; });
    navigator.mediaSession.setActionHandler('stop',  () => stopPlayback(true));
    try { navigator.mediaSession.setActionHandler('seekbackward', null); } catch (_) {}
    try { navigator.mediaSession.setActionHandler('seekforward',  null); } catch (_) {}
    try { navigator.mediaSession.setActionHandler('nexttrack',    null); } catch (_) {}
    try { navigator.mediaSession.setActionHandler('previoustrack',null); } catch (_) {}
    navigator.mediaSession.playbackState = 'playing';
  }
}

function stopPlayback(clearStation = true) {
  audio.pause();
  audio.src = '';
  isPlaying = false;
  if ('mediaSession' in navigator) navigator.mediaSession.playbackState = 'none';

  if (sseSource) {
    sseSource.close();
    sseSource = null;
  }

  $('play-stop-btn').textContent = '▶ Abspielen';
  $('play-stop-btn').classList.remove('playing');
  $('save-station-btn').style.display = 'none';
  $('creamfresh-vote-up-btn').style.display = 'none';
  $('creamfresh-vote-down-btn').style.display = 'none';
  $('affiliate-section').style.display = 'none';

  stopPlaySession();

  const stationEl = $('now-playing-station');
  const trackEl = $('now-playing-track');

  if (clearStation) {
    currentStation = null;
    currentTrack = '';
    stationEl.textContent = '— kein Sender —';
    trackEl.textContent = '';
    $('play-stop-btn').style.display = 'none';
  }
}

function togglePlayStop() {
  if (isPlaying) {
    stopPlayback(true);
  } else if (currentStation) {
    playStation(currentStation.url, currentStation.name, currentStation.id);
  }
}

// ---------------------------------------------------------------------------
// Play session tracking
// ---------------------------------------------------------------------------

async function startPlaySession(stationName, stationUrl) {
  try {
    const res = await fetch('/radio/play/start/', {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body: JSON.stringify({station_name: stationName, station_url: stationUrl})
    });
    if (res.ok) {
      const data = await res.json();
      currentPlayId = data.play_id;
    }
  } catch (e) {}
}

async function stopPlaySession() {
  // Take the id before awaiting: playStation() calls this without waiting and
  // starts the next session right away, whose id must not be cleared here.
  const playId = currentPlayId;
  if (!playId) return;
  currentPlayId = null;
  try {
    await fetch('/radio/play/stop/', {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body: JSON.stringify({play_id: playId})
    });
  } catch (e) {}
}

window.addEventListener('beforeunload', () => {
  if (currentPlayId) {
    navigator.sendBeacon('/radio/play/stop/', JSON.stringify({play_id: currentPlayId}));
  }
  // Flush cached encrypted payloads for reader data (encryption is async so we
  // use pre-computed blobs stored by the debounced savers)
  // The last position written (it's in the outbox too, in case the beacon is lost).
  if (_lastProgressBeacon) navigator.sendBeacon(`/books/${_lastProgressBeacon.book}/progress/`, _progressBody(_lastProgressBeacon));
  if (_lastBookmarkBeacon) navigator.sendBeacon(_lastBookmarkBeacon.url, _lastBookmarkBeacon.body);
  if (_lastHighlightBeacon) navigator.sendBeacon(_lastHighlightBeacon.url, _lastHighlightBeacon.body);
});

document.addEventListener('visibilitychange', () => {
  if (document.visibilityState === 'hidden' && currentBookId) {
    if (bookmarksDirty) saveBookmarks();
    if (highlightsDirty) saveHighlights();
    saveReaderProgress();
  }
  // Back in front: maybe the book was read on another device meanwhile.
  if (document.visibilityState === 'visible' && currentBookId) _checkNewerPositionElsewhere();
});

// Cached beacon payloads — updated after each successful encrypt in save functions
let _lastBookmarkBeacon = null;
let _lastHighlightBeacon = null;
let _lastProgressBeacon = null;

// ---------------------------------------------------------------------------
// Recommendations
// ---------------------------------------------------------------------------

async function loadRecommendations() {
  const container = document.getElementById('recommendations');
  if (!container) return;
  try {
    const res = await fetch('/radio/recommendations/');
    const data = await res.json();
    if (!data.recommendations.length) {
      container.innerHTML = '<p class="muted">Hör mehr Sender, dann gibt es hier Empfehlungen.</p>';
      return;
    }
    const label = data.context;
    let html = `<p class="recommendations-context">Was du ${label} oft hörst:</p><ul class="recommendations-list">`;
    for (const r of data.recommendations) {
      html += `<li>
          <button class="btn btn-sm" onclick="playStation('${escapeAttr(r.station_url)}', '${escapeAttr(r.station_name)}', ${r.saved_id || 'null'})">
              &#9654; ${escapeHtml(r.station_name)}
          </button>
          <span class="muted">${r.play_count}&times;</span>
      </li>`;
    }
    html += '</ul>';
    container.innerHTML = html;
  } catch (e) {}
}

function escapeAttr(s) {
  return String(s).replace(/'/g, "\\'").replace(/"/g, '&quot;');
}

// ---------------------------------------------------------------------------
// Volume
// ---------------------------------------------------------------------------

function setVolume(val) {
  val = Math.max(0, Math.min(255, Math.round(val)));
  audio.volume = val / 255;
  localStorage.setItem('diora_volume', val);
  const slider = $('volume');
  const numInput = $('volume-num');
  if (slider) slider.value = val;
  if (numInput) numInput.value = val;
  _ambientVolume(val);
}

const volSliderEl = document.getElementById('volume');
if (volSliderEl) {
  ['input', 'change', 'mousemove', 'touchmove'].forEach(evt =>
    volSliderEl.addEventListener(evt, function () { setVolume(this.value); })
  );
}

const volNumEl = document.getElementById('volume-num');
if (volNumEl) {
  volNumEl.addEventListener('change', function () { setVolume(this.value); });
  volNumEl.addEventListener('input', function () { setVolume(this.value); });
  volNumEl.addEventListener('click', function () { this.select(); });
}

const volSliderEl2 = document.getElementById('volume');
const volWheelTarget = volSliderEl2 || volNumEl;
if (volWheelTarget) {
  volWheelTarget.addEventListener('wheel', function (e) {
    e.preventDefault();
    const current = parseInt(document.getElementById('volume').value, 10);
    setVolume(current + (e.deltaY < 0 ? 4 : -4));
  }, { passive: false });
}

// ---------------------------------------------------------------------------
// SSE metadata
// ---------------------------------------------------------------------------

function startMetadataSSE(streamUrl) {
  if (sseSource) { sseSource.close(); sseSource = null; }

  const endpoint = '/radio/sse/?url=' + encodeURIComponent(streamUrl);
  sseSource = new EventSource(endpoint);

  sseSource.onmessage = function (e) {
    let data;
    try { data = JSON.parse(e.data); } catch (_) { return; }

    if (data.error) {
      console.warn('SSE stream ended:', data.error);
      return;
    }

    if (data.track && data.track !== currentTrack) {
      currentTrack = data.track;
      updateNowPlayingUI(data.track);
      recordTrack(currentStation ? currentStation.name : '', data.track);
      fetchAffiliateLinks(data.track);
    }
  };

  sseSource.onerror = function () {
    // Connection dropped; the browser will attempt to reconnect automatically
    console.warn('SSE connection error, browser will retry.');
  };
}

function updateNowPlayingUI(track) {
  $('now-playing-track').textContent = track;
}

// ---------------------------------------------------------------------------
// Record track
// ---------------------------------------------------------------------------

async function recordTrack(stationName, track) {
  try {
    const res = await fetch('/radio/record/', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-CSRFToken': getCsrfToken(),
      },
      body: JSON.stringify({ station_name: stationName, track, scrobble: true }),
    });
    if (res.ok) {
      addHistoryRow(stationName, track);
    }
  } catch (err) {
    console.error('recordTrack error:', err);
  }
}

function addHistoryRow(stationName, track) {
  const tbody = $('history-tbody');
  if (!tbody) return;

  // Remove the "no history" placeholder row if present
  const emptyRow = $('history-empty-row');
  if (emptyRow) emptyRow.remove();

  const tr = document.createElement('tr');
  const now = new Date().toISOString();
  tr.innerHTML = `
    <td class="history-time">${escapeHtml(formatDateTime(now))}</td>
    <td>${escapeHtml(stationName)}</td>
    <td>${escapeHtml(track)}</td>
    <td></td>
    <td><button class="btn-delete-history" onclick="deleteHistoryEntry(null, this)" title="Entfernen">✕</button></td>
  `;
  tbody.insertBefore(tr, tbody.firstChild);
}

async function deleteHistoryEntry(id, btn) {
  const tr = btn.closest('tr');
  if (!id) { tr.remove(); return; }
  try {
    const res = await fetch(`/radio/history/${id}/delete/`, {
      method: 'POST',
      headers: {'X-CSRFToken': getCsrfToken()},
    });
    if (res.ok) tr.remove();
  } catch (e) {}
}

// ---------------------------------------------------------------------------
// Affiliate links
// ---------------------------------------------------------------------------

async function fetchAffiliateLinks(track) {
  const section = $('affiliate-section');
  if (section && section.dataset.disabled) return;
  try {
    const res = await fetch('/radio/affiliate/?track=' + encodeURIComponent(track));
    if (!res.ok) return;
    const data = await res.json();

    const itunes = data.itunes_data || {};

    $('affiliate-track-name').textContent = itunes.name || track;
    $('affiliate-artist-name').textContent = itunes.artist || '';
    $('affiliate-album-name').textContent = itunes.album || '';

    const artEl = $('affiliate-artwork');
    if (itunes.artwork) {
      artEl.src = itunes.artwork;
      artEl.style.display = '';
    } else {
      artEl.style.display = 'none';
    }

    const amzLink = $('affiliate-amazon-link');
    if (data.amazon_url) {
      amzLink.href = data.amazon_url;
      amzLink.style.display = '';
    } else {
      amzLink.style.display = 'none';
    }

    section.style.display = 'flex';
  } catch (err) {
    console.error('fetchAffiliateLinks error:', err);
    section.style.display = 'none';
  }
}

// ---------------------------------------------------------------------------
// Search (radio-browser.info)
// ---------------------------------------------------------------------------

async function doSearch() {
  const query = $('search-input').value.trim();
  if (!query) return;

  const statusEl = $('search-status');
  const tableEl = $('search-results-table');
  const tbody = $('search-results-body');

  tableEl.style.display = 'none';
  tbody.innerHTML = '';

  // A stream address instead of a name: offer to play or save it directly.
  if (/^https?:\/\/\S+$/i.test(query)) {
    showStreamAddressResult(query);
    return;
  }

  statusEl.textContent = 'Suche …';

  try {
    const url = `https://de1.api.radio-browser.info/json/stations/search?name=${encodeURIComponent(query)}&limit=50&hidebroken=true&order=clickcount&reverse=true`;
    const res = await fetch(url);
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    const stations = await res.json();

    if (!stations.length) {
      statusEl.textContent = 'Keine Sender gefunden.';
      return;
    }

    statusEl.textContent = stations.length === 1 ? '1 Treffer' : `${stations.length} Treffer`;
    tableEl.style.display = '';
    const curated = document.getElementById('curated-lists');
    if (curated) curated.style.display = 'none';

    stations.forEach(st => {
      const tr = document.createElement('tr');
      const safeName = escapeHtml(st.name || '');
      const safeUrl  = escapeHtml(st.url_resolved || st.url || '');
      const safeBr   = escapeHtml(st.bitrate ? st.bitrate + ' kbps' : '');
      const safeCC   = escapeHtml(st.countrycode || st.country || '');
      const safeTags = escapeHtml((st.tags || '').split(',').slice(0, 3).join(', '));

      tr.innerHTML = `
        <td title="${safeName}">${safeName}</td>
        <td>${safeBr}</td>
        <td>${safeCC}</td>
        <td title="${escapeHtml(st.tags || '')}">${safeTags}</td>
        <td>
          <button class="btn btn-sm btn-play"
                  onclick='searchPlay(${JSON.stringify(safeUrl)}, ${JSON.stringify(safeName)}, ${JSON.stringify({
                    name: st.name,
                    url: st.url_resolved || st.url,
                    bitrate: st.bitrate ? String(st.bitrate) : '',
                    country: st.country || '',
                    tags: st.tags || '',
                    favicon_url: st.favicon || '',
                  })})'>
            &#9654; Abspielen
          </button>
        </td>
      `;
      tbody.appendChild(tr);
    });
  } catch (err) {
    statusEl.textContent = 'Suche fehlgeschlagen: ' + err.message;
  }
}

// A name to start from for a pasted address: "klassik.mp3" on radio.example.org
// -> "Klassik (radio.example.org)". The query string is left out on purpose —
// it often carries an access token, which shouldn't end up on screen.
function _streamAddressName(url) {
  try {
    const u = new URL(url);
    const file = decodeURIComponent(u.pathname.split('/').filter(Boolean).pop() || '');
    const base = file.replace(/\.(mp3|aac|aacp|ogg|opus|m3u8?|pls|flac)$/i, '').replace(/[-_]+/g, ' ').trim();
    const nice = base ? base.charAt(0).toUpperCase() + base.slice(1) : '';
    return nice ? `${nice} (${u.host})` : u.host;
  } catch (e) {
    return url;
  }
}

function showStreamAddressResult(url) {
  const statusEl = $('search-status');
  const tableEl = $('search-results-table');
  const tbody = $('search-results-body');
  const name = _streamAddressName(url);
  const shown = url.split('?')[0];
  const data = {name, url, bitrate: '', country: '', tags: '', favicon_url: ''};

  statusEl.textContent = 'Stream-Adresse';
  const curated = document.getElementById('curated-lists');
  if (curated) curated.style.display = 'none';

  // Same five columns as a radio-browser result: name, bitrate, country, tags, actions.
  const tr = document.createElement('tr');
  tr.className = 'stream-address-row';
  for (let i = 0; i < 4; i++) tr.appendChild(document.createElement('td'));
  tr.children[0].textContent = name;
  tr.children[0].title = shown;
  tr.children[3].textContent = shown;
  tr.children[3].title = shown;

  const actions = document.createElement('td');
  const play = document.createElement('button');
  play.className = 'btn btn-sm btn-play';
  play.innerHTML = '&#9654; Abspielen';
  play.addEventListener('click', () => searchPlay(url, name, data));
  const save = document.createElement('button');
  save.className = 'btn btn-sm';
  save.innerHTML = '&#9733; Speichern';
  save.style.marginLeft = '4px';
  save.addEventListener('click', async e => {
    e.stopPropagation();
    const chosen = await customPrompt('Name für diesen Sender', name);
    if (chosen == null) return;
    const finalName = chosen.trim() || name;
    await saveStation({...data, name: finalName});
    statusEl.textContent = `Gespeichert als „${finalName}“.`;
  });
  actions.append(play, save);
  tr.appendChild(actions);
  tbody.appendChild(tr);
  tableEl.style.display = '';
}

function searchPlay(url, name, stationData) {
  // Store station data on the window so saveCurrentStation() can use it
  window._pendingStationData = stationData;
  playStation(url, name, null);
}

// ---------------------------------------------------------------------------
// Save current station
// ---------------------------------------------------------------------------

async function saveCurrentStation() {
  if (!currentStation) return;

  // Use the rich data from search results if available, otherwise minimal data
  const data = window._pendingStationData || {
    name: currentStation.name,
    url: currentStation.url,
    bitrate: '',
    country: '',
    tags: '',
    favicon_url: '',
  };

  await saveStation(data);
}

// ---------------------------------------------------------------------------
// creamfresh radio: DJ feedback (hardcoded to this one station, see
// CREAMFRESH_RADIO_URL above)
// ---------------------------------------------------------------------------

async function creamfreshVote(direction) {
  const upBtn = $('creamfresh-vote-up-btn');
  const downBtn = $('creamfresh-vote-down-btn');
  upBtn.disabled = true;
  downBtn.disabled = true;
  try {
    const res = await fetch('/radio/creamfresh-feedback/', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-CSRFToken': getCsrfToken(),
      },
      body: JSON.stringify({ vote: direction }),
    });
    if (!res.ok) throw new Error(`feedback returned ${res.status}`);
    upBtn.classList.toggle('active', direction === 'up');
    downBtn.classList.toggle('active', direction === 'down');
  } catch (err) {
    console.warn('creamfresh vote failed', err);
  } finally {
    upBtn.disabled = false;
    downBtn.disabled = false;
  }
}

async function saveStation(station) {
  try {
    const res = await fetch('/radio/save/', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-CSRFToken': getCsrfToken(),
      },
      body: JSON.stringify(station),
    });

    if (res.status === 401) {
      await customAlert('Bitte anmelden, um Sender zu speichern.');
      return;
    }

    const data = await res.json();
    if (data.ok) {
      if (data.created) {
        addSavedRow({ id: data.id, ...station, is_favorite: false });
      }
    }
  } catch (err) {
    console.error('saveStation error:', err);
  }
}

function addSavedRow(station) {
  const tbody = $('saved-tbody');
  if (!tbody) return;

  const emptyRow = $('saved-empty-row');
  if (emptyRow) emptyRow.remove();

  // Check for duplicate
  if (document.getElementById(`saved-row-${station.id}`)) return;

  const tr = document.createElement('tr');
  tr.id = `saved-row-${station.id}`;
  tr.dataset.id = station.id;
  tr.dataset.url = station.url;
  tr.dataset.name = station.name;

  const safeName = escapeHtml(station.name || '');
  const safeBr   = escapeHtml(station.bitrate || '');
  const safeCC   = escapeHtml(station.country || '');
  const safeUrl  = escapeHtml(station.url || '');

  tr.innerHTML = `
    <td>
      <button class="btn-icon fav-btn${station.is_favorite ? ' active' : ''}"
              onclick="toggleFav(${station.id}, this)"
              title="Favorit an/aus">&#9733;</button>
    </td>
    <td class="station-name-cell">${safeName}</td>
    <td>${safeBr}</td>
    <td>${safeCC}</td>
    <td class="notes-cell" onclick="editNotes(${station.id}, this.textContent.trim())" title="" style="cursor:pointer; color:#666; max-width:120px; overflow:hidden; text-overflow:ellipsis; white-space:nowrap;"></td>
    <td>
      <button class="btn btn-sm"
              onclick="playStation('${safeUrl}', '${safeName}', ${station.id})">
        &#9654; Abspielen
      </button>
    </td>
    <td>
      <button class="btn btn-sm btn-danger"
              onclick="removeStation(${station.id})">
        Entfernen
      </button>
    </td>
  `;
  tbody.appendChild(tr);
}

// ---------------------------------------------------------------------------
// Remove station
// ---------------------------------------------------------------------------

// The only toggleFav: a second definition further down (expecting the button
// as an argument) used to shadow this one, so the server-rendered rows — which
// pass no button — toggled the favourite on the server without the star ever
// changing, and a second click silently took it back.
async function toggleFav(pk, btnEl) {
  try {
    const res = await fetch(`/radio/favorite/${pk}/`, {
      method: 'POST',
      headers: { 'X-CSRFToken': getCsrfToken() },
    });
    if (!res.ok) return;
    const data = await res.json();

    // Flip the star button state
    const btn = btnEl || document.querySelector(`#saved-row-${pk} .fav-btn`);
    if (btn) btn.classList.toggle('active', !!data.is_favorite);

    // Re-sort rows in the DOM: favorites first, then alphabetically
    const tbody = $('saved-tbody');
    if (!tbody) return;
    const rows = Array.from(tbody.querySelectorAll('tr[data-id]'));
    rows.sort((a, b) => {
      const aFav = a.querySelector('.fav-btn')?.classList.contains('active') ? 0 : 1;
      const bFav = b.querySelector('.fav-btn')?.classList.contains('active') ? 0 : 1;
      if (aFav !== bFav) return aFav - bFav;
      return a.dataset.name.localeCompare(b.dataset.name);
    });
    rows.forEach(row => tbody.appendChild(row));
  } catch (err) {
    console.error('toggleFav error', err);
  }
}

async function removeStation(pk) {
  try {
    const res = await fetch(`/radio/remove/${pk}/`, {
      method: 'POST',
      headers: { 'X-CSRFToken': getCsrfToken() },
    });
    if (res.ok) {
      const row = $(`saved-row-${pk}`);
      if (row) row.remove();

      const tbody = $('saved-tbody');
      if (tbody && tbody.querySelectorAll('tr').length === 0) {
        const tr = document.createElement('tr');
        tr.id = 'saved-empty-row';
        tr.innerHTML = '<td colspan="7" class="empty-msg">Noch keine gespeicherten Sender.</td>';
        tbody.appendChild(tr);
      }
    }
  } catch (err) {
    console.error('removeStation error:', err);
  }
}

// ---------------------------------------------------------------------------
// Focus Timer
// ---------------------------------------------------------------------------

const TIMER_WORK = 25 * 60;
const TIMER_BREAK = 5 * 60;
let timerSeconds = TIMER_WORK;
let timerRunning = false;
let timerIsBreak = false;
let timerInterval = null;

function timerTick() {
  timerSeconds--;
  renderTimer();
  if (timerSeconds <= 0) {
    clearInterval(timerInterval);
    timerInterval = null;
    timerRunning = false;
    if (!timerIsBreak) {
      // work session ended → start break
      timerIsBreak = true;
      recordFocusSession();
      timerSeconds = TIMER_BREAK;
      showTimerNotification('Pause! 5 Minuten.');
      // auto-pause playback during break
      if (audio.src && !audio.paused) audio.pause();
    } else {
      // break ended → reset to work
      timerIsBreak = false;
      timerSeconds = TIMER_WORK;
      showTimerNotification('Pause vorbei. Weiter geht’s.');
    }
    renderTimer();
  }
}

function toggleTimer() {
  if (timerRunning) {
    clearInterval(timerInterval);
    timerInterval = null;
    timerRunning = false;
  } else {
    if ('Notification' in window && Notification.permission === 'default') {
      Notification.requestPermission();
    }
    timerRunning = true;
    timerInterval = setInterval(timerTick, 1000);
  }
  renderTimer();
}

function resetTimer() {
  clearInterval(timerInterval);
  timerInterval = null;
  timerRunning = false;
  timerIsBreak = false;
  timerSeconds = TIMER_WORK;
  renderTimer();
}

function renderTimer() {
  const m = String(Math.floor(timerSeconds / 60)).padStart(2, '0');
  const s = String(timerSeconds % 60).padStart(2, '0');
  const display = $('timer-display');
  const btn = $('timer-toggle-btn');
  const label = $('timer-phase-label');
  if (display) display.textContent = `${m}:${s}`;
  if (btn) btn.textContent = timerRunning ? '⏸' : '▶';
  if (label) label.textContent = timerIsBreak ? 'Pause' : 'Fokus';
  // colour the display red when break
  if (display) display.style.color = timerIsBreak ? '#e63946' : '';
}

function showTimerNotification(msg) {
  if ('Notification' in window && Notification.permission === 'granted') {
    new Notification('diora', { body: msg });
  }
  // also flash in the timer label
  const label = $('timer-phase-label');
  if (label) { label.textContent = msg; setTimeout(() => renderTimer(), 3000); }
}

// ---------------------------------------------------------------------------
// Focus session recording
// ---------------------------------------------------------------------------

async function recordFocusSession() {
  try {
    await fetch('/radio/focus/record/', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken() },
      body: JSON.stringify({
        station_name: currentStation ? currentStation.name : '',
        duration_minutes: 25,
      }),
    });
    loadFocusStats();
  } catch (e) {}
}

async function loadFocusStats() {
  try {
    const res = await fetch('/radio/focus/stats/');
    const data = await res.json();
    const widget = document.getElementById('focus-today-widget');
    if (widget) {
      if (data.today_sessions > 0) {
        widget.textContent = `Heute: ${data.today_sessions} ${data.today_sessions !== 1 ? 'Sitzungen' : 'Sitzung'} · ${data.today_minutes} min`;
        widget.style.display = '';
      } else {
        widget.style.display = 'none';
      }
    }
    // populate focus tab
    const tbody = document.getElementById('focus-tbody');
    if (!tbody) return;
    tbody.innerHTML = '';
    if (!data.sessions.length) {
      tbody.innerHTML = '<tr><td colspan="3" class="empty-msg">Noch keine Fokus-Sitzungen. Starte den Timer!</td></tr>';
      return;
    }
    data.sessions.forEach(s => {
      const tr = document.createElement('tr');
      const dt = new Date(s.completed_at).toLocaleString([], {dateStyle: 'short', timeStyle: 'short'});
      tr.innerHTML = `<td>${dt}</td><td>${escapeHtml(s.station_name || '—')}</td><td>${s.duration_minutes} min</td>`;
      tbody.appendChild(tr);
    });
  } catch (e) {}
}

// ---------------------------------------------------------------------------
// Do Not Disturb / focus mode
// ---------------------------------------------------------------------------

let dndActive = false;

function toggleDNDLight() {
  document.body.classList.toggle('dnd-dark');
  const btn = $('dnd-light-btn');
  if (btn) btn.style.opacity = document.body.classList.contains('dnd-dark') ? '0.4' : '1';
}

function toggleDND() {
  dndActive = !dndActive;
  if (!dndActive) document.body.classList.remove('dnd-dark');
  document.body.classList.toggle('dnd-mode', dndActive);
  const btn = $('dnd-btn');
  if (btn) btn.classList.toggle('active', dndActive);
  if (dndActive) {
    const el = document.documentElement;
    if (el.requestFullscreen) el.requestFullscreen();
    else if (el.webkitRequestFullscreen) el.webkitRequestFullscreen();
  } else {
    if (document.fullscreenElement && document.exitFullscreen) document.exitFullscreen();
    else if (document.webkitFullscreenElement && document.webkitExitFullscreen) document.webkitExitFullscreen();
  }
}

// Exit DND on Escape (browser also exits fullscreen on Escape, so sync state)
document.addEventListener('fullscreenchange', () => {
  if (!document.fullscreenElement && dndActive) {
    dndActive = false;
    document.body.classList.remove('dnd-mode');
    const btn = $('dnd-btn');
    if (btn) btn.classList.remove('active');
  }
});

document.addEventListener('keydown', e => {
  if (e.key === 'Escape' && dndActive) toggleDND();
});

// ---------------------------------------------------------------------------
// Mood / genre tag filter
// ---------------------------------------------------------------------------

const MOOD_TAGS = [
  { label: 'Fokus', tag: 'ambient' },
  { label: 'Lo-fi', tag: 'lofi' },
  { label: 'Jazz', tag: 'jazz' },
  { label: 'Klassik', tag: 'classical' },
  { label: 'Ambient', tag: 'ambient' },
  { label: 'Metal', tag: 'metal' },
  { label: 'Elektronisch', tag: 'electronic' },
  { label: 'Wort', tag: 'talk' },
];

function initMoodChips() {
  const container = $('mood-chips');
  if (!container) return;
  MOOD_TAGS.forEach(({ label, tag }) => {
    const btn = document.createElement('button');
    btn.className = 'mood-chip';
    btn.textContent = label;
    btn.onclick = () => {
      const input = $('search-input');
      if (input) input.value = tag;
      doSearch();
    };
    container.appendChild(btn);
  });
}

// ---------------------------------------------------------------------------
// Curated station lists
// ---------------------------------------------------------------------------

const CURATED_LISTS = [
  {
    id: 'focus',
    label: 'Fokus',
    stations: [
      { name: 'SomaFM Drone Zone', url: 'https://ice6.somafm.com/dronezone-256-mp3' },
      { name: 'SomaFM Groove Salad', url: 'https://ice5.somafm.com/groovesalad-128-aac' },
      { name: 'Nightride FM', url: 'https://stream.nightride.fm/nightride.mp3' },
      { name: 'Nightride FM Chillsynth', url: 'https://stream.nightride.fm/chillsynth.mp3' },
    ],
  },
  {
    id: 'lofi',
    label: 'Lo-fi / Chill',
    stations: [
      { name: 'SomaFM Groove Salad Classic', url: 'https://ice6.somafm.com/gsclassic-128-mp3' },
      { name: 'SomaFM Secret Agent', url: 'https://ice4.somafm.com/secretagent-128-mp3' },
      { name: 'dublab DE', url: 'https://dublabde.out.airtime.pro/dublabde_a' },
    ],
  },
  {
    id: 'dark',
    label: 'Dark / Industrial',
    stations: [
      { name: 'SomaFM Doomed', url: 'https://ice2.somafm.com/doomed-256-mp3' },
      { name: 'Nightride FM Darksynth', url: 'https://stream.nightride.fm/darksynth.mp3' },
      { name: 'Radio Caprice Industrial', url: 'http://79.120.39.202:9095/' },
    ],
  },
  {
    id: 'classical',
    label: 'Klassik',
    stations: [
      { name: 'BR Klassik', url: 'https://dispatcher.rndfnk.com/br/brklassik/live/mp3/high' },
      { name: 'SWR Kultur', url: 'https://f111.rndfnk.com/ard/swr/swr2/live/mp3/256/stream.mp3?aggregator=web' },
      { name: 'Deutschlandfunk Kultur', url: 'https://st02.sslstream.dlf.de/dlf/02/high/aac/stream.aac?aggregator=web' },
    ],
  },
];

function initCuratedLists() {
  const container = document.getElementById('curated-lists');
  if (!container) return;

  if (INITIAL_FEATURED && INITIAL_FEATURED.length) {
    const section = document.createElement('div');
    section.className = 'curated-section';
    section.innerHTML = `<div class="curated-label">&#9733; Empfohlen</div>`;
    const ul = document.createElement('ul');
    ul.className = 'curated-stations';
    INITIAL_FEATURED.forEach(s => {
      const li = document.createElement('li');
      li.innerHTML = `<button class="btn btn-sm" onclick="playStation('${escapeAttr(s.url)}', '${escapeAttr(s.name)}', null)">▶</button>
                      <span class="curated-name">${escapeHtml(s.name)}</span>
                      ${s.description ? `<span class="muted" style="font-size:0.78rem">${escapeHtml(s.description)}</span>` : ''}`;
      ul.appendChild(li);
    });
    section.appendChild(ul);
    container.appendChild(section);
  }

  CURATED_LISTS.forEach(list => {
    const section = document.createElement('div');
    section.className = 'curated-section';
    section.innerHTML = `<div class="curated-label">${list.label}</div>`;
    const ul = document.createElement('ul');
    ul.className = 'curated-stations';
    list.stations.forEach(s => {
      const li = document.createElement('li');
      li.innerHTML = `<button class="btn btn-sm" onclick="playStation('${escapeAttr(s.url)}', '${escapeAttr(s.name)}', null)">▶</button>
                      <span class="curated-name">${escapeHtml(s.name)}</span>`;
      ul.appendChild(li);
    });
    section.appendChild(ul);
    container.appendChild(section);
  });
}

// ---------------------------------------------------------------------------
// Donation hint
// ---------------------------------------------------------------------------

const DONATION_HINT_THRESHOLD = 10;
const DONATION_HINT_COOLDOWN_MS = 7 * 24 * 60 * 60 * 1000; // 7 days

function maybeShowDonationHint(stationUrl, stationName) {
  const station = INITIAL_SAVED.find(s => s.url === stationUrl);
  if (!station || station.play_count < DONATION_HINT_THRESHOLD) return;

  const key = `diora_donation_hint_${stationUrl}`;
  const last = parseInt(localStorage.getItem(key) || '0', 10);
  if (Date.now() - last < DONATION_HINT_COOLDOWN_MS) return;

  // Past the threshold just means "this station is a regular" — from then on
  // every single play would otherwise qualify, so only actually show the hint
  // on roughly 1 in 10 of those plays instead of every time.
  if (Math.random() >= 0.1) return;

  const existing = document.getElementById('donation-hint');
  if (existing) existing.remove();

  const el = document.createElement('div');
  el.id = 'donation-hint';
  el.innerHTML = `
    <span>Du hörst <strong>${escapeHtml(stationName)}</strong> oft – vielleicht magst du den Sender unterstützen ♥</span>
    <button onclick="dismissDonationHint('${escapeAttr(stationUrl)}')" title="Ausblenden">✕</button>
  `;
  document.body.appendChild(el);

  setTimeout(() => dismissDonationHint(stationUrl), 12000);
}

function dismissDonationHint(stationUrl) {
  localStorage.setItem(`diora_donation_hint_${stationUrl}`, Date.now());
  const el = document.getElementById('donation-hint');
  if (el) { el.classList.add('hiding'); setTimeout(() => el.remove(), 400); }
}

// ---------------------------------------------------------------------------
// Station notes
// ---------------------------------------------------------------------------

async function editNotes(pk, current) {
  const note = await customPrompt('Notiz zum Sender:', current || '');
  if (note === null) return; // cancelled
  fetch(`/radio/notes/${pk}/`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken() },
    body: JSON.stringify({ notes: note }),
  }).then(r => {
    if (r.ok) {
      const cell = document.querySelector(`#saved-row-${pk} .notes-cell`);
      if (cell) cell.textContent = note;
    }
  });
}

// ---------------------------------------------------------------------------
// Tabs
// ---------------------------------------------------------------------------

const TOP_TABS = ['home', 'radio', 'focus', 'podcasts', 'books', 'feeds', 'ambient'];
const RADIO_SUB_TABS = ['search', 'saved', 'history'];

// ---------------------------------------------------------------------------
// URL hash routing — makes tabs deep-linkable/shareable and lets the browser
// back/forward buttons move between them. Deliberately hash-based rather
// than real paths: /podcasts/ and /books/ etc. are already taken by the
// JSON API, so this avoids touching Django's urls.py at all.
// ---------------------------------------------------------------------------
let _routingFromHash = false;
let _currentTopTab = 'radio';

function _syncHash() {
  if (_routingFromHash) return;
  let hash = _currentTopTab;
  if (_currentTopTab === 'radio') {
    hash += '/' + (localStorage.getItem('diora_active_radio_tab') || 'saved');
  }
  if (location.hash.slice(1) !== hash) history.pushState(null, '', '#' + hash);
}

function _routeFromHash() {
  const [tab, sub] = (location.hash || '').replace(/^#/, '').split('/').filter(Boolean);
  if (!TOP_TABS.includes(tab)) return;
  _routingFromHash = true;
  try {
    showTab(tab);
    if (tab === 'radio' && RADIO_SUB_TABS.includes(sub)) showRadioTab(sub);
  } finally {
    _routingFromHash = false;
  }
}

window.addEventListener('popstate', _routeFromHash);
window.addEventListener('hashchange', _routeFromHash);

function showOfflineBanner(offline) {
  document.body.classList.toggle('app-offline', offline);
  const uploadArea = $('book-upload-area');
  if (uploadArea) uploadArea.style.display = offline ? 'none' : '';
}

function showTab(name) {
  TOP_TABS.forEach(p => {
    const panel = $(`tab-${p}`);
    if (panel) panel.style.display = (p === name) ? '' : 'none';
  });

  document.querySelectorAll('#tabs .tab-btn').forEach((btn, i) => {
    btn.classList.toggle('active', TOP_TABS[i] === name);
  });

  localStorage.setItem('diora_active_tab', name);
  _currentTopTab = name;
  _syncHash();

  if (name === 'books') loadBookList();
  if (name === 'ambient') _ambientLoad();
  if (name === 'home' && window.__dioraHomeShow) window.__dioraHomeShow();   // static/js/home.js
  if (name === 'feeds' && window.__dioraFeedsShow) window.__dioraFeedsShow(); // static/js/feeds.js
}

// ---------------------------------------------------------------------------
// Ambient: "Drift" (static/ambient/), a generative synthesizer in a frame of its
// own. It and the radio / podcast player take turns — one starting stops the
// other — by postMessage: {type: 'ambient', cmd: 'start'|'stop'} to the frame,
// {type: 'ambient', state: 'playing'|'stopped'} from it.
// ---------------------------------------------------------------------------
let _ambientPlaying = false;
let _ambientLast = false;   // Ambient was started last: the player bar shows it (native-podcast.js)

function _ambientFrame() {
  return $('ambient-frame');
}

function _ambientLoad() {
  const f = _ambientFrame();
  if (!f) return;
  if (!f.getAttribute('src')) {
    // Drift takes the page's volume before its first sound; the bar follows its sound world.
    f.addEventListener('load', () => {
      _ambientVolume();
      try {
        const sel = f.contentDocument.getElementById('mode');
        // The sound world chosen last comes back (Drift itself starts with its default).
        let last = '';
        try { last = localStorage.getItem('diora_ambient_mode') || ''; } catch (e) {}
        if (last && last !== sel.value && [...sel.options].some(o => o.value === last)) {
          f.contentWindow.postMessage({type: 'ambient', cmd: 'mode', mode: last}, '*');
        }
        sel.addEventListener('change', () => {
          try {
            localStorage.setItem('diora_ambient_mode', sel.value);
            localStorage.setItem('diora_ambient_mode_label', sel.selectedOptions[0] ? sel.selectedOptions[0].text : '');
          } catch (e) {}
          if (window.__dioraAmbientChanged) window.__dioraAmbientChanged();
        });
      } catch (e) {}
    });
    f.src = f.dataset.src;
  }
  requestAnimationFrame(_ambientSize);
}

// The frame fills the room between the tabs and the player bar at the bottom.
function _ambientSize() {
  const f = _ambientFrame();
  if (!f || _currentTopTab !== 'ambient') return;
  const root = getComputedStyle(document.documentElement);
  const bar = parseFloat(root.getPropertyValue('--nui-dock-h')) || parseFloat(root.getPropertyValue('--dpw-bar-h')) || 0;
  const top = f.getBoundingClientRect().top + window.scrollY;
  f.style.height = Math.max(320, Math.floor(window.innerHeight - top - bar)) + 'px';
}
window.addEventListener('resize', () => requestAnimationFrame(_ambientSize));
// The bar at the bottom grows or shrinks (the player appears, a second line …): its height
// comes as --nui-dock-h / --dpw-bar-h on <html>, set inline — measure again then.
new MutationObserver(() => requestAnimationFrame(_ambientSize))
  .observe(document.documentElement, {attributes: true, attributeFilter: ['style']});

// A command for Drift ('start' | 'stop'): the app's notification, the sleep timer.
window.__dioraAmbientCmd = function (cmd, value) {
  const f = _ambientFrame();
  if (f && f.contentWindow && f.getAttribute('src')) f.contentWindow.postMessage({type: 'ambient', cmd, value}, '*');
};

// Start Drift from elsewhere (Home): load the frame if needed, then start it — with the
// sound world chosen last, which the frame's load handler above sets.
window.__dioraAmbientStart = function () {
  const f = _ambientFrame();
  if (!f) return;
  const go = () => window.__dioraAmbientCmd('start');
  let ready = false;
  try { ready = !!f.getAttribute('src') && f.contentDocument.readyState === 'complete' && !!f.contentDocument.getElementById('mode'); } catch (e) {}
  if (ready) { go(); return; }
  f.addEventListener('load', () => setTimeout(go, 0), {once: true});
  _ambientLoad();
};

// The radio or a podcast starts: Ambient stops, and the player bar is theirs again.
window.__dioraAmbientStop = function () {
  if (_ambientPlaying) window.__dioraAmbientCmd('stop');
  if (_ambientLast) {
    _ambientLast = false;
    if (window.__dioraAmbientChanged) window.__dioraAmbientChanged();
  }
};
window.__dioraAmbientPlaying = () => _ambientPlaying;

// For the player bar: playing, started last, the sound world's name (the frame is ours).
window.__dioraAmbientInfo = function () {
  const f = _ambientFrame();
  let mode = '';
  try {
    const sel = f && f.contentDocument && f.contentDocument.getElementById('mode');
    if (sel && sel.selectedOptions[0]) mode = sel.selectedOptions[0].text;
  } catch (e) {}
  return {playing: _ambientPlaying, last: _ambientLast, mode};
};

// The page's volume (0–255, the bar's slider) is Drift's too; its own slider hides when
// embedded. Not in the Android app: there the volume keys set it, as for everything.
function _ambientVolume(val) {
  if (window.DioraNative && DioraNative.ambientState) return;
  if (val == null) {
    const s = $('volume');
    val = s ? +s.value : +(localStorage.getItem('diora_volume') || 102);
  }
  window.__dioraAmbientCmd && window.__dioraAmbientCmd('volume', val / 255);
}

window.addEventListener('message', e => {
  const f = _ambientFrame();
  const d = e.data;
  if (!f || e.source !== f.contentWindow || !d || d.type !== 'ambient' || !d.state) return;
  _ambientPlaying = d.state === 'playing';
  if (_ambientPlaying) _ambientLast = true;
  if (window.__dioraAmbientChanged) window.__dioraAmbientChanged();
  // The app keeps it going with the screen off (AmbientService); the browser's sleep timer counts it.
  if (window.DioraNative && DioraNative.ambientState) DioraNative.ambientState(_ambientPlaying);
  if (window.__dioraOnAmbient) window.__dioraOnAmbient(_ambientPlaying);
  if (!_ambientPlaying) return;
  // Ambient starts: the radio and a podcast here stop.
  if (typeof isPlaying !== 'undefined' && isPlaying) stopPlayback(false);
  if (window.__dioraPausePlayer) window.__dioraPausePlayer();
});

function showRadioTab(name) {
  RADIO_SUB_TABS.forEach(p => {
    const panel = $(`tab-${p}`);
    if (panel) panel.style.display = (p === name) ? '' : 'none';
  });

  document.querySelectorAll('#radio-sub-tabs .tab-btn').forEach((btn, i) => {
    btn.classList.toggle('active', RADIO_SUB_TABS[i] === name);
  });

  localStorage.setItem('diora_active_radio_tab', name);
  _syncHash();

  if (name === 'saved') loadRecommendations();
}

// ---------------------------------------------------------------------------
// Sidebar
// ---------------------------------------------------------------------------

function openSidebar(title, htmlContent) {
  $('sidebar-title').textContent = title;
  $('sidebar-body').innerHTML = sanitizeSidebarHtml(htmlContent);
  $('sidebar-overlay').style.display = '';
  $('sidebar').classList.add('open');
}

function closeSidebar() {
  $('sidebar').classList.remove('open');
  $('sidebar-overlay').style.display = 'none';
}

document.addEventListener('keydown', e => {
  const overlay = $('reader-overlay');
  const readerOpen = overlay && overlay.style.display !== 'none';

  if (e.key === 'Escape') {
    if (readerOpen) {
      closeReader();
    } else {
      closeSidebar();
    }
  }

  if (readerOpen) {
    if ((e.ctrlKey && e.key === 'f') || e.key === 'F3') {
      e.preventDefault();
      toggleReaderSearch();
    }
    if (readerSearchOpen) {
      if (e.key === 'ArrowDown') { e.preventDefault(); readerSearchNext(); }
      if (e.key === 'ArrowUp')   { e.preventDefault(); readerSearchPrev(); }
    }
    if (readerSettings.pdfPaginated && currentPdfDoc) {
      if (e.key === 'ArrowRight') { e.preventDefault(); pdfGoToPage(pdfCurrentPage + 1); }
      if (e.key === 'ArrowLeft')  { e.preventDefault(); pdfGoToPage(pdfCurrentPage - 1); }
    }

    // Vim-style scroll — ignore when typing in an input
    const tag = document.activeElement?.tagName;
    if (tag !== 'INPUT' && tag !== 'TEXTAREA') {
      const contentEl = $('reader-content');
      if (contentEl) {
        const large = Math.round(contentEl.clientHeight * 0.85);
        const continuousKeys = {'j': 1, 'k': -1};
        if (continuousKeys[e.key] !== undefined && !e.repeat) {
          e.preventDefault();
          _readerScrollDir = continuousKeys[e.key];
          if (!_readerScrollInterval) {
            _readerScrollLastTs = performance.now();
            _readerScrollInterval = setInterval(_readerScrollTick, READER_SCROLL_TICK_MS);
          }
        }
        if (e.key === 'd') { e.preventDefault(); contentEl.scrollBy({top:  large / 2, behavior: 'smooth'}); }
        if (e.key === 'u') { e.preventDefault(); contentEl.scrollBy({top: -large / 2, behavior: 'smooth'}); }
        if (e.key === 'f') { e.preventDefault(); contentEl.scrollBy({top:  large, behavior: 'smooth'}); }
        if (e.key === 'b') { e.preventDefault(); contentEl.scrollBy({top: -large, behavior: 'smooth'}); }
        if (e.key === 'g') { e.preventDefault(); contentEl.scrollTop = 0; }
        if (e.key === 'G') { e.preventDefault(); contentEl.scrollTop = contentEl.scrollHeight; }
        if (currentPdfDoc && !readerSettings.pdfPaginated) {
          if (e.key === 'n') { e.preventDefault(); pdfGoToPage(pdfCurrentPage + 1); }
          if (e.key === 'p') { e.preventDefault(); pdfGoToPage(pdfCurrentPage - 1); }
        }
      }
    }
  }
});

document.addEventListener('keyup', e => {
  if (e.key === 'j' || e.key === 'k') {
    clearInterval(_readerScrollInterval);
    _readerScrollInterval = null;
    _readerScrollDir = 0;
  }
});

function sanitizeSidebarHtml(html) {
  if (!html) return '<p class="muted">Keine Shownotes vorhanden.</p>';
  const div = document.createElement('div');
  div.innerHTML = html;
  div.querySelectorAll('script, iframe, object, embed, style').forEach(el => el.remove());
  div.querySelectorAll('*').forEach(el => {
    Array.from(el.attributes).forEach(attr => {
      if (attr.name.startsWith('on')) el.removeAttribute(attr.name);
    });
    if (el.tagName === 'A') {
      el.setAttribute('target', '_blank');
      el.setAttribute('rel', 'noopener noreferrer');
    }
  });
  return div.innerHTML;
}

// ---------------------------------------------------------------------------
// Service Worker
// ---------------------------------------------------------------------------

if ('serviceWorker' in navigator) {
  window.addEventListener('load', () => {
    // Registered from '/sw.js' (root), not '/static/js/sw.js': a service
    // worker's default scope is its own script's directory, so registering
    // it from under /static/js/ would only ever let it control requests
    // under that path — page navigations to '/', '/books/' etc. would never
    // be intercepted, breaking offline entirely.
    navigator.serviceWorker.register('/sw.js', {scope: '/'}).catch(err => {
      console.warn('Service worker registration failed:', err);
    });
    // Drop any leftover registration from the old, wrongly-scoped '/static/js/sw.js'
    // path so it doesn't keep running or fight the new root-scoped worker.
    navigator.serviceWorker.getRegistrations().then(regs => {
      regs.forEach(r => { if (r.scope.endsWith('/static/js/')) r.unregister(); });
    });
  });
  // When a new SW activates it sends SW_ACTIVATED — reload to get fresh assets,
  // but never in the middle of something: not while a book is open, radio or a
  // podcast plays, or a text field has the focus — then as soon as that's over.
  let reloadPending = false;
  const busy = () => {
    if (currentBookId || isPlaying) return true;
    const host = window.DioraPodcastHost;
    if (host && host.playerState) {
      try { if (JSON.parse(host.playerState()).playing) return true; } catch (_) {}
    }
    const el = document.activeElement;
    return !!el && (el.isContentEditable || /^(INPUT|TEXTAREA|SELECT)$/.test(el.tagName));
  };
  const reloadWhenIdle = () => {
    if (busy()) setTimeout(reloadWhenIdle, 5000);
    else window.location.reload();
  };
  navigator.serviceWorker.addEventListener('message', e => {
    if (e.data?.type === 'SW_ACTIVATED' && !reloadPending) {
      reloadPending = true;
      reloadWhenIdle();
    }
  });
}

// ---------------------------------------------------------------------------
// M3U import
// ---------------------------------------------------------------------------

async function importM3U(input) {
  const file = input.files[0];
  if (!file) return;
  const status = document.getElementById('import-status');
  status.textContent = 'Importiere …';

  const form = new FormData();
  form.append('file', file);
  form.append('csrfmiddlewaretoken', getCsrfToken());

  try {
    const res = await fetch('/radio/import/', { method: 'POST', body: form });
    const data = await res.json();
    if (data.ok) {
      status.textContent = `✓ ${data.added} hinzugefügt, ${data.skipped} schon gespeichert`;
      if (data.added > 0) location.reload();
    } else {
      status.textContent = `Fehler: ${_germanError(data.error)}`;
    }
  } catch (e) {
    status.textContent = 'Hochladen fehlgeschlagen';
  }
  input.value = '';
}

// ---------------------------------------------------------------------------
// Contrast scheme
// ---------------------------------------------------------------------------

// Accent palette — ordered by preference. Algorithm picks the one with the
// highest WCAG contrast ratio against the detected background luminance.
const ACCENT_PALETTE = [
  { base: '#e63946', hover: '#ff4d58' }, // red
  { base: '#ff9500', hover: '#ffaa33' }, // orange
  { base: '#f1c40f', hover: '#f9d439' }, // yellow
  { base: '#2ecc71', hover: '#4ee88a' }, // green
  { base: '#00b4d8', hover: '#33c7e5' }, // cyan
  { base: '#4361ee', hover: '#6d84f4' }, // blue
  { base: '#c77dff', hover: '#d89fff' }, // purple
  { base: '#ff6b9d', hover: '#ff8fb5' }, // pink
  { base: '#ffffff', hover: '#cccccc' }, // white (last resort)
];

function _linearise(c) {
  c /= 255;
  return c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
}
function _luminance(r, g, b) {
  return 0.2126 * _linearise(r) + 0.7152 * _linearise(g) + 0.0722 * _linearise(b);
}
function _contrast(l1, l2) {
  return (Math.max(l1, l2) + 0.05) / (Math.min(l1, l2) + 0.05);
}
function _hexRgb(hex) {
  return [parseInt(hex.slice(1,3),16), parseInt(hex.slice(3,5),16), parseInt(hex.slice(5,7),16)];
}

function analyzeBackground(url) {
  return new Promise(resolve => {
    const img = new Image();
    img.crossOrigin = 'anonymous';
    img.onload = () => {
      const canvas = document.createElement('canvas');
      canvas.width = 64; canvas.height = 64;
      const ctx = canvas.getContext('2d');
      ctx.drawImage(img, 0, 0, 64, 64);
      const data = ctx.getImageData(0, 0, 64, 64).data;
      let tR = 0, tG = 0, tB = 0, tBt601 = 0;
      const n = data.length / 4;
      for (let i = 0; i < data.length; i += 4) {
        tR += data[i]; tG += data[i+1]; tB += data[i+2];
        tBt601 += 0.299*data[i] + 0.587*data[i+1] + 0.114*data[i+2];
      }
      resolve({
        bright: (tBt601 / n) > 127,
        bgLuminance: _luminance(tR/n, tG/n, tB/n),
      });
    };
    img.onerror = () => resolve({ bright: false, bgLuminance: 0 });
    img.src = url;
  });
}

function pickBestAccent(bgLuminance) {
  let best = ACCENT_PALETTE[0], bestRatio = 0;
  for (const entry of ACCENT_PALETTE) {
    const [r, g, b] = _hexRgb(entry.base);
    const ratio = _contrast(bgLuminance, _luminance(r, g, b));
    if (ratio > bestRatio) { bestRatio = ratio; best = entry; }
  }
  return best;
}

function applyAccent(entry) {
  const root = document.documentElement;
  root.style.setProperty('--accent', entry.base);
  root.style.setProperty('--accent-hover', entry.hover);
}

// Light and dark: the switch is in base.html (every page has it). The reader's
// "Wie die App" follows it.
window.addEventListener('diora-theme', () => {
  if (currentBookId) applyReaderSettings(!!currentPdfDoc);
});

function setScheme(bright) {
  document.body.classList.toggle('bright-bg', bright);
  const btn = document.getElementById('contrast-toggle');
  if (btn) btn.style.opacity = bright ? '1' : '0.5';
}

function toggleContrast() {
  setScheme(!document.body.classList.contains('bright-bg'));
}

// ---------------------------------------------------------------------------
// E2E Encryption utilities (Web Crypto API)
// ---------------------------------------------------------------------------

let _encKey = null;

function bytesToBase64(buf) {
  const bytes = new Uint8Array(buf);
  let str = '';
  for (const b of bytes) str += String.fromCharCode(b);
  return btoa(str);
}

function base64ToBytes(b64) {
  const str = atob(b64);
  const buf = new Uint8Array(str.length);
  for (let i = 0; i < str.length; i++) buf[i] = str.charCodeAt(i);
  return buf;
}

function bytesToHex(buf) {
  return Array.from(new Uint8Array(buf)).map(b => b.toString(16).padStart(2, '0')).join('');
}

function hexToBytes(hex) {
  const arr = new Uint8Array(hex.length / 2);
  for (let i = 0; i < arr.length; i++) arr[i] = parseInt(hex.slice(i*2, i*2+2), 16);
  return arr;
}

async function getOrCreateEncKey() {
  if (_encKey) return _encKey;
  const storageKey = `diora_enc_key_${window.USER_ID || 0}`;
  const stored = localStorage.getItem(storageKey);
  if (stored) {
    try {
      const raw = base64ToBytes(stored);
      _encKey = await crypto.subtle.importKey('raw', raw, {name: 'AES-GCM'}, false, ['encrypt', 'decrypt']);
      return _encKey;
    } catch (e) { /* fall through, generate new */ }
  }
  // No key found — generate one and store it
  _encKey = await crypto.subtle.generateKey({name: 'AES-GCM', length: 256}, true, ['encrypt', 'decrypt']);
  const raw = await crypto.subtle.exportKey('raw', _encKey);
  localStorage.setItem(storageKey, bytesToBase64(new Uint8Array(raw)));
  return _encKey;
}

async function encryptBytes(key, plainBytes) {
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const ct = await crypto.subtle.encrypt({name: 'AES-GCM', iv}, key, plainBytes);
  return {iv: bytesToHex(iv), ciphertext: bytesToBase64(ct)};
}

async function decryptBytes(key, ivHex, ctB64) {
  const iv = hexToBytes(ivHex);
  const ct = base64ToBytes(ctB64);
  return crypto.subtle.decrypt({name: 'AES-GCM', iv}, key, ct);
}

// ---------------------------------------------------------------------------
// Encrypted wallpaper
// ---------------------------------------------------------------------------

async function uploadBackground(file) {
  if (!file) return;
  const allowedTypes = ['image/jpeg', 'image/png', 'image/webp'];
  if (!allowedTypes.includes(file.type)) {
    await customAlert('Nur JPEG-, PNG- oder WebP-Bilder sind erlaubt.');
    return;
  }
  if (file.size > DIORA_CONFIG.bgMaxBytes) {
    await customAlert(`Das Bild darf höchstens ${DIORA_CONFIG.bgMaxBytes / 1024 / 1024} MB groß sein.`);
    return;
  }

  const key = await getOrCreateEncKey();
  const buf = await file.arrayBuffer();
  const {iv, ciphertext} = await encryptBytes(key, buf);

  const res = await fetch('/accounts/background/upload/', {
    method: 'POST',
    headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
    body: JSON.stringify({iv, ciphertext, mime_type: file.type, file_size: file.size}),
  });
  const data = await res.json();
  if (!data.ok) throw new Error(data.error || 'upload failed');
}

async function applyEncryptedBackground() {
  if (typeof ENCRYPTED_BG === 'undefined' || !ENCRYPTED_BG.ciphertext) return;
  try {
    const key = await getOrCreateEncKey();
    const plain = await decryptBytes(key, ENCRYPTED_BG.iv, ENCRYPTED_BG.ciphertext);
    const blob = new Blob([plain], {type: ENCRYPTED_BG.mime || 'image/jpeg'});
    const url = URL.createObjectURL(blob);
    document.body.style.backgroundImage = `url('${url}')`;
    const contrastBtn = document.getElementById('contrast-toggle');
    if (contrastBtn) contrastBtn.hidden = false; // only with a picture behind the page
    document.body.style.backgroundSize = 'cover';
    document.body.style.backgroundPosition = 'center';
    document.body.style.backgroundAttachment = 'fixed';

    // Analyze brightness for accent/scheme
    analyzeBackground(url).then(({bright, bgLuminance}) => {
      setScheme(bright);
      applyAccent(pickBestAccent(bgLuminance));
    });
  } catch (e) {
    console.warn('Could not decrypt background:', e);
  }
}

// ---------------------------------------------------------------------------
// EPUB parser (requires JSZip)
// ---------------------------------------------------------------------------

function resolveEpubPath(base, relative) {
  if (!relative) return '';
  if (relative.startsWith('/')) return relative.slice(1);
  const hashIdx = relative.indexOf('#');
  const frag = hashIdx >= 0 ? relative.slice(hashIdx) : '';
  const rel = hashIdx >= 0 ? relative.slice(0, hashIdx) : relative;
  const parts = (base + rel).split('/');
  const resolved = [];
  for (const p of parts) {
    if (p === '..') resolved.pop();
    else if (p !== '.') resolved.push(p);
  }
  return resolved.join('/') + frag;
}

async function parseEpub(arrayBuffer) {
  const zip = await JSZip.loadAsync(arrayBuffer);

  // 1. Find OPF via container.xml
  const containerXml = await zip.file('META-INF/container.xml').async('text');
  const containerDoc = new DOMParser().parseFromString(containerXml, 'application/xml');
  const rootfileEl = containerDoc.querySelector('rootfile');
  if (!rootfileEl) throw new Error('Ungültige EPUB-Datei (container.xml ohne rootfile)');
  const opfPath = rootfileEl.getAttribute('full-path');
  const opfDir = opfPath.includes('/') ? opfPath.substring(0, opfPath.lastIndexOf('/') + 1) : '';

  // 2. Parse OPF
  const opfText = await zip.file(opfPath).async('text');
  const opfDoc = new DOMParser().parseFromString(opfText, 'application/xml');

  const title = opfDoc.querySelector('metadata > title, metadata > *|title')?.textContent?.trim() || 'Unbekannter Titel';
  const author = opfDoc.querySelector('metadata > creator, metadata > *|creator')?.textContent?.trim() || 'Unbekannter Autor';

  // 3. Build manifest: id → {href, mediaType, properties}
  const manifest = {};
  opfDoc.querySelectorAll('manifest > item').forEach(item => {
    manifest[item.getAttribute('id')] = {
      href: opfDir + item.getAttribute('href'),
      mediaType: item.getAttribute('media-type') || '',
      properties: item.getAttribute('properties') || '',
    };
  });

  // 4. Build image map: abs zip path → blob URL (parallel)
  const imageMap = {};
  await Promise.all(
    Object.values(manifest)
      .filter(({mediaType}) => mediaType.startsWith('image/'))
      .map(async ({href, mediaType}) => {
        try {
          const buf = await zip.file(href).async('arraybuffer');
          imageMap[href] = URL.createObjectURL(new Blob([buf], {type: mediaType}));
        } catch (e) { /* missing asset */ }
      })
  );

  // 5. Parse TOC
  const toc = await _parseEpubToc(zip, opfDoc, manifest);

  // 6. Get spine items; chapters are returned raw for progressive DOM injection
  const spineItems = Array.from(opfDoc.querySelectorAll('spine > itemref'))
    .map(ref => manifest[ref.getAttribute('idref')]?.href)
    .filter(Boolean);

  // All chapters unpacked at once: one after the other, every chapter waits for
  // JSZip's own ticks (a book like Das Kapital has 148 of them).
  const texts = await Promise.all(spineItems.map(href => {
    const f = zip.file(href);
    return f ? f.async('text').catch(() => null) : null;
  }));

  const chapters = [];
  let slice = performance.now();
  for (let i = 0; i < spineItems.length; i++) {
    const href = spineItems[i];
    if (texts[i] == null) continue;   // missing
    try {
      let chapterText = texts[i];
      texts[i] = null;
      // Strip style/script blocks early — publisher EPUBs often embed large base64 fonts in CSS.
      // This shrinks the string before regex and DOMParser work on it.
      chapterText = chapterText.replace(/<style\b[^>]*>[\s\S]*?<\/style>/gi, '');
      chapterText = chapterText.replace(/<script\b[^>]*>[\s\S]*?<\/script>/gi, '');
      const chapterDir = href.includes('/') ? href.substring(0, href.lastIndexOf('/') + 1) : '';
      const withBlobs = _injectImageBlobs(chapterText, chapterDir, imageMap);
      const sanitized = sanitizeEpubHtml(withBlobs);
      chapters.push(`<div id="epub-chapter-${i}" data-epub-src="${href}">${sanitized}</div>`);
      // Let the page breathe (spinner, taps) every ~50 ms of work, not after a fixed count.
      if (performance.now() - slice > 50) {
        await new Promise(r => setTimeout(r, 0));
        slice = performance.now();
      }
    } catch (e) { /* skip unreadable */ }
  }

  return {title, author, chapters, toc, imageMap};
}

async function _parseEpubToc(zip, opfDoc, manifest) {
  // Try EPUB3 nav document
  const navItem = Object.values(manifest).find(m => m.properties.includes('nav'));
  if (navItem) {
    try {
      const navText = await zip.file(navItem.href).async('text');
      const navDoc = new DOMParser().parseFromString(navText, 'application/xhtml+xml');
      const tocNav = navDoc.querySelector('nav[epub\\:type="toc"]') || navDoc.querySelector('nav');
      if (tocNav) {
        const ol = tocNav.querySelector('ol');
        if (ol) return _parseTocOl(ol, navItem.href, 0);
      }
    } catch (e) {}
  }

  // Fall back to EPUB2 NCX
  const ncxItem = Object.values(manifest).find(m => m.mediaType === 'application/x-dtbncx+xml');
  if (ncxItem) {
    try {
      const ncxText = await zip.file(ncxItem.href).async('text');
      const ncxDoc = new DOMParser().parseFromString(ncxText, 'application/xml');
      const ncxDir = ncxItem.href.includes('/') ? ncxItem.href.substring(0, ncxItem.href.lastIndexOf('/') + 1) : '';
      return _parseNcxNavMap(ncxDoc.querySelector('navMap'), ncxDir, 0);
    } catch (e) {}
  }

  return [];
}

function _parseTocOl(ol, navHref, depth) {
  if (!ol || depth > 5) return [];
  const navDir = navHref.includes('/') ? navHref.substring(0, navHref.lastIndexOf('/') + 1) : '';
  const items = [];
  for (const li of Array.from(ol.children)) {
    const a = li.querySelector(':scope > a') || li.querySelector(':scope > span');
    if (a) {
      const rawHref = a.getAttribute('href') || '';
      items.push({
        label: a.textContent.trim(),
        href: rawHref ? resolveEpubPath(navDir, rawHref) : '',
        depth,
      });
    }
    const childOl = li.querySelector(':scope > ol');
    if (childOl) items.push(..._parseTocOl(childOl, navHref, depth + 1));
  }
  return items;
}

function _parseNcxNavMap(navMap, ncxDir, depth) {
  if (!navMap || depth > 5) return [];
  const items = [];
  for (const navPoint of Array.from(navMap.children)) {
    if (navPoint.tagName !== 'navPoint') continue;
    const label = navPoint.querySelector('navLabel > text')?.textContent?.trim() || '';
    const src = navPoint.querySelector('content')?.getAttribute('src') || '';
    items.push({label, href: src ? resolveEpubPath(ncxDir, src) : '', depth});
    items.push(..._parseNcxNavMap(navPoint, ncxDir, depth + 1));
  }
  return items;
}

function _resolveImageBlob(imageMap, absPath) {
  if (imageMap[absPath]) return imageMap[absPath];
  // Fallback: match by decoded filename only
  const name = decodeURIComponent(absPath.split('/').pop()).toLowerCase();
  for (const [k, v] of Object.entries(imageMap)) {
    if (decodeURIComponent(k.split('/').pop()).toLowerCase() === name) return v;
  }
  return null;
}

// Replace image src/href in raw chapter HTML text with blob URLs before DOMParser sees it.
// This avoids relying on innerHTML serialisation preserving attributes we set on DOM nodes.
function _injectImageBlobs(html, chapterDir, imageMap) {
  function subst(src) {
    if (!src || src.startsWith('blob:') || src.startsWith('data:') || src.startsWith('http')) return src;
    return _resolveImageBlob(imageMap, resolveEpubPath(chapterDir, src)) || '';
  }
  // <img src="...">
  html = html.replace(/(<img\b[^>]*?)\bsrc="([^"]*)"/gi,
    (_, pre, src) => { const b = subst(src); return b ? `${pre}src="${b}"` : pre; });
  // SVG <image xlink:href="...">
  html = html.replace(/(<image\b[^>]*?)\bxlink:href="([^"]*)"/gi,
    (_, pre, src) => { const b = subst(src); return b ? `${pre}xlink:href="${b}"` : pre; });
  // SVG <image href="...">
  html = html.replace(/(<image\b[^>]*?)\bhref="([^"]*)"/gi,
    (_, pre, src) => { const b = subst(src); return b ? `${pre}href="${b}"` : pre; });
  return html;
}

// EPUBs mark footnote/endnote reference links very inconsistently across
// editions/tools — some use class="footnote" (same-file '#frag' href), some
// use the EPUB3 epub:type="noteref" attribute, and some (e.g. older
// Calibre/zeno.org conversions) use neither and just wrap a plain link to
// another chapter file's fragment in a <sup> — in either direction
// (<sup><a>…</a></sup> or <a><sup>…</sup></a>). Recognize all of these
// rather than only the single hardcoded class name.
function _looksLikeFootnoteLink(el, href) {
  if (!href.includes('#')) return false;
  const cls = (el.getAttribute('class') || '').toLowerCase();
  if (/\bnote|\bfootnote|\bfn\b/.test(cls)) return true;
  const epubType = (el.getAttribute('epub:type') || '').toLowerCase();
  if (epubType.includes('noteref')) return true;
  return !!(el.closest('sup') || el.querySelector('sup'));
}

// Chapters are XHTML, but parsed as HTML (forgiving with broken books). HTML
// knows no self-closing <a id="x"/>: the anchor stays open and swallows the
// text after it — and being a formatting element it is re-opened in every
// following paragraph (Suhrkamp/transpect books put one in each heading and
// note). Close the inline ones; block elements are left alone so the block
// indexes that highlights are anchored to stay the same.
const _SELF_CLOSING_INLINE = /<(a|span|b|i|em|strong|sup|sub|small|u|s|code|font|abbr|cite|q|mark|var)(\s(?:[^<>"']|"[^"]*"|'[^']*')*)?\/>/gi;

function sanitizeEpubHtml(html) {
  html = html.replace(_SELF_CLOSING_INLINE, '<$1$2></$1>');
  const doc = new DOMParser().parseFromString(html, 'text/html');

  doc.querySelectorAll('script, iframe, object, embed, style, head, meta, link').forEach(el => el.remove());

  doc.querySelectorAll('*').forEach(el => {
    Array.from(el.attributes).forEach(attr => {
      if (attr.name.startsWith('on') || attr.name === 'title') el.removeAttribute(attr.name);
    });
    const tag = el.tagName.toLowerCase();
    if (tag === 'img') {
      const src = el.getAttribute('src') || '';
      // Remove any non-blob, non-data src that slipped through (broken relative paths)
      if (src && !src.startsWith('blob:') && !src.startsWith('data:')) el.removeAttribute('src');
    }
    // The printed edition's page numbers ("[12]") as small marks, not glued to the text.
    const etype = el.getAttribute('epub:type') || '';
    if (/\bpagebreak\b/.test(etype) || el.getAttribute('role') === 'doc-pagebreak') {
      el.classList.add('epub-pagenum');
    }
    if (el.tagName === 'A') {
      const href = el.getAttribute('href') || '';
      if (href.startsWith('http://') || href.startsWith('https://')) {
        el.setAttribute('target', '_blank');
        el.setAttribute('rel', 'noopener noreferrer');
      } else if (_looksLikeFootnoteLink(el, href)) {
        // The whole book is one concatenated DOM, so a fragment id resolves
        // via getElementById regardless of which chapter file it originally
        // pointed into — strip any "../Text/other.html" path prefix and keep
        // just the id after the last '#'.
        el.dataset.footnoteRef = href.slice(href.indexOf('#') + 1);
        el.removeAttribute('href');
        el.style.cursor = 'pointer';
      } else {
        el.removeAttribute('href');
        el.style.cursor = 'default';
      }
    }
  });

  return doc.body ? doc.body.innerHTML : doc.documentElement.innerHTML;
}

// ---------------------------------------------------------------------------
// Books
// ---------------------------------------------------------------------------

let currentBookId = null;
let currentBookToc = [];
let currentImageMap = {};
let readerScrollSaveTimer = null;
let _resizeObserver = null;
let _currentPositionAnchor = '';
let _currentBookCharCount = 0;
// Rough characters per printed book page, used to estimate a real page count for EPUBs.
const CHARS_PER_BOOK_PAGE = 1800;
const bookMetaCache = {}; // id → {title, author, type}

// Reading-position percentages (the progress readout, annotation "% im Buch"
// coordinates): a whole percent is fine for a normal book, but on a long one
// (~600-700 physical pages and up) it barely moves during a whole scrolling
// session, which reads as broken. Past that length, show one decimal —
// formatted with the browser locale's own decimal separator.
const LONG_BOOK_CHAR_THRESHOLD = 1000000;

function _formatBookPercent(fraction) {
  const pct = Math.max(0, Math.min(100, fraction * 100));
  const decimals = _currentBookCharCount > LONG_BOOK_CHAR_THRESHOLD ? 1 : 0;
  return pct.toLocaleString(undefined, {minimumFractionDigits: decimals, maximumFractionDigits: decimals});
}

// Accepts both '45.3' and '45,3' (locale-typed input)
function _parseLocalePercent(str) {
  const v = parseFloat(String(str).trim().replace(',', '.'));
  return isNaN(v) ? 0 : v;
}

// ---------------------------------------------------------------------------
// Reader "scrolled too far" safety net — offers a toast to jump back after a
// sudden, large scroll (accidental fling, fat-fingered keybind, etc.). Only
// watches organic scrolling; explicit destination jumps (TOC, bookmarks, the
// progress input, search) call _suppressScrollJumpDetect() first so they
// don't trigger it.
// ---------------------------------------------------------------------------
let _scrollRestTop = null;       // scrollTop last "settled" at, before the current burst
let _scrollRestDebounce = null;
let _scrollJumpSuppressed = false; // true while an explicit/programmatic jump is in flight
let _scrollJumpToastEl = null;

// Marks the current (and any immediately-following, possibly animated) scroll
// as deliberate, so _checkScrollJump ignores it. Suppression lifts itself
// once scrolling actually settles (see _armScrollJumpSettle) — not after a
// fixed delay — so it stays active for however long a `smooth` scroll
// animation to a far-away target actually takes, and calling this again
// (e.g. from repeated resize-triggered corrections while a book settles)
// simply pushes that settle point further out instead of racing it.
function _suppressScrollJumpDetect() {
  _scrollJumpSuppressed = true;
  _armScrollJumpSettle();
}

function _armScrollJumpSettle() {
  clearTimeout(_scrollRestDebounce);
  _scrollRestDebounce = setTimeout(() => {
    const contentEl = $('reader-content');
    if (contentEl) _scrollRestTop = contentEl.scrollTop;
    _scrollJumpSuppressed = false;
  }, 500);
}

function _dismissScrollJumpToast() {
  if (_scrollJumpToastEl) {
    _scrollJumpToastEl.remove();
    _scrollJumpToastEl = null;
  }
  if (_readPos && _readPos.hold === 'jump') _readPos.hold = false;
}

function _showScrollJumpToast(backTop) {
  _dismissScrollJumpToast();
  const toast = document.createElement('div');
  toast.className = 'reader-toast reader-toast-action';
  toast.innerHTML = `<span>Weit gescrollt</span><button type="button" class="reader-toast-btn">Zurückspringen</button>`;
  document.body.appendChild(toast);
  _scrollJumpToastEl = toast;
  // Until it's gone, the place before the jump stays the reading position.
  if (_readPos && !_readPos.hold) _readPos.hold = 'jump';
  toast.querySelector('.reader-toast-btn').addEventListener('click', () => {
    const contentEl = $('reader-content');
    if (contentEl) {
      _suppressScrollJumpDetect();
      contentEl.scrollTo({top: backTop, behavior: 'smooth'});
    }
    _dismissScrollJumpToast();
    // Back where it was: that's no new reading.
    _readerInteractedAt = 0;
  });
  setTimeout(() => {
    if (_scrollJumpToastEl !== toast) return;
    _dismissScrollJumpToast();
    // Stayed there: the far place is where the reading goes on.
    _noteReaderInteraction();
    if (_readPos) _readPos.key = null;
  }, 6000);
}

function _checkScrollJump(contentEl) {
  const top = contentEl.scrollTop;
  if (_scrollRestTop === null) _scrollRestTop = top; // first sample this session

  if (!_scrollJumpSuppressed && !_scrollJumpToastEl) {
    const screen = contentEl.clientHeight || 1;
    if (Math.abs(top - _scrollRestTop) > screen * 3.5) {
      _showScrollJumpToast(_scrollRestTop);
    }
  }

  // Only adopt the new position as the "settled" baseline — and lift any
  // suppression — once scrolling has paused for a bit. That's what lets a
  // fast, still-in-progress fling (or a long smooth-scroll animation) be
  // compared against/protected until it actually finishes, not mid-flight.
  _armScrollJumpSettle();
}

const EPUB_BLOCK_SELECTOR = 'p, h1, h2, h3, h4, h5, h6, li, blockquote, dt, dd, figcaption, div:not(:has(*))';

// The open book's text blocks (EPUB_BLOCK_SELECTOR), with the chapter each one
// belongs to — found once and kept until the book's content changes (a
// highlight wrapping text can turn a leaf div into a non-leaf one). Selecting
// them is the expensive part on an e-reader: Chrome 61 has no :has(), so
// compat61.js filters every div in JavaScript.
let _blockCache = null; // {content, blocks, chapterOf: Int32Array, chapters: Element[]}

function _epubBlocks(contentEl) {
  if (_blockCache && _blockCache.content === contentEl) return _blockCache;
  const blocks = Array.from(contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR));
  const chapters = Array.from(contentEl.querySelectorAll('[data-epub-src]'));
  const chapterOf = new Int32Array(blocks.length);
  for (let i = 0, ch = -1; i < blocks.length; i++) {
    while (ch + 1 < chapters.length && chapters[ch + 1].compareDocumentPosition(blocks[i]) & Node.DOCUMENT_POSITION_FOLLOWING) ch++;
    chapterOf[i] = ch;
  }
  const observer = new MutationObserver(() => {
    if (_blockCache && _blockCache.content === contentEl) _blockCache = null;
    observer.disconnect();
  });
  observer.observe(contentEl, {childList: true, subtree: true});
  _blockCache = {content: contentEl, blocks, chapterOf, chapters};
  return _blockCache;
}

// The anchor of the reading position: "block:inner" — the last block (with a
// height) that starts at or above the top of the view, the first of several
// starting at the same height; else the first block below. Blocks are in
// document order and so top to bottom: a binary search over the chapters on
// screen (the e-reader mode shows one), not every block from the book's start.
function getPositionAnchor(contentEl) {
  const {blocks, chapterOf, chapters} = _epubBlocks(contentEl);
  if (!blocks.length) return '';
  const containerTop = contentEl.getBoundingClientRect().top;
  const containerBottom = containerTop + contentEl.clientHeight;
  // Index ranges of the blocks in chapters that are laid out (all, when reading by scrolling).
  const shown = new Set();
  chapters.forEach((ch, i) => { if (ch.getClientRects().length) shown.add(i); });
  const order = [];
  for (let i = 0; i < blocks.length; i++) {
    if (chapterOf[i] < 0 || shown.has(chapterOf[i])) {
      let j = i;
      while (j + 1 < blocks.length && chapterOf[j + 1] === chapterOf[i]) j++;
      order.push([i, j]);
      i = j;
    }
  }
  const count = order.reduce((n, r) => n + r[1] - r[0] + 1, 0);
  const at = k => { // k-th block on screen -> block index
    for (const [a, b] of order) { if (k <= b - a) return a + k; k -= b - a + 1; }
    return -1;
  };
  const rectOf = k => blocks[at(k)].getBoundingClientRect();
  // A block without height says nothing about the position: use the next one with a height.
  const measured = k => {
    for (let n = k; n < count; n++) { const r = rectOf(n); if (r.height >= 1) return {k: n, top: r.top}; }
    return null;
  };
  // Binary search for the last block with a height whose top <= containerTop.
  let lo = 0, hi = count - 1, best = -1;
  while (lo <= hi) {
    const mid = (lo + hi) >> 1;
    const m = measured(mid);
    if (m && m.top <= containerTop) { best = m.k; lo = m.k + 1; }
    else hi = mid - 1;
  }
  let bestIndex;
  if (best >= 0) {
    // Several blocks starting at the same height (a blockquote and its first paragraph): the first.
    const top = rectOf(best).top;
    let k = best;
    for (let n = best - 1; n >= 0; n--) {
      const r = rectOf(n);
      if (r.height < 1) continue;
      if (r.top !== top) break;
      k = n;
    }
    bestIndex = at(k);
  } else {
    const first = measured(0);
    bestIndex = first && first.top <= containerBottom ? at(first.k) : 0;
  }
  const rect = blocks[bestIndex].getBoundingClientRect();
  const innerFraction = Math.max(0, Math.min(1, (containerTop - rect.top) / (rect.height || 1)));
  return `${bestIndex}:${innerFraction.toFixed(6)}`;
}

// Reading progress as a share of the book's text (characters), from a
// position anchor. Independent of layout — font size, screen width, which
// chapters are rendered (the Android app's e-reader mode lays out one chapter
// at a time) — so every client shows the same percentage for the same place.
// The pixel share (scrollTop / scrollHeight) used before differed between
// layouts and counted margins, headings and images as reading.
let _charIndex = null; // {content, starts[], lens[], total} for the open book

function _bookCharIndex(contentEl) {
  if (_charIndex && _charIndex.content === contentEl) return _charIndex;
  const offsets = new Map();
  let pos = 0;
  const walker = document.createTreeWalker(contentEl, NodeFilter.SHOW_TEXT);
  let node;
  while ((node = walker.nextNode())) {
    offsets.set(node, pos);
    pos += node.nodeValue.length;
  }
  const blocks = contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR);
  const starts = new Array(blocks.length);
  const lens = new Array(blocks.length);
  for (let i = 0; i < blocks.length; i++) {
    const first = document.createTreeWalker(blocks[i], NodeFilter.SHOW_TEXT).nextNode();
    starts[i] = first ? offsets.get(first) : (i ? starts[i - 1] + lens[i - 1] : 0);
    lens[i] = blocks[i].textContent.length;
  }
  _charIndex = {content: contentEl, starts, lens, total: pos || 1};
  return _charIndex;
}

// Share of the text before the anchored place (0..1), or null.
function _fractionFromAnchor(contentEl, anchor) {
  const [block, inner] = _anchorParts(anchor);
  if (block < 0) return null;
  const idx = _bookCharIndex(contentEl);
  if (block >= idx.starts.length) return null;
  return Math.max(0, Math.min(1, (idx.starts[block] + inner * idx.lens[block]) / idx.total));
}

// Anchor of the place where `fraction` of the text has been read.
function _anchorForFraction(contentEl, fraction) {
  const idx = _bookCharIndex(contentEl);
  if (!idx.starts.length) return '';
  const target = Math.max(0, Math.min(1, fraction)) * idx.total;
  let lo = 0, hi = idx.starts.length - 1;
  while (lo < hi) {
    const mid = (lo + hi + 1) >> 1;
    if (idx.starts[mid] <= target) lo = mid; else hi = mid - 1;
  }
  const inner = idx.lens[lo] ? Math.max(0, Math.min(1, (target - idx.starts[lo]) / idx.lens[lo])) : 0;
  return `${lo}:${inner.toFixed(6)}`;
}

function restoreFromAnchor(contentEl, anchor) {
  if (!anchor) return false;
  const parts = anchor.split(':');
  if (parts.length !== 2) return false;
  const idx = parseInt(parts[0], 10);
  const innerFraction = parseFloat(parts[1]);
  if (isNaN(idx) || isNaN(innerFraction)) return false;
  const blocks = Array.from(contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR));
  if (idx >= blocks.length) return false;
  const el = blocks[idx];
  contentEl.scrollTop = el.offsetTop + Math.round(innerFraction * el.offsetHeight);
  return true;
}

// Split 'blockIndex:innerFraction' into [block, inner]; [-1, 0] if invalid/empty.
function _anchorParts(anchor) {
  if (typeof anchor !== 'string') return [-1, 0];
  const c = anchor.indexOf(':');
  if (c < 0) return [-1, 0];
  const b = parseInt(anchor.slice(0, c), 10);
  const f = parseFloat(anchor.slice(c + 1));
  return [Number.isFinite(b) ? b : -1, Number.isFinite(f) ? f : 0];
}

// >0 if position A is further into the book than B, <0 if behind, 0 if equal.
// Compares by anchor block index (precise); falls back to scroll_fraction only
// when an anchor is missing (e.g. PDFs), matching the server's _progress_is_further.
function _cmpProgress(anchorA, fracA, anchorB, fracB) {
  const [ba, ia] = _anchorParts(anchorA);
  const [bb, ib] = _anchorParts(anchorB);
  if (ba >= 0 && bb >= 0) return ba !== bb ? ba - bb : ia - ib;
  return (fracA || 0) - (fracB || 0);
}

// ---------------------------------------------------------------------------
// Reading position: the place last read wins, on any device (docs/progress-sync.md).
//
// A position counts as read when the reader got there by reading (scrolling,
// turning pages, choosing a chapter); its time is that moment, not the time it
// is saved. So re-saving an unchanged place, on a timer or on closing, carries
// the old time and can never beat a newer place read on another device. A book
// just opened at the server's place has read nothing here yet: nothing is sent.
// Own writes wait in a small outbox (localStorage) until the server has them.
// ---------------------------------------------------------------------------
let _serverOffset = 0;      // the server's clock minus this device's (ms)
let _readPos = null;        // the open book: {bookId, ready, key, readAt (device ms), moved, hold}
let _readerInteractedAt = 0;

function _progressDevice() {
  return window.DIORA_DEVICE_NAME || 'Browser';
}

function _noteServerNow(ms) {
  if (typeof ms === 'number' && ms > 1e12) _serverOffset = ms - Date.now();
}

function _noteServerNowHeader(res) {
  try { _noteServerNow(Number(res.headers.get('X-Server-Now'))); } catch (e) {}
}

// The reader did something (scroll wheel, touch, key, mouse): the next change
// of position is reading, not a layout settling.
function _noteReaderInteraction() {
  _readerInteractedAt = Date.now();
  if (_readPos && _readPos.hold === 'until-moved') _readPos.hold = false;
}
window.__dioraReaderInteraction = _noteReaderInteraction;

// While a jump is only a look (a footnote's place, "Zurück zum Text"), the
// place before it stays the reading position. true: until the next
// interaction; false: released now.
window.__dioraHoldProgress = function (on) {
  if (_readPos) _readPos.hold = on ? 'until-moved' : false;
};

function _positionKey(anchor, fraction) {
  return anchor || 'f' + (fraction || 0).toFixed(4);
}

// Called with every computed position: a change that follows an interaction is reading.
function _noteReadingPosition(anchor, fraction) {
  if (!_readPos || !_readPos.ready || _readPos.hold) return;
  const key = _positionKey(anchor, fraction);
  if (key === _readPos.key) return;
  _readPos.key = key;
  if (Date.now() - _readerInteractedAt < 10000) {
    _readPos.readAt = Date.now();
    _readPos.moved = true;
  }
}

function _progressOutboxKey() {
  return `diora_progress_outbox_${window.USER_ID || 0}`;
}

function _progressOutbox() {
  try { return JSON.parse(localStorage.getItem(_progressOutboxKey()) || '{}') || {}; } catch (e) { return {}; }
}

function _progressOutboxPut(entry) {
  try {
    const box = _progressOutbox();
    const old = box[entry.book];
    if (old && !entry.force && old.read_at > entry.read_at) return;
    box[entry.book] = entry;
    localStorage.setItem(_progressOutboxKey(), JSON.stringify(box));
  } catch (e) {}
}

function _progressOutboxDone(bookId, readAt) {
  try {
    const box = _progressOutbox();
    if (box[bookId] && box[bookId].read_at === readAt) {
      delete box[bookId];
      localStorage.setItem(_progressOutboxKey(), JSON.stringify(box));
    }
  } catch (e) {}
}

function _progressBody(e) {
  return JSON.stringify({
    scroll_fraction: e.fraction, position_anchor: e.anchor, read_at: e.read_at,
    sent_at: Date.now(), device: e.device, ...(e.force && {force: true}),
  });
}

// Send one queued position; true once the server has it (stored or not: it decides).
async function _sendProgress(e) {
  try {
    const res = await fetch(`/books/${e.book}/progress/`, {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body: _progressBody(e),
    });
    if (!(res.ok || (res.status >= 400 && res.status < 500))) return false;
    try { _noteServerNow((await res.json()).server_now); } catch (err) {}
    _progressOutboxDone(e.book, e.read_at);
    return true;
  } catch (err) {
    return false;
  }
}

let _progressFlushing = null;
function _flushProgressOutbox() {
  if (!_progressFlushing) {
    _progressFlushing = (async () => {
      for (const e of Object.values(_progressOutbox())) await _sendProgress(e);
    })().finally(() => { _progressFlushing = null; });
  }
  return _progressFlushing;
}

// A book's state from the server list, made newer by an own write the server doesn't have yet.
function _withPendingProgress(b) {
  const e = _progressOutbox()[b.id];
  if (!e) return b;
  const at = e.read_at + _serverOffset;
  if (b.read_at != null && at < b.read_at && !e.force) return b;
  return {...b, scroll_fraction: e.fraction, position_anchor: e.anchor, read_at: at,
          device: e.device, last_read: new Date(at).toISOString()};
}

function _bookRecency(b) {
  if (typeof b.read_at === 'number') return b.read_at;
  const t = b.last_read ? Date.parse(b.last_read) : NaN;
  return isNaN(t) ? 0 : t;
}

function _readerToast(text, button, onClick, ms) {
  const toast = document.createElement('div');
  toast.className = 'reader-toast reader-toast-action';
  toast.innerHTML = '<span></span><button type="button" class="reader-toast-btn"></button>';
  toast.querySelector('span').textContent = text;
  toast.querySelector('button').textContent = button;
  document.body.appendChild(toast);
  const done = () => toast.remove();
  toast.querySelector('button').addEventListener('click', () => { done(); onClick(); });
  setTimeout(done, ms || 10000);
  return toast;
}

function _jumpToPosition(anchor, fraction) {
  const contentEl = $('reader-content');
  if (!contentEl) return;
  _suppressScrollJumpDetect();
  if (currentPdfDoc && readerSettings.pdfPaginated && pdfTotalPages > 1) {
    pdfCurrentPage = Math.max(1, Math.round(fraction * (pdfTotalPages - 1)) + 1);
    enterPdfPaginatedMode();
  } else if (currentPdfDoc) {
    contentEl.scrollTop = fraction * (contentEl.scrollHeight - contentEl.clientHeight);
  } else if (!restoreFromAnchor(contentEl, anchor)) {
    restoreFromAnchor(contentEl, _anchorForFraction(contentEl, fraction));
  }
}

// Another device read this book after the place shown here: offer to go there.
let _newerOfferShown = null;
async function _checkNewerPositionElsewhere() {
  const pos = _readPos;
  if (!pos || !pos.ready || !currentBookId || pos.bookId !== currentBookId) return;
  let b;
  try {
    const res = await fetch('/books/', {cache: 'no-store'});
    _noteServerNowHeader(res);
    b = (await res.json()).find(x => x.id === pos.bookId);
  } catch (e) { return; }
  if (!b || b.read_at == null || _readPos !== pos) return;
  if (b.read_at <= pos.readAt + _serverOffset + 3000) return;
  if (_positionKey(b.position_anchor || '', b.scroll_fraction) === pos.key) return;
  const offerKey = `${pos.bookId}:${b.read_at}`;
  if (_newerOfferShown === offerKey) return;
  _newerOfferShown = offerKey;
  const where = b.device ? `Auf ${b.device}` : 'Auf einem anderen Gerät';
  _readerToast(`${where} weitergelesen · ${_formatBookPercent(b.scroll_fraction || 0)} %`, 'Dorthin', () => {
    if (_readPos !== pos) return;
    _jumpToPosition(b.position_anchor || '', b.scroll_fraction || 0);
    // That place and its time are the server's: nothing new to tell it.
    pos.key = null;
    pos.readAt = b.read_at - _serverOffset;
    pos.moved = false;
    setTimeout(() => {
      const contentEl = $('reader-content');
      if (_readPos === pos && contentEl) {
        pos.key = currentPdfDoc ? _positionKey('', b.scroll_fraction || 0) : _positionKey(getPositionAnchor(contentEl), 0);
      }
    }, 300);
  }, 15000);
}
window.__dioraCheckNewerPosition = _checkNewerPositionElsewhere;

// ---------------------------------------------------------------------------
// Book cache — IndexedDB, evict after 4 weeks of inactivity
// ---------------------------------------------------------------------------
const _BOOK_CACHE_STORE       = 'books';
const _BOOK_META_STORE        = 'book_meta';
const _BOOK_ANNOTATIONS_STORE = 'book_annotations';
const _BOOK_PARSED_STORE      = 'parsed';   // prepared chapters, see _getParsedBook
const _BOOK_CACHE_EVICT_MS    = 4 * 7 * 24 * 60 * 60 * 1000;

function _openBookCacheDb() {
  return new Promise((resolve, reject) => {
    const req = indexedDB.open('diora_book_cache', 3);
    req.onupgradeneeded = e => {
      const db = e.target.result;
      if (!db.objectStoreNames.contains(_BOOK_CACHE_STORE))
        db.createObjectStore(_BOOK_CACHE_STORE, {keyPath: 'id'});
      if (!db.objectStoreNames.contains(_BOOK_META_STORE))
        db.createObjectStore(_BOOK_META_STORE, {keyPath: 'id'});
      if (!db.objectStoreNames.contains(_BOOK_ANNOTATIONS_STORE))
        db.createObjectStore(_BOOK_ANNOTATIONS_STORE, {keyPath: 'id'});
      if (!db.objectStoreNames.contains(_BOOK_PARSED_STORE))
        db.createObjectStore(_BOOK_PARSED_STORE, {keyPath: 'id'});
    };
    req.onsuccess  = e => resolve(e.target.result);
    req.onerror    = ()  => reject();
  });
}

// ---------------------------------------------------------------------------
// Prepared books: an EPUB's chapters after unpacking and sanitizing, so opening
// it again skips both (for a book like Das Kapital that's most of the time an
// e-reader needs to open it). Encrypted with the book key like everything else
// on the device. Valid for one version of the book file (its IV) and of the
// code that prepares chapters (a hash of its source: changing the sanitizer
// makes every book be prepared anew). Images stay in the book file: the
// chapters keep "diora-img:<path>" in place of the session's blob URLs.
// ---------------------------------------------------------------------------
let _parseCodeSig = null;

function _parsePreparationSig() {
  if (_parseCodeSig) return _parseCodeSig;
  const src = [parseEpub, sanitizeEpubHtml, _injectImageBlobs, _resolveImageBlob, _parseEpubToc]
    .map(f => String(f)).join('\n');
  let h = 5381;
  for (let i = 0; i < src.length; i++) h = ((h << 5) + h + src.charCodeAt(i)) | 0;
  return (_parseCodeSig = (h >>> 0).toString(36) + '.' + src.length);
}

async function _getParsedBook(bookId, dataIv, key) {
  try {
    const db = await _openBookCacheDb();
    const row = await new Promise(resolve => {
      const req = db.transaction(_BOOK_PARSED_STORE).objectStore(_BOOK_PARSED_STORE).get(bookId);
      req.onsuccess = e => resolve(e.target.result || null);
      req.onerror = () => resolve(null);
    });
    if (!row || row.sig !== dataIv + ':' + _parsePreparationSig()) return null;
    const plain = await crypto.subtle.decrypt({name: 'AES-GCM', iv: row.iv}, key, row.ct);
    return JSON.parse(new TextDecoder().decode(plain));
  } catch (e) { return null; }
}

async function _setParsedBook(bookId, dataIv, key, result) {
  try {
    // Blob URLs live as long as this page; the stored chapters name the image instead.
    const pathOf = {};
    for (const [path, url] of Object.entries(result.imageMap || {})) pathOf[url] = path;
    const blobRe = /blob:[^"'\s)]+/g;
    const chapters = result.chapters.map(c => c.replace(blobRe, u => pathOf[u] ? 'diora-img:' + pathOf[u] : u));
    const doc = {title: result.title, author: result.author, toc: result.toc, chapters,
                 images: Object.keys(result.imageMap || {})};
    // Raw bytes, not base64: IndexedDB keeps an ArrayBuffer as it is (megabytes for a big book).
    const iv = crypto.getRandomValues(new Uint8Array(12));
    const ct = await crypto.subtle.encrypt({name: 'AES-GCM', iv}, key, new TextEncoder().encode(JSON.stringify(doc)));
    const db = await _openBookCacheDb();
    await new Promise(resolve => {
      const tx = db.transaction(_BOOK_PARSED_STORE, 'readwrite');
      const store = tx.objectStore(_BOOK_PARSED_STORE);
      store.put({id: bookId, sig: dataIv + ':' + _parsePreparationSig(), iv, ct, cached_at: Date.now()});
      // Prepared books not opened for a while go (they come back on the next open).
      const all = store.getAll();
      all.onsuccess = () => all.result.forEach(r => {
        if (r.id !== bookId && Date.now() - (r.cached_at || 0) > _BOOK_CACHE_EVICT_MS) store.delete(r.id);
      });
      tx.oncomplete = resolve;
      tx.onerror = resolve;
    });
  } catch (e) {}
}

/** A prepared book back to what parseEpub returns: fresh blob URLs for its images. */
async function _restoreParsedBook(doc, epubBytes) {
  const imageMap = {};
  if (doc.images && doc.images.length) {
    const zip = await JSZip.loadAsync(epubBytes);
    await Promise.all(doc.images.map(async path => {
      const f = zip.file(path);
      if (!f) return;
      try {
        const buf = await f.async('arraybuffer');
        const ext = path.split('.').pop().toLowerCase();
        const type = {jpg: 'image/jpeg', jpeg: 'image/jpeg', png: 'image/png', gif: 'image/gif',
                      svg: 'image/svg+xml', webp: 'image/webp'}[ext] || '';
        imageMap[path] = URL.createObjectURL(new Blob([buf], type ? {type} : {}));
      } catch (e) {}
    }));
  }
  const placeholder = /diora-img:([^"'\s)]+)/g;
  const chapters = doc.chapters.map(c => c.replace(placeholder, (m, path) => imageMap[path] || ''));
  return {title: doc.title, author: doc.author, toc: doc.toc, chapters, imageMap};
}

async function _getCachedBook(bookId) {
  try {
    const db = await _openBookCacheDb();
    return await new Promise((resolve) => {
      const req = db.transaction(_BOOK_CACHE_STORE).objectStore(_BOOK_CACHE_STORE).get(bookId);
      req.onsuccess = e => resolve(e.target.result || null);
      req.onerror   = ()  => resolve(null);
    });
  } catch { return null; }
}

async function _setCachedBook(bookId, data_ct, data_iv) {
  try {
    const db = await _openBookCacheDb();
    await new Promise((resolve) => {
      const tx = db.transaction(_BOOK_CACHE_STORE, 'readwrite');
      tx.objectStore(_BOOK_CACHE_STORE).put({id: bookId, data_ct, data_iv, cached_at: Date.now()});
      tx.oncomplete = resolve;
      tx.onerror    = resolve;
    });
    // Request persistent storage so the browser doesn't evict cached books
    // under storage pressure. Chrome grants this silently for installed PWAs;
    // Firefox may show a permission prompt.
    if (navigator.storage?.persist) navigator.storage.persist();
  } catch {}
}

async function _evictCachedBook(bookId) {
  try {
    const db = await _openBookCacheDb();
    await new Promise((resolve) => {
      const tx = db.transaction(_BOOK_CACHE_STORE, 'readwrite');
      tx.objectStore(_BOOK_CACHE_STORE).delete(bookId);
      tx.oncomplete = resolve;
      tx.onerror    = resolve;
    });
  } catch {}
}

async function _evictBookCache(bookList) {
  try {
    const db = await _openBookCacheDb();
    const now = Date.now();
    const metaById = Object.fromEntries(bookList.map(b => [b.id, b]));
    await new Promise((resolve) => {
      const tx = db.transaction(_BOOK_CACHE_STORE, 'readwrite');
      const store = tx.objectStore(_BOOK_CACHE_STORE);
      store.openCursor().onsuccess = e => {
        const cursor = e.target.result;
        if (!cursor) { resolve(); return; }
        const meta = metaById[cursor.value.id];
        const lastRead = meta?.last_read ? new Date(meta.last_read).getTime() : 0;
        if (!meta || (now - lastRead) > _BOOK_CACHE_EVICT_MS) cursor.delete();
        cursor.continue();
      };
      tx.onerror = resolve;
    });
  } catch {}
}

async function _saveBookMeta(books) {
  try {
    const db = await _openBookCacheDb();
    const ids = new Set(books.map(b => String(b.id)));
    await new Promise(resolve => {
      const tx = db.transaction(_BOOK_META_STORE, 'readwrite');
      const store = tx.objectStore(_BOOK_META_STORE);
      for (const b of books) store.put(b);
      store.openCursor().onsuccess = e => {
        const cursor = e.target.result;
        if (!cursor) return;
        if (!ids.has(String(cursor.value.id))) cursor.delete();
        cursor.continue();
      };
      tx.oncomplete = resolve;
      tx.onerror    = resolve;
    });
  } catch {}
}

async function _loadCachedBookMeta() {
  try {
    const db = await _openBookCacheDb();
    return await new Promise(resolve => {
      const req = db.transaction(_BOOK_META_STORE).objectStore(_BOOK_META_STORE).getAll();
      req.onsuccess = e => resolve(e.target.result || []);
      req.onerror   = ()  => resolve([]);
    });
  } catch { return []; }
}

async function _updateCachedBookProgress(bookId, fraction, anchor, force = false, readAt = null) {
  const at = (readAt == null ? Date.now() : readAt) + _serverOffset;
  try {
    const db = await _openBookCacheDb();
    await new Promise(resolve => {
      const tx = db.transaction(_BOOK_META_STORE, 'readwrite');
      const store = tx.objectStore(_BOOK_META_STORE);
      const req = store.get(bookId);
      req.onsuccess = e => {
        const entry = e.target.result;
        // The place read last, as on the server (docs/progress-sync.md).
        if (entry && (force || entry.read_at == null || at >= entry.read_at)) {
          entry.scroll_fraction  = fraction;
          entry.position_anchor  = anchor;
          entry.read_at          = at;
          entry.device           = _progressDevice();
          entry.last_read        = new Date(at).toISOString();
          if (_cmpProgress(anchor, fraction, entry.furthest_anchor || '', entry.furthest_fraction || 0) > 0) {
            entry.furthest_anchor = anchor;
            entry.furthest_fraction = fraction;
          }
          store.put(entry);
        }
      };
      tx.oncomplete = resolve;
      tx.onerror    = resolve;
    });
  } catch {}
}

async function _saveAnnotationsCache(bookId, type, ct, iv) {
  try {
    const db = await _openBookCacheDb();
    await new Promise(resolve => {
      const tx = db.transaction(_BOOK_ANNOTATIONS_STORE, 'readwrite');
      tx.objectStore(_BOOK_ANNOTATIONS_STORE).put({id: `${bookId}_${type}`, ct, iv});
      tx.oncomplete = resolve;
      tx.onerror    = resolve;
    });
  } catch {}
}

async function _loadAnnotationsCache(bookId, type) {
  try {
    const db = await _openBookCacheDb();
    return await new Promise(resolve => {
      const req = db.transaction(_BOOK_ANNOTATIONS_STORE).objectStore(_BOOK_ANNOTATIONS_STORE).get(`${bookId}_${type}`);
      req.onsuccess = e => resolve(e.target.result || null);
      req.onerror   = ()  => resolve(null);
    });
  } catch { return null; }
}

const _PENDING_SYNC_KEY = 'diora_pending_sync';

function _markPendingSync(bookId, type) {
  try {
    const pending = JSON.parse(localStorage.getItem(_PENDING_SYNC_KEY) || '[]');
    const key = `${bookId}:${type}`;
    if (!pending.includes(key)) pending.push(key);
    localStorage.setItem(_PENDING_SYNC_KEY, JSON.stringify(pending));
  } catch {}
}

async function _syncPendingAnnotations() {
  try {
    const pending = JSON.parse(localStorage.getItem(_PENDING_SYNC_KEY) || '[]');
    if (!pending.length) return;
    const remaining = [];
    for (const key of pending) {
      const sep = key.indexOf(':');
      const bookId = key.slice(0, sep);
      const type   = key.slice(sep + 1);
      const cached = await _loadAnnotationsCache(bookId, type);
      if (!cached?.ct) continue;
      const url = type === 'bookmarks'
        ? `/books/${bookId}/bookmarks/`
        : `/books/${bookId}/highlights/`;
      try {
        await fetch(url, {
          method: 'POST',
          headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
          body: JSON.stringify({ct: cached.ct, iv: cached.iv}),
        });
      } catch { remaining.push(key); }
    }
    localStorage.setItem(_PENDING_SYNC_KEY, JSON.stringify(remaining));
  } catch {}
}

// Reader settings
let readerSettings = { fontSize: 16, lineHeight: 1.8, maxWidth: 65, theme: 'dark',
                        fontFamily: 'serif', noBold: false, fontWeight: null,
                        pdfZoom: 100, pdfInverted: false, pdfPaginated: false, pdfSpread: false };
let readerSettingsPanelOpen = false;
let currentPdfDoc = null;
let currentPdfBuffer = null;

// Bookmarks
let currentBookmarks = [];
let bookmarksDirty = false;

// Highlights
let currentHighlights = [];
let highlightsDirty = false;
let currentHighlightPopover = null;

// Search
let searchMatches = [];
let searchMatchIndex = -1;
let searchOriginalContent = null;
let readerSearchOpen = false;

// PDF paginated
let pdfCurrentPage = 1;
let pdfTotalPages = 0;
let _pdfPageTextBoxCache = {};
let _pdfRenderGen = 0;
let _touchStartX = 0;
let _readerScrollInterval = null;
let _readerScrollDir = 0;
let _readerScrollLastTs = 0;
const READER_SCROLL_SPEED = 1200;    // constant px/s, no ramp-up
const READER_SCROLL_TICK_MS = 20;    // fixed cadence, independent of the
                                      // display's refresh rate — rAF runs at
                                      // that rate (120/144/165Hz on plenty of
                                      // laptops), which was driving 2-3x more
                                      // scrollBy + scroll-listener work per
                                      // second than intended and read as lag.
function _readerScrollTick() {
  const now = performance.now();
  const dt = now - _readerScrollLastTs;
  _readerScrollLastTs = now;
  $('reader-content')?.scrollBy({top: Math.round(_readerScrollDir * READER_SCROLL_SPEED * dt / 1000)});
}
let _pinchStartDist = 0;
let _pinchStartZoom = 100;
let _isPinching = false;

if (typeof pdfjsLib !== 'undefined') {
  pdfjsLib.GlobalWorkerOptions.workerSrc = '/static/js/pdf.worker.min.js';
}

async function loadBookList() {
  if (!IS_AUTHENTICATED) return;
  const listEl = $('book-list');
  if (!listEl) return;
  listEl.innerHTML = '<p class="muted">Bücher werden geladen …</p>';

  try {
    listEl.innerHTML = '<p class="muted">Bücherliste wird vom Server geholt …</p>';
    _flushProgressOutbox(); // own positions the server doesn't have yet
    const res = await fetch('/books/', {cache: 'no-store'});
    _noteServerNowHeader(res);
    if (!res.ok) {
      listEl.innerHTML = `<p class="muted">Serverfehler ${res.status} beim Laden der Bücher.</p>`;
      return;
    }
    const books = await res.json();
    _evictBookCache(books); // fire-and-forget
    if (!Array.isArray(books)) {
      listEl.innerHTML = `<p class="muted">Unerwartete Antwort vom Server.</p>`;
      return;
    }
    if (!books.length) {
      listEl.innerHTML = '<p class="muted">Noch keine Bücher. Zieh oben eine .epub- oder .pdf-Datei hinein.</p>';
      return;
    }

    listEl.innerHTML = `<p class="muted">${books.length === 1 ? '1 Buch' : books.length + ' Bücher'} auf dem Server. Entschlüssele …</p>`;

    let key;
    try {
      key = await getOrCreateEncKey();
    } catch (e) {
      listEl.innerHTML = `<p class="muted">Verschlüsselung nicht verfügbar: ${e.message}. Die Seite muss über HTTPS laufen.</p>`;
      return;
    }

    const decrypted = [];
    for (const b of books) {
      try {
        const metaBuf = await decryptBytes(key, b.meta_iv, b.meta_ct);
        const meta = JSON.parse(new TextDecoder().decode(metaBuf));
        bookMetaCache[b.id] = {title: meta.title || '?', author: meta.author || '', type: meta.type || 'epub', filename: meta.filename || '', folder: meta.folder || '', isbn: meta.isbn || '', shelfTag: meta.shelfTag || '', pages: meta.pages || 0};
        decrypted.push({id: b.id, title: meta.title || '?', author: meta.author || '', type: meta.type || 'epub', folder: meta.folder || '', isbn: meta.isbn || '', shelfTag: meta.shelfTag || '', pages: meta.pages || 0, scroll_fraction: b.scroll_fraction, position_anchor: b.position_anchor || '', read_at: b.read_at == null ? null : b.read_at, device: b.device || '', furthest_fraction: b.furthest_fraction || 0, furthest_anchor: b.furthest_anchor || '', uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: true, is_read: !!b.is_read, has_highlights: !!b.has_highlights});
      } catch (e) {
        bookMetaCache[b.id] = {title: `Buch #${b.id}`, author: '', type: 'epub', filename: '', folder: '', isbn: '', shelfTag: ''};
        decrypted.push({id: b.id, title: `Buch #${b.id}`, author: '', type: 'epub', folder: '', isbn: '', shelfTag: '', scroll_fraction: b.scroll_fraction, position_anchor: b.position_anchor || '', read_at: b.read_at == null ? null : b.read_at, device: b.device || '', furthest_fraction: b.furthest_fraction || 0, furthest_anchor: b.furthest_anchor || '', uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: false, is_read: !!b.is_read, has_highlights: !!b.has_highlights});
      }
    }
    // An own position the server doesn't have yet (sent above) shows if it's the newer one.
    for (let i = 0; i < decrypted.length; i++) decrypted[i] = _withPendingProgress(decrypted[i]);

    decrypted.sort((a, b) => (_bookRecency(b) - _bookRecency(a)) || b.uploaded_at.localeCompare(a.uploaded_at));
    _saveBookMeta(decrypted); // persist for offline
    renderBookList(decrypted);
  } catch (e) {
    // Network error — try offline fallback
    const cachedBooks = (await _loadCachedBookMeta()).map(_withPendingProgress);
    if (cachedBooks.length) {
      cachedBooks.sort((a, b) => (_bookRecency(b) - _bookRecency(a)) || (b.uploaded_at || '').localeCompare(a.uploaded_at || ''));
      for (const b of cachedBooks) bookMetaCache[b.id] = {title: b.title, author: b.author, type: b.type || 'epub', filename: b.filename || '', folder: b.folder || '', isbn: b.isbn || '', shelfTag: b.shelfTag || '', pages: b.pages || 0};
      const uploadArea = $('book-upload-area');
      if (uploadArea) uploadArea.style.display = 'none';
      renderBookList(cachedBooks);
      const notice = document.createElement('p');
      notice.className = 'muted offline-notice';
      notice.textContent = 'Offline — gespeicherte Bücher. Fortschritt wird beim nächsten Öffnen synchronisiert.';
      listEl.prepend(notice);
    } else {
      if (listEl) listEl.innerHTML = `<p class="muted">Fehler beim Laden der Bücher: ${e.message}</p>`;
    }
  }
}

const _brokenBooks = new Set();

function markBookBroken(bookId) {
  _brokenBooks.add(bookId);
  const item = document.querySelector(`.book-item[data-book-id="${bookId}"]`);
  if (!item) return;
  if (!item.querySelector('.book-broken-btn')) {
    const btn = document.createElement('button');
    btn.className = 'btn btn-sm btn-danger book-broken-btn';
    btn.title = 'Buch konnte nicht geöffnet werden — Datei erneut hochladen';
    btn.textContent = '!';
    btn.onclick = () => repairBook(bookId);
    item.querySelector('.book-item-actions').prepend(btn);
  }
}

function _extractIsbnFromOpf(opfDoc) {
  const identifiers = opfDoc.querySelectorAll('metadata > identifier, metadata > *|identifier');
  for (const el of identifiers) {
    const digits = (el.textContent || '').replace(/[^0-9Xx]/g, '');
    if (digits.length === 10 || digits.length === 13) return digits;
  }
  return '';
}

function repairBook(bookId) {
  const input = document.createElement('input');
  input.type = 'file';
  input.accept = '.epub,.pdf';
  input.onchange = async () => {
    const file = input.files[0];
    if (!file) return;
    const item = document.querySelector(`.book-item[data-book-id="${bookId}"]`);
    const btn = item?.querySelector('.book-broken-btn');
    if (btn) btn.textContent = '…';
    try {
      const key = await getOrCreateEncKey();
      const buf = await file.arrayBuffer();
      const isPdf = /\.pdf$/i.test(file.name);
      const type = isPdf ? 'pdf' : 'epub';

      let title = file.name.replace(/\.(epub|pdf)$/i, ''), author = '', isbn = '';
      try {
        if (isPdf) {
          const pdfDoc = await pdfjsLib.getDocument({data: new Uint8Array(buf.slice(0))}).promise;
          const meta = await pdfDoc.getMetadata();
          title = meta.info?.Title?.trim() || title;
          author = meta.info?.Author?.trim() || '';
        } else {
          const zip = await JSZip.loadAsync(buf.slice(0));
          const containerXml = await zip.file('META-INF/container.xml').async('text');
          const opfPath = new DOMParser()
            .parseFromString(containerXml, 'application/xml')
            .querySelector('rootfile')?.getAttribute('full-path');
          if (opfPath) {
            const opfDoc = new DOMParser().parseFromString(
              await zip.file(opfPath).async('text'), 'application/xml');
            title  = opfDoc.querySelector('metadata > title, metadata > *|title')?.textContent?.trim() || title;
            author = opfDoc.querySelector('metadata > creator, metadata > *|creator')?.textContent?.trim() || '';
            isbn   = _extractIsbnFromOpf(opfDoc);
          }
        }
      } catch (e) { /* keep filename as title */ }

      // Preserve folder/shelfTag assigned before this repair — replacing the book's
      // data shouldn't silently wipe organization the user already set up.
      const prevMeta = bookMetaCache[bookId] || {};
      const metaJson = new TextEncoder().encode(JSON.stringify({
        title, author, filename: file.name, type,
        isbn: isbn || prevMeta.isbn || '',
        folder: prevMeta.folder || '',
        shelfTag: prevMeta.shelfTag || '',
      }));
      const [metaEnc, dataEnc] = await Promise.all([
        encryptBytes(key, metaJson),
        encryptBytes(key, buf),
      ]);
      const res = await fetch(`/books/${bookId}/replace-data/`, {
        method: 'POST',
        headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
        body: JSON.stringify({
          data_ct: dataEnc.ciphertext, data_iv: dataEnc.iv,
          meta_ct: metaEnc.ciphertext, meta_iv: metaEnc.iv,
        }),
      });
      if (!(await res.json()).ok) throw new Error('Serverfehler');
      await _evictCachedBook(bookId);
      _brokenBooks.delete(bookId);
      if (btn) btn.remove();
      openBook(bookId);
    } catch (e) {
      if (btn) btn.textContent = '!';
      await customAlert('Reparatur fehlgeschlagen: ' + e.message);
    }
  };
  input.click();
}

let _lastBookListData = [];
const _bookShowReadKey = 'diora_book_show_read';
let _bookShowRead = localStorage.getItem(_bookShowReadKey) === '1';

function _onBookShowReadToggle(checked) {
  _bookShowRead = checked;
  localStorage.setItem(_bookShowReadKey, checked ? '1' : '0');
  renderBookList(_lastBookListData);
}

async function toggleBookRead(bookId, currentlyRead) {
  const verb = currentlyRead ? 'als ungelesen markieren' : 'als gelesen markieren';
  if (!await customConfirm(`Dieses Buch ${verb}?`)) return;
  try {
    const res = await fetch(`/books/${bookId}/read/`, {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body: JSON.stringify({is_read: !currentlyRead}),
    });
    const data = await res.json();
    if (!data.ok) throw new Error('Serverfehler');
    const book = _lastBookListData.find(b => b.id === bookId);
    if (book) book.is_read = data.is_read;
    renderBookList(_lastBookListData);
  } catch (e) {
    await customAlert('Konnte Lesestatus nicht ändern: ' + e.message);
  }
}

// Folder assigned to a book lives inside its encrypted meta blob (like title/author), so the
// server never sees plaintext folder names — no schema change needed, and it rides along for
// free in /api/sync/. One level only: folders don't nest.
let _currentBookFolder = null; // null = root view (folder tiles + unfiled books)

function _recentlyReadBooks(books) {
  return books
    .filter(b => b.last_read)
    .sort((a, b) => b.last_read.localeCompare(a.last_read))
    .slice(0, 7);
}

function _renderBookItemHtml(b) {
  const pct = Math.round((b.scroll_fraction || 0) * 100);
  const keyWarning = b.keyOk === false ? '<span title="Falscher Schlüssel – importiere den richtigen Schlüssel, um dieses Buch zu öffnen" style="color:var(--accent,#e63946);margin-left:4px;">⚠ falscher Schlüssel</span>' : '';
  const broken = _brokenBooks.has(b.id);
  return `<div class="book-item" data-book-id="${b.id}">
      <div class="book-item-info">
        <strong class="book-title">${escapeHtml(b.title)}${keyWarning}${b.is_read ? ' <span class="muted book-read-badge">✓ gelesen</span>' : ''}</strong>
        <span class="muted book-author">${escapeHtml(b.author)}</span>
        <span class="book-item-meta-row">
          ${pct > 0 ? `<span class="muted book-progress">${pct} % gelesen${b.pages ? ` (≈ ${Math.max(1, Math.round(b.pages * pct / 100))} von ${b.pages} Seiten)` : ''}</span>` : (b.pages ? `<span class="muted book-progress">ca. ${b.pages} Seiten</span>` : '')}
          ${b.shelfTag ? `<span class="book-shelf-badge" title="Regal-Kategorie">${escapeHtml(b.shelfTag)}</span>` : ''}
        </span>
      </div>
      <div class="book-item-actions">
        <button class="btn btn-sm" onclick="openBook(${b.id})"${b.keyOk === false ? ' disabled title="Erst den richtigen Schlüssel importieren"' : ''}>Öffnen</button>
        <div class="book-item-menu">
          <button class="btn btn-sm book-menu-toggle" title="Weitere Optionen" onclick="toggleBookMenu(this)">⋮</button>
          <div class="book-item-menu-list">
            ${broken ? `<button class="book-menu-item book-menu-item--danger book-broken-btn" onclick="repairBook(${b.id})">🔧 Reparieren (Datei erneut hochladen)</button>` : ''}
            ${b.has_highlights ? `<button class="book-menu-item" onclick="downloadBookAnnotationsFromList(${b.id}, this)">⭳ Markierungen &amp; Notizen herunterladen</button>` : ''}
            <button class="book-menu-item" onclick="assignBookFolder(${b.id})">📁 Ordner zuweisen</button>
            <button class="book-menu-item" onclick="lookupBookMetadata(${b.id})">🏷️ Metadaten abrufen (Regal)</button>
            <button class="book-menu-item" onclick="toggleBookRead(${b.id}, ${!!b.is_read})">${b.is_read ? '↺ Als ungelesen markieren' : '✓ Als gelesen markieren'}</button>
            <button class="book-menu-item book-menu-item--danger" onclick="deleteBook(${b.id})">🗑 Löschen</button>
          </div>
        </div>
      </div>
    </div>`;
}

function toggleBookMenu(toggleBtn) {
  // Looked up relative to the clicked button (not by id) because the same book — and
  // thus the same rendered menu — can appear twice at once: once in the "Zuletzt
  // gelesen" section and again further down in the folder/unfiled list.
  const menu = toggleBtn.closest('.book-item-menu')?.querySelector('.book-item-menu-list');
  if (!menu) return;
  const willOpen = !menu.classList.contains('open');
  document.querySelectorAll('.book-item-menu-list.open').forEach(m => m.classList.remove('open'));
  if (willOpen) menu.classList.add('open');
}

// Close any open book menu on an outside click, or right after an item inside it is
// clicked (the toggle button manages its own open/close state above, so it's excluded).
document.addEventListener('click', (e) => {
  if (e.target.closest('.book-menu-toggle')) return;
  document.querySelectorAll('.book-item-menu-list.open').forEach(m => m.classList.remove('open'));
});

function _openBookFolder(name) {
  _currentBookFolder = name;
  renderBookList(_lastBookListData);
}

function renderBookList(books) {
  const listEl = $('book-list');
  if (!listEl) return;
  _lastBookListData = books;

  if (!books.length) {
    listEl.innerHTML = '';
    return;
  }

  let html = '';

  // Always-visible "recently read" section, independent of folder navigation and the
  // read/unread filter below — it's a shortcut back into whatever was open last. Same
  // vertical list-item look as the rest of the list (not a card shelf).
  const recent = _recentlyReadBooks(books);
  if (recent.length) {
    html += '<div class="book-recent-section">'
      + '<h3 class="book-recent-title">Zuletzt gelesen</h3>'
      + recent.map(_renderBookItemHtml).join('')
      + '</div>';
  }

  const visible = _bookShowRead ? books : books.filter(b => !b.is_read);
  if (!visible.length) {
    html += books.length
      ? '<p class="muted">Keine ungelesenen Bücher. „Gelesene Bücher anzeigen“ aktivieren, um alle zu sehen.</p>'
      : '';
    listEl.innerHTML = html;
    return;
  }

  const grouped = new Map();
  for (const b of visible) {
    const key = b.folder || '';
    if (!grouped.has(key)) grouped.set(key, []);
    grouped.get(key).push(b);
  }
  // Folder emptied out (last book moved/deleted, or read-filter hid it) — fall back to root.
  if (_currentBookFolder !== null && !grouped.has(_currentBookFolder)) {
    _currentBookFolder = null;
  }

  if (_currentBookFolder === null) {
    const folderNames = [...grouped.keys()].filter(k => k !== '').sort((a, b) => a.localeCompare(b, 'de'));
    if (folderNames.length) {
      html += '<div class="book-folder-grid">'
        + folderNames.map(name => `<button class="book-folder-tile" data-folder="${escapeHtml(name)}">
            <span class="book-folder-tile-icon">📁</span>
            <span class="book-folder-tile-name">${escapeHtml(name)}</span>
            <span class="book-folder-tile-count">${grouped.get(name).length}</span>
          </button>`).join('')
        + '</div>';
    }
    html += (grouped.get('') || []).map(_renderBookItemHtml).join('');
  } else {
    html += `<div class="book-folder-header">
        <button class="btn btn-sm" onclick="_openBookFolder(null)">← Alle Ordner</button>
        <strong>${escapeHtml(_currentBookFolder)}</strong>
      </div>`;
    html += grouped.get(_currentBookFolder).map(_renderBookItemHtml).join('');
  }

  listEl.innerHTML = html;
  listEl.querySelectorAll('.book-folder-tile').forEach(tile => {
    tile.addEventListener('click', () => _openBookFolder(tile.dataset.folder));
  });
}

// Shared by assignBookFolder/lookupBookMetadata: re-encrypts the meta blob with the given
// field overrides applied on top of whatever is already cached, and pushes it to the server.
async function _updateBookMeta(bookId, overrides) {
  const book = _lastBookListData.find(b => b.id === bookId);
  if (!book) return false;
  const cached = bookMetaCache[bookId] || {};
  const merged = {
    title: cached.title || book.title,
    author: cached.author || book.author,
    filename: cached.filename || '',
    type: cached.type || book.type || 'epub',
    isbn: cached.isbn || book.isbn || '',
    folder: cached.folder || book.folder || '',
    shelfTag: cached.shelfTag || book.shelfTag || '',
    pages: cached.pages || book.pages || 0,
    ...overrides,
  };
  const key = await getOrCreateEncKey();
  const metaJson = new TextEncoder().encode(JSON.stringify(merged));
  const metaEnc = await encryptBytes(key, metaJson);
  const res = await fetch(`/books/${bookId}/meta/`, {
    method: 'POST',
    headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
    body: JSON.stringify({meta_ct: metaEnc.ciphertext, meta_iv: metaEnc.iv}),
  });
  const data = await res.json();
  if (!data.ok) throw new Error('Serverfehler');
  Object.assign(book, overrides);
  bookMetaCache[bookId] = merged;
  _saveBookMeta(_lastBookListData);
  return true;
}

async function assignBookFolder(bookId) {
  const book = _lastBookListData.find(b => b.id === bookId);
  if (!book) return;
  const folders = [...new Set(_lastBookListData.map(b => b.folder).filter(Boolean))].sort((a, b) => a.localeCompare(b, 'de'));
  const hint = folders.length ? ` Vorhandene Ordner: ${folders.join(', ')}.` : '';
  const result = await customPrompt(`Ordner für „${book.title}“ (leer = kein Ordner).${hint}`, book.folder || '');
  if (result === null) return;
  const folder = result.trim();
  if (folder === (book.folder || '')) return;

  try {
    await _updateBookMeta(bookId, {folder});
    if (folder) _currentBookFolder = folder;
    renderBookList(_lastBookListData);
  } catch (e) {
    await customAlert('Konnte Ordner nicht ändern: ' + e.message);
  }
}

// Fallback for books uploaded before ISBN extraction existed (or repaired/re-encrypted
// without it): pulls the already-accessible encrypted book bytes, decrypts and unzips just
// far enough to read the OPF identifiers — same source openBook() itself parses — without
// doing a full reader render. EPUB only; PDFs never carried a reliable ISBN via pdf.js.
async function _extractIsbnFromBookFile(bookId) {
  try {
    const key = await getOrCreateEncKey();
    let data_ct, data_iv;
    const cached = await _getCachedBook(bookId);
    if (cached) {
      ({data_ct, data_iv} = cached);
    } else {
      const res = await fetch(`/books/${bookId}/data/`);
      ({data_ct, data_iv} = await res.json());
    }
    const plain = await decryptBytes(key, data_iv, data_ct);
    const zip = await JSZip.loadAsync(plain);
    const containerXml = await zip.file('META-INF/container.xml').async('text');
    const opfPath = new DOMParser()
      .parseFromString(containerXml, 'application/xml')
      .querySelector('rootfile')?.getAttribute('full-path');
    if (!opfPath) return '';
    const opfDoc = new DOMParser().parseFromString(await zip.file(opfPath).async('text'), 'application/xml');
    return _extractIsbnFromOpf(opfDoc);
  } catch (e) {
    return '';
  }
}

async function _fetchShelfLookup(isbn, title, author) {
  const params = new URLSearchParams();
  if (isbn) params.set('isbn', isbn);
  if (title) params.set('title', title);
  if (author) params.set('author', author);
  const res = await fetch(`/books/metadata-lookup/?${params.toString()}`);
  return res.json();
}

// Manually triggered (never automatic) — looks up which library shelf/DDC category this
// book falls under via the server-side DNB→Open Library proxy, purely as an organizational
// hint (shown as a badge). See books/views.py:lookup_book_metadata for why this one call is
// allowed to briefly touch the server with a plaintext ISBN/title/author.
//
// Fallback chain when there's no ISBN (older upload, or a book that never had one — e.g.
// every PDF, since pdf.js doesn't expose one): (1) extract ISBN from the file itself, for
// EPUBs, (2) server-side title/author text search (less precise — could match the wrong
// edition/translation), (3) if that also comes up empty, ask the user to type in an ISBN
// by hand (from the book's cover/an online store) and retry once.
async function lookupBookMetadata(bookId) {
  const book = _lastBookListData.find(b => b.id === bookId);
  if (!book) return;
  const cached = bookMetaCache[bookId] || {};
  let isbn = cached.isbn || book.isbn || '';
  const isPdf = (cached.type || book.type) === 'pdf';
  const title = cached.title || book.title || '';
  const author = cached.author || book.author || '';

  if (!isbn && !isPdf) {
    // Older upload without a stored ISBN — extract it from the book file itself (may take
    // a moment for large books, since it downloads/decrypts the full file if not cached).
    isbn = await _extractIsbnFromBookFile(bookId);
  }

  try {
    let data = await _fetchShelfLookup(isbn, title, author);

    if (!data.label) {
      const manual = await customPrompt(
        'Keine Regal-Kategorie per ISBN/Titel/Autor gefunden. ISBN manuell eingeben (z. B. vom Buchrücken oder Online-Shop), oder leer lassen zum Abbrechen:', ''
      );
      const manualIsbn = (manual || '').replace(/[^0-9Xx]/g, '');
      if (manualIsbn) {
        isbn = manualIsbn;
        data = await _fetchShelfLookup(isbn, title, author);
      }
    }

    // Persist whatever we ended up with either way, so a repeat lookup never needs to
    // re-extract/re-search from scratch.
    const overrides = {};
    if (isbn) overrides.isbn = isbn;
    if (data.label) overrides.shelfTag = data.label;
    if (Object.keys(overrides).length) {
      await _updateBookMeta(bookId, overrides);
      renderBookList(_lastBookListData);
    }

    if (!data.label) {
      await customAlert('Keine Regal-Kategorie gefunden (weder DNB noch Open Library, per ISBN oder Titel/Autor).');
    }
  } catch (e) {
    await customAlert('Metadaten-Abruf fehlgeschlagen: ' + e.message);
  }
}

function bookFileSelected(input) {
  const file = input.files[0];
  if (!file) return;
  uploadEbook(file);
  input.value = '';
}

function initBookDropZone() {
  // Prevent Firefox from opening dragged files when dropped outside the zone
  document.addEventListener('dragover', e => e.preventDefault());
  document.addEventListener('drop', e => {
    const zone = $('book-drop-zone');
    if (!zone || !zone.contains(e.target)) e.preventDefault();
  });

  const zone = $('book-drop-zone');
  if (!zone) return;

  zone.addEventListener('dragover', e => {
    e.preventDefault();
    zone.classList.add('drag-over');
  });
  zone.addEventListener('dragleave', () => zone.classList.remove('drag-over'));
  zone.addEventListener('drop', e => {
    e.preventDefault();
    zone.classList.remove('drag-over');
    const file = e.dataTransfer.files[0];
    if (file) uploadEbook(file);
  });
}

async function deriveAndStoreKey() {
  const pwInput = document.getElementById('enc-key-password');
  const statusEl = $('enc-key-status');
  const pw = pwInput ? pwInput.value : '';
  if (!pw) { if (statusEl) statusEl.textContent = 'Bitte gib dein Passwort ein.'; return; }

  if (statusEl) statusEl.textContent = 'Schlüssel wird abgeleitet …';
  try {
    const enc = new TextEncoder();
    const username = document.querySelector('meta[name="username"]')?.content || '';
    const mat = await crypto.subtle.importKey('raw', enc.encode(pw), 'PBKDF2', false, ['deriveKey']);
    const key = await crypto.subtle.deriveKey(
      {name: 'PBKDF2', salt: enc.encode('diora:' + username), iterations: 200000, hash: 'SHA-256'},
      mat, {name: 'AES-GCM', length: 256}, true, ['encrypt', 'decrypt']
    );
    const raw = await crypto.subtle.exportKey('raw', key);
    const storageKey = `diora_enc_key_${window.USER_ID || 0}`;
    localStorage.setItem(storageKey, bytesToBase64(new Uint8Array(raw)));
    _encKey = null; // reset cached key
    if (statusEl) statusEl.textContent = '✓ Entsperrt';
    const prompt = $('enc-key-prompt');
    const uploadArea = $('book-upload-area');
    if (prompt) prompt.style.display = 'none';
    if (uploadArea) uploadArea.style.display = '';
    loadBookList();
  } catch (err) {
    if (statusEl) statusEl.textContent = 'Fehler: ' + err.message;
  }
}

async function uploadEbook(file) {
  const statusEl = $('book-upload-status');
  if (file.size > DIORA_CONFIG.ebookMaxBytes) {
    if (statusEl) statusEl.textContent = `Datei zu groß (höchstens ${DIORA_CONFIG.ebookMaxBytes / 1024 / 1024} MB).`;
    return false;
  }
  return _importEbookBuffer(await file.arrayBuffer(), file.name, statusEl);
}

// Shared tail of every import path (local file, cloud): parse metadata, encrypt
// with the user's key and POST ciphertext. Plaintext never leaves the browser.
async function _importEbookBuffer(buf, filename, statusEl) {
  const isPdf = /\.pdf$/i.test(filename);
  const isEpub = /\.epub$/i.test(filename);
  if (!isPdf && !isEpub) {
    if (statusEl) statusEl.textContent = 'Nur .epub- und .pdf-Dateien werden unterstützt.';
    return false;
  }
  if (buf.byteLength > DIORA_CONFIG.ebookMaxBytes) {
    if (statusEl) statusEl.textContent = `Datei zu groß (höchstens ${DIORA_CONFIG.ebookMaxBytes / 1024 / 1024} MB).`;
    return false;
  }

  if (statusEl) statusEl.textContent = 'Verschlüssele …';

  try {
    let title = filename.replace(/\.(epub|pdf)$/i, '');
    let author = '';
    let isbn = '';
    const type = isPdf ? 'pdf' : 'epub';

    if (isPdf) {
      try {
        const pdfDoc = await pdfjsLib.getDocument({data: new Uint8Array(buf.slice(0))}).promise;
        const meta = await pdfDoc.getMetadata();
        title = meta.info?.Title?.trim() || title;
        author = meta.info?.Author?.trim() || '';
      } catch (e) { /* use filename as title */ }
    } else {
      try {
        const zip = await JSZip.loadAsync(buf.slice(0));
        const containerXml = await zip.file('META-INF/container.xml').async('text');
        const containerDoc = new DOMParser().parseFromString(containerXml, 'application/xml');
        const opfPath = containerDoc.querySelector('rootfile')?.getAttribute('full-path');
        if (opfPath) {
          const opfText = await zip.file(opfPath).async('text');
          const opfDoc = new DOMParser().parseFromString(opfText, 'application/xml');
          title = opfDoc.querySelector('metadata > title, metadata > *|title')?.textContent?.trim() || title;
          author = opfDoc.querySelector('metadata > creator, metadata > *|creator')?.textContent?.trim() || '';
          isbn = _extractIsbnFromOpf(opfDoc);
        }
      } catch (e) { /* use filename as title */ }
    }

    const key = await getOrCreateEncKey();
    const metaJson = new TextEncoder().encode(JSON.stringify({title, author, filename, type, isbn, folder: '', shelfTag: ''}));
    const [metaEnc, dataEnc] = await Promise.all([
      encryptBytes(key, metaJson),
      encryptBytes(key, buf),
    ]);

    if (statusEl) statusEl.textContent = 'Lade hoch …';

    const res = await fetch('/books/upload/', {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body: JSON.stringify({
        meta_ct: metaEnc.ciphertext,
        meta_iv: metaEnc.iv,
        data_ct: dataEnc.ciphertext,
        data_iv: dataEnc.iv,
      }),
    });
    const data = await res.json();
    if (data.ok) {
      if (statusEl) statusEl.textContent = `✓ „${title}“ hochgeladen`;
      loadBookList();
      return true;
    }
    if (statusEl) statusEl.textContent = 'Fehler: ' + (data.error ? _germanError(data.error) : 'Hochladen fehlgeschlagen');
    return false;
  } catch (e) {
    if (statusEl) statusEl.textContent = 'Hochladen fehlgeschlagen: ' + e.message;
    return false;
  }
}

// ---------------------------------------------------------------------------
// Cloud import — browse a user-configured WebDAV server and pull a book in.
//
// The download is proxied by the server because the remote host is a different
// origin and sends no CORS headers. It still lands here as raw bytes and goes
// through _importEbookBuffer like any local file, so what gets stored is
// ciphertext the server cannot read.
// ---------------------------------------------------------------------------

let _cloudSources = [];
let _cloudSourceId = null;
let _cloudPath = '';

async function toggleCloudImport() {
  const panel = $('cloud-browser');
  if (!panel) return;
  if (panel.style.display !== 'none') { closeCloudImport(); return; }

  try {
    const res = await fetch('/books/cloud/sources/');
    _cloudSources = (await res.json()).sources || [];
  } catch (e) {
    await customAlert('Cloud-Verbindungen konnten nicht geladen werden: ' + e.message);
    return;
  }

  if (!_cloudSources.length) {
    await customAlert(
      'Noch keine Cloud-Verbindung eingerichtet. Unter Einstellungen → '
      + '„Cloud-Verbindungen für Bücher“ kannst du eine hinzufügen.'
    );
    return;
  }

  const select = $('cloud-source-select');
  if (select) {
    select.innerHTML = '';
    for (const source of _cloudSources) {
      const option = document.createElement('option');
      option.value = source.id;
      option.textContent = source.label;
      select.appendChild(option);
    }
    select.style.display = _cloudSources.length > 1 ? '' : 'none';
  }

  panel.style.display = '';
  _cloudSourceId = _cloudSources[0].id;
  _cloudBrowse('');
}

function closeCloudImport() {
  const panel = $('cloud-browser');
  if (panel) panel.style.display = 'none';
}

function _onCloudSourceChange(value) {
  _cloudSourceId = parseInt(value, 10);
  _cloudBrowse('');
}

function _cloudParentPath(path) {
  const parts = path.split('/').filter(Boolean);
  parts.pop();
  return parts.join('/');
}

function _formatBytes(n) {
  if (!n) return '';
  if (n < 1024) return n + ' B';
  if (n < 1024 * 1024) return Math.round(n / 1024) + ' KB';
  return (n / 1024 / 1024).toFixed(1) + ' MB';
}

function _cloudEntryRow(label, onClick, sizeText) {
  const li = document.createElement('li');
  li.className = 'cloud-entry';

  const button = document.createElement('button');
  button.type = 'button';
  button.className = 'cloud-entry-name';
  button.textContent = label;
  button.addEventListener('click', onClick);
  li.appendChild(button);

  if (sizeText) {
    const size = document.createElement('span');
    size.className = 'cloud-entry-size';
    size.textContent = sizeText;
    li.appendChild(size);
  }
  return li;
}

async function _cloudBrowse(path) {
  const listEl = $('cloud-entries');
  const pathEl = $('cloud-path');
  const statusEl = $('cloud-status');
  if (!listEl) return;

  if (statusEl) statusEl.textContent = 'Lade…';
  listEl.innerHTML = '';

  let data;
  try {
    const res = await fetch(`/books/cloud/${_cloudSourceId}/browse/?path=${encodeURIComponent(path)}`);
    data = await res.json();
    if (!res.ok) throw new Error(data.error || `HTTP ${res.status}`);
  } catch (e) {
    if (statusEl) statusEl.textContent = 'Fehler: ' + e.message;
    return;
  }

  _cloudPath = data.path || '';
  if (pathEl) pathEl.textContent = '/' + _cloudPath;
  if (statusEl) statusEl.textContent = '';

  if (_cloudPath) {
    listEl.appendChild(_cloudEntryRow('⬑ ..', () => _cloudBrowse(_cloudParentPath(_cloudPath))));
  }

  const entries = (data.entries || []).filter(e => e.is_dir || e.is_book);
  if (!entries.length && statusEl) {
    statusEl.textContent = 'Keine Bücher oder Ordner in diesem Verzeichnis.';
  }

  for (const entry of entries) {
    listEl.appendChild(entry.is_dir
      ? _cloudEntryRow('📁 ' + entry.name, () => _cloudBrowse(entry.path))
      : _cloudEntryRow('📖 ' + entry.name, () => _cloudImport(entry), _formatBytes(entry.size)));
  }
}

async function _cloudImport(entry) {
  const statusEl = $('cloud-status');
  if (statusEl) statusEl.textContent = `Lade „${entry.name}“…`;

  try {
    const res = await fetch(`/books/cloud/${_cloudSourceId}/fetch/?path=${encodeURIComponent(entry.path)}`);
    if (!res.ok) {
      const err = await res.json().catch(() => ({}));
      throw new Error(err.error || `HTTP ${res.status}`);
    }
    const buf = await res.arrayBuffer();
    if (await _importEbookBuffer(buf, entry.name, statusEl) && statusEl) {
      statusEl.textContent = `✓ „${entry.name}“ importiert`;
    }
  } catch (e) {
    if (statusEl) statusEl.textContent = 'Import fehlgeschlagen: ' + e.message;
  }
}

async function _parsePdfOutline(pdf, items, depth) {
  depth = depth || 0;
  const result = [];
  for (const item of items) {
    let href = '';
    if (item.dest) {
      try {
        const dest = typeof item.dest === 'string' ? await pdf.getDestination(item.dest) : item.dest;
        if (dest) {
          const pageIndex = await pdf.getPageIndex(dest[0]);
          href = `#pdf-page-${pageIndex + 1}`;
        }
      } catch (e) {}
    }
    result.push({label: item.title || '(untitled)', href, depth});
    if (item.items && item.items.length) {
      result.push(...await _parsePdfOutline(pdf, item.items, depth + 1));
    }
  }
  return result;
}

async function renderPdf(arrayBuffer, contentEl, scaleOverride, pivotPage) {
  const myGen = ++_pdfRenderGen;
  const pdf = currentPdfDoc || await pdfjsLib.getDocument({data: new Uint8Array(arrayBuffer.slice(0))}).promise;
  if (_pdfRenderGen !== myGen) return null;
  currentPdfDoc = pdf;

  let pdfTitle = '', pdfAuthor = '';
  try {
    const meta = await pdf.getMetadata();
    pdfTitle = meta.info?.Title?.trim() || '';
    pdfAuthor = meta.info?.Author?.trim() || '';
  } catch (e) {}

  let toc = [];
  try {
    const outline = await pdf.getOutline();
    if (outline && outline.length) toc = await _parsePdfOutline(pdf, outline);
  } catch (e) {}

  contentEl.innerHTML = '';

  const pdfVp = document.createElement('div');
  pdfVp.id = 'pdf-viewport';
  contentEl.appendChild(pdfVp);

  const containerWidth = readerSettings.pdfSpread
    ? contentEl.clientWidth - 32
    : Math.min(contentEl.clientWidth - 32, 900);
  const pageWidth = readerSettings.pdfSpread ? (containerWidth - 8) / 2 : containerWidth;
  const dpr = window.devicePixelRatio || 1;

  // Pass 1: build DOM structure and size all canvases (no pixel rendering yet)
  const pageEntries = [];
  let spreadContainer = null;

  for (let pageNum = 1; pageNum <= pdf.numPages; pageNum++) {
    if (_pdfRenderGen !== myGen) { contentEl.innerHTML = ''; return null; }
    const page = await pdf.getPage(pageNum);
    const naturalVp = page.getViewport({scale: 1});
    const scale = scaleOverride != null ? scaleOverride
      : Math.max(0.5, pageWidth / naturalVp.width) * (readerSettings.pdfZoom / 100);
    const viewport = page.getViewport({scale});

    const wrapper = document.createElement('div');
    wrapper.className = 'pdf-page-wrapper';
    wrapper.id = `pdf-page-${pageNum}`;

    const inner = document.createElement('div');
    inner.className = 'pdf-page-inner';

    const canvas = document.createElement('canvas');
    canvas.className = 'pdf-page';
    canvas.width = Math.round(viewport.width * dpr);
    canvas.height = Math.round(viewport.height * dpr);
    canvas.style.width = viewport.width + 'px';
    canvas.style.height = viewport.height + 'px';
    inner.appendChild(canvas);
    wrapper.appendChild(inner);

    if (!readerSettings.pdfSpread) {
      pdfVp.appendChild(wrapper);
    } else if (pageNum === 1) {
      wrapper.classList.add('pdf-spread-cover');
      pdfVp.appendChild(wrapper);
      spreadContainer = null;
    } else {
      if (pageNum % 2 === 0) {
        spreadContainer = document.createElement('div');
        spreadContainer.className = 'pdf-spread-wrapper';
        pdfVp.appendChild(spreadContainer);
      }
      if (spreadContainer) spreadContainer.appendChild(wrapper);
      else pdfVp.appendChild(wrapper);
    }

    pageEntries.push({page, canvas, viewport});
  }

  pdfTotalPages = pdf.numPages;

  // Scroll to pivot page immediately — DOM and canvas sizes are set
  const pivot = Math.max(1, Math.min(pdf.numPages, pivotPage || 1));
  const pivotEl = document.getElementById(`pdf-page-${pivot}`);
  if (pivotEl && pivot > 1) pivotEl.scrollIntoView({block: 'start'});

  // Pass 2: render pixels from pivot outward (pivot→end, then pivot-1→start)
  const order = [];
  for (let i = pivot - 1; i < pdf.numPages; i++) order.push(i);
  for (let i = pivot - 2; i >= 0; i--) order.push(i);

  for (const idx of order) {
    if (_pdfRenderGen !== myGen) { contentEl.innerHTML = ''; return null; }
    const {page, canvas, viewport} = pageEntries[idx];
    const ctx = canvas.getContext('2d');
    ctx.scale(dpr, dpr);
    await page.render({canvasContext: ctx, viewport}).promise;
  }

  return {title: pdfTitle, author: pdfAuthor, toc, numPages: pdf.numPages};
}

// ---------------------------------------------------------------------------
// Read-aloud (TTS) — server-side Piper synthesis, one sentence per request.
// EPUB only (no block model for PDFs). Highlights the sentence currently
// playing and scrolls it into view; playback advances sentence-by-sentence,
// then block-by-block, until stopped or the book ends.
// ---------------------------------------------------------------------------
const TTS_MAX_CHARS = 480; // stay under the server's 500-char cap with margin

let ttsActive = false;
let ttsPaused = false;
let ttsRunToken = 0;
let ttsAudio = null;
let ttsCurrentMark = null;
let ttsBarEl = null;
let ttsLang = localStorage.getItem('diora_tts_lang') || 'de';
let _ttsBlocks = null;  // the book's blocks while reading aloud
let _ttsCur = null;     // what's being read: {bi, si, sentence, block}

function setTtsLang(lang) {
  ttsLang = lang;
  localStorage.setItem('diora_tts_lang', lang);
}

function _ttsSplitSentences(text) {
  const raw = text.split(/(?<=[.!?])\s+/).map(s => s.trim()).filter(Boolean);
  const pieces = raw.length ? raw : [text];
  const out = [];
  for (const piece of pieces) {
    let rest = piece;
    while (rest.length > TTS_MAX_CHARS) {
      let cut = rest.lastIndexOf(' ', TTS_MAX_CHARS);
      if (cut <= 0) cut = TTS_MAX_CHARS;
      out.push(rest.slice(0, cut).trim());
      rest = rest.slice(cut).trim();
    }
    if (rest) out.push(rest);
  }
  return out;
}

async function _ttsFetchAudio(sentence) {
  const resp = await fetch('/tts/synthesize/', {
    method: 'POST',
    headers: {'Content-Type': 'application/json'},
    body: JSON.stringify({text: sentence, lang: ttsLang}),
  });
  if (!resp.ok) throw new Error('tts request failed');
  return await resp.blob();
}

function _ttsClearHighlight() {
  if (ttsCurrentMark && ttsCurrentMark.parentNode) {
    const parent = ttsCurrentMark.parentNode;
    while (ttsCurrentMark.firstChild) parent.insertBefore(ttsCurrentMark.firstChild, ttsCurrentMark);
    parent.removeChild(ttsCurrentMark);
    parent.normalize();
  }
  ttsCurrentMark = null;
}

// Finds `sentence` as a substring of block.textContent starting at fromOffset
// (so repeated sentence text earlier in the block isn't matched again), turns
// it into a DOM Range via the same char-offset addressing highlights use, and
// wraps it in a <mark>. Returns the offset to resume searching from.
function _ttsHighlightSentence(block, sentence, fromOffset) {
  // Listening is reading: where the voice is counts as the reading position.
  _noteReaderInteraction();
  _ttsClearHighlight();
  const full = block.textContent;
  const idx = full.indexOf(sentence, fromOffset);
  if (idx === -1) return fromOffset;
  const start = _nodeAtCharOffset(block, idx);
  const end = _nodeAtCharOffset(block, idx + sentence.length);
  if (!start || !end) return idx + sentence.length;
  try {
    const range = document.createRange();
    range.setStart(start.node, start.offset);
    range.setEnd(end.node, end.offset);
    const mark = document.createElement('mark');
    mark.className = 'tts-current';
    range.surroundContents(mark);
    ttsCurrentMark = mark;
    _ttsScrollIntoView(mark);
  } catch (e) {}
  return idx + sentence.length;
}

function _ttsScrollIntoView(el) {
  const contentEl = $('reader-content');
  if (!contentEl) return;
  const top = el.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
  if (top < 40 || top > contentEl.clientHeight - 80) {
    _suppressScrollJumpDetect();
    contentEl.scrollBy({top: top - contentEl.clientHeight * 0.3, behavior: 'smooth'});
  }
}

function _ttsPlayBlob(blob) {
  return new Promise((resolve) => {
    const url = URL.createObjectURL(blob);
    const audio = new Audio(url);
    ttsAudio = audio;
    const done = () => { URL.revokeObjectURL(url); resolve(); };
    audio.addEventListener('ended', done);
    audio.addEventListener('error', done);
    if (!ttsPaused) audio.play().catch(done);
  });
}

// Walks blocks/sentences from startBlockIndex (and its sentence startSentence)
// onward, fetching one sentence ahead while the current one plays so there's
// no gap between them.
async function _ttsPlayLoop(blocks, startBlockIndex, runToken, startSentence = 0) {
  function* sentenceStream() {
    for (let bi = startBlockIndex; bi < blocks.length; bi++) {
      const block = blocks[bi];
      const text = (block.textContent || '').trim();
      if (!text) continue;
      const sentences = _ttsSplitSentences(text);
      for (let si = bi === startBlockIndex ? startSentence : 0; si < sentences.length; si++) {
        yield {block, sentence: sentences[si], bi, si};
      }
    }
  }

  const iter = sentenceStream();
  let cur = iter.next();
  if (cur.done) { stopReadAloud(); return; }
  let curFetch = _ttsFetchAudio(cur.value.sentence);
  let lastBlock = null;
  let blockSearchOffset = 0;

  while (!cur.done) {
    if (runToken !== ttsRunToken) return;
    const {block, sentence} = cur.value;
    const next = iter.next();
    const nextFetch = next.done ? null : _ttsFetchAudio(next.value.sentence).catch(() => null);

    let audioBlob;
    try {
      audioBlob = await curFetch;
    } catch (e) {
      stopReadAloud();
      return;
    }
    if (runToken !== ttsRunToken) return;

    if (block !== lastBlock) {
      lastBlock = block;
      // Started in the middle of a block (previous/next sentence): find it from there.
      blockSearchOffset = _ttsOffsetOf(block, cur.value.si);
    }
    _ttsCur = {bi: cur.value.bi, si: cur.value.si, sentence, block};
    blockSearchOffset = _ttsHighlightSentence(block, sentence, blockSearchOffset);
    _ttsNotify();

    await _ttsPlayBlob(audioBlob);
    if (runToken !== ttsRunToken) return;

    cur = next;
    curFetch = nextFetch;
  }
  if (runToken === ttsRunToken) stopReadAloud();
}

function _ttsTogglePause() {
  ttsPaused = !ttsPaused;
  if (ttsAudio) {
    if (ttsPaused) ttsAudio.pause();
    else ttsAudio.play().catch(() => {});
  }
  _ttsUpdateBar();
  _ttsNotify();
}

// ---- read-aloud for a player bar (the shared dock in native-podcast.js) ----------
// window.__dioraTts: state(), toggle(), stop(), next(), prev(); a 'diora-tts'
// event on window after every change. A dock that shows it sets
// window.__dioraTtsDock = true, and the reader's own little bar stays away.

function _ttsState() {
  const meta = (currentBookId && bookMetaCache[currentBookId]) || {};
  const cur = _ttsCur;
  const chapterEl = cur && cur.block.closest('[data-epub-src]');
  const blocks = _ttsBlocks || [];
  return {
    active: ttsActive,
    paused: ttsPaused,
    bookId: currentBookId,
    title: meta.title || '',
    author: meta.author || '',
    chapter: chapterEl ? _tocTitleForChapterSrc(chapterEl.dataset.epubSrc) : '',
    sentence: cur ? cur.sentence : '',
    progress: cur && blocks.length ? cur.bi / blocks.length : 0,
  };
}

function _ttsNotify() {
  try { window.dispatchEvent(new CustomEvent('diora-tts', {detail: _ttsState()})); } catch (e) {}
}

// Read from another sentence on: the one before/after the current one.
function _ttsRestartAt(bi, si) {
  const blocks = _ttsBlocks;
  if (!ttsActive || !blocks) return;
  ttsRunToken++;
  const runToken = ttsRunToken;
  if (ttsAudio) {
    try { ttsAudio.pause(); ttsAudio.src = ''; } catch (e) {}
    ttsAudio = null;
  }
  _ttsPlayLoop(blocks, bi, runToken, si);
}

// Where sentence si of a block starts in its text (for the highlight).
function _ttsOffsetOf(block, si) {
  const full = block.textContent || '';
  let off = 0;
  _ttsSplitSentences(full.trim()).slice(0, si).forEach(s => {
    const k = full.indexOf(s, off);
    if (k >= 0) off = k + s.length;
  });
  return off;
}

function _ttsSentenceCount(block) {
  const text = (block.textContent || '').trim();
  return text ? _ttsSplitSentences(text).length : 0;
}

function _ttsStep(dir) {
  const cur = _ttsCur;
  const blocks = _ttsBlocks;
  if (!cur || !blocks) return;
  if (dir > 0) {
    if (cur.si + 1 < _ttsSentenceCount(cur.block)) return _ttsRestartAt(cur.bi, cur.si + 1);
    for (let bi = cur.bi + 1; bi < blocks.length; bi++) if (_ttsSentenceCount(blocks[bi])) return _ttsRestartAt(bi, 0);
    stopReadAloud();
  } else {
    if (cur.si > 0) return _ttsRestartAt(cur.bi, cur.si - 1);
    for (let bi = cur.bi - 1; bi >= 0; bi--) {
      const n = _ttsSentenceCount(blocks[bi]);
      if (n) return _ttsRestartAt(bi, n - 1);
    }
    _ttsRestartAt(cur.bi, 0);
  }
}

window.__dioraTts = {
  state: _ttsState,
  toggle: () => (ttsActive ? _ttsTogglePause() : startReadAloud()),
  stop: () => stopReadAloud(),
  next: () => _ttsStep(1),
  prev: () => _ttsStep(-1),
};

function _ttsUpdateBar() {
  if (!ttsBarEl) return;
  const btn = ttsBarEl.querySelector('.tts-pause-btn');
  if (btn) btn.textContent = ttsPaused ? '▶' : '⏸';
}

function _ttsShowBar() {
  _ttsRemoveBar();
  if (window.__dioraTtsDock) return; // the player bar shows it
  const bar = document.createElement('div');
  bar.className = 'tts-bar';
  bar.innerHTML = `
    <button type="button" class="tts-pause-btn" title="Pause/Weiter">⏸</button>
    <button type="button" class="tts-stop-btn" title="Vorlesen beenden">■</button>
  `;
  document.body.appendChild(bar);
  ttsBarEl = bar;
  bar.querySelector('.tts-pause-btn').addEventListener('click', _ttsTogglePause);
  bar.querySelector('.tts-stop-btn').addEventListener('click', stopReadAloud);
}

function _ttsRemoveBar() {
  if (ttsBarEl) { ttsBarEl.remove(); ttsBarEl = null; }
}

function toggleReadAloud() {
  if (ttsActive) stopReadAloud();
  else startReadAloud();
}

function startReadAloud() {
  if (ttsActive) return;
  if (currentPdfDoc) {
    const toast = document.createElement('div');
    toast.className = 'reader-toast';
    toast.textContent = 'Vorlesen ist aktuell nur für EPUB-Bücher verfügbar.';
    document.body.appendChild(toast);
    setTimeout(() => toast.remove(), 2200);
    return;
  }
  const contentEl = $('reader-content');
  if (!contentEl) return;
  const blocks = Array.from(contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR));
  if (!blocks.length) return;

  const [anchorBlock] = _anchorParts(getPositionAnchor(contentEl));
  const startIndex = (anchorBlock >= 0 && anchorBlock < blocks.length) ? anchorBlock : 0;

  ttsActive = true;
  ttsPaused = false;
  ttsRunToken++;
  const runToken = ttsRunToken;
  _ttsBlocks = blocks;
  _ttsCur = null;

  const btn = $('reader-tts-btn');
  if (btn) { btn.classList.add('active'); btn.title = 'Vorlesen beenden'; }
  _ttsShowBar();
  _ttsNotify();

  _ttsPlayLoop(blocks, startIndex, runToken);
}

function stopReadAloud() {
  ttsRunToken++;
  ttsActive = false;
  ttsPaused = false;
  if (ttsAudio) {
    try { ttsAudio.pause(); ttsAudio.src = ''; } catch (e) {}
    ttsAudio = null;
  }
  _ttsClearHighlight();
  _ttsRemoveBar();
  _ttsBlocks = null;
  _ttsCur = null;
  const btn = $('reader-tts-btn');
  if (btn) { btn.classList.remove('active'); btn.title = 'Vorlesen'; }
  _ttsNotify();
}

// ---------------------------------------------------------------------------
// Immersive reader mode — tap centre of screen to toggle bars
// ---------------------------------------------------------------------------
let _immBarsVisible = true;

function _immHandleTap(e) {
  // Ignore taps on interactive elements (buttons, links, inputs, settings panel, footnote popover)
  if (e.target.closest('button, a, input, select, label, #reader-settings-panel, .reader-header, .footnote-popover, #reader-margin, #highlight-popover, .note-bottom-sheet, .tts-bar')) return;
  // In marker mode, taps have a dedicated meaning (highlight/create a note) —
  // don't also toggle the immersive bars underneath.
  if (markerModeActive) return;
  // Don't toggle bars while the user has just finished selecting text (e.g. to highlight it)
  const sel = window.getSelection();
  if (sel && !sel.isCollapsed) return;
  // If a footnote popover is open, dismiss it instead of toggling bars
  if (currentFootnotePopover && !currentFootnotePopover.contains(e.target)) {
    dismissFootnotePopover();
    return;
  }
  _immBarsVisible = !_immBarsVisible;
  document.body.classList.toggle('reader-immersive', !_immBarsVisible);
  // Close settings panel when bars disappear
  if (!_immBarsVisible && readerSettingsPanelOpen) {
    const sp = document.getElementById('reader-settings-panel');
    if (sp) sp.remove();
    readerSettingsPanelOpen = false;
  }
}

function enterReaderImmersiveMode() {
  _immBarsVisible = true;
  document.body.classList.remove('reader-immersive');
  document.addEventListener('click', _immHandleTap);
}

function exitReaderImmersiveMode() {
  _immBarsVisible = true;
  document.body.classList.remove('reader-immersive');
  document.removeEventListener('click', _immHandleTap);
}

// Serializes openBook: it empties #reader-content, then appends the chapters
// across several awaits. A second call in between (a second tap while a slow
// e-reader is still decrypting) appended the whole book a second time — and
// progress saved from that doubled DOM had block indices beyond the real book,
// which then out-ranked every real position on the server.
let _openBookInFlight = null;

async function openBook(bookId) {
  if (_openBookInFlight) {
    if (_openBookInFlight.bookId === bookId) return _openBookInFlight.promise;
    await _openBookInFlight.promise.catch(() => {});
  }
  const promise = _openBookOnce(bookId);
  _openBookInFlight = {bookId, promise};
  try {
    return await promise;
  } finally {
    if (_openBookInFlight && _openBookInFlight.promise === promise) _openBookInFlight = null;
  }
}

async function _openBookOnce(bookId) {
  // Nothing is saved for this book until its place is restored.
  _readPos = {bookId, ready: false, key: null, readAt: 0, moved: false, hold: false};
  const overlay = $('reader-overlay');
  const contentEl = $('reader-content');
  const titleEl = $('reader-title');
  if (!overlay || !contentEl) return;

  titleEl.textContent = 'Lade …';
  contentEl.innerHTML = '';
  overlay.style.display = '';

  try {
    loadReaderSettings(bookId);
    _charIndex = null;
    const key = await getOrCreateEncKey();
    let data_ct, data_iv;
    const cached = await _getCachedBook(bookId);
    if (cached) {
      ({data_ct, data_iv} = cached);
    } else {
      let res;
      try {
        res = await fetch(`/books/${bookId}/data/`);
      } catch {
        // offline and book not cached yet
        overlay.style.display = 'none';
        const toast = document.createElement('div');
        toast.className = 'reader-toast';
        toast.textContent = 'Buch nicht offline verfügbar — einmal online öffnen zum Cachen.';
        document.body.appendChild(toast);
        setTimeout(() => toast.remove(), 3500);
        return;
      }
      ({data_ct, data_iv} = await res.json());
      _setCachedBook(bookId, data_ct, data_iv); // fire-and-forget
    }
    const plain = await decryptBytes(key, data_iv, data_ct);

    // Revoke any previous image blob URLs
    for (const url of Object.values(currentImageMap)) URL.revokeObjectURL(url);
    currentImageMap = {};

    const cachedMeta = bookMetaCache[bookId] || {};
    let title = cachedMeta.title || '';
    let author = cachedMeta.author || '';
    let toc = [];
    let numPages = 0;
    const isPdfBook = cachedMeta.type === 'pdf';

    if (isPdfBook) {
      currentPdfDoc = null; // reset so renderPdf creates fresh doc
      const loadingEl = document.createElement('div');
      loadingEl.className = 'pdf-loading-overlay';
      loadingEl.innerHTML = '<span class="pdf-loading-spinner"></span>';
      overlay.appendChild(loadingEl);
      const result = await renderPdf(plain, contentEl);
      loadingEl.remove();
      title = result.title || title;
      author = result.author || author;
      toc = result.toc;
      numPages = result.numPages;
      currentPdfBuffer = plain;
    } else {
      currentPdfBuffer = null;
      // Prepared before (same book file, same preparation code): only the images to unpack.
      const prepared = await _getParsedBook(bookId, data_iv, key);
      const result = prepared ? await _restoreParsedBook(prepared, plain) : await parseEpub(plain);
      if (!prepared) {
        // Kept for the next open once the book is on screen (encrypting takes a moment).
        setTimeout(() => _setParsedBook(bookId, data_iv, key, result), 3000);
      }
      title = result.title || title;
      author = result.author || author;
      toc = result.toc;
      currentImageMap = result.imageMap;
      // Inject chapters progressively so the browser stays responsive on large books:
      // a batch per ~50 ms of work (a fixed count waited a frame every 8 chapters).
      const tmp = document.createElement('div');
      for (let i = 0; i < result.chapters.length;) {
        const frag = document.createDocumentFragment();
        const start = performance.now();
        do {
          tmp.innerHTML = result.chapters[i++];
          while (tmp.firstChild) frag.appendChild(tmp.firstChild);
        } while (i < result.chapters.length && performance.now() - start < 50);
        contentEl.appendChild(frag);
        if (i < result.chapters.length) await new Promise(r => setTimeout(r, 0));
      }
      // Used to decide whole-percent vs one-decimal display further down —
      // see _formatBookPercent().
      _currentBookCharCount = contentEl.textContent.length;
    }

    currentBookToc = toc;
    titleEl.textContent = title + (author ? ` — ${author}` : '');

    currentBookId = bookId;

    // Remember the book's real (PDF) or estimated (EPUB) page count in its encrypted meta so
    // the book list can show it; rewritten only when it changed.
    const bookPages = isPdfBook ? numPages : Math.max(1, Math.round(_currentBookCharCount / CHARS_PER_BOOK_PAGE));
    if (bookPages > 0 && cachedMeta.pages !== bookPages) {
      _updateBookMeta(bookId, {pages: bookPages}).catch(() => {});
    }

    // Load bookmarks and highlights
    await Promise.all([
      loadBookmarks(bookId),
      loadHighlights(bookId),
    ]);

    // Apply reader settings (theme, font size, etc.)
    applyReaderSettings(isPdfBook);

    // If this book already has notes/highlights, surface them right away
    // instead of making the reader hide them behind a manual toggle.
    // Not on phones: there the margin covers the text; it stays one tap away (✎).
    if (!isPdfBook && currentHighlights.length && !readerAnnotationsMarginOpen && !_isMobileReader()) {
      toggleAnnotationsMargin();
    }

    // Touch: swipe (paginated) + pinch-to-zoom
    contentEl.addEventListener('touchstart',  _pdfTouchStart,  {passive: true});
    contentEl.addEventListener('touchmove',   _pdfTouchMove,   {passive: false});
    contentEl.addEventListener('touchend',    _pdfTouchEnd,    {passive: true});
    contentEl.addEventListener('touchcancel', _pdfTouchEnd,    {passive: true});

    // Set up progress input
    const progressInput = $('reader-progress-input');
    const progressSuffix = $('reader-progress-suffix');
    const isPdf = isPdfBook;

    if (progressInput) {
      progressInput.style.display = '';
      if (isPdf) {
        progressInput.value = 1;
        if (progressSuffix) progressSuffix.textContent = `/ ${numPages}`;
      } else {
        progressInput.value = _formatBookPercent(0);
        if (progressSuffix) progressSuffix.textContent = '%';
      }

      progressInput.addEventListener('change', function () {
        _suppressScrollJumpDetect();
        if (isPdf) {
          const page = Math.min(numPages, Math.max(1, parseInt(this.value, 10) || 1));
          this.value = page;
          const target = contentEl.querySelector(`#pdf-page-${page}`);
          if (target) {
            const top = target.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
            contentEl.scrollBy({top: top - 8, behavior: 'smooth'});
          }
        } else {
          const pct = Math.min(100, Math.max(0, _parseLocalePercent(this.value)));
          this.value = _formatBookPercent(pct / 100);
          restoreFromAnchor(contentEl, _anchorForFraction(contentEl, pct / 100));
        }
      });

      progressInput.addEventListener('click', function () { this.select(); });
    }

    // Restore scroll position — must happen BEFORE auto-save timer is started
    _suppressScrollJumpDetect();
    let openedProgress = null;
    try {
      let fraction = 0, anchor = '';
      let bookData = null;
      try {
        const progressRes = await fetch('/books/', {cache: 'no-store'});
        _noteServerNowHeader(progressRes);
        const allBooks = await progressRes.json();
        bookData = allBooks.find(b => b.id === bookId) || null;
      } catch {
        // offline — use cached meta
        const cached = await _loadCachedBookMeta();
        bookData = cached.find(b => b.id === bookId) || null;
      }
      // The newer of the server's place and an own one it doesn't have yet.
      if (bookData) bookData = _withPendingProgress(bookData);
      fraction = bookData ? (bookData.scroll_fraction || 0) : 0;
      anchor   = bookData ? (bookData.position_anchor || '') : '';
      openedProgress = bookData;
      _currentPositionAnchor = anchor;
      if (isPdf && readerSettings.pdfPaginated) {
        if (fraction > 0 && pdfTotalPages > 1)
          pdfCurrentPage = Math.max(1, Math.round(fraction * (pdfTotalPages - 1)) + 1);
        enterPdfPaginatedMode();
      } else if (isPdf) {
        // PDF scroll mode
        await new Promise(r => requestAnimationFrame(r));
        if (fraction > 0)
          contentEl.scrollTop = fraction * (contentEl.scrollHeight - contentEl.clientHeight);
      } else {
        // EPUB — wait for images so scrollHeight is final
        const imgs = Array.from(contentEl.querySelectorAll('img'));
        if (imgs.length) {
          await Promise.all(imgs.map(img =>
            img.complete ? Promise.resolve()
              : new Promise(r => { img.onload = r; img.onerror = r; })
          ));
        }
        await new Promise(r => requestAnimationFrame(r));
        if (!restoreFromAnchor(contentEl, anchor) && fraction > 0) {
          restoreFromAnchor(contentEl, _anchorForFraction(contentEl, fraction));
        }
      }
    } catch (e) {}

    // From here on, what the reader does is reading. The place shown has the
    // time it was read at (elsewhere, or here earlier): nothing new to send yet.
    if (_readPos && _readPos.bookId === bookId && currentBookId === bookId) {
      const shownAnchor = isPdf ? '' : getPositionAnchor(contentEl);
      const readAtServer = openedProgress && openedProgress.read_at != null ? openedProgress.read_at : null;
      _readPos.key = _positionKey(shownAnchor, openedProgress ? (openedProgress.scroll_fraction || 0) : 0);
      _readPos.readAt = readAtServer == null ? 0 : readAtServer - _serverOffset;
      _readPos.ready = true;
      _offerFurthestPosition(openedProgress);
    }

    // Prime the "settled" baseline to wherever we just restored to, rather
    // than waiting to lazily pick up whatever scroll event happens to fire
    // first — that could otherwise be a later, unrelated layout correction.
    _scrollRestTop = contentEl.scrollTop;

    // Update progress input on scroll
    contentEl.addEventListener('scroll', () => {
      if (!progressInput) return;
      if (isPdf) {
        const wrappers = contentEl.querySelectorAll('.pdf-page-wrapper');
        const cTop = contentEl.getBoundingClientRect().top;
        let currentPage = 1;
        for (const w of wrappers) {
          if (w.getBoundingClientRect().bottom > cTop + 20) {
            currentPage = parseInt(w.id.replace('pdf-page-', ''), 10) || 1;
            break;
          }
        }
        progressInput.value = currentPage;
      }
      // EPUB: shown from the position anchor, see the anchor tracking below.
    });

    // Auto-save progress every 10s and on scroll (debounced 2s)
    // Started AFTER restore so an early visibilitychange can't overwrite with position 0
    readerScrollSaveTimer = setInterval(saveReaderProgress, 10000);
    let _scrollDebounce = null;
    contentEl.addEventListener('scroll', () => {
      clearTimeout(_scrollDebounce);
      _scrollDebounce = setTimeout(saveReaderProgress, 2000);
    }, {passive: true});

    // Keep _currentPositionAnchor fresh independent of the slower save debounce
    // above: the resize observer below (or an immersive-bars toggle right after
    // scrolling) would otherwise restore to a stale, pre-scroll anchor.
    if (!isPdf) {
      let _anchorTrackDebounce = null;
      contentEl.addEventListener('scroll', () => {
        clearTimeout(_anchorTrackDebounce);
        _anchorTrackDebounce = setTimeout(() => {
          _currentPositionAnchor = getPositionAnchor(contentEl);
          const f = _fractionFromAnchor(contentEl, _currentPositionAnchor);
          _noteReadingPosition(_currentPositionAnchor, f === null ? 0 : f);
          if (progressInput && f !== null && document.activeElement !== progressInput) {
            progressInput.value = _formatBookPercent(f);
          }
        }, 150);
      }, {passive: true});
    }

    // Restore anchor on viewport resize (e.g. screen rotation, font zoom)
    if (!isPdf) {
      _resizeObserver = new ResizeObserver(() => {
        if (_currentPositionAnchor) {
          _suppressScrollJumpDetect();
          requestAnimationFrame(() => restoreFromAnchor(contentEl, _currentPositionAnchor));
        }
        _repositionMarginMarkers();
      });
      _resizeObserver.observe(contentEl);
    }

    // Offer to jump back after a sudden, large scroll (accidental fling,
    // fat-fingered 'g'/'G' keybind, etc.) — see _checkScrollJump above.
    _scrollRestTop = null;
    let _scrollJumpRaf = null;
    contentEl.addEventListener('scroll', () => {
      if (_scrollJumpRaf) return;
      _scrollJumpRaf = requestAnimationFrame(() => {
        _scrollJumpRaf = null;
        _checkScrollJump(contentEl);
        _repositionMarginMarkers();
      });
    }, {passive: true});

    enterReaderImmersiveMode();

  } catch (e) {
    console.error('openBook failed:', e);
    overlay.style.display = 'none';
    markBookBroken(bookId);
  }
}

async function exportEncKey() {
  const statusEl = $('book-key-status');
  try {
    const key = await getOrCreateEncKey();
    const raw = await crypto.subtle.exportKey('raw', key);
    const b64 = bytesToBase64(raw);
    await navigator.clipboard.writeText(b64);
    if (statusEl) statusEl.textContent = '✓ Schlüssel in die Zwischenablage kopiert';
    setTimeout(() => { if (statusEl) statusEl.textContent = ''; }, 3000);
  } catch (e) {
    if (statusEl) statusEl.textContent = 'Export fehlgeschlagen: ' + e.message;
  }
}

function showImportKey() {
  const body = $('sidebar-body');
  openSidebar('Schlüssel importieren', `
    <p class="muted">Füge den Schlüssel ein, den du im anderen Browser exportiert hast:</p>
    <textarea id="import-key-input" class="search-input" rows="3" style="width:100%;resize:none;font-family:monospace;font-size:0.75rem;"></textarea>
    <button class="btn" style="margin-top:8px;" data-import-key-apply>Übernehmen</button>
    <p class="muted" style="margin-top:8px;">Das ersetzt den Schlüssel in diesem Browser. Hier hochgeladene Bücher sind erst wieder lesbar, wenn du den Schlüssel zurück abgleichst.</p>
  `);
  body.addEventListener('click', async function _importClick(e) {
    if (!e.target.closest('[data-import-key-apply]')) return;
    body.removeEventListener('click', _importClick);
    const b64 = (body.querySelector('#import-key-input')?.value || '').trim();
    const statusEl = $('book-key-status');
    try {
      const raw = base64ToBytes(b64);
      const importedKey = await crypto.subtle.importKey('raw', raw, {name: 'AES-GCM', length: 256}, true, ['encrypt', 'decrypt']);
      const re_exported = await crypto.subtle.exportKey('raw', importedKey);
      localStorage.setItem(`diora_enc_key_${window.USER_ID}`, bytesToBase64(re_exported));
      closeSidebar();
      if (statusEl) statusEl.textContent = '✓ Schlüssel importiert – Bücher werden neu geladen …';
      await loadBookList();
      if (statusEl) setTimeout(() => { statusEl.textContent = ''; }, 3000);
    } catch (e) {
      if ($('book-key-status')) $('book-key-status').textContent = 'Import fehlgeschlagen: ungültiger Schlüssel';
    }
  });
}

async function deleteBook(bookId) {
  if (!await customConfirm('Dieses Buch löschen? Das lässt sich nicht rückgängig machen.', { danger: true })) return;
  try {
    const res = await fetch(`/books/${bookId}/delete/`, {
      method: 'POST',
      headers: {'X-CSRFToken': getCsrfToken()},
    });
    const data = await res.json();
    if (data.ok) loadBookList();
  } catch (e) {}
}

// Opened somewhere before the furthest place reached: offer it.
function _offerFurthestPosition(p) {
  if (!p) return;
  const furthest = p.furthest_fraction || 0;
  if (furthest - (p.scroll_fraction || 0) < 0.02 || furthest >= 0.999) return;
  const pos = _readPos;
  _readerToast(`Weiteste Stelle: ${_formatBookPercent(furthest)} %`, 'Dorthin', () => {
    if (_readPos !== pos) return;
    _noteReaderInteraction();
    _jumpToPosition(p.furthest_anchor || '', furthest);
  }, 8000);
}

async function saveReaderProgress(force = false) {
  if (!currentBookId) return;
  const contentEl = $('reader-content');
  if (!contentEl) return;

  let fraction;
  if (readerSettings.pdfPaginated && currentPdfDoc && pdfTotalPages > 1) {
    fraction = (pdfCurrentPage - 1) / (pdfTotalPages - 1);
  } else {
    fraction = contentEl.scrollTop / (contentEl.scrollHeight - contentEl.clientHeight || 1);
  }

  // Chapter wrappers carry unique ids; seeing one twice means the book was
  // rendered twice. Positions from that DOM are wrong — don't store them.
  if (!currentPdfDoc && contentEl.querySelectorAll('#epub-chapter-0').length > 1) {
    console.warn('Book rendered twice, progress not saved');
    return;
  }

  // Not restored yet (or another book): what's shown isn't a place read.
  const pos = _readPos;
  if (!pos || !pos.ready || pos.bookId !== currentBookId) return;
  // A jump that's only a look: the place before it stays.
  if (pos.hold && !force) return;

  let anchor = '';
  if (!currentPdfDoc) {
    anchor = getPositionAnchor(contentEl);
    _currentPositionAnchor = anchor;
    // EPUB: share of the text, the same on every device and layout.
    const textFraction = _fractionFromAnchor(contentEl, anchor);
    if (textFraction !== null) fraction = textFraction;
  }
  fraction = Math.min(1.0, Math.max(0.0, fraction));

  _noteReadingPosition(anchor, fraction);
  if (force) {
    pos.readAt = Date.now();
    pos.moved = true;
  }
  // Nothing read here since opening: the server has this place already.
  if (!pos.moved) return;

  const entry = {book: currentBookId, fraction, anchor, read_at: pos.readAt, device: _progressDevice(), ...(force && {force: true})};
  const sig = `${entry.book}|${anchor}|${fraction.toFixed(5)}|${entry.read_at}`;
  _lastProgressBeacon = entry;
  if (!force && sig === pos.sentSig) return; // unchanged since the last save
  pos.sentSig = sig;
  _progressOutboxPut(entry);
  _updateCachedBookProgress(currentBookId, fraction, anchor, force, pos.readAt);
  const sent = await _sendProgress(entry);
  if (!sent) pos.sentSig = null; // try again with the next save
  if (sent && force) {
    const toast = document.createElement('div');
    toast.className = 'reader-toast';
    toast.textContent = 'Position gesetzt';
    document.body.appendChild(toast);
    setTimeout(() => toast.remove(), 1800);
  }
}

function closeReader() {
  exitReaderImmersiveMode();
  stopReadAloud();
  // Save progress BEFORE hiding — scrollHeight/clientHeight return 0 once display:none
  saveReaderProgress();
  _readPos = null; // nothing more is saved for this book
  if (bookmarksDirty) saveBookmarks();
  if (highlightsDirty) saveHighlights();

  const overlay = $('reader-overlay');
  if (overlay) overlay.style.display = 'none';
  if (readerScrollSaveTimer) {
    clearInterval(readerScrollSaveTimer);
    readerScrollSaveTimer = null;
  }
  if (_resizeObserver) {
    _resizeObserver.disconnect();
    _resizeObserver = null;
  }
  _currentPositionAnchor = '';

  // Close the margin panel
  readerAnnotationsMarginOpen = false;
  const marginEl = $('reader-margin');
  if (marginEl) marginEl.classList.remove('open');
  const marginMarkersEl = $('reader-margin-markers');
  if (marginMarkersEl) marginMarkersEl.innerHTML = '';

  // Disarm marker mode
  markerModeActive = false;
  document.querySelectorAll('.marker-mode-btn').forEach(b => b.classList.remove('active'));
  dismissNoteBottomSheet();

  // Clear search before wiping content
  clearReaderSearch();

  // Close settings panel if open
  readerSettingsPanelOpen = false;
  const sp = document.getElementById('reader-settings-panel');
  if (sp) sp.remove();

  // Reset progress input
  const progressInput = $('reader-progress-input');
  if (progressInput) { progressInput.style.display = 'none'; progressInput.value = 0; }
  const progressSuffix = $('reader-progress-suffix');
  if (progressSuffix) progressSuffix.textContent = '';

  // Remove touch handlers and free image blob URLs
  const contentEl = $('reader-content');
  if (contentEl) {
    contentEl.removeEventListener('touchstart',  _pdfTouchStart);
    contentEl.removeEventListener('touchmove',   _pdfTouchMove);
    contentEl.removeEventListener('touchend',    _pdfTouchEnd);
    contentEl.removeEventListener('touchcancel', _pdfTouchEnd);
    contentEl.classList.remove('pinch-active');
    contentEl.innerHTML = '';
  }
  for (const url of Object.values(currentImageMap)) URL.revokeObjectURL(url);
  currentImageMap = {};

  // Reset all state
  currentBookId = null;
  currentBookToc = [];
  _currentBookCharCount = 0;
  currentPdfDoc = null;
  currentPdfBuffer = null;
  currentBookmarks = [];
  bookmarksDirty = false;
  currentHighlights = [];
  highlightsDirty = false;
  _lastProgressBeacon = null;
  _lastBookmarkBeacon = null;
  _lastHighlightBeacon = null;
  dismissHighlightPopover();
  pdfCurrentPage = 1;
  pdfTotalPages = 0;
  _pdfPageTextBoxCache = {};

  // Remove PDF invert class
  if (overlay) overlay.classList.remove('pdf-inverted');

}

function openTocSidebar() {
  if (!currentBookToc.length) {
    openSidebar('Inhaltsverzeichnis', '<p class="muted">Dieses Buch hat kein Inhaltsverzeichnis.</p>');
    return;
  }
  let html = '<ul class="toc-list">';
  for (const entry of currentBookToc) {
    const indent = entry.depth * 14;
    // Use data-toc-href — onclick would be stripped by sanitizeSidebarHtml
    html += `<li style="padding-left:${indent}px">
      <button class="btn-link toc-entry" data-toc-href="${escapeHtml(entry.href)}">${escapeHtml(entry.label)}</button>
    </li>`;
  }
  html += '</ul>';
  openSidebar('Inhaltsverzeichnis', html);
  // Attach delegated listener after sidebar body is populated
  const body = $('sidebar-body');
  body.addEventListener('click', function _tocClick(e) {
    const btn = e.target.closest('.toc-entry');
    if (btn) {
      body.removeEventListener('click', _tocClick);
      jumpToTocEntry(btn.getAttribute('data-toc-href') || '');
    }
  });
}

function jumpToTocEntry(href) {
  closeSidebar();
  _suppressScrollJumpDetect();
  setTimeout(() => {
    const contentEl = $('reader-content');
    if (!contentEl) return;

    // PDF page jump
    if (href.startsWith('#pdf-page-')) {
      const target = contentEl.querySelector(href);
      if (target) {
        const top = target.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
        contentEl.scrollBy({top: top - 16, behavior: 'smooth'});
      }
      return;
    }

    const hashIdx = href.indexOf('#');
    const fragment = hashIdx >= 0 ? href.slice(hashIdx + 1) : '';
    const filePath = hashIdx >= 0 ? href.slice(0, hashIdx) : href;

    let target = null;
    if (fragment) {
      target = contentEl.querySelector(`#${CSS.escape(fragment)}`);
    }
    if (!target && filePath) {
      target = Array.from(contentEl.querySelectorAll('[data-epub-src]'))
        .find(el => el.getAttribute('data-epub-src') === filePath) || null;
    }
    if (target) {
      const top = target.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
      contentEl.scrollBy({top: top - 16, behavior: 'smooth'});
    }
  }, 50);
}

// ---------------------------------------------------------------------------
// Reader Settings
// ---------------------------------------------------------------------------

// Typography defaults. Phones keep the long-standing ones; a wide screen
// (desktop browser, diora desktop) starts bigger and wider.
const _READER_TYPE_DEFAULTS_NARROW = { fontSize: 16, lineHeight: 1.8, maxWidth: 65, fontWeight: null };
const _READER_TYPE_DEFAULTS_WIDE = { fontSize: 20, lineHeight: 1.6, maxWidth: 90, fontWeight: 375 };
const _READER_WIDTH_MAX = 140; // ch, the width slider's upper end ("Full" stays separate)

function _readerTypeDefaults() {
  return window.matchMedia('(min-width: 900px)').matches
    ? _READER_TYPE_DEFAULTS_WIDE : _READER_TYPE_DEFAULTS_NARROW;
}

function loadReaderSettings(bookId) {
  // Reset to defaults, then apply per-book overrides
  Object.assign(readerSettings, { theme: 'app', fontFamily: 'serif', noBold: false,
                                   pdfZoom: 100, pdfInverted: false, pdfPaginated: false, pdfSpread: false },
                _readerTypeDefaults());
  try {
    const saved = JSON.parse(localStorage.getItem(`diora_reader_settings_${bookId}`) || '{}');
    // Settings saved before v2 hold every value, changed or not. A value equal
    // to the old default was never chosen, so it gives way to today's default.
    if (!saved.v) {
      for (const [key, old] of Object.entries(_READER_TYPE_DEFAULTS_NARROW)) {
        if (saved[key] === old) delete saved[key];
      }
    }
    // Before v3 the reader's theme was always stored, "dark" by default: that now means "Wie die App".
    if ((saved.v || 0) < 3 && saved.theme === 'dark') delete saved.theme;
    delete saved.v;
    Object.assign(readerSettings, saved);
    if (saved.pdfPaginated === undefined) {
      readerSettings.pdfPaginated = window.innerWidth < 768;
    }
  } catch (e) {}
}

function saveReaderSettings() {
  if (currentBookId) {
    localStorage.setItem(`diora_reader_settings_${currentBookId}`, JSON.stringify({ ...readerSettings, v: 3 }));
  }
}

function applyReaderSettings(isPdf) {
  const overlay = $('reader-overlay');
  const contentEl = $('reader-content');
  if (!overlay || !contentEl) return;

  if (!isPdf) {
    contentEl.style.fontSize = readerSettings.fontSize + 'px';
    contentEl.style.lineHeight = readerSettings.lineHeight;
    contentEl.style.setProperty('--reader-max-width', readerSettings.maxWidth + 'ch');
    const fontMap = {
      serif:    "'Source Serif 4', Georgia, 'Times New Roman', serif",
      sans:     'system-ui, -apple-system, sans-serif',
      humanist: 'Verdana, Geneva, sans-serif',
      mono:     "'Courier New', monospace",
    };
    contentEl.style.fontFamily = fontMap[readerSettings.fontFamily] || fontMap.serif;
    contentEl.classList.toggle('reader-no-bold', !!readerSettings.noBold);
    // Weight: null keeps the stylesheet's. --reader-weight lets old WebViews
    // without variable-font support (which drop weights like 425) pick a
    // static cut instead.
    contentEl.style.fontWeight = '';
    if (readerSettings.fontWeight) {
      contentEl.style.fontWeight = String(readerSettings.fontWeight);
      contentEl.style.setProperty('--reader-weight', String(readerSettings.fontWeight));
    } else {
      contentEl.style.removeProperty('--reader-weight');
    }
    if (_currentPositionAnchor && currentBookId) {
      _suppressScrollJumpDetect();
      requestAnimationFrame(() => restoreFromAnchor($('reader-content'), _currentPositionAnchor));
    }
  }

  // Theme
  overlay.classList.remove('reader-theme-sepia', 'reader-theme-bright');
  const readerTheme = readerSettings.theme === 'app'
    ? (document.documentElement.getAttribute('data-theme') === 'light' ? 'bright' : 'dark')
    : readerSettings.theme;
  if (readerTheme === 'sepia') overlay.classList.add('reader-theme-sepia');
  else if (readerTheme === 'bright') overlay.classList.add('reader-theme-bright');

  // PDF invert
  if (isPdf && readerSettings.pdfInverted) overlay.classList.add('pdf-inverted');
  else overlay.classList.remove('pdf-inverted');

  // Annotations (marker mode + margin panel) are EPUB-only for now — PDFs have no text layer yet
  const marginBtn = $('reader-margin-btn');
  if (marginBtn) marginBtn.style.display = isPdf ? 'none' : '';
  if (isPdf && readerAnnotationsMarginOpen) toggleAnnotationsMargin();
  document.querySelectorAll('.marker-mode-btn').forEach(b => { b.style.display = isPdf ? 'none' : ''; });
  if (isPdf && markerModeActive) toggleMarkerMode();
}

// Font weight slider: the variable Source Serif 4 takes any weight, the
// system fonts only their fixed cuts (multiples of 100).
function _readerWeightStep() {
  return readerSettings.fontFamily === 'serif' ? 25 : 100;
}

function _readerWeight() {
  const step = _readerWeightStep();
  const w = readerSettings.fontWeight
    || parseInt(getComputedStyle($('reader-content')).fontWeight, 10) || 400;
  return Math.round(w / step) * step;
}

function toggleSettingsPanel() {
  const overlay = $('reader-overlay');
  const contentEl = $('reader-content');
  if (!overlay || !contentEl) return;

  const existing = document.getElementById('reader-settings-panel');
  if (existing) {
    existing.remove();
    readerSettingsPanelOpen = false;
    return;
  }

  readerSettingsPanelOpen = true;
  const isPdf = !!currentPdfDoc;

  const panel = document.createElement('div');
  panel.id = 'reader-settings-panel';
  panel.className = 'reader-settings-panel';

  if (!isPdf) {
    panel.innerHTML = `
      <label>Schrift <button class="btn btn-sm" id="rs-font-minus">−</button> <input type="range" id="rs-font" min="12" max="24" step="1" value="${readerSettings.fontSize}"> <button class="btn btn-sm" id="rs-font-plus">+</button> <span id="rs-font-val">${readerSettings.fontSize}px</span></label>
      <label>Zeilen <button class="btn btn-sm" id="rs-line-minus">−</button> <input type="range" id="rs-line" min="12" max="30" step="1" value="${Math.round(readerSettings.lineHeight * 10)}"> <button class="btn btn-sm" id="rs-line-plus">+</button> <span id="rs-line-val">${readerSettings.lineHeight}</span></label>
      <label>Breite <button class="btn btn-sm" id="rs-width-minus">−</button> <input type="range" id="rs-width" min="40" max="${_READER_WIDTH_MAX}" step="5" value="${Math.min(readerSettings.maxWidth, _READER_WIDTH_MAX)}"> <button class="btn btn-sm" id="rs-width-plus">+</button> <span id="rs-width-val">${readerSettings.maxWidth}ch</span></label>
      <button class="btn btn-sm" id="rs-width-full">Volle Breite</button>
      <label>Stärke <button class="btn btn-sm" id="rs-weight-minus">−</button> <input type="range" id="rs-weight" min="200" max="800" step="${_readerWeightStep()}" value="${_readerWeight()}"> <button class="btn btn-sm" id="rs-weight-plus">+</button> <span id="rs-weight-val">${_readerWeight()}</span></label>
      <button class="btn btn-sm ${readerSettings.fontFamily === 'serif'    ? 'active' : ''}" data-rs-font="serif">Serif</button>
      <button class="btn btn-sm ${readerSettings.fontFamily === 'sans'     ? 'active' : ''}" data-rs-font="sans">Sans</button>
      <button class="btn btn-sm ${readerSettings.fontFamily === 'humanist' ? 'active' : ''}" data-rs-font="humanist">Verdana</button>
      <button class="btn btn-sm ${readerSettings.fontFamily === 'mono'     ? 'active' : ''}" data-rs-font="mono">Mono</button>
      <button class="btn btn-sm ${readerSettings.noBold ? 'active' : ''}" id="rs-no-bold">Kein Fett</button>
      <button class="btn btn-sm ${readerSettings.theme === 'app'    ? 'active' : ''}" data-rs-theme="app">Wie die App</button>
      <button class="btn btn-sm ${readerSettings.theme === 'dark'   ? 'active' : ''}" data-rs-theme="dark">Dunkel</button>
      <button class="btn btn-sm ${readerSettings.theme === 'sepia'  ? 'active' : ''}" data-rs-theme="sepia">Sepia</button>
      <button class="btn btn-sm ${readerSettings.theme === 'bright' ? 'active' : ''}" data-rs-theme="bright">Hell</button>
    `;
  } else {
    panel.innerHTML = `
      <label>Zoom <button class="btn btn-sm" id="rs-zoom-minus">−</button> <input type="range" id="rs-zoom" min="50" max="200" step="10" value="${readerSettings.pdfZoom}"> <button class="btn btn-sm" id="rs-zoom-plus">+</button> <span id="rs-zoom-val">${readerSettings.pdfZoom}%</span></label>
      <button class="btn btn-sm ${readerSettings.pdfInverted ? 'active' : ''}" id="rs-invert">Invertieren</button>
      <button class="btn btn-sm ${readerSettings.pdfSpread ? 'active' : ''}" id="rs-spread">Doppelseite</button>
    `;
  }

  overlay.insertBefore(panel, $('reader-body-row'));

  if (!isPdf) {
    const fontRange = panel.querySelector('#rs-font');
    const fontVal   = panel.querySelector('#rs-font-val');
    fontRange.addEventListener('input', () => {
      readerSettings.fontSize = parseInt(fontRange.value, 10);
      fontVal.textContent = readerSettings.fontSize + 'px';
      applyReaderSettings(false);
      saveReaderSettings();
    });
    panel.querySelector('#rs-font-minus').addEventListener('click', () => {
      fontRange.value = Math.max(+fontRange.min, parseInt(fontRange.value, 10) - 1);
      fontRange.dispatchEvent(new Event('input'));
    });
    panel.querySelector('#rs-font-plus').addEventListener('click', () => {
      fontRange.value = Math.min(+fontRange.max, parseInt(fontRange.value, 10) + 1);
      fontRange.dispatchEvent(new Event('input'));
    });

    const lineRange = panel.querySelector('#rs-line');
    const lineVal   = panel.querySelector('#rs-line-val');
    lineRange.addEventListener('input', () => {
      readerSettings.lineHeight = (parseInt(lineRange.value, 10) / 10).toFixed(1);
      lineVal.textContent = readerSettings.lineHeight;
      applyReaderSettings(false);
      saveReaderSettings();
    });
    panel.querySelector('#rs-line-minus').addEventListener('click', () => {
      lineRange.value = Math.max(+lineRange.min, parseInt(lineRange.value, 10) - 1);
      lineRange.dispatchEvent(new Event('input'));
    });
    panel.querySelector('#rs-line-plus').addEventListener('click', () => {
      lineRange.value = Math.min(+lineRange.max, parseInt(lineRange.value, 10) + 1);
      lineRange.dispatchEvent(new Event('input'));
    });

    const widthRange = panel.querySelector('#rs-width');
    const widthVal   = panel.querySelector('#rs-width-val');
    widthRange.addEventListener('input', () => {
      readerSettings.maxWidth = parseInt(widthRange.value, 10);
      widthVal.textContent = readerSettings.maxWidth + 'ch';
      applyReaderSettings(false);
      saveReaderSettings();
    });
    panel.querySelector('#rs-width-minus').addEventListener('click', () => {
      widthRange.value = Math.max(+widthRange.min, parseInt(widthRange.value, 10) - 5);
      widthRange.dispatchEvent(new Event('input'));
    });
    panel.querySelector('#rs-width-plus').addEventListener('click', () => {
      widthRange.value = Math.min(+widthRange.max, parseInt(widthRange.value, 10) + 5);
      widthRange.dispatchEvent(new Event('input'));
    });

    panel.querySelector('#rs-width-full').addEventListener('click', () => {
      readerSettings.maxWidth = 999;
      widthRange.value = 90;
      widthVal.textContent = 'full';
      applyReaderSettings(false);
      saveReaderSettings();
    });

    const weightRange = panel.querySelector('#rs-weight');
    const weightVal   = panel.querySelector('#rs-weight-val');
    weightRange.addEventListener('input', () => {
      readerSettings.fontWeight = parseInt(weightRange.value, 10);
      weightVal.textContent = readerSettings.fontWeight;
      applyReaderSettings(false);
      saveReaderSettings();
    });
    panel.querySelector('#rs-weight-minus').addEventListener('click', () => {
      weightRange.value = Math.max(+weightRange.min, parseInt(weightRange.value, 10) - +weightRange.step);
      weightRange.dispatchEvent(new Event('input'));
    });
    panel.querySelector('#rs-weight-plus').addEventListener('click', () => {
      weightRange.value = Math.min(+weightRange.max, parseInt(weightRange.value, 10) + +weightRange.step);
      weightRange.dispatchEvent(new Event('input'));
    });

    panel.querySelectorAll('[data-rs-font]').forEach(btn => {
      btn.addEventListener('click', () => {
        readerSettings.fontFamily = btn.dataset.rsFont;
        panel.querySelectorAll('[data-rs-font]').forEach(b => b.classList.toggle('active', b === btn));
        // The system fonts only have cuts at multiples of 100.
        weightRange.step = _readerWeightStep();
        if (readerSettings.fontWeight) {
          readerSettings.fontWeight = Math.round(readerSettings.fontWeight / weightRange.step) * weightRange.step;
        }
        applyReaderSettings(false);
        saveReaderSettings();
        weightRange.value = _readerWeight();
        weightVal.textContent = _readerWeight();
      });
    });

    panel.querySelector('#rs-no-bold').addEventListener('click', function () {
      readerSettings.noBold = !readerSettings.noBold;
      this.classList.toggle('active', readerSettings.noBold);
      applyReaderSettings(false);
      saveReaderSettings();
    });

    panel.querySelectorAll('[data-rs-theme]').forEach(btn => {
      btn.addEventListener('click', () => {
        readerSettings.theme = btn.dataset.rsTheme;
        panel.querySelectorAll('[data-rs-theme]').forEach(b => b.classList.toggle('active', b === btn));
        applyReaderSettings(false);
        saveReaderSettings();
      });
    });
  } else {
    const zoomRange = panel.querySelector('#rs-zoom');

    zoomRange.addEventListener('input', () => applyPdfZoom(parseInt(zoomRange.value, 10)));
    panel.querySelector('#rs-zoom-minus').addEventListener('click', () =>
      applyPdfZoom(Math.max(50,  readerSettings.pdfZoom - 10)));
    panel.querySelector('#rs-zoom-plus').addEventListener('click', () =>
      applyPdfZoom(Math.min(200, readerSettings.pdfZoom + 10)));

    panel.querySelector('#rs-invert').addEventListener('click', function () {
      readerSettings.pdfInverted = !readerSettings.pdfInverted;
      this.classList.toggle('active', readerSettings.pdfInverted);
      applyReaderSettings(true);
      saveReaderSettings();
    });

    panel.querySelector('#rs-spread').addEventListener('click', function () {
      readerSettings.pdfSpread = !readerSettings.pdfSpread;
      this.classList.toggle('active', readerSettings.pdfSpread);
      saveReaderSettings();
      reRenderPdf();
    });

  }
}

async function applyPdfZoom(newZoom) {
  readerSettings.pdfZoom = newZoom;
  const zoomRange = document.getElementById('rs-zoom');
  const zoomVal = document.getElementById('rs-zoom-val');
  if (zoomRange) zoomRange.value = newZoom;
  if (zoomVal) zoomVal.textContent = newZoom + '%';
  saveReaderSettings();
  if (readerSettings.pdfPaginated) {
    pdfSmartZoomPage(pdfCurrentPage);
  } else {
    await reRenderPdf();
  }
}

function _currentScrollPage(contentEl) {
  const wrappers = contentEl.querySelectorAll('.pdf-page-wrapper');
  const viewTop = contentEl.scrollTop;
  for (const w of wrappers) {
    if (w.offsetTop + w.offsetHeight > viewTop) {
      const n = parseInt(w.id.replace('pdf-page-', ''), 10);
      if (n) return n;
    }
  }
  return pdfCurrentPage || 1;
}

async function reRenderPdf() {
  if (!currentPdfBuffer) return;
  const contentEl = $('reader-content');
  if (!contentEl) return;
  const pivot = readerSettings.pdfPaginated ? pdfCurrentPage : _currentScrollPage(contentEl);
  await renderPdf(currentPdfBuffer, contentEl, undefined, pivot);
  if (readerSettings.pdfPaginated) enterPdfPaginatedMode();
}

// ---------------------------------------------------------------------------
// PDF Paginated Mode
// ---------------------------------------------------------------------------

function enterPdfPaginatedMode() {
  const contentEl = $('reader-content');
  if (!contentEl) return;
  contentEl.classList.add('pdf-paginated');
  contentEl.style.overflow = 'hidden';
  const pdfVp = document.getElementById('pdf-viewport');
  if (pdfVp) pdfVp.style.zoom = 1;

  const wrappers = contentEl.querySelectorAll('.pdf-page-wrapper');
  wrappers.forEach((w, i) => {
    w.style.display = (i + 1 === pdfCurrentPage) ? '' : 'none';
  });

  pdfSmartZoomPage(pdfCurrentPage);

  // Tap left/right to navigate
  contentEl.addEventListener('click', _pdfPaginatedClick);
}

function exitPdfPaginatedMode() {
  const contentEl = $('reader-content');
  if (!contentEl) return;
  contentEl.classList.remove('pdf-paginated');
  contentEl.style.overflow = '';
  contentEl.removeEventListener('click', _pdfPaginatedClick);
  reRenderPdf();
}

function _pdfPaginatedClick(e) {
  const w = e.currentTarget.clientWidth;
  if (e.clientX < w * 0.4) pdfGoToPage(pdfCurrentPage - 1);
  else if (e.clientX > w * 0.6) pdfGoToPage(pdfCurrentPage + 1);
}

function _pdfTouchStart(e) {
  if (e.touches.length === 2) {
    const dx = e.touches[0].clientX - e.touches[1].clientX;
    const dy = e.touches[0].clientY - e.touches[1].clientY;
    _pinchStartDist = Math.hypot(dx, dy);
    _pinchStartZoom = readerSettings.pdfZoom;
    _isPinching = true;
    const ce = $('reader-content');
    if (ce) ce.classList.add('pinch-active');
  } else {
    _touchStartX = e.touches[0].clientX;
    _isPinching = false;
  }
}

function _pdfTouchMove(e) {
  if (e.touches.length !== 2 || !_isPinching) return;
  e.preventDefault();
  const dx = e.touches[0].clientX - e.touches[1].clientX;
  const dy = e.touches[0].clientY - e.touches[1].clientY;
  const dist = Math.hypot(dx, dy);
  if (_pinchStartDist === 0) return;
  const liveZoom = Math.max(50, Math.min(200, _pinchStartZoom * (dist / _pinchStartDist)));
  const vp = document.getElementById('pdf-viewport');
  if (vp) vp.style.zoom = liveZoom / 100;
}

function _pdfTouchEnd(e) {
  if (_isPinching) {
    _isPinching = false;
    const ce = $('reader-content');
    if (ce) ce.classList.remove('pinch-active');
    const vp = document.getElementById('pdf-viewport');
    const liveZoom = vp ? parseFloat(vp.style.zoom) * 100 : readerSettings.pdfZoom;
    const snapped = Math.max(50, Math.min(200, Math.round(liveZoom / 10) * 10));
    applyPdfZoom(snapped);
    return;
  }
  if (!readerSettings.pdfPaginated) return;
  const delta = e.changedTouches[0].clientX - _touchStartX;
  if (delta > 50) pdfGoToPage(pdfCurrentPage - 1);
  else if (delta < -50) pdfGoToPage(pdfCurrentPage + 1);
}

function pdfGoToPage(n) {
  if (!currentPdfDoc) return;
  n = Math.max(1, Math.min(pdfTotalPages, n));
  if (n === pdfCurrentPage) return;
  const contentEl = $('reader-content');
  if (!contentEl) return;

  const oldWrapper = contentEl.querySelector(`#pdf-page-${pdfCurrentPage}`);
  if (oldWrapper) oldWrapper.style.display = 'none';

  pdfCurrentPage = n;
  const newWrapper = contentEl.querySelector(`#pdf-page-${pdfCurrentPage}`);
  if (newWrapper) newWrapper.style.display = '';

  pdfSmartZoomPage(pdfCurrentPage);

  const progressInput = $('reader-progress-input');
  if (progressInput) progressInput.value = pdfCurrentPage;
}

async function pdfSmartZoomPage(pageNum) {
  if (!currentPdfDoc) return;
  const contentEl = $('reader-content');
  if (!contentEl) return;
  const wrapper = contentEl.querySelector(`#pdf-page-${pageNum}`);
  if (!wrapper) return;
  const canvas = wrapper.querySelector('canvas');
  if (!canvas) return;

  const page = await currentPdfDoc.getPage(pageNum);
  const naturalVp = page.getViewport({scale: 1});
  const pageW = naturalVp.width;
  const pageH = naturalVp.height;

  let bbox = _pdfPageTextBoxCache[pageNum];
  if (!bbox) {
    bbox = await _computePdfTextBox(page, pageW, pageH);
    _pdfPageTextBoxCache[pageNum] = bbox;
  }

  const containerW = contentEl.clientWidth;
  const containerH = contentEl.clientHeight;
  const contentW = bbox.x2 - bbox.x1;
  const contentH = bbox.y2 - bbox.y1;
  const pad = 12;
  const scale = Math.min(
    (containerW - pad * 2) / contentW,
    (containerH - pad * 2) / contentH
  ) * (readerSettings.pdfZoom / 100);

  // Re-render canvas at new scale if significantly different
  const currentScale = canvas.width / naturalVp.width;
  if (Math.abs(scale - currentScale) / currentScale > 0.05) {
    const vp = page.getViewport({scale});
    canvas.width = vp.width;
    canvas.height = vp.height;
    await page.render({canvasContext: canvas.getContext('2d'), viewport: vp}).promise;
  }

  // Position canvas to center the text bounding box
  const renderedScale = canvas.width / naturalVp.width;
  const offsetX = -renderedScale * (bbox.x1 - pad) + (containerW - renderedScale * contentW - pad * 2) / 2;
  // PDF y-axis is bottom-up; canvas is top-down
  const offsetY = -renderedScale * (pageH - bbox.y2 - pad) + (containerH - renderedScale * contentH - pad * 2) / 2;
  canvas.style.transform = `translate(${offsetX}px, ${offsetY}px)`;
  wrapper.style.overflow = 'hidden';
  wrapper.style.width = containerW + 'px';
  wrapper.style.height = containerH + 'px';
}

async function _computePdfTextBox(page, pageW, pageH) {
  // Tier 1: text-based
  try {
    const tc = await page.getTextContent();
    if (tc.items && tc.items.length) {
      let x1 = Infinity, y1 = Infinity, x2 = -Infinity, y2 = -Infinity;
      for (const item of tc.items) {
        if (!item.transform) continue;
        const tx = item.transform[4], ty = item.transform[5];
        const iw = item.width || 0, ih = item.height || 0;
        if (tx < x1) x1 = tx;
        if (ty < y1) y1 = ty;
        if (tx + iw > x2) x2 = tx + iw;
        if (ty + ih > y2) y2 = ty + ih;
      }
      const area = (x2 - x1) * (y2 - y1);
      if (isFinite(x1) && area > pageW * pageH * 0.25) {
        return {x1, y1, x2, y2};
      }
    }
  } catch (e) {}

  // Tier 2: pixel analysis at scale 0.3
  try {
    const lowScale = 0.3;
    const vp = page.getViewport({scale: lowScale});
    const offCanvas = document.createElement('canvas');
    offCanvas.width = vp.width;
    offCanvas.height = vp.height;
    const ctx = offCanvas.getContext('2d');
    await page.render({canvasContext: ctx, viewport: vp}).promise;
    const {data, width, height} = ctx.getImageData(0, 0, vp.width, vp.height);

    let rMin = height, rMax = 0, cMin = width, cMax = 0;
    for (let r = 0; r < height; r++) {
      for (let c = 0; c < width; c++) {
        const idx = (r * width + c) * 4;
        if (data[idx] + data[idx+1] + data[idx+2] < 720) {
          if (r < rMin) rMin = r;
          if (r > rMax) rMax = r;
          if (c < cMin) cMin = c;
          if (c > cMax) cMax = c;
        }
      }
    }
    if (rMin < rMax && cMin < cMax) {
      return {
        x1: cMin / lowScale,
        y1: (height - rMax) / lowScale,
        x2: cMax / lowScale,
        y2: (height - rMin) / lowScale,
      };
    }
  } catch (e) {}

  // Fallback: full page
  return {x1: 0, y1: 0, x2: pageW, y2: pageH};
}

// ---------------------------------------------------------------------------
// Bookmarks
// ---------------------------------------------------------------------------

async function loadBookmarks(bookId) {
  try {
    const res = await fetch(`/books/${bookId}/bookmarks/`);
    const {ct, iv} = await res.json();
    if (ct) {
      _saveAnnotationsCache(bookId, 'bookmarks', ct, iv); // persist for offline
      const key = await getOrCreateEncKey();
      const plain = await decryptBytes(key, iv, ct);
      currentBookmarks = JSON.parse(new TextDecoder().decode(plain));
    } else {
      currentBookmarks = [];
    }
  } catch (e) {
    // offline fallback
    const cached = await _loadAnnotationsCache(bookId, 'bookmarks');
    if (cached?.ct) {
      try {
        const key = await getOrCreateEncKey();
        const plain = await decryptBytes(key, cached.iv, cached.ct);
        currentBookmarks = JSON.parse(new TextDecoder().decode(plain));
      } catch { currentBookmarks = []; }
    } else {
      currentBookmarks = [];
    }
  }
}

async function saveBookmarks() {
  if (!currentBookId) return;
  try {
    const key = await getOrCreateEncKey();
    const plain = new TextEncoder().encode(JSON.stringify(currentBookmarks));
    const {iv, ciphertext} = await encryptBytes(key, plain);
    const body = JSON.stringify({ct: ciphertext, iv});
    const url = `/books/${currentBookId}/bookmarks/`;
    _lastBookmarkBeacon = {url, body};
    _saveAnnotationsCache(currentBookId, 'bookmarks', ciphertext, iv); // keep local cache current
    await fetch(url, {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body,
    });
    bookmarksDirty = false;
  } catch (e) {
    _markPendingSync(currentBookId, 'bookmarks');
  }
}

function addBookmark() {
  const contentEl = $('reader-content');
  if (!contentEl || !currentBookId) return;

  let label, anchor, scrollFraction;

  if (currentPdfDoc) {
    const page = pdfCurrentPage || parseInt($('reader-progress-input')?.value, 10) || 1;
    label = `Seite ${page}`;
    anchor = `pdf-page-${page}`;
    scrollFraction = (page - 1) / Math.max(1, pdfTotalPages - 1);
  } else {
    // Find first visible chapter div
    const chapters = contentEl.querySelectorAll('[data-epub-src]');
    let visibleChapter = null;
    for (const ch of chapters) {
      const rect = ch.getBoundingClientRect();
      if (rect.bottom > 0 && rect.top < window.innerHeight) {
        visibleChapter = ch;
        break;
      }
    }
    const src = visibleChapter?.getAttribute('data-epub-src') || '';
    label = src.split('/').pop().replace(/\.x?html?$/i, '') || 'Bookmark';
    anchor = src;
    scrollFraction = contentEl.scrollTop / (contentEl.scrollHeight - contentEl.clientHeight || 1);
  }

  const bm = {
    id: crypto.randomUUID(),
    label,
    anchor,
    scrollFraction,
    createdAt: new Date().toISOString(),
  };
  currentBookmarks.unshift(bm);
  bookmarksDirty = true;
  saveBookmarks();

  // Toast
  const toast = document.createElement('div');
  toast.className = 'reader-toast';
  toast.textContent = `★ Lesezeichen: ${label}`;
  document.body.appendChild(toast);
  setTimeout(() => toast.remove(), 2200);
}

function openBookmarksSidebar() {
  if (!currentBookmarks.length) {
    openSidebar('Lesezeichen', '<p class="muted">Noch keine Lesezeichen. Tippe beim Lesen auf ★.</p>');
    return;
  }
  let html = '<ul style="list-style:none;padding:0;">';
  for (const bm of currentBookmarks) {
    html += `<li class="bookmark-entry">
      <button class="btn-link" data-jump-bookmark="${escapeHtml(bm.id)}" style="flex:1;text-align:left;">
        ${escapeHtml(bm.label)}
      </button>
      <button class="btn-icon" data-delete-bookmark="${escapeHtml(bm.id)}" title="Löschen">✕</button>
    </li>`;
  }
  html += '</ul>';
  openSidebar('Lesezeichen', html);

  const body = $('sidebar-body');
  body.addEventListener('click', function _bmClick(e) {
    const jumpBtn = e.target.closest('[data-jump-bookmark]');
    const delBtn  = e.target.closest('[data-delete-bookmark]');
    if (jumpBtn) {
      body.removeEventListener('click', _bmClick);
      jumpToBookmark(jumpBtn.dataset.jumpBookmark);
    }
    if (delBtn) {
      const id = delBtn.dataset.deleteBookmark;
      currentBookmarks = currentBookmarks.filter(b => b.id !== id);
      bookmarksDirty = true;
      saveBookmarks();
      openBookmarksSidebar(); // re-render
    }
  });
}

function jumpToBookmark(id) {
  const bm = currentBookmarks.find(b => b.id === id);
  if (!bm) return;
  closeSidebar();
  _suppressScrollJumpDetect();
  setTimeout(() => {
    const contentEl = $('reader-content');
    if (!contentEl) return;
    if (bm.anchor.startsWith('pdf-page-')) {
      if (readerSettings.pdfPaginated) {
        pdfGoToPage(parseInt(bm.anchor.replace('pdf-page-', ''), 10) || 1);
      } else {
        const target = contentEl.querySelector('#' + bm.anchor);
        if (target) {
          const top = target.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
          contentEl.scrollBy({top: top - 16, behavior: 'smooth'});
        }
      }
    } else {
      const target = Array.from(contentEl.querySelectorAll('[data-epub-src]'))
        .find(el => el.getAttribute('data-epub-src') === bm.anchor);
      if (target) {
        const top = target.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
        contentEl.scrollBy({top: top - 16, behavior: 'smooth'});
      } else {
        contentEl.scrollTop = bm.scrollFraction * (contentEl.scrollHeight - contentEl.clientHeight);
      }
    }
  }, 50);
}

// ---------------------------------------------------------------------------
// Reader Search
// ---------------------------------------------------------------------------

let _readerSearchDebounce = null;

function toggleReaderSearch() {
  const overlay = $('reader-overlay');
  const contentEl = $('reader-content');
  if (!overlay || !contentEl) return;

  const existing = document.getElementById('reader-search-bar');
  if (existing) {
    existing.remove();
    readerSearchOpen = false;
    clearReaderSearch();
    return;
  }

  readerSearchOpen = true;
  const bar = document.createElement('div');
  bar.id = 'reader-search-bar';
  bar.className = 'reader-search-bar';
  bar.innerHTML = `
    <input type="text" id="reader-search-input" class="search-input" placeholder="Suchen …" style="width:160px;">
    <button class="btn-icon" id="rs-search-prev" title="Vorheriger Treffer">↑</button>
    <button class="btn-icon" id="rs-search-next" title="Nächster Treffer">↓</button>
    <span id="rs-search-count" class="muted"></span>
    <button class="btn-icon" id="rs-search-clear" title="Close">✕</button>
  `;
  overlay.insertBefore(bar, $('reader-body-row'));

  const input = bar.querySelector('#reader-search-input');
  input.focus();
  input.addEventListener('input', () => {
    clearTimeout(_readerSearchDebounce);
    _readerSearchDebounce = setTimeout(() => doReaderSearch(input.value.trim()), 300);
  });
  input.addEventListener('keydown', e => {
    if (e.key === 'Enter') { e.shiftKey ? readerSearchPrev() : readerSearchNext(); }
    if (e.key === 'Escape') { toggleReaderSearch(); }
  });
  bar.querySelector('#rs-search-prev').addEventListener('click', readerSearchPrev);
  bar.querySelector('#rs-search-next').addEventListener('click', readerSearchNext);
  bar.querySelector('#rs-search-clear').addEventListener('click', toggleReaderSearch);
}

async function doReaderSearch(query) {
  const contentEl = $('reader-content');
  if (!contentEl) return;
  const countEl = document.getElementById('rs-search-count');

  clearReaderSearchHighlights();
  searchMatches = [];
  searchMatchIndex = -1;

  if (!query) { if (countEl) countEl.textContent = ''; return; }

  if (!currentPdfDoc) {
    // EPUB: snapshot original content
    if (!searchOriginalContent) {
      searchOriginalContent = contentEl.innerHTML;
    } else {
      contentEl.innerHTML = searchOriginalContent;
      applyHighlightsToContent();
    }

    const walker = document.createTreeWalker(contentEl, NodeFilter.SHOW_TEXT);
    const lq = query.toLowerCase();
    const ranges = [];
    let node;
    while ((node = walker.nextNode())) {
      const text = node.textContent;
      const lt = text.toLowerCase();
      let idx = 0;
      while ((idx = lt.indexOf(lq, idx)) !== -1) {
        const range = document.createRange();
        range.setStart(node, idx);
        range.setEnd(node, idx + query.length);
        ranges.push(range);
        idx += query.length;
      }
    }

    // Insert marks in reverse to preserve range validity
    for (let i = ranges.length - 1; i >= 0; i--) {
      try {
        const mark = document.createElement('mark');
        mark.className = 'reader-search-match';
        ranges[i].surroundContents(mark);
        searchMatches.unshift(mark);
      } catch (e) {}
    }
  } else {
    // PDF: collect text layer spans
    const spans = contentEl.querySelectorAll('.pdf-text-layer > span');
    const lq = query.toLowerCase();
    for (const span of spans) {
      if (span.textContent.toLowerCase().includes(lq)) {
        span.classList.add('reader-search-match');
        searchMatches.push(span);
      }
    }
  }

  if (countEl) countEl.textContent = searchMatches.length ? `1 / ${searchMatches.length}` : '0';
  if (searchMatches.length) {
    searchMatchIndex = 0;
    scrollToSearchMatch(0);
  }
}

function clearReaderSearchHighlights() {
  if (!currentPdfDoc) {
    // EPUB: restore from snapshot
    if (searchOriginalContent !== null) {
      const contentEl = $('reader-content');
      if (contentEl) {
        contentEl.innerHTML = searchOriginalContent;
        applyHighlightsToContent();
      }
      searchOriginalContent = null;
    } else {
      // Just remove marks without full restore
      document.querySelectorAll('mark.reader-search-match').forEach(m => {
        const parent = m.parentNode;
        while (m.firstChild) parent.insertBefore(m.firstChild, m);
        parent.removeChild(m);
      });
    }
  } else {
    // PDF: remove highlight class from spans
    document.querySelectorAll('.reader-search-match').forEach(el => {
      el.classList.remove('reader-search-match', 'active');
    });
  }
  searchMatches = [];
  searchMatchIndex = -1;
}

function clearReaderSearch() {
  clearTimeout(_readerSearchDebounce);
  clearReaderSearchHighlights();
  readerSearchOpen = false;
  const countEl = document.getElementById('rs-search-count');
  if (countEl) countEl.textContent = '';
}

function scrollToSearchMatch(idx) {
  if (!searchMatches.length) return;
  _suppressScrollJumpDetect();
  searchMatches.forEach((m, i) => m.classList.toggle('active', i === idx));
  searchMatches[idx].scrollIntoView({behavior: 'smooth', block: 'center'});
  const countEl = document.getElementById('rs-search-count');
  if (countEl) countEl.textContent = `${idx + 1} / ${searchMatches.length}`;
}

function readerSearchNext() {
  if (!searchMatches.length) return;
  searchMatchIndex = (searchMatchIndex + 1) % searchMatches.length;
  scrollToSearchMatch(searchMatchIndex);
}

function readerSearchPrev() {
  if (!searchMatches.length) return;
  searchMatchIndex = (searchMatchIndex - 1 + searchMatches.length) % searchMatches.length;
  scrollToSearchMatch(searchMatchIndex);
}

// ---------------------------------------------------------------------------
// Highlights
// ---------------------------------------------------------------------------

async function loadHighlights(bookId) {
  try {
    const res = await fetch(`/books/${bookId}/highlights/`);
    const {ct, iv} = await res.json();
    if (ct) {
      _saveAnnotationsCache(bookId, 'highlights', ct, iv); // persist for offline
      const key = await getOrCreateEncKey();
      const plain = await decryptBytes(key, iv, ct);
      currentHighlights = JSON.parse(new TextDecoder().decode(plain));
    } else {
      currentHighlights = [];
    }
    applyHighlightsToContent();
  } catch (e) {
    // offline fallback
    const cached = await _loadAnnotationsCache(bookId, 'highlights');
    if (cached?.ct) {
      try {
        const key = await getOrCreateEncKey();
        const plain = await decryptBytes(key, cached.iv, cached.ct);
        currentHighlights = JSON.parse(new TextDecoder().decode(plain));
      } catch { currentHighlights = []; }
    } else {
      currentHighlights = [];
    }
    applyHighlightsToContent();
  }
}

async function saveHighlights() {
  if (!currentBookId) return;
  try {
    const key = await getOrCreateEncKey();
    const plain = new TextEncoder().encode(JSON.stringify(currentHighlights));
    const {iv, ciphertext} = await encryptBytes(key, plain);
    const body = JSON.stringify({ct: ciphertext, iv});
    const url = `/books/${currentBookId}/highlights/`;
    _lastHighlightBeacon = {url, body};
    _saveAnnotationsCache(currentBookId, 'highlights', ciphertext, iv); // keep local cache current
    await fetch(url, {
      method: 'POST',
      headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
      body,
    });
    highlightsDirty = false;
  } catch (e) {
    _markPendingSync(currentBookId, 'highlights');
  }
}

let _highlightSaveDebounce = null;
function debounceSaveHighlights() {
  clearTimeout(_highlightSaveDebounce);
  _highlightSaveDebounce = setTimeout(saveHighlights, 2000);
}

function applyHighlightsToContent() {
  const contentEl = $('reader-content');
  if (!contentEl || currentPdfDoc) return;
  for (const h of currentHighlights) {
    try { renderHighlight(h); } catch (e) {}
  }
  _repositionMarginMarkers();
}

// Resolves a highlight/note's stored anchor back to a live DOM Range. Shared by
// rendering, margin-marker positioning and export ordering — all three need the
// same "where in the current DOM is this annotation" answer.
function resolveAnchorRange(h) {
  const contentEl = $('reader-content');
  if (!contentEl || !h.anchor) return null;

  let range = null;
  try {
    const {blocks} = _epubBlocks(contentEl);
    const startBlock = blocks[h.anchor.startBlockIndex];
    const endBlock = blocks[h.anchor.endBlockIndex] ?? startBlock;
    if (startBlock && endBlock) {
      const start = _nodeAtCharOffset(startBlock, h.anchor.startChar);
      const end = _nodeAtCharOffset(endBlock, h.anchor.endChar);
      if (start && end) {
        range = document.createRange();
        range.setStart(start.node, start.offset);
        range.setEnd(end.node, end.offset);
      }
    }
  } catch (e) {}

  // Fallback: quote substring search within the chapter
  if (!range && h.anchor.quote) {
    const chapterEl = contentEl.querySelector(`[data-epub-src="${CSS.escape(h.anchor.chapterSrc || '')}"]`)
      || contentEl;
    const walker = document.createTreeWalker(chapterEl, NodeFilter.SHOW_TEXT);
    let node;
    while ((node = walker.nextNode())) {
      const idx = node.textContent.indexOf(h.anchor.quote);
      if (idx !== -1) {
        range = document.createRange();
        range.setStart(node, idx);
        range.setEnd(node, idx + h.anchor.quote.length);
        break;
      }
    }
  }

  return range;
}

function renderHighlight(h) {
  // Freeform notes carry no in-text mark — their anchor exists purely to
  // position the note card in the margin (resolveAnchorRange handles that
  // directly from the stored xpath, no DOM wrapper needed).
  if (h.type === 'note') return;

  const range = resolveAnchorRange(h);
  if (!range) return;

  try {
    const mark = document.createElement('mark');
    mark.dataset.highlightId = h.id;
    mark.className = 'epub-highlight';
    mark.dataset.color = h.color || 'yellow';
    range.surroundContents(mark);
  } catch (e) {}
}

// Character-offset addressing within a block element (p, li, ...), rather
// than XPath-to-a-specific-text-node: XPath sibling indices shift whenever
// ANY highlight in the same block gets wrapped/unwrapped in a <mark> (that
// splits/merges text nodes), silently corrupting OTHER highlights' anchors
// in the same block. A block's overall textContent length/order is never
// touched by mark-wrapping, so a character offset into it stays valid no
// matter how many other highlights come and go around it.
function _charOffsetInBlock(block, node, nodeOffset) {
  const walker = document.createTreeWalker(block, NodeFilter.SHOW_TEXT);
  let count = 0, n;
  while ((n = walker.nextNode())) {
    if (n === node) return count + nodeOffset;
    count += n.textContent.length;
  }
  return count;
}

function _nodeAtCharOffset(block, targetOffset) {
  const walker = document.createTreeWalker(block, NodeFilter.SHOW_TEXT);
  let count = 0, lastNode = null, n;
  while ((n = walker.nextNode())) {
    lastNode = n;
    const len = n.textContent.length;
    if (targetOffset <= count + len) {
      return {node: n, offset: Math.max(0, targetOffset - count)};
    }
    count += len;
  }
  return lastNode ? {node: lastNode, offset: lastNode.textContent.length} : null;
}

function _blockAncestor(node) {
  const el = node.nodeType === Node.ELEMENT_NODE ? node : node.parentElement;
  return el ? el.closest(EPUB_BLOCK_SELECTOR) : null;
}

function buildEpubAnchor(range) {
  const contentEl = $('reader-content');
  const chapterEl = range.commonAncestorContainer.nodeType === Node.ELEMENT_NODE
    ? range.commonAncestorContainer.closest('[data-epub-src]')
    : range.commonAncestorContainer.parentElement?.closest('[data-epub-src]');

  const startBlock = _blockAncestor(range.startContainer);
  const endBlock = _blockAncestor(range.endContainer) || startBlock;
  const blocks = Array.from(contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR));

  return {
    type: 'epub',
    chapterSrc: chapterEl?.getAttribute('data-epub-src') || '',
    startBlockIndex: startBlock ? blocks.indexOf(startBlock) : -1,
    startChar: startBlock ? _charOffsetInBlock(startBlock, range.startContainer, range.startOffset) : 0,
    endBlockIndex: endBlock ? blocks.indexOf(endBlock) : -1,
    endChar: endBlock ? _charOffsetInBlock(endBlock, range.endContainer, range.endOffset) : 0,
    quote: range.toString().slice(0, 200),
  };
}

// Marker mode — armed via the pen button in the reader header. Text selection
// only opens the highlight popover while this is active, so normal selection
// (e.g. to copy text) isn't hijacked, and the feature has a discoverable
// on/off switch instead of being an invisible "just select text" gesture.
let markerModeActive = false;

function toggleMarkerMode() {
  markerModeActive = !markerModeActive;
  document.querySelectorAll('.marker-mode-btn').forEach(b => b.classList.toggle('active', markerModeActive));
}

// Note editing/creation happens in the margin column on desktop, but a note
// bottom sheet (see showNoteBottomSheet) on narrow viewports — typing into a
// 150px margin strip on a phone keyboard is unpleasant, and opening that
// column at all is exactly the friction we're trying to remove for mobile
// note-taking. Reviewing existing notes in depth is expected to stay a
// desktop activity; this only affects where the editor for a note appears.
function _isMobileReader() {
  return window.innerWidth <= 600;
}

function handleReaderSelection(e) {
  // Clicking an existing highlight always shows its tooltip, regardless of marker mode
  const hlMark = e.target.closest('.epub-highlight');
  if (hlMark) {
    dismissHighlightPopover();
    const id = hlMark.dataset.highlightId;
    const h = currentHighlights.find(x => x.id === id);
    showHighlightTooltip(hlMark, h);
    return;
  }

  if (!markerModeActive) return;
  // Don't hijack taps on real interactive content (footnote refs, external
  // links) — but plenty of EPUBs wrap plain reading text in a bare, hrefless
  // <a id="..."> used only as an internal jump target (sanitizeEpubHtml
  // strips its href but the tag itself stays); those aren't actually
  // clickable and must not block note-taking, so check for a surviving
  // href/footnote-ref rather than just "is inside some <a>".
  if (e.target.closest('button, [data-footnote-ref], a[href]')) return;

  dismissHighlightPopover();
  const sel = window.getSelection();
  if (sel && !sel.isCollapsed && sel.rangeCount) {
    const range = sel.getRangeAt(0);
    const contentEl = $('reader-content');
    if (!contentEl || !contentEl.contains(range.commonAncestorContainer)) return;
    if (range.toString().trim().length === 0) return;
    showHighlightPopover(range);
    return;
  }

  // A plain tap with nothing selected — in marker mode this means "drop a
  // freeform note here" instead of doing nothing, so a note-only annotation
  // never depends on finding the margin's precise click target (especially
  // hard on a narrow phone screen — see createFreeformNote/_openNoteEditor).
  if (typeof e.clientX === 'number' && typeof e.clientY === 'number') {
    const range = _wordRangeAtPoint(e.clientX, e.clientY);
    if (range) createFreeformNote(range);
  }
}

function showHighlightPopover(range) {
  const rect = range.getBoundingClientRect();
  const popover = document.createElement('div');
  popover.id = 'highlight-popover';
  popover.className = 'highlight-popover';
  popover.innerHTML = `
    <button class="hl-color-btn" data-hl-color="yellow" style="background:#f1c40f" title="Gelb">A</button>
    <button class="hl-color-btn" data-hl-color="green"  style="background:#2ecc71" title="Grün">A</button>
    <button class="hl-color-btn" data-hl-color="blue"   style="background:#3498db" title="Blau">A</button>
    <button class="hl-color-btn" data-hl-color="red"    style="background:#e63946" title="Rot">A</button>
    <button class="hl-note-btn" title="Notiz hinzufügen">✎</button>
  `;
  popover.style.visibility = 'hidden'; // measure before showing, to avoid a flash at the wrong spot
  document.body.appendChild(popover);
  currentHighlightPopover = popover;

  // Clamp within the viewport — a selection near the top/edge of the page must
  // not produce an invisible, off-screen popover (flip below when there's no
  // room above; keep it horizontally on-screen).
  const pRect = popover.getBoundingClientRect();
  const minTop = window.scrollY + 8;
  const maxTop = window.scrollY + window.innerHeight - pRect.height - 8;
  let top = rect.top + window.scrollY - 44;
  if (top < minTop) top = rect.bottom + window.scrollY + 8; // no room above -> try below
  top = Math.max(minTop, Math.min(top, maxTop));
  let left = rect.left + window.scrollX + rect.width / 2 - pRect.width / 2;
  left = Math.max(window.scrollX + 8, Math.min(left, window.scrollX + window.innerWidth - pRect.width - 8));
  popover.style.top = top + 'px';
  popover.style.left = left + 'px';
  popover.style.visibility = '';

  // Store range info before selection is cleared
  const savedRange = range.cloneRange();

  popover.addEventListener('click', e => {
    const colorBtn = e.target.closest('.hl-color-btn');
    const noteBtn  = e.target.closest('.hl-note-btn');
    if (colorBtn) {
      createHighlight(colorBtn.dataset.hlColor, savedRange);
    } else if (noteBtn) {
      createHighlightWithNote(savedRange);
    }
  });
}

function showHighlightTooltip(markEl, h) {
  const rect = markEl.getBoundingClientRect();
  const popover = document.createElement('div');
  popover.id = 'highlight-popover';
  popover.className = 'highlight-popover';
  popover.style.flexDirection = 'column';
  popover.style.maxWidth = '220px';
  const noteText = h?.note ? escapeHtml(h.note) : '<span class="muted">Keine Notiz</span>';
  popover.innerHTML = `
    <div style="font-size:12px;padding-bottom:4px;">${noteText}</div>
    <div style="display:flex;gap:6px;">
      <button class="btn btn-sm" data-hl-edit-note="${escapeHtml(h?.id || '')}">Notiz bearbeiten</button>
      <button class="btn btn-sm btn-danger" data-hl-delete="${escapeHtml(h?.id || '')}">Löschen</button>
    </div>
  `;
  popover.style.visibility = 'hidden';
  document.body.appendChild(popover);
  currentHighlightPopover = popover;

  const pRect = popover.getBoundingClientRect();
  const minTop = window.scrollY + 8;
  const maxTop = window.scrollY + window.innerHeight - pRect.height - 8;
  let top = rect.bottom + window.scrollY + 4;
  if (top > maxTop) top = rect.top + window.scrollY - pRect.height - 4; // flip above if no room below
  top = Math.max(minTop, Math.min(top, maxTop));
  let left = rect.left + window.scrollX;
  left = Math.max(window.scrollX + 8, Math.min(left, window.scrollX + window.innerWidth - pRect.width - 8));
  popover.style.top = top + 'px';
  popover.style.left = left + 'px';
  popover.style.visibility = '';

  popover.addEventListener('click', ev => {
    const editBtn = ev.target.closest('[data-hl-edit-note]');
    const delBtn  = ev.target.closest('[data-hl-delete]');
    if (editBtn && h) {
      dismissHighlightPopover();
      _openNoteEditor(h);
    }
    if (delBtn && h) {
      dismissHighlightPopover();
      deleteHighlight(h.id);
    }
  });

  // Close on outside click
  setTimeout(() => {
    document.addEventListener('click', dismissHighlightPopover, {once: true});
  }, 0);
}

function createHighlight(color, range) {
  const anchor = buildEpubAnchor(range);
  const h = {
    id: crypto.randomUUID(),
    type: 'highlight',
    anchor,
    color,
    note: '',
    createdAt: new Date().toISOString(),
  };
  currentHighlights.push(h);
  highlightsDirty = true;
  window.getSelection()?.removeAllRanges();
  dismissHighlightPopover();
  renderHighlight(h);
  _repositionMarginMarkers();
  debounceSaveHighlights();
}

function createHighlightWithNote(range) {
  const anchor = buildEpubAnchor(range);
  const h = {
    id: crypto.randomUUID(),
    type: 'highlight',
    anchor,
    color: 'yellow',
    note: '',
    createdAt: new Date().toISOString(),
  };
  currentHighlights.push(h);
  highlightsDirty = true;
  window.getSelection()?.removeAllRanges();
  dismissHighlightPopover();
  renderHighlight(h);
  _repositionMarginMarkers();
  _openNoteEditor(h);
}

// Every "add/edit a note" entry point routes here — notes are always edited
// right where they conceptually live (the margin), never in the separate
// right-hand sidebar, EXCEPT on narrow viewports, where the margin itself is
// too cramped to type into and a full-width bottom sheet takes over instead.
// `pending` is only set for a not-yet-created freeform note (see
// createFreeformNote); h is null in that case until the user actually saves
// text, so an empty tap doesn't leave a permanent ghost entry behind.
function _openNoteEditor(h, pending) {
  if (_isMobileReader()) {
    showNoteBottomSheet(h, pending);
  } else {
    if (!readerAnnotationsMarginOpen) toggleAnnotationsMargin();
    editNoteInlineInMargin(h, pending);
  }
}

function deleteHighlight(id) {
  currentHighlights = currentHighlights.filter(h => h.id !== id);
  highlightsDirty = true;
  // Re-apply all highlights after removing the deleted one
  const contentEl = $('reader-content');
  if (contentEl && !currentPdfDoc) {
    // Snapshot restore not available mid-session, so remove the mark manually
    const mark = contentEl.querySelector(`mark[data-highlight-id="${id}"]`);
    if (mark) {
      const parent = mark.parentNode;
      while (mark.firstChild) parent.insertBefore(mark.firstChild, mark);
      parent.removeChild(mark);
    }
  }
  _repositionMarginMarkers();
  debounceSaveHighlights();
}

function dismissHighlightPopover() {
  if (currentHighlightPopover) {
    currentHighlightPopover.remove();
    currentHighlightPopover = null;
  }
}

// ---------------------------------------------------------------------------
// Margin panel — a "page margin" strip left of the reader content. Shows small
// markers next to the on-screen highlights/notes, and lets you click empty
// space to anchor a freeform note at that line's height (EPUB only).
// ---------------------------------------------------------------------------
let readerAnnotationsMarginOpen = false;

function toggleAnnotationsMargin() {
  const el = $('reader-margin');
  const markersEl = $('reader-margin-markers');
  if (!el || !markersEl || currentPdfDoc) return;
  readerAnnotationsMarginOpen = !readerAnnotationsMarginOpen;
  el.classList.toggle('open', readerAnnotationsMarginOpen);
  if (readerAnnotationsMarginOpen) {
    // Reposition once now (pre-transition) and once more after the width
    // transition settles, since content reflow can shift line heights.
    _repositionMarginMarkers();
    el.addEventListener('transitionend', _repositionMarginMarkers, {once: true});
  } else {
    markersEl.innerHTML = '';
  }
}

// Renders each highlight/note at its text position in the margin. Entries
// with note text become a readable "post-it" card (the whole point of the
// margin — you can read notes there, not just see that one exists); a plain
// highlight with no note is just a small color dot. Cards are stacked
// top-to-bottom so overlapping anchors don't overlap visually.
// Where each highlight sits in the book's scroll coordinates. Finding a range
// and measuring it is the expensive part, and scrolling doesn't change it:
// kept until the layout does (content, width, height) or the anchor changes.
let _marginPosCache = null;
const _marginCardHeights = new Map(); // `${stripWidth}|${note}` (or 'dot') → px

function _marginDocY(h, contentEl) {
  const {blocks} = _epubBlocks(contentEl);
  const key = `${contentEl.clientWidth}x${contentEl.scrollHeight}`;
  if (!_marginPosCache || _marginPosCache.blocks !== blocks || _marginPosCache.key !== key) {
    _marginPosCache = {blocks, key, byId: new Map()};
  }
  const hit = _marginPosCache.byId.get(h.id);
  if (hit && hit.anchor === h.anchor) return hit.y;
  let y = null;
  try {
    const range = resolveAnchorRange(h);
    const rect = range && range.getBoundingClientRect();
    if (rect && (rect.width || rect.height)) {
      y = rect.top + rect.height / 2 - contentEl.getBoundingClientRect().top + contentEl.scrollTop;
    }
  } catch (e) {}
  _marginPosCache.byId.set(h.id, {anchor: h.anchor, y});
  return y;
}

// The cards live on one layer in the book's coordinates, built when the
// highlights or the layout change; scrolling only moves the layer (a transform,
// no layout). Rebuilding and measuring the cards on every scroll frame made a
// long book with the margin open stutter.
let _marginLayerKey = null;

function _repositionMarginMarkers() {
  const markersEl = $('reader-margin-markers');
  if (!markersEl) return;
  if (!readerAnnotationsMarginOpen || currentPdfDoc) {
    markersEl.innerHTML = '';
    _marginLayerKey = null;
    return;
  }
  if (markersEl.querySelector('.margin-note-editor')) return; // don't blow away an active inline edit
  const contentEl = $('reader-content');
  if (!contentEl) return;

  const {blocks} = _epubBlocks(contentEl);
  const areaRect = markersEl.getBoundingClientRect();
  const width = Math.round(areaRect.width);
  const key = `${width}x${contentEl.clientWidth}x${contentEl.scrollHeight}|` +
    currentHighlights.map(h => `${h.id}:${h.color || ''}:${h.note || ''}`).join('|');
  let layer = markersEl.querySelector('.margin-layer');
  if (!layer || key !== _marginLayerKey || !_marginPosCache || _marginPosCache.blocks !== blocks) {
    markersEl.innerHTML = '';
    layer = document.createElement('div');
    layer.className = 'margin-layer';
    markersEl.appendChild(layer);
    _renderMarginLayer(layer, contentEl, width);
    _marginLayerKey = key;
  }
  // Book coordinates → this strip's.
  const shift = contentEl.getBoundingClientRect().top - contentEl.scrollTop - areaRect.top;
  layer.style.transform = `translateY(${Math.round(shift)}px)`;
}

// Renders each highlight/note at its text position, in book coordinates.
// Entries with note text become a readable "post-it" card (the whole point of
// the margin — you can read notes there, not just see that one exists); a
// plain highlight with no note is a small colour dot. Cards are stacked top to
// bottom so overlapping anchors don't overlap visually.
function _renderMarginLayer(layer, contentEl, width) {
  const entries = [];
  for (const h of currentHighlights) {
    const y = _marginDocY(h, contentEl);
    if (y !== null) entries.push({h, y});
  }
  entries.sort((a, b) => a.y - b.y);

  // All cards first, then their heights in one go (each measured right after
  // adding it, the browser laid out the whole book once per card). Heights are
  // kept per note text and strip width.
  const cards = entries.map(({h, y}) => {
    const hasText = !!h.note;
    const el = document.createElement('div');
    el.className = 'margin-note ' + (hasText ? 'margin-note-text' : 'margin-note-dot');
    el.dataset.highlightId = h.id;
    if (h.type === 'note') {
      if (hasText) el.classList.add('margin-note-freeform');
    } else {
      el.dataset.color = h.color || 'yellow';
    }
    if (hasText) el.textContent = h.note;
    layer.appendChild(el);
    return {el, y, hasText, key: hasText ? `${width}|${h.note}` : 'dot'};
  });
  if (_marginCardHeights.size > 500) _marginCardHeights.clear();
  const unmeasured = cards.filter(c => !_marginCardHeights.has(c.key));
  for (const c of unmeasured) _marginCardHeights.set(c.key, c.el.getBoundingClientRect().height || (c.hasText ? 20 : 12));

  let nextTop = -Infinity;
  const GAP = 4;
  for (const {el, y, hasText, key} of cards) {
    const top = Math.max(hasText ? y - 8 : y - 6, nextTop);
    el.style.top = top + 'px';
    nextTop = top + _marginCardHeights.get(key) + GAP;
  }
}

function handleMarginClick(e) {
  const markerBtn = e.target.closest('.margin-note');
  if (markerBtn) {
    const h = currentHighlights.find(x => x.id === markerBtn.dataset.highlightId);
    if (h) _openNoteEditor(h);
    return;
  }

  // Empty space in the markers area → place a new freeform note anchored to
  // the first word of whatever line sits at this click height.
  if (!readerAnnotationsMarginOpen || currentPdfDoc) return;
  const markersEl = $('reader-margin-markers');
  if (!markersEl || !markersEl.contains(e.target)) return;
  // If an editor is already open, this click just blurs/commits it (see its
  // own blur handler) — it shouldn't also create a second, unrelated note.
  if (markersEl.querySelector('.margin-note-editor')) return;
  const contentEl = $('reader-content');
  if (!contentEl) return;

  const x = contentEl.getBoundingClientRect().left + 4;
  const range = _wordRangeAtPoint(x, e.clientY);
  if (range) createFreeformNote(range);
}

// Finds the word starting at (or just after) the given viewport point, by
// probing near the left edge of the reader content at that height — since
// text is left-aligned, that lands at (or very near) the start of the line.
function _wordRangeAtPoint(x, y) {
  let caret = null;
  if (document.caretRangeFromPoint) {
    caret = document.caretRangeFromPoint(x, y);
  } else if (document.caretPositionFromPoint) {
    const pos = document.caretPositionFromPoint(x, y);
    if (pos) {
      caret = document.createRange();
      caret.setStart(pos.offsetNode, pos.offset);
    }
  }
  if (!caret) return null;

  const contentEl = $('reader-content');
  if (!contentEl || !contentEl.contains(caret.startContainer)) return null;

  let node = caret.startContainer;
  let offset = caret.startOffset;
  if (node.nodeType !== Node.TEXT_NODE) {
    const walker = document.createTreeWalker(contentEl, NodeFilter.SHOW_TEXT);
    walker.currentNode = node;
    node = walker.nextNode();
    if (!node) return null;
    offset = 0;
  }

  const text = node.textContent;
  let start = offset;
  while (start < text.length && /\s/.test(text[start])) start++;
  if (start >= text.length) return null;
  let wordStart = start;
  while (wordStart > 0 && !/\s/.test(text[wordStart - 1])) wordStart--;
  let wordEnd = start;
  while (wordEnd < text.length && !/\s/.test(text[wordEnd])) wordEnd++;
  if (wordEnd <= wordStart) return null;

  const range = document.createRange();
  range.setStart(node, wordStart);
  range.setEnd(node, wordEnd);
  return range;
}

function createFreeformNote(range) {
  const anchor = buildEpubAnchor(range);
  // Where the note's card/dot would sit in the margin, computed from the live
  // range right now (before it goes stale) — used to position the editor,
  // whether or not the margin is actually open.
  let top = 0;
  const markersEl = $('reader-margin-markers');
  if (markersEl) {
    const areaRect = markersEl.getBoundingClientRect();
    const rangeRect = range.getBoundingClientRect();
    top = Math.max(0, rangeRect.top + rangeRect.height / 2 - areaRect.top - 8);
  }
  // The highlight object itself isn't created yet — see _openNoteEditor's
  // `pending` param — so a tap that's immediately cancelled or left empty
  // never leaves a ghost entry in currentHighlights.
  _openNoteEditor(null, {anchor, top});
}

// Commits an edit for both note-editor UIs (inline margin + mobile bottom
// sheet): updates an existing note in place, or — only if there's actual
// text — creates and persists a not-yet-existing freeform note. An empty
// tap/cancel on a pending note must never leave a permanent ghost entry.
function _commitNoteEdit(h, pending, text) {
  if (h) {
    if (h.note !== text) {
      h.note = text;
      highlightsDirty = true;
      debounceSaveHighlights();
    }
    return h;
  }
  if (!text) return null;
  const newH = {
    id: crypto.randomUUID(), type: 'note', anchor: pending.anchor,
    color: null, note: text, createdAt: new Date().toISOString(),
  };
  currentHighlights.push(newH);
  highlightsDirty = true;
  debounceSaveHighlights();
  return newH;
}

// Edit a note's text right where it lives in the margin, instead of jumping
// to the separate right-hand sidebar — the whole point of setting a note in
// the margin is that you shouldn't have to look away from it to write it.
// `h` is null for a not-yet-created freeform note (see createFreeformNote);
// `pending` then carries its anchor + intended margin position instead.
function editNoteInlineInMargin(h, pending) {
  const markersEl = $('reader-margin-markers');
  if (!markersEl) return;
  markersEl.querySelector('.margin-note-editor')?.remove();

  let top = pending?.top || 0;
  if (h) {
    const existingCard = markersEl.querySelector(`[data-highlight-id="${h.id}"]`);
    // The card sits on the moving layer: where it shows in the strip right now.
    top = existingCard ? existingCard.getBoundingClientRect().top - markersEl.getBoundingClientRect().top : 0;
    if (existingCard) existingCard.style.display = 'none';
  }

  const editor = document.createElement('div');
  editor.className = 'margin-note-editor';
  editor.style.top = top + 'px';
  editor.innerHTML = '<textarea class="margin-note-textarea"></textarea>';
  markersEl.appendChild(editor);
  const textarea = editor.querySelector('textarea');
  textarea.value = h?.note || '';

  function commit() {
    _commitNoteEdit(h, pending, textarea.value.trim());
    editor.remove();
    _marginLayerKey = null; // the edited card was hidden: draw the layer anew
    _repositionMarginMarkers();
  }

  textarea.addEventListener('blur', commit);
  textarea.addEventListener('keydown', e => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      e.stopPropagation();
      textarea.blur(); // triggers commit()
    } else if (e.key === 'Escape') {
      // Stop this from bubbling to the document-level Escape handler, which
      // would otherwise close the whole reader (it doesn't know we just want
      // to cancel this one edit) — see the global keydown listener.
      e.stopPropagation();
      textarea.removeEventListener('blur', commit); // discard, don't save
      editor.remove();
      _marginLayerKey = null;
      _repositionMarginMarkers();
    }
  });

  textarea.focus();
  textarea.select();
}

// Mobile alternative to editNoteInlineInMargin — a full-width sheet instead
// of squeezing a textarea into the 150px margin column (see _openNoteEditor).
let currentNoteBottomSheet = null;

function dismissNoteBottomSheet() {
  currentNoteBottomSheet?.remove();
  currentNoteBottomSheet = null;
}

function showNoteBottomSheet(h, pending) {
  dismissNoteBottomSheet();

  const sheet = document.createElement('div');
  sheet.className = 'note-bottom-sheet';
  sheet.innerHTML = `
    <div class="note-bottom-sheet-backdrop"></div>
    <div class="note-bottom-sheet-panel">
      <textarea class="note-bottom-sheet-textarea" placeholder="Notiz…"></textarea>
      <div class="note-bottom-sheet-actions">
        <button class="btn btn-sm" data-nbs-cancel>Abbrechen</button>
        <button class="btn btn-sm btn-primary" data-nbs-save>Speichern</button>
      </div>
    </div>
  `;
  document.body.appendChild(sheet);
  currentNoteBottomSheet = sheet;

  const textarea = sheet.querySelector('.note-bottom-sheet-textarea');
  textarea.value = h?.note || '';

  function commit() {
    _commitNoteEdit(h, pending, textarea.value.trim());
    dismissNoteBottomSheet();
    if (readerAnnotationsMarginOpen) _repositionMarginMarkers();
  }
  function cancel() { dismissNoteBottomSheet(); }

  sheet.querySelector('[data-nbs-save]').addEventListener('click', commit);
  sheet.querySelector('[data-nbs-cancel]').addEventListener('click', cancel);
  sheet.querySelector('.note-bottom-sheet-backdrop').addEventListener('click', cancel);
  textarea.addEventListener('keydown', e => {
    if (e.key === 'Escape') { e.stopPropagation(); cancel(); }
  });

  requestAnimationFrame(() => {
    sheet.classList.add('open');
    textarea.focus();
  });
}

// Same plain-text export as exportAnnotations(), but callable straight from the
// book list (no open reader, so no live DOM/TOC to resolve percent position or
// chapter titles against — falls back to the raw chapterSrc path and orders by
// the anchor's block index, which is already a global reading-order index).
async function downloadBookAnnotationsFromList(bookId, btnEl) {
  if (btnEl) btnEl.disabled = true;
  try {
    const res = await fetch(`/books/${bookId}/highlights/`);
    const {ct, iv} = await res.json();
    if (!ct) { await customAlert('In diesem Buch gibt es noch keine Markierungen oder Notizen.'); return; }
    const key = await getOrCreateEncKey();
    const plain = await decryptBytes(key, iv, ct);
    const highlights = JSON.parse(new TextDecoder().decode(plain));
    if (!highlights.length) { await customAlert('In diesem Buch gibt es noch keine Markierungen oder Notizen.'); return; }

    highlights.sort((a, b) => {
      const ab = a.anchor?.startBlockIndex ?? 0, bb = b.anchor?.startBlockIndex ?? 0;
      if (ab !== bb) return ab - bb;
      return (a.anchor?.startChar ?? 0) - (b.anchor?.startChar ?? 0);
    });

    const bookTitle = bookMetaCache[bookId]?.title || `Buch #${bookId}`;
    const lines = [`${bookTitle} — Markierungen & Notizen`, `Exportiert: ${new Date().toISOString().slice(0, 10)}`, ''];

    let lastChapter = null;
    for (const h of highlights) {
      const chapterTitle = h.anchor?.chapterSrc || '';
      if (chapterTitle !== lastChapter) {
        lines.push(`── ${chapterTitle || 'Abschnitt ohne Titel'} ──`);
        lastChapter = chapterTitle;
      }
      if (h.type === 'note') {
        lines.push(`[Notiz] bei: „${(h.anchor?.quote || '').trim()}“`);
        if (h.note) lines.push(`    ${h.note}`);
      } else {
        lines.push(`[Markierung · ${_hlColorName(h.color || 'yellow')}] „${(h.anchor?.quote || '').trim()}“`);
        if (h.note) lines.push(`    Notiz: ${h.note}`);
      }
      lines.push('');
    }

    const blob = new Blob([lines.join('\n')], {type: 'text/plain;charset=utf-8'});
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `${bookTitle.replace(/[^\w\-]+/g, '_')}-notizen.txt`;
    document.body.appendChild(a);
    a.click();
    a.remove();
    URL.revokeObjectURL(url);
  } catch (e) {
    await customAlert('Export fehlgeschlagen: ' + e.message);
  } finally {
    if (btnEl) btnEl.disabled = false;
  }
}

// ---------------------------------------------------------------------------
// Export annotations — walks all highlights/notes of the current book in
// reading order and offers them as a downloadable plain-text file.
// ---------------------------------------------------------------------------
function _tocTitleForChapterSrc(chapterSrc) {
  if (!chapterSrc) return '';
  const entry = currentBookToc.find(t => (t.href || '').split('#')[0] === chapterSrc);
  return entry ? entry.label : '';
}

// Rough "how far through the book" position for a resolved range — there's no
// real page concept for reflowable EPUB text, so this is a coordinate of last
// resort: percent of total scrollable content height, good enough to roughly
// relocate a highlight/note later.
function _percentFromRange(range) {
  const contentEl = $('reader-content');
  if (!contentEl || !range) return null;
  // Share of the text before the range, like the reading progress.
  const block = _blockAncestor(range.startContainer);
  if (block && contentEl.contains(block)) {
    const blocks = Array.from(contentEl.querySelectorAll(EPUB_BLOCK_SELECTOR));
    const i = blocks.indexOf(block);
    if (i >= 0) {
      const idx = _bookCharIndex(contentEl);
      const at = idx.starts[i] + _charOffsetInBlock(block, range.startContainer, range.startOffset);
      return Math.max(0, Math.min(100, (at / idx.total) * 100));
    }
  }
  if (!contentEl.scrollHeight) return null;
  const contentRect = contentEl.getBoundingClientRect();
  const rangeRect = range.getBoundingClientRect();
  if (!rangeRect.width && !rangeRect.height) return null;
  const offsetWithinScroll = (rangeRect.top - contentRect.top) + contentEl.scrollTop;
  return Math.max(0, Math.min(100, (offsetWithinScroll / contentEl.scrollHeight) * 100));
}

function _sortedAnnotations() {
  const resolved = currentHighlights.map(h => {
    let range;
    try { range = resolveAnchorRange(h); } catch (e) { range = null; }
    return {h, range};
  });
  resolved.sort((a, b) => {
    if (!a.range || !b.range) return 0;
    return a.range.compareBoundaryPoints(Range.START_TO_START, b.range);
  });
  return resolved;
}

// Highlight colours as the export and the list name them.
function _hlColorName(color) {
  return ({yellow: 'gelb', green: 'grün', blue: 'blau', red: 'rot'})[color] || color;
}

function exportAnnotations() {
  if (!currentHighlights.length) {
    customAlert('In diesem Buch gibt es noch keine Markierungen oder Notizen.');
    return;
  }

  const resolved = _sortedAnnotations();

  const titleEl = $('reader-title');
  const bookTitle = (titleEl?.textContent || 'Buch').split(' — ')[0];
  const lines = [`${bookTitle} — Markierungen & Notizen`, `Exportiert: ${new Date().toISOString().slice(0, 10)}`, ''];

  let lastChapter = null;
  for (const {h, range} of resolved) {
    const chapterTitle = _tocTitleForChapterSrc(h.anchor?.chapterSrc) || h.anchor?.chapterSrc || '';
    if (chapterTitle !== lastChapter) {
      lines.push(`── ${chapterTitle || 'Abschnitt ohne Titel'} ──`);
      lastChapter = chapterTitle;
    }
    const pct = _percentFromRange(range);
    const coord = pct !== null ? ` (≈${_formatBookPercent(pct / 100)}% im Buch)` : '';
    if (h.type === 'note') {
      lines.push(`[Notiz]${coord} bei: „${(h.anchor?.quote || '').trim()}“`);
      if (h.note) lines.push(`    ${h.note}`);
    } else {
      lines.push(`[Markierung · ${_hlColorName(h.color || 'yellow')}]${coord} „${(h.anchor?.quote || '').trim()}“`);
      if (h.note) lines.push(`    Notiz: ${h.note}`);
    }
    lines.push('');
  }

  const blob = new Blob([lines.join('\n')], {type: 'text/plain;charset=utf-8'});
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = `${bookTitle.replace(/[^\w\-]+/g, '_')}-notizen.txt`;
  document.body.appendChild(a);
  a.click();
  a.remove();
  URL.revokeObjectURL(url);
}

// List of every highlight/note in the book, in reading order, each jumpable —
// the same pattern as the bookmarks sidebar, but for annotations. Unlike the
// margin panel (which only shows what's currently on-screen), this is a full
// overview, useful once a book has annotations scattered throughout.
function openAnnotationsSidebar() {
  if (!currentHighlights.length) {
    openSidebar('Markierungen & Notizen', '<p class="muted">Noch keine Markierungen oder Notizen.</p>');
    return;
  }

  const resolved = _sortedAnnotations();
  let html = '<ul style="list-style:none;padding:0;">';
  for (const {h, range} of resolved) {
    const pct = _percentFromRange(range);
    const pctLabel = pct !== null ? `≈${_formatBookPercent(pct / 100)}%` : '';
    const kind = h.type === 'note' ? 'Notiz' : `Markierung${h.color ? ' · ' + _hlColorName(h.color) : ''}`;
    const preview = h.note || h.anchor?.quote || '(kein Text)';
    html += `<li class="bookmark-entry">
      <button class="btn-link" data-jump-annotation="${escapeHtml(h.id)}" style="flex:1;text-align:left;">
        <span class="muted" style="font-size:11px;">${escapeHtml(kind)} ${pctLabel}</span><br>
        ${escapeHtml(preview.slice(0, 80))}
      </button>
      <button class="btn-icon" data-delete-annotation="${escapeHtml(h.id)}" title="Löschen">✕</button>
    </li>`;
  }
  html += '</ul>';
  openSidebar('Markierungen & Notizen', html);

  const body = $('sidebar-body');
  body.addEventListener('click', function _annClick(e) {
    const jumpBtn = e.target.closest('[data-jump-annotation]');
    const delBtn  = e.target.closest('[data-delete-annotation]');
    if (jumpBtn) {
      body.removeEventListener('click', _annClick);
      jumpToAnnotation(jumpBtn.dataset.jumpAnnotation);
    }
    if (delBtn) {
      deleteHighlight(delBtn.dataset.deleteAnnotation);
      openAnnotationsSidebar(); // re-render
    }
  });
}

function jumpToAnnotation(id) {
  const h = currentHighlights.find(x => x.id === id);
  if (!h) return;
  closeSidebar();
  _suppressScrollJumpDetect();
  setTimeout(() => {
    const contentEl = $('reader-content');
    if (!contentEl) return;
    let range;
    try { range = resolveAnchorRange(h); } catch (e) { range = null; }
    if (range) {
      const top = range.getBoundingClientRect().top - contentEl.getBoundingClientRect().top;
      contentEl.scrollBy({top: top - 16, behavior: 'smooth'});
    }
  }, 50);
}

// ---------------------------------------------------------------------------
// Footnote popover
// ---------------------------------------------------------------------------

let currentFootnotePopover = null;
let _footnotePopoverTimer = null;

function showFootnotePopover(link) {
  dismissFootnotePopover();
  const targetEl = document.getElementById(link.dataset.footnoteRef);
  if (!targetEl) return;
  // The note's paragraph, also when the id sits on an inline element in it
  // (<p><span><a id="F400" …>143</a></span> Note…</p>).
  const inline = /^(A|SPAN|SUP|SUB|B|I|EM|STRONG|SMALL)$/.test(targetEl.tagName);
  const container = targetEl.closest('.footnote') ||
    (inline && targetEl.closest('p, li, dd, blockquote')) || targetEl.parentElement;
  if (!container) return;

  const clone = container.cloneNode(true);
  clone.querySelector('sup')?.remove();
  clone.querySelectorAll('.epub-pagenum').forEach(e => e.remove());
  // The note's own number at its start, a link back to the text ("1 Note…").
  const first = Array.from(clone.querySelectorAll('a')).find(a => a.textContent.trim());
  const num = first ? first.textContent.trim() : '';
  if (/^[\[(]?\d{1,4}[\])]?\.?$/.test(num) && clone.textContent.trim().startsWith(num)) first.remove();
  // Only the number: the note (a poem, a long quote) runs on in the next
  // paragraphs, up to the next note's anchor.
  if (!clone.textContent.trim()) {
    let len = 0;
    for (let next = container.nextElementSibling; next && len < 6000; next = next.nextElementSibling) {
      if (/^H[1-6]$/.test(next.tagName) || next.querySelector('[id]')) break;
      if (!next.textContent.trim()) continue;
      clone.appendChild(next.cloneNode(true));
      len += next.textContent.length;
    }
  }

  const popover = document.createElement('div');
  popover.className = 'footnote-popover';
  const _overlay = document.getElementById('reader-overlay');
  ['reader-theme-sepia', 'reader-theme-bright'].forEach(cls => {
    if (_overlay?.classList.contains(cls)) popover.classList.add(cls);
  });
  popover.innerHTML = clone.innerHTML;

  const closeBtn = document.createElement('button');
  closeBtn.className = 'footnote-popover-close';
  closeBtn.textContent = '✕';
  closeBtn.addEventListener('click', dismissFootnotePopover);
  popover.appendChild(closeBtn);

  const rect = link.getBoundingClientRect();
  popover.style.top  = (rect.bottom + 8) + 'px';
  popover.style.left = Math.max(8, rect.left - 8) + 'px';

  popover.addEventListener('mouseenter', () => clearTimeout(_footnotePopoverTimer));
  popover.addEventListener('mouseleave', () => {
    _footnotePopoverTimer = setTimeout(dismissFootnotePopover, 250);
  });

  document.body.appendChild(popover);
  currentFootnotePopover = popover;
  currentFootnotePopover._refLink = link;

  const pr = popover.getBoundingClientRect();
  if (pr.right  > window.innerWidth  - 8) popover.style.left = (window.innerWidth  - pr.width  - 8) + 'px';
  if (pr.bottom > window.innerHeight - 8) popover.style.top  = (rect.top - pr.height - 8) + 'px';
}

function dismissFootnotePopover() {
  clearTimeout(_footnotePopoverTimer);
  currentFootnotePopover?.remove();
  currentFootnotePopover = null;
}

// ---------------------------------------------------------------------------
// Radio sidebar (compact player)
// ---------------------------------------------------------------------------

function openRadioSidebar() {
  const stationName = currentStation ? escapeHtml(currentStation.name) : '— kein Sender —';
  const track = currentTrack ? escapeHtml(currentTrack) : '';
  const vol = document.getElementById('volume')?.value ?? 204;

  const rows = [...document.querySelectorAll('#saved-tbody tr[data-id]')];
  const stationsHtml = rows.length
    ? rows.map(r => `<li><button class="btn btn-sm rsb-play-btn" data-url="${escapeHtml(r.dataset.url || '')}" data-name="${escapeHtml(r.dataset.name || '')}">${escapeHtml(r.dataset.name || '')}</button></li>`).join('')
    : `<li class="muted">Keine gespeicherten Sender.</li>`;

  const html = `
    <div class="rsb-nowplaying">
      <div class="rsb-station-name">${stationName}</div>
      ${track ? `<div class="rsb-track muted">${track}</div>` : ''}
    </div>
    <div class="rsb-controls">
      <button class="btn ${isPlaying ? 'playing' : ''}" id="rsb-playstop">${isPlaying ? '⏹ Stopp' : '▶ Abspielen'}</button>
      <label class="rsb-vol">Lautst. <input type="range" id="rsb-volume" min="0" max="255" value="${vol}"></label>
    </div>
    <ul class="rsb-station-list">${stationsHtml}</ul>
  `;

  openSidebar('Radio', html);

  const body = $('sidebar-body');
  body.querySelector('#rsb-playstop').addEventListener('click', togglePlayStop);
  body.querySelector('#rsb-volume').addEventListener('input', function () {
    const v = this.value;
    const mainSlider = document.getElementById('volume');
    const mainNum = document.getElementById('volume-num');
    if (mainSlider) mainSlider.value = v;
    if (mainNum) mainNum.value = v;
    audio.volume = v / 255;
  });
  body.querySelectorAll('.rsb-play-btn').forEach(btn => {
    btn.addEventListener('click', () => playStation(btn.dataset.url, btn.dataset.name, null));
  });
}

// ---------------------------------------------------------------------------
// Init
// ---------------------------------------------------------------------------

(function init() {
  // Migrate PBKDF2-derived key stored by login/register form
  if (window.USER_ID) {
    const pending = localStorage.getItem('diora_pending_enc_key');
    if (pending) {
      localStorage.setItem(`diora_enc_key_${window.USER_ID}`, pending);
      localStorage.removeItem('diora_pending_enc_key');
    }
  }

  // Populate saved stations from server-side context if available
  if (typeof INITIAL_SAVED !== 'undefined' && Array.isArray(INITIAL_SAVED)) {
    // The server already renders saved stations in the template; nothing extra needed.
    // But if JS-rendered saved tab were needed we'd call addSavedRow here.
  }

  // Restore persisted volume, fall back to slider default
  const volSlider = $('volume');
  if (volSlider) {
    const saved = localStorage.getItem('diora_volume');
    const vol = saved !== null ? parseInt(saved, 10) : parseInt(volSlider.value, 10);
    setVolume(vol);
  }

  // Restore persisted read-aloud language
  const ttsLangSelect = $('reader-tts-lang');
  if (ttsLangSelect) ttsLangSelect.value = ttsLang;

  // Load recommendations on page load
  loadRecommendations();

  // Initialise focus timer display
  renderTimer();

  // Initialise mood/genre chips
  initMoodChips();

  // Initialise curated station lists
  initCuratedLists();

  // Show curated lists again when search input is cleared
  const searchInput = document.getElementById('search-input');
  if (searchInput) {
    searchInput.addEventListener('input', function () {
      if (this.value === '') {
        const curated = document.getElementById('curated-lists');
        if (curated) curated.style.display = '';
      }
    });
  }

  // Load focus session stats
  loadFocusStats();

  // Apply encrypted wallpaper (if set)
  applyEncryptedBackground();

  // Init book drop zone
  initBookDropZone();
  const showReadToggle = $('book-show-read-toggle');
  if (showReadToggle) showReadToggle.checked = _bookShowRead;

  // Restore active tab: a URL hash (shared/bookmarked link, or browser
  // back/forward) wins over the last-used tab remembered in localStorage —
  // except when offline, where books (usable offline) always takes over.
  const offlineOverride = !navigator.onLine && IS_AUTHENTICATED;
  const hashTab = (location.hash || '').replace(/^#/, '').split('/')[0];
  if (!offlineOverride && TOP_TABS.includes(hashTab)) {
    _routeFromHash();
  } else {
    const savedTab = localStorage.getItem('diora_active_tab') || 'radio';
    const savedRadioTab = localStorage.getItem('diora_active_radio_tab') || 'saved';
    showTab(offlineOverride ? 'books' : savedTab);
    showRadioTab(savedRadioTab);
  }

  // React to connectivity changes
  window.addEventListener('offline', () => {
    showOfflineBanner(true);
    if (IS_AUTHENTICATED) showTab('books');
  });
  window.addEventListener('online', async () => {
    showOfflineBanner(false);
    await _syncPendingAnnotations();
    loadBookList(); // sends the positions read offline first (the progress outbox)
  });

  // Show banner immediately if already offline at startup
  if (!navigator.onLine) showOfflineBanner(true);

  // Reading position: positions reached by the reader's own doing count (see _noteReadingPosition).
  {
    const content = $('reader-content');
    if (content) {
      for (const type of ['wheel', 'touchstart', 'mousedown']) {
        content.addEventListener(type, _noteReaderInteraction, {passive: true, capture: true});
      }
    }
    document.addEventListener('keydown', () => { if (currentBookId) _noteReaderInteraction(); }, true);
    if (IS_AUTHENTICATED) _flushProgressOutbox();
  }

  // Footnote hover (desktop) + tap (mobile) via event delegation
  const _readerContentEl = $('reader-content');
  if (_readerContentEl) {
    _readerContentEl.addEventListener('mouseover', e => {
      const link = e.target.closest('[data-footnote-ref]');
      if (!link) return;
      clearTimeout(_footnotePopoverTimer);
      _footnotePopoverTimer = setTimeout(() => showFootnotePopover(link), 120);
    });
    _readerContentEl.addEventListener('mouseout', e => {
      if (!e.target.closest('[data-footnote-ref]')) return;
      _footnotePopoverTimer = setTimeout(dismissFootnotePopover, 250);
    });
    _readerContentEl.addEventListener('click', e => {
      const link = e.target.closest('[data-footnote-ref]');
      if (!link) return;
      e.preventDefault();
      if (currentFootnotePopover?._refLink === link) {
        dismissFootnotePopover();
      } else {
        showFootnotePopover(link);
      }
    });

    // Text selection → highlight color/note popover
    _readerContentEl.addEventListener('mouseup', handleReaderSelection);
    _readerContentEl.addEventListener('touchend', e => {
      const target = e.target;
      const touch = e.changedTouches && e.changedTouches[0];
      const clientX = touch ? touch.clientX : undefined;
      const clientY = touch ? touch.clientY : undefined;
      setTimeout(() => handleReaderSelection({target, clientX, clientY}), 50);
    });
  }

  // Margin ("page margin") panel — click a marker to view/edit, click empty
  // space to anchor a new freeform note at that line's height
  const _readerMarginEl = $('reader-margin');
  if (_readerMarginEl) {
    _readerMarginEl.addEventListener('click', handleMarginClick);
  }
})();