diora-web/static/js/app/52-book-list.js

'use strict';

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, magazine: meta.magazine};
        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, magazine: meta.magazine, 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, magazine: b.magazine};
      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 || '',
        magazine: prevMeta.magazine,
      }));
      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)

// Bücher and Zeitschriften are two sections of Lesen (static/js/nav.js), one list: a
// magazine is an issue marked as one (⋮ → Als Zeitschrift, kept in the encrypted meta),
// or, unmarked, a book in a folder called "Zeitschriften" (or "Magazine").
let _bookSection = 'books';
const _MAGAZINE_FOLDER = /^(zeitschriften|magazine|magazines)$/i;
const _isMagazine = b => b.magazine === true || (b.magazine !== false && _MAGAZINE_FOLDER.test((b.folder || '').trim()));
window._isMagazine = _isMagazine;

// The periodical an issue belongs to: its title up to the issue's number ("Jacobin #24",
// "New Left Review 157", "LuXemburg 1/2026"), else its author ("Vol 9 – Issue 2–3" by Catalyst).
function _periodicalOf(b) {
  const m = /^(.*?)\s*(?:#|\bno\.|\bnr\.|\bheft\b|\bausgabe\b|\bissue\b|\bvol\b|\d)/i.exec(b.title || '');
  const name = (m ? m[1] : '').replace(/[\s–—:,-]+$/, '').trim();
  return name.length >= 3 ? name : (b.author || '').trim() || (b.title || '').trim();
}

async function toggleBookMagazine(bookId) {
  const book = _lastBookListData.find(b => b.id === bookId);
  if (!book) return;
  try {
    await _updateBookMeta(bookId, {magazine: !_isMagazine(book)});
    renderBookList(_lastBookListData);
  } catch (e) {
    customAlert('Das ließ sich nicht speichern: ' + e.message);
  }
}
window.toggleBookMagazine = toggleBookMagazine;

// The books of the section shown (all of them where there are no sections).
function _bookSectionFilter(books) {
  if (!window.DioraNav) return books;
  return books.filter(b => (_bookSection === 'magazines') === _isMagazine(b));
}
window._bookSectionFilter = _bookSectionFilter;

window.__dioraBooksView = function (view) {
  const next = view === 'magazines' ? 'magazines' : 'books';
  if (next === _bookSection) return;
  _bookSection = next;
  _currentBookFolder = null;
  if (_lastBookListData) renderBookList(_lastBookListData);
};

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(${b.id})">📁 Ordner zuweisen</button>
            <button class="book-menu-item" onclick="toggleBookMagazine(${b.id})">${_isMagazine(b) ? '▤ Als Buch führen' : '📰 Als Zeitschrift führen'}</button>
            <button class="book-menu-item" onclick="lookupBookMetadata(${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(allBooks) {
  const listEl = $('book-list');
  if (!listEl) return;
  _lastBookListData = allBooks;
  const books = _bookSectionFilter(allBooks);

  if (!books.length) {
    listEl.innerHTML = window.DioraNav && allBooks.length
      ? (_bookSection === 'magazines'
        ? '<p class="muted">Noch keine Zeitschriften. Ein Heft unter Bücher über ⋮ → „Als Zeitschrift führen“ hierher holen.</p>'
        : '<p class="muted">Alle Bücher liegen bei den Zeitschriften.</p>')
      : '';
    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();
  const magazines = _bookSection === 'magazines' && !!window.DioraNav;
  for (const b of visible) {
    const key = magazines ? _periodicalOf(b) : (b.folder || '');
    if (!grouped.has(key)) grouped.set(key, []);
    grouped.get(key).push(b);
  }
  if (magazines) {
    // A periodical with one issue is no tile; issues newest first.
    const loose = grouped.get('') || [];
    for (const [k, list] of [...grouped]) {
      if (k !== '' && list.length < 2) { loose.push(...list); grouped.delete(k); }
    }
    grouped.set('', loose);
    const issue = (a, b) => b.title.localeCompare(a.title, 'de', {numeric: true});
    for (const list of grouped.values()) list.sort(issue);
  }
  // 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="${escapeHtml(name)}">
            <span class="book-folder-tile-icon">${magazines ? '📰' : '📁'}</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,
    magazine: cached.magazine !== undefined ? cached.magazine : book.magazine,
    ...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;
  }
}