'use strict';

// ---------------------------------------------------------------------------
// 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};
}