peoplelib/src/ui/cover-renderer.mjs

import * as pdfjs from './vendor/pdf.min.mjs';

pdfjs.GlobalWorkerOptions.workerSrc = new URL('./vendor/pdf.worker.min.mjs', import.meta.url).href;

const WIDTH = 320;
const HEIGHT = 440;
const PDF_ASSET_OPTIONS = Object.freeze({
  cMapUrl: new URL('./vendor/pdfjs/cmaps/', import.meta.url).href,
  cMapPacked: true,
  iccUrl: new URL('./vendor/pdfjs/iccs/', import.meta.url).href,
  standardFontDataUrl: new URL('./vendor/pdfjs/standard_fonts/', import.meta.url).href,
  wasmUrl: new URL('./vendor/pdfjs/wasm/', import.meta.url).href
});
const IMAGE_MIMES = new Set([
  'image/jpeg', 'image/png', 'image/webp', 'image/gif', 'image/bmp', 'image/svg+xml', 'image/avif'
]);
const EXT_MIMES = {
  jpg: 'image/jpeg',
  jpeg: 'image/jpeg',
  png: 'image/png',
  webp: 'image/webp',
  gif: 'image/gif',
  bmp: 'image/bmp',
  svg: 'image/svg+xml',
  avif: 'image/avif'
};

function toBytes(value) {
  if (value instanceof Uint8Array) return value.slice();
  if (value instanceof ArrayBuffer) return new Uint8Array(value.slice(0));
  if (value && value.buffer instanceof ArrayBuffer) {
    return new Uint8Array(value.buffer, value.byteOffset || 0, value.byteLength).slice();
  }
  throw new Error('文件数据无效');
}

function resolvePath(base, href) {
  const raw = String(href || '').split('#')[0].split('?')[0].trim();
  if (!raw || /^[a-z][a-z0-9+.\-]*:/i.test(raw)) return '';
  const parts = (raw.startsWith('/') ? raw.slice(1) : base + raw).split('/');
  const out = [];
  for (const part of parts) {
    if (!part || part === '.') continue;
    if (part === '..') out.pop();
    else out.push(part);
  }
  return out.join('/');
}

function zipEntry(zip, name) {
  let entry = zip.file(name);
  if (entry) return entry;
  let decoded = name;
  try { decoded = decodeURIComponent(name); } catch (e) { /* keep original */ }
  const target = decoded.toLowerCase();
  return (zip.file(/./) || []).find((item) => {
    let itemName = item.name;
    try { itemName = decodeURIComponent(itemName); } catch (e) { /* keep original */ }
    return itemName.toLowerCase() === target;
  }) || null;
}

async function zipText(entry, maxBytes) {
  const declared = entry && entry._data && Number(entry._data.uncompressedSize);
  if (!entry || (Number.isFinite(declared) && declared > maxBytes)) throw new Error('EPUB 资源过大');
  const text = await entry.async('text');
  if (text.length > maxBytes) throw new Error('EPUB 资源过大');
  return text;
}

async function zipBytes(entry, maxBytes) {
  const declared = entry && entry._data && Number(entry._data.uncompressedSize);
  if (!entry || (Number.isFinite(declared) && declared > maxBytes)) return null;
  const bytes = await entry.async('uint8array');
  return bytes.length <= maxBytes ? bytes : null;
}

function canvasToJpeg(canvas) {
  return canvas.toDataURL('image/jpeg', 0.86);
}

async function pdfCover(bytes) {
  const loadingTask = pdfjs.getDocument({
    ...PDF_ASSET_OPTIONS,
    data: toBytes(bytes),
    isEvalSupported: false,
    enableXfa: false
  });
  let doc;
  try {
    doc = await loadingTask.promise;
    const page = await doc.getPage(1);
    const base = page.getViewport({ scale: 1 });
    const scale = Math.min(WIDTH / base.width, HEIGHT / base.height);
    const viewport = page.getViewport({ scale });
    const canvas = document.createElement('canvas');
    canvas.width = Math.max(1, Math.round(viewport.width));
    canvas.height = Math.max(1, Math.round(viewport.height));
    const context = canvas.getContext('2d', { alpha: false });
    context.fillStyle = '#fff';
    context.fillRect(0, 0, canvas.width, canvas.height);
    await page.render({ canvasContext: context, viewport }).promise;
    page.cleanup();
    const cover = document.createElement('canvas');
    cover.width = WIDTH;
    cover.height = HEIGHT;
    const coverContext = cover.getContext('2d', { alpha: false });
    coverContext.fillStyle = '#e7e3dc';
    coverContext.fillRect(0, 0, WIDTH, HEIGHT);
    coverContext.drawImage(canvas, (WIDTH - canvas.width) / 2, (HEIGHT - canvas.height) / 2);
    return canvasToJpeg(cover);
  } finally {
    if (doc && typeof doc.destroy === 'function') await doc.destroy();
    else if (loadingTask && typeof loadingTask.destroy === 'function') await loadingTask.destroy();
  }
}

async function loadImage(data, mime) {
  const blobUrl = URL.createObjectURL(new Blob([data], { type: mime }));
  try {
    const image = new Image();
    image.decoding = 'async';
    image.src = blobUrl;
    await image.decode();
    return image;
  } finally {
    URL.revokeObjectURL(blobUrl);
  }
}

function imageCover(image) {
  const canvas = document.createElement('canvas');
  canvas.width = WIDTH;
  canvas.height = HEIGHT;
  const context = canvas.getContext('2d', { alpha: false });
  context.fillStyle = '#f5f1e8';
  context.fillRect(0, 0, WIDTH, HEIGHT);
  const scale = Math.min(WIDTH / image.naturalWidth, HEIGHT / image.naturalHeight);
  const width = Math.max(1, image.naturalWidth * scale);
  const height = Math.max(1, image.naturalHeight * scale);
  context.drawImage(image, (WIDTH - width) / 2, (HEIGHT - height) / 2, width, height);
  return canvasToJpeg(canvas);
}

function titleCover(title, authors) {
  const canvas = document.createElement('canvas');
  canvas.width = WIDTH;
  canvas.height = HEIGHT;
  const context = canvas.getContext('2d', { alpha: false });
  const gradient = context.createLinearGradient(0, 0, WIDTH, HEIGHT);
  gradient.addColorStop(0, '#242225');
  gradient.addColorStop(1, '#6f5546');
  context.fillStyle = gradient;
  context.fillRect(0, 0, WIDTH, HEIGHT);
  context.fillStyle = '#c49a6c';
  context.fillRect(28, 34, 3, HEIGHT - 68);

  const text = String(title || '未命名书籍').trim() || '未命名书籍';
  context.fillStyle = '#fffaf2';
  context.font = '600 28px sans-serif';
  context.textBaseline = 'top';
  const maxWidth = WIDTH - 76;
  const lines = [];
  let line = '';
  for (const char of text) {
    const next = line + char;
    if (line && context.measureText(next).width > maxWidth) {
      lines.push(line);
      line = char;
      if (lines.length === 6) break;
    } else {
      line = next;
    }
  }
  if (line && lines.length < 7) lines.push(line);
  lines.forEach((value, index) => context.fillText(value, 48, 84 + index * 38, maxWidth));

  const authorText = (Array.isArray(authors) ? authors : []).filter(Boolean).join(' · ');
  if (authorText) {
    context.fillStyle = '#decbb8';
    context.font = '16px sans-serif';
    context.fillText(authorText, 48, HEIGHT - 72, maxWidth);
  }
  return canvasToJpeg(canvas);
}

async function epubCover(bytes, fallbackTitle, authors) {
  if (!window.JSZip) throw new Error('缺少 JSZip');
  const zip = await window.JSZip.loadAsync(toBytes(bytes));
  const encryptedPaths = new Set();
  const encryptionEntry = zipEntry(zip, 'META-INF/encryption.xml');
  if (encryptionEntry) {
    try {
      const encryption = new DOMParser().parseFromString(await zipText(encryptionEntry, 1024 * 1024), 'text/xml');
      Array.from(encryption.getElementsByTagName('*'))
        .filter((item) => item.localName === 'CipherReference')
        .forEach((item) => {
          const encryptedPath = resolvePath('', item.getAttribute('URI'));
          if (encryptedPath) encryptedPaths.add(encryptedPath);
        });
    } catch (e) { /* individual encrypted resources will fail safely if selected */ }
  }
  const containerEntry = zipEntry(zip, 'META-INF/container.xml');
  if (!containerEntry) throw new Error('EPUB 缺少 container.xml');
  const container = new DOMParser().parseFromString(await zipText(containerEntry, 512 * 1024), 'text/xml');
  const rootfile = container.querySelector('rootfile');
  const opfPath = resolvePath('', rootfile && rootfile.getAttribute('full-path'));
  const opfEntry = zipEntry(zip, opfPath);
  if (!opfEntry) throw new Error('EPUB 缺少 OPF');
  const opf = new DOMParser().parseFromString(await zipText(opfEntry, 2 * 1024 * 1024), 'text/xml');
  if (opf.querySelector('parsererror')) throw new Error('EPUB 的 OPF 无法解析');
  const opfBase = opfPath.includes('/') ? opfPath.slice(0, opfPath.lastIndexOf('/') + 1) : '';
  const manifest = Array.from(opf.querySelectorAll('manifest > item, item')).map((item) => ({
    id: item.getAttribute('id') || '',
    href: item.getAttribute('href') || '',
    mime: (item.getAttribute('media-type') || '').toLowerCase(),
    properties: (item.getAttribute('properties') || '').split(/\s+/)
  })).filter((item, index, all) => item.id && all.findIndex((other) => other.id === item.id) === index);
  manifest.forEach((item) => { item.path = resolvePath(opfBase, item.href); });
  const byId = new Map(manifest.map((item) => [item.id, item]));
  const byPath = new Map(manifest.map((item) => [item.path, item]));
  const mimeFromPath = (value) => EXT_MIMES[value.slice(value.lastIndexOf('.') + 1).toLowerCase()] || '';
  const pageImage = async (pagePath) => {
    const entry = zipEntry(zip, pagePath);
    if (!entry) return null;
    let text;
    try { text = await zipText(entry, 2 * 1024 * 1024); } catch (e) { return null; }
    const page = new DOMParser().parseFromString(text, 'text/html');
    const image = page.querySelector('img[src], image[href], image[xlink\\:href]');
    if (!image) return null;
    const href = image.getAttribute('src') || image.getAttribute('href') || image.getAttribute('xlink:href');
    const base = pagePath.includes('/') ? pagePath.slice(0, pagePath.lastIndexOf('/') + 1) : '';
    const imagePath = resolvePath(base, href);
    const known = byPath.get(imagePath);
    return imagePath ? { path: imagePath, mime: (known && known.mime) || mimeFromPath(imagePath) } : null;
  };
  const coverMeta = Array.from(opf.querySelectorAll('meta')).find((item) => (
    (item.getAttribute('name') || '').toLowerCase() === 'cover'
  ));
  const declared = manifest.find((item) => item.properties.includes('cover-image'))
    || (coverMeta && byId.get(coverMeta.getAttribute('content')));
  const guideRef = Array.from(opf.querySelectorAll('guide > reference, reference')).find((item) => (
    /\bcover\b/i.test(item.getAttribute('type') || '')
  ));
  const guidePath = resolvePath(opfBase, guideRef && guideRef.getAttribute('href'));
  let guideCandidate = guidePath && byPath.get(guidePath);
  if (guidePath && (!guideCandidate || !IMAGE_MIMES.has(guideCandidate.mime))) {
    guideCandidate = await pageImage(guidePath);
  }
  const firstSpineRef = opf.querySelector('spine > itemref, itemref');
  const firstSpineItem = firstSpineRef && byId.get(firstSpineRef.getAttribute('idref'));
  const firstPageCandidate = firstSpineItem && await pageImage(firstSpineItem.path);
  const candidates = [
    declared,
    guideCandidate,
    firstPageCandidate,
    ...manifest.filter((item) => IMAGE_MIMES.has(item.mime)
      && /(^|[\/_.-])(cover|title|front|book)([\/_.-]|$)/i.test(item.href)),
    ...manifest.filter((item) => IMAGE_MIMES.has(item.mime))
  ].filter(Boolean);

  const seen = new Set();
  for (const item of candidates) {
    const imagePath = item.path || resolvePath(opfBase, item.href);
    if (!imagePath || seen.has(imagePath) || encryptedPaths.has(imagePath)) continue;
    seen.add(imagePath);
    const entry = zipEntry(zip, imagePath);
    if (!entry) continue;
    const data = await zipBytes(entry, 12 * 1024 * 1024);
    if (!data || !data.length) continue;
    try {
      const image = await loadImage(data, item.mime || mimeFromPath(imagePath));
      if (image.naturalWidth < 32 || image.naturalHeight < 32) continue;
      return imageCover(image);
    } catch (e) { /* try the next image */ }
  }

  const titleNode = Array.from(opf.querySelectorAll('title')).find((node) => /(^|:)title$/i.test(node.nodeName));
  return titleCover((titleNode && titleNode.textContent) || fallbackTitle, authors);
}

window.coverBridge.onExtract(async (payload) => {
  const id = payload && payload.id;
  try {
    const format = String(payload && payload.format || '').toLowerCase();
    const dataUrl = format === 'pdf'
      ? await pdfCover(payload.bytes)
      : await epubCover(payload.bytes, payload.title, payload.authors);
    window.coverBridge.complete({ id, ok: true, dataUrl });
  } catch (error) {
    window.coverBridge.complete({ id, ok: false, error: (error && error.message) || String(error) });
  }
});

window.coverBridge.ready();