window.COURSE  ─┐
                ├─→ compose-ebook.mjs ─→ master.md ─→ pandoc ─→ ebook.docx
asset folders ─┤                                  └─→ Playwright page.pdf() ─→ ebook.pdf
materials/   ─┘

scripts/
├── build-ebook.mjs              ← CLI entry point (--md-only, --no-docx, --no-pdf, --output, --keep-html)
├── render-pdf.mjs               ← markdown → HTML → PDF via Playwright
└── lib/
    ├── compose-ebook.mjs        ← loadSources + composeXxx functions (cover, TOC, chapters, appendix)
    └── reference.docx           ← pandoc style template (generated by gen-reference-docx.mjs)

style-ebook.css                   ← @page rules, cover, page-number footer, print-only styles
dist/                             ← output: ebook.md, ebook.pdf, ebook.docx

import vm from 'node:vm';
async function loadCourseFromIndexHtml(htmlPath) {
  const html = await fs.readFile(htmlPath, 'utf8');
  const match = html.match(/<script>\s*window\.COURSE\s*=\s*\{[\s\S]*?\};\s*<\/script>/);
  if (!match) throw new Error('window.COURSE 區塊找不到');
  const code = match[0].replace(/<\/?script>/g, '');
  const sandbox = { window: {}, console };
  vm.createContext(sandbox);
  vm.runInContext(code, sandbox);
  return sandbox.window.COURSE;
}

import { chromium } from 'playwright';
const browser = await chromium.launch();
const page = await browser.newPage();
await page.goto(`file://${path.resolve(htmlPath)}`, { waitUntil: 'networkidle' });
await page.pdf({
  path: outputPath,
  format: 'A4',
  printBackground: true,
  displayHeaderFooter: true,
  headerTemplate: '<div></div>',
  footerTemplate: `
    <div style="font-size:9pt; width:100%; text-align:center; color:#666;">
      <span class="pageNumber"></span> / <span class="totalPages"></span>
    </div>`,
  margin: { top: '20mm', right: '20mm', bottom: '20mm', left: '20mm' },
});
await browser.close();

@page { margin: 20mm; }
@page :first { margin: 0; }    /* full bleed cover */

/* 章首跨頁分頁 */
h1.chapter { page-break-before: always; }

/* 圖文並排（Grid 排版） */
.figure-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12mm;
}
.figure-grid .three-up { grid-template-columns: repeat(3, 1fr); }

/* 提示詞區塊：橘色 PROMPT 徽章 + 暗底 code */
.prompt-block {
  background: #1a1a1a; color: #e0e0e0;
  border-left: 4px solid #ff8c00;
  padding: 12pt; margin: 8pt 0;
}
.prompt-block::before {
  content: 'PROMPT'; display: inline-block;
  background: #ff8c00; color: white;
  padding: 2pt 8pt; border-radius: 3pt;
  font-size: 8pt; margin-bottom: 6pt;
}

/* 任務勾選方框（純印刷） */
.task::before {
  content: '☐'; margin-right: 8pt;
  font-size: 14pt; color: #888;
}

/* 學習目標綠色徽章 */
.goal::before {
  content: '✓'; margin-right: 6pt;
  color: #2e7d32; font-weight: bold;
}

const args = [
  mdPath,
  '-f', 'gfm+attributes+raw_html',
  '-t', 'docx',
  '--standalone',
  '--toc', '--toc-depth=2',
  '--resource-path', path.dirname(mdPath),
  '--reference-doc', 'scripts/lib/reference.docx',
  '-o', outPath,
];
spawn('pandoc', args);

export async function loadSources() { /* read COURSE + materials + assets */ }
export async function composeCover(meta) { /* big title, day list, meta card */ }
export async function composeOverview(meta) { /* TOC + course overview */ }
export async function composeChapter(day, assetIndex) { /* hero image + units */ }
export async function composeAppendixMaterials(materials) { /* full-text material appendix */ }
export async function composeAppendixSkills(skills) { /* QR-coded skill links */ }

async function pickAsset(name, roots) {
  for (const root of roots) {
    const full = path.join(root, name);
    try { await fs.access(full); return path.relative(mdDir, full); }
    catch { continue; }
  }
  return null;  // caller decides whether to drop the image or fall back to placeholder
}

// scripts/verify-ebook.mjs
// - PDF file exists and is > 100KB
// - First page (cover) has no page number
// - TOC pages have entries
// - Every image reference resolved (no broken-image placeholders)