/**
 * One-time migration: extract nav/footer from index.html, rewrite all HTML pages.
 */
import fs from "fs";
import path from "path";
import { fileURLToPath } from "url";
import crypto from "crypto";

const ROOT = path.join(path.dirname(fileURLToPath(import.meta.url)), "..");
const COMPONENTS = path.join(ROOT, "components");
const REPORT_PATH = path.join(ROOT, "docs", "layout-migration-report.md");

const SKIP_DIRS = new Set(["temp", "node_modules", "assets", "components", "scripts", "docs"]);
const SKIP_FILES = new Set(["test.html"]);

const NAV_PARTIAL_RE =
  /<!--\s*@partial\s+nav\s*-->[\s\S]*?<!--\s*@endpartial\s+nav\s*-->/i;
const NAV_LEGACY_RE =
  /<!--\s*fixed-header glass-panel\s*-->\s*<nav id="nav"[\s\S]*?<\/nav>/i;
const NAV_ANY_RE = /<nav id="nav"[\s\S]*?<\/nav>/i;

const FOOTER_RE = /<footer class="pb-3 footer\s+footer-dark">[\s\S]*?<\/footer>/i;

const NAV_CONTAINER = '<div id="nav-container"></div>';
const FOOTER_CONTAINER = '<div id="footer-container"></div>';
const LAYOUT_SCRIPT = '<script src="/js/layout.js"></script>';

function collectHtmlFiles(dir, list = []) {
  if (!fs.existsSync(dir)) return list;
  for (const name of fs.readdirSync(dir)) {
    if (SKIP_DIRS.has(name)) continue;
    const full = path.join(dir, name);
    const stat = fs.statSync(full);
    if (stat.isDirectory()) collectHtmlFiles(full, list);
    else if (name.endsWith(".html") && !SKIP_FILES.has(name)) list.push(full);
  }
  return list;
}

function hashContent(s) {
  return crypto.createHash("sha1").update(s).digest("hex").slice(0, 10);
}

function rootifyAssetPaths(html) {
  let out = html;
  const rules = [
    [/src="\.\/assets\//g, 'src="/assets/'],
    [/src="\.\.\/assets\//g, 'src="/assets/'],
    [/src="assets\//g, 'src="/assets/'],
    [/href="\.\/assets\//g, 'href="/assets/'],
    [/href="\.\.\/assets\//g, 'href="/assets/'],
    [/href="assets\//g, 'href="/assets/'],
    [/href="\.\/pages\//g, 'href="/pages/'],
    [/href="\.\.\/pages\//g, 'href="/pages/'],
    [/href="pages\//g, 'href="/pages/'],
    [/href="\.\/index\.html"/g, 'href="/"'],
    [/href="\.\.\/index\.html"/g, 'href="/"'],
    [/href="\.\/"/g, 'href="/"'],
    [/href="\.\.\/"/g, 'href="/"'],
  ];
  for (const [re, rep] of rules) out = out.replace(re, rep);
  return out;
}

function extractNavFromIndex(html) {
  let m = html.match(NAV_PARTIAL_RE);
  if (m) {
    let inner = m[0]
      .replace(/<!--\s*@partial\s+nav\s*-->/i, "")
      .replace(/<!--\s*@endpartial\s+nav\s*-->/i, "")
      .trim();
    return inner;
  }
  m = html.match(NAV_LEGACY_RE) || html.match(NAV_ANY_RE);
  return m ? m[0].replace(/<!--\s*fixed-header glass-panel\s*-->\s*/i, "").trim() : null;
}

function extractFooterFromIndex(html) {
  const m = html.match(FOOTER_RE);
  return m ? m[0].trim() : null;
}

function addYearSpan(footerHtml) {
  return footerHtml.replace(
    /&copy;\s*\d{4}/i,
    "&copy; <span id=\"current-year\"></span>"
  );
}

function stripNav(html) {
  if (NAV_PARTIAL_RE.test(html)) return html.replace(NAV_PARTIAL_RE, NAV_CONTAINER);
  if (NAV_LEGACY_RE.test(html)) return html.replace(NAV_LEGACY_RE, NAV_CONTAINER);
  if (NAV_ANY_RE.test(html)) return html.replace(NAV_ANY_RE, NAV_CONTAINER);
  return html;
}

function stripFooter(html) {
  if (!FOOTER_RE.test(html)) return html;
  return html.replace(FOOTER_RE, FOOTER_CONTAINER);
}

function ensureLayoutScript(html) {
  if (html.includes("/js/layout.js")) return html;
  if (html.includes("</body>")) {
    return html.replace("</body>", `  ${LAYOUT_SCRIPT}\n</body>`);
  }
  return html + `\n${LAYOUT_SCRIPT}\n`;
}

function normalizeForCompare(html) {
  return html.replace(/\s+/g, " ").trim();
}

function main() {
  const indexPath = path.join(ROOT, "index.html");
  const indexHtml = fs.readFileSync(indexPath, "utf8");

  let nav = extractNavFromIndex(indexHtml);
  let footer = extractFooterFromIndex(indexHtml);
  if (!nav || !footer) {
    console.error("Could not extract nav or footer from index.html");
    process.exit(1);
  }

  nav = rootifyAssetPaths(nav);
  footer = addYearSpan(rootifyAssetPaths(footer));

  fs.mkdirSync(COMPONENTS, { recursive: true });
  fs.mkdirSync(path.join(ROOT, "js"), { recursive: true });
  fs.mkdirSync(path.dirname(REPORT_PATH), { recursive: true });

  fs.writeFileSync(path.join(COMPONENTS, "nav.html"), nav + "\n", "utf8");
  fs.writeFileSync(path.join(COMPONENTS, "footer.html"), footer + "\n", "utf8");

  const files = [
    indexPath,
    ...collectHtmlFiles(path.join(ROOT, "pages")),
    ...collectHtmlFiles(ROOT).filter((f) => f !== indexPath),
  ];
  const uniqueFiles = [...new Set(files)];

  const navHashes = new Map();
  const footerHashes = new Map();
  const report = {
    canonicalNavHash: hashContent(normalizeForCompare(nav)),
    canonicalFooterHash: hashContent(normalizeForCompare(footer)),
    updated: [],
    skipped: [],
    navVariants: [],
    footerVariants: [],
  };

  for (const file of uniqueFiles) {
    let html = fs.readFileSync(file, "utf8");
    const rel = path.relative(ROOT, file).replace(/\\/g, "/");

    const navMatch =
      html.match(NAV_PARTIAL_RE) ||
      html.match(NAV_LEGACY_RE) ||
      html.match(NAV_ANY_RE);
    const footerMatch = html.match(FOOTER_RE);

    if (navMatch) {
      const h = hashContent(normalizeForCompare(rootifyAssetPaths(navMatch[0])));
      navHashes.set(h, (navHashes.get(h) || 0) + 1);
      if (h !== report.canonicalNavHash) {
        report.navVariants.push({ file: rel, hash: h });
      }
    }
    if (footerMatch) {
      const raw = rootifyAssetPaths(footerMatch[0]);
      const h = hashContent(normalizeForCompare(raw));
      footerHashes.set(h, (footerHashes.get(h) || 0) + 1);
      if (h !== report.canonicalFooterHash) {
        report.footerVariants.push({ file: rel, hash: h });
      }
    }

    if (!navMatch && !footerMatch) {
      report.skipped.push(rel);
      continue;
    }

    let next = html;
    if (navMatch) next = stripNav(next);
    if (footerMatch) next = stripFooter(next);
    if (navMatch || footerMatch) next = ensureLayoutScript(next);

    if (next !== html) {
      fs.writeFileSync(file, next, "utf8");
      report.updated.push(rel);
    }
  }

  const navStats = [...navHashes.entries()].sort((a, b) => b[1] - a[1]);
  const footerStats = [...footerHashes.entries()].sort((a, b) => b[1] - a[1]);

  const md = `# Layout migration report

Generated: ${new Date().toISOString()}

## Canonical templates (from \`index.html\`)

- Nav hash: \`${report.canonicalNavHash}\`
- Footer hash: \`${report.canonicalFooterHash}\`

## Nav variant counts

${navStats.map(([h, c]) => `- \`${h}\`: ${c} page(s)`).join("\n")}

## Footer variant counts

${footerStats.map(([h, c]) => `- \`${h}\`: ${c} page(s)`).join("\n")}

## Pages with non-canonical nav (${report.navVariants.length})

${report.navVariants.length ? report.navVariants.map((v) => `- ${v.file} (\`${v.hash}\`) — TODO: review if custom nav needed`).join("\n") : "_None_"}

## Pages with non-canonical footer (${report.footerVariants.length})

${report.footerVariants.length ? report.footerVariants.map((v) => `- ${v.file} (\`${v.hash}\`) — TODO: review if custom footer needed`).join("\n") : "_None_"}

## Updated (${report.updated.length})

${report.updated.map((f) => `- ${f}`).join("\n")}

## Skipped (no nav/footer) (${report.skipped.length})

${report.skipped.map((f) => `- ${f}`).join("\n")}
`;

  fs.writeFileSync(REPORT_PATH, md, "utf8");
  console.log("Wrote components/nav.html, components/footer.html");
  console.log("Updated", report.updated.length, "files");
  console.log("Report:", REPORT_PATH);
}

main();