// Internal link check of the site: every href="..." and src="..." in site/*.html that is not an external URL,
// an anchor, a mailto or a data URI must resolve to a file under site/ (clean URLs: /bench -> bench.html).
// Fragment links (#id) inside a page must name an element id in that page. Template literals (${...}) in scripts are
// skipped; /api/<name> resolves to the function file site/api/<name>.mjs.
//   node tools/ci/link-check.mjs        exit 1 on the first broken link, listing every one
import { readFileSync, readdirSync, existsSync, statSync } from 'node:fs';
import { join, dirname } from 'node:path';
import { fileURLToPath } from 'node:url';

const site = join(dirname(fileURLToPath(import.meta.url)), '..', '..', 'site');
const pages = readdirSync(site).filter(f => f.endsWith('.html'));
const broken = [];
let checked = 0;

function resolves(target) {
  const clean = target.replace(/[?#].*$/, '');
  if (clean === '' || clean === '/') return true;
  const rel = clean.replace(/^\//, '');
  // /api/<name> is a function: site/api/<name>.mjs (Vercel routes the path to it)
  const api = /^api\/([a-z0-9_-]+)$/.exec(rel);
  if (api) return existsSync(join(site, 'api', `${api[1]}.mjs`));
  const candidates = [join(site, rel), join(site, `${rel}.html`), join(site, rel, 'index.html')];
  return candidates.some(c => existsSync(c) && statSync(c).isFile());
}

for (const page of pages) {
  const html = readFileSync(join(site, page), 'utf8');
  const ids = new Set([...html.matchAll(/\sid="([^"]+)"/g)].map(m => m[1]));
  for (const m of html.matchAll(/\s(?:href|src)="([^"]*)"/g)) {
    const t = m[1];
    if (/^(https?:|mailto:|data:|tel:|javascript:)/i.test(t) || t.startsWith('//')) continue;
    // a template literal inside a page's script builds the href at run time (the explorer pages: /block/${hash})
    if (t.includes('${')) continue;
    checked++;
    if (t.startsWith('#')) { if (t.length > 1 && !ids.has(t.slice(1))) broken.push(`${page}: fragment ${t}`); continue; }
    const [path, frag] = t.split('#');
    if (!resolves(path)) { broken.push(`${page}: ${t}`); continue; }
    if (frag) {
      const rel = path.replace(/[?].*$/, '').replace(/^\//, '');
      const file = [join(site, rel), join(site, `${rel}.html`), join(site, rel, 'index.html')].find(c => existsSync(c) && statSync(c).isFile());
      if (file && file.endsWith('.html') && !new Set([...readFileSync(file, 'utf8').matchAll(/\sid="([^"]+)"/g)].map(x => x[1])).has(frag)) broken.push(`${page}: ${t} (no id ${frag})`);
    }
  }
}
if (broken.length) { console.error(`link check: ${broken.length} broken internal link(s) of ${checked}:`); for (const b of broken) console.error(`  ${b}`); process.exit(1); }
console.log(`link check: ${checked} internal links across ${pages.length} pages, 0 broken`);