#!/usr/bin/env node
/**
 * Check internal doc links: resolve relative paths from each source file
 * and report only targets that are missing (file or directory).
 * Usage: node scripts/check-doc-links.mjs
 */
import { readdirSync, readFileSync, existsSync } from 'fs';
import { join, resolve, dirname, normalize } from 'path';
import { fileURLToPath } from 'url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const REPO_ROOT = resolve(__dirname, '..');
const DOCS = join(REPO_ROOT, 'docs');

function* walkMd(dir, prefix = '') {
  const entries = readdirSync(dir, { withFileTypes: true });
  for (const e of entries) {
    const rel = prefix ? `${prefix}/${e.name}` : e.name;
    if (e.isDirectory()) {
      if (e.name === 'node_modules' || e.name === '.git') continue;
      yield* walkMd(join(dir, e.name), rel);
    } else if (e.name.endsWith('.md')) {
      yield { path: join(dir, e.name), rel: join(prefix, e.name) };
    }
  }
}

const linkRe = /\]\(([^)]+)\)/g;

function resolveTarget(fromDir, href) {
  const pathOnly = href.replace(/#.*$/, '').trim();
  if (!pathOnly || pathOnly.startsWith('http://') || pathOnly.startsWith('https://') || pathOnly.startsWith('mailto:')) return null;
  if (pathOnly.startsWith('#')) return null;
  if (pathOnly.startsWith('~/')) return null; // skip home-relative
  let resolved;
  if (pathOnly.startsWith('/')) {
    // repo-root-relative: /docs/... or /reports/...
    resolved = normalize(join(REPO_ROOT, pathOnly.slice(1)));
  } else {
    resolved = normalize(join(fromDir, pathOnly));
  }
  return resolved.startsWith(REPO_ROOT) ? resolved : null;
}

const broken = [];
const seen = new Set();

for (const { path: filePath, rel } of walkMd(DOCS)) {
  const fromDir = dirname(filePath);
  const content = readFileSync(filePath, 'utf8');
  let m;
  linkRe.lastIndex = 0;
  while ((m = linkRe.exec(content)) !== null) {
    const href = m[1];
    const targetPath = resolveTarget(fromDir, href);
    if (!targetPath) continue;
    const key = `${rel} -> ${href}`;
    if (seen.has(key)) continue;
    seen.add(key);
    if (!existsSync(targetPath)) {
      broken.push({ source: rel, link: href, resolved: targetPath.replace(REPO_ROOT + '/', '') });
    }
  }
}

console.log('=== Doc link check (docs/ only, relative links resolved from source file) ===\n');
if (broken.length === 0) {
  console.log('No broken internal links found.');
  process.exit(0);
}
console.log(`Found ${broken.length} broken link(s):\n`);
broken.forEach(({ source, link, resolved }) => {
  console.log(`  ${source}`);
  console.log(`    -> ${link}`);
  console.log(`    resolved: ${resolved}`);
  console.log('');
});
process.exit(1);