/**
 * Import-boundary law (Bottom-Up §06 dependency law; Critics §12).
 *
 * Layers, low → high: contracts < testkit < service. A LOWER layer must never
 * import a HIGHER one. This guards the "no specialization leaks into the kernel"
 * rule from day one. Runnable as `pnpm boundary` (CI) and imported by a test.
 */
import { readFileSync, readdirSync, statSync, existsSync } from 'node:fs';
import { fileURLToPath } from 'node:url';
import { dirname, join, resolve } from 'node:path';

const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '..');

/** Lower rank = lower layer. A package may only import packages of <= its rank. */
const RANK = {
  '@insignia/iios-contracts': 0,
  '@insignia/iios-testkit': 1,
  '@insignia/iios-service': 2,
};

function listTsFiles(dir) {
  if (!existsSync(dir)) return [];
  const out = [];
  for (const entry of readdirSync(dir)) {
    if (entry === 'node_modules' || entry === 'dist') continue;
    const full = join(dir, entry);
    if (statSync(full).isDirectory()) out.push(...listTsFiles(full));
    else if (full.endsWith('.ts')) out.push(full);
  }
  return out;
}

function packageOf(importPath) {
  return Object.keys(RANK).find((k) => importPath === k || importPath.startsWith(k + '/'));
}

export function findBoundaryViolations() {
  const pkgsDir = join(ROOT, 'packages');
  const violations = [];
  if (!existsSync(pkgsDir)) return violations;

  for (const pkg of readdirSync(pkgsDir)) {
    const pkgJsonPath = join(pkgsDir, pkg, 'package.json');
    if (!existsSync(pkgJsonPath)) continue;
    const name = JSON.parse(readFileSync(pkgJsonPath, 'utf8')).name;
    const ownRank = RANK[name];
    if (ownRank === undefined) continue;

    // Catch every module-specifier form: `from '…'`, side-effect `import '…'`,
    // dynamic `import('…')`, and `require('…')`.
    const patterns = [
      /from\s*['"](@insignia\/iios-[^'"]+)['"]/g,
      /import\s*['"](@insignia\/iios-[^'"]+)['"]/g,
      /import\s*\(\s*['"](@insignia\/iios-[^'"]+)['"]/g,
      /require\(\s*['"](@insignia\/iios-[^'"]+)['"]/g,
    ];
    for (const file of listTsFiles(join(pkgsDir, pkg, 'src'))) {
      const content = readFileSync(file, 'utf8');
      for (const re of patterns) {
        let m;
        while ((m = re.exec(content))) {
          const targetPkg = packageOf(m[1]);
          if (targetPkg && RANK[targetPkg] > ownRank) {
            violations.push({ file: file.replace(ROOT + '/', ''), from: name, imports: targetPkg });
          }
        }
      }
    }
  }
  return violations;
}

if (import.meta.url === `file://${process.argv[1]}`) {
  const violations = findBoundaryViolations();
  if (violations.length > 0) {
    console.error('✗ import-boundary violations (a lower layer imports a higher one):');
    for (const v of violations) console.error(`  ${v.file}: ${v.from} → ${v.imports}`);
    process.exit(1);
  }
  console.log('✓ import-boundary: OK (no lower→higher imports)');
}