// Minimal test reporter: silent on pass, prints failures in full, ends with one summary line.
export default async function* summaryReporter(source) {
  const failures = [];
  let passed = 0,
    failed = 0,
    totalMs = 0;

  for await (const event of source) {
    // Skip file-level wrapper events (name ends in .js) — only count individual tests.
    if (event.data?.name?.endsWith('.js')) continue;

    if (event.type === 'test:pass') {
      passed++;
      totalMs += event.data.details?.duration_ms ?? 0;
    } else if (event.type === 'test:fail') {
      failed++;
      totalMs += event.data.details?.duration_ms ?? 0;
      const err = event.data.details?.error;
      failures.push({
        name: event.data.name,
        reason: err?.cause?.message ?? err?.message ?? 'unknown',
      });
    }
  }

  if (failures.length) {
    yield '\nFailed tests:\n';
    for (const f of failures) yield `  ❌ ${f.name}\n     ${f.reason}\n`;
    yield '\n';
  }

  const status = failed === 0 ? '✅' : '❌';
  const time = (totalMs / 1000).toFixed(2);
  yield `${status} ${passed + failed} tests: ${passed} passed`;
  if (failed) yield `, ${failed} failed`;
  yield `  (${time}s)\n`;
}