/**
 * Map in input order with bounded parallelism. After the first failure, stop
 * scheduling work and drain every in-flight worker before rejecting.
 */
export async function mapBounded(items, limit, worker) {
  if (!Number.isSafeInteger(limit) || limit < 1) throw new Error('并发数量必须为正整数');
  const source = Array.from(items);
  const results = new Array(source.length);
  let next = 0;
  let failed = false;
  let firstError;

  async function run() {
    while (!failed && next < source.length) {
      const index = next++;
      try {
        results[index] = await worker(source[index], index);
      } catch (error) {
        if (!failed) {
          failed = true;
          firstError = error;
        }
      }
    }
  }

  await Promise.all(Array.from({ length: Math.min(limit, source.length) }, () => run()));
  if (failed) throw firstError;
  return results;
}