export class AsyncQueue {
  private queue: (() => Promise<void>)[] = [];
  private activeCount = 0;

  constructor(private concurrency: number) {}

  async add<T>(task: () => Promise<T>): Promise<T> {
    return new Promise<T>((resolve, reject) => {
      this.queue.push(async () => {
        try {
          resolve(await task());
        } catch (e) {
          reject(e);
        }
      });
      this.process();
    });
  }

  private async process() {
    if (this.activeCount >= this.concurrency || this.queue.length === 0) return;
    this.activeCount++;
    const task = this.queue.shift();
    if (task) {
      try {
        await task();
      } finally {
        this.activeCount--;
        this.process();
      }
    }
  }
}