export class AsyncQueue<T> {
  private items: T[] = [];
  private resolvers: ((value: T) => void)[] = [];

  push(item: T): void {
    if (this.resolvers.length > 0) {
      const resolve = this.resolvers.shift()!;
      resolve(item);
    } else {
      this.items.push(item);
    }
  }

  pushAll(items: Iterable<T>): void {
    for (const item of items) {
      this.push(item);
    }
  }

  async pop(): Promise<T> {
    if (this.items.length > 0) {
      return this.items.shift()!;
    }
    return new Promise<T>((resolve) => {
      this.resolvers.push(resolve);
    });
  }

  get length(): number {
    return this.items.length - this.resolvers.length;
  }
}