class Queue<T extends { run: () => Promise<any> }> {
  private current?: Node<T>;
  private end?: Node<T>;
  private status: "waiting" | "running" = "waiting";
  private _myResolve?: (v: "finished" | "stopped") => void;
  private _promise?: Promise<"finished" | "stopped">;

  append(item: T, autoRun = false) {
    const node = new Node(item);
    if (!this.current || !this.end) {
      this.current = this.end = node;
    } else {
      this.end.setNext(node);
      this.end = node;
    }

    if (autoRun) {
      this.startRun();
    }
  }

  startRun() {
    if (this.status === "waiting") {
      this.run();
      this._promise = new Promise<"finished" | "stopped">((resolve) => {
        this._myResolve = resolve;
      });
    }
    return this._promise;
  }

  async run() {
    if (this.current) {
      this.status = "running";
      const current = this.current;
      const self = current.getSelf();
      this.current = this.current.getNext();
      const res = await self.run();
      current.destroy();
      if (res === false) {
        this.status = "waiting";
        this._myResolve("stopped");
        this._promise = undefined;
        this._myResolve = undefined;
      } else {
        this.run();
      }
    } else {
      this.end = undefined;
      this.status = "waiting";
      this._myResolve("finished");
      this._promise = undefined;
      this._myResolve = undefined;
    }
  }
}

class Node<T = any> {
  private prev?: Node<T>;
  private next?: Node<T>;
  private self: T;

  constructor(self: T) {
    this.self = self;
  }

  getSelf() {
    return this.self;
  }

  setPrev(prev?: Node<T>) {
    this.prev = prev;
    if (prev) {
      prev.next = this;
    }
  }

  setNext(next?: Node<T>) {
    this.next = next;
    if (next) {
      next.prev = this;
    }
  }

  getPrev() {
    return this.prev;
  }

  getNext() {
    return this.next;
  }

  destroy() {
    if (this.prev) {
      this.prev.setNext(undefined);
    }
    if (this.next) {
      this.next.setPrev(undefined);
    }
    this.prev = undefined;
    this.next = undefined;
    this.self = undefined;
  }
}

export { Queue };