export class CancelError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CancelError";
  }

  public get isCancelled(): boolean {
    return true;
  }
}

export interface OnCancel {
  readonly isResolved: boolean;
  readonly isRejected: boolean;
  readonly isCancelled: boolean;

  (cancelHandler: () => void): void;
}

export class CancelablePromise<T> implements Promise<T> {
  #isResolved: boolean;
  #isRejected: boolean;
  #isCancelled: boolean;
  readonly #cancelHandlers: (() => void)[];
  readonly #promise: Promise<T>;
  #resolve?: (value: T | PromiseLike<T>) => void;
  #reject?: (reason?: any) => void;

  constructor(
    executor: (
      resolve: (value: T | PromiseLike<T>) => void,
      reject: (reason?: any) => void,
      onCancel: OnCancel
    ) => void
  ) {
    this.#isResolved = false;
    this.#isRejected = false;
    this.#isCancelled = false;
    this.#cancelHandlers = [];
    this.#promise = new Promise<T>((resolve, reject) => {
      this.#resolve = resolve;
      this.#reject = reject;

      const onResolve = (value: T | PromiseLike<T>): void => {
        if (this.#isResolved || this.#isRejected || this.#isCancelled) {
          return;
        }
        this.#isResolved = true;
        this.#resolve?.(value);
      };

      const onReject = (reason?: any): void => {
        if (this.#isResolved || this.#isRejected || this.#isCancelled) {
          return;
        }
        this.#isRejected = true;
        this.#reject?.(reason);
      };

      const onCancel = (cancelHandler: () => void): void => {
        if (this.#isResolved || this.#isRejected || this.#isCancelled) {
          return;
        }
        this.#cancelHandlers.push(cancelHandler);
      };

      Object.defineProperty(onCancel, "isResolved", {
        get: (): boolean => this.#isResolved,
      });

      Object.defineProperty(onCancel, "isRejected", {
        get: (): boolean => this.#isRejected,
      });

      Object.defineProperty(onCancel, "isCancelled", {
        get: (): boolean => this.#isCancelled,
      });

      return executor(onResolve, onReject, onCancel as OnCancel);
    });
  }

  get [Symbol.toStringTag]() {
    return "Cancellable Promise";
  }

  public then<TResult1 = T, TResult2 = never>(
    onFulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null,
    onRejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null
  ): Promise<TResult1 | TResult2> {
    return this.#promise.then(onFulfilled, onRejected);
  }

  public catch<TResult = never>(
    onRejected?: ((reason: any) => TResult | PromiseLike<TResult>) | null
  ): Promise<T | TResult> {
    return this.#promise.catch(onRejected);
  }

  public finally(onFinally?: (() => void) | null): Promise<T> {
    return this.#promise.finally(onFinally);
  }

  public cancel(): void {
    if (this.#isResolved || this.#isRejected || this.#isCancelled) {
      return;
    }
    this.#isCancelled = true;
    if (this.#cancelHandlers.length) {
      try {
        for (const cancelHandler of this.#cancelHandlers) {
          cancelHandler();
        }
      } catch (error) {
        console.warn("Cancellation threw an error", error);
        return;
      }
    }
    this.#cancelHandlers.length = 0;
    this.#reject?.(new CancelError("Request aborted"));
  }

  public get isCancelled(): boolean {
    return this.#isCancelled;
  }
}