import {Subject, Subscriber, Subscription} from "rxjs";

export class AdvancedAsyncSubject<T> extends Subject<T>{
  private _value: T = null;
  private hasNext: boolean = false;
  private hasFinished: boolean = false;
  
  /** @deprecated This is an internal implementation detail, do not use. */
  _subscribe(subscriber: Subscriber<any>): Subscription {
    if (this.hasError) {
      subscriber.error(this.thrownError);
      return Subscription.EMPTY;
    } else if (this.hasFinished && this.hasNext) {
      subscriber.next(this._value);
    }
    return super._subscribe(subscriber);
  }
  
  next(value: T): void {
    if (!this.hasFinished) {
      this._value = value;
      this.hasNext = true;
      this.finish();
    } else {
      this._value = value;
      super.next(value);
    }
  }
  
  get value() {
    return this.getValue();
  }
  
  getValue() {
    return this._value;
  }
  
  error(error: any): void {
    if (!this.hasFinished) {
      super.error(error);
    }
  }
  
  finish(): void {
    this.hasFinished = true;
    if (this.hasNext) {
      super.next(this._value);
    }
  }
}