import {
  Injectable,
  OnDestroy,
} from '@angular/core';
import {
  Observable,
  Subscription,
} from 'rxjs';
import {
  delay,
  map,
} from 'rxjs/operators';
import { ToggleSubject } from '@rxap/rxjs';

@Injectable()
export class LoadingIndicatorService implements OnDestroy {

  public isLoading$: Observable<boolean>;
  private readonly loading$ = new ToggleSubject(true);
  private readonly _attachedLoadingSubscription = new Subscription();

  constructor() {
    this.isLoading$ = this.loading$.asObservable();
  }

  public attachLoading(loading$: Observable<any>) {
    this._attachedLoadingSubscription.add(
      loading$.pipe(map(Boolean), delay(0)).subscribe(this.loading$.next),
    );
  }

  public ngOnDestroy() {
    this._attachedLoadingSubscription.unsubscribe();
  }

  public disable() {
    setTimeout(() => {
      this.loading$.disable();
    });
  }

  public enable() {
    setTimeout(() => {
      this.loading$.enable();
    });
  }

}