import { Injectable, OnDestroy } from '@angular/core';
import { SettingsService } from './settings.service';
import { SelfUpdaterService } from './self-updater.service';
import { Subject, timer, Subscription } from 'rxjs';
import { ActivationStart, Router } from '@angular/router';
import { SlideShowService } from '../../display/slide-show.service';
import { filter, switchMap } from 'rxjs/operators';

const TIMER_UPDATE_POLL_INTERVAL = 30000;

@Injectable()
export class TimerService implements OnDestroy {
  private autoSwitch = false;
  private slideShowTimer: Subscription;
  private selfUpdateCheckerTimer: Subscription;
  private slideTimerSubject: Subject<number> = new Subject<number>();
  private slideIntervalSubscription: Subscription;

  constructor(private settings: SettingsService,
              private selfUpdaterService: SelfUpdaterService,
              private router: Router,
              private slideShowService: SlideShowService) {

    const timerSUC = timer(TIMER_UPDATE_POLL_INTERVAL, TIMER_UPDATE_POLL_INTERVAL);
    this.selfUpdateCheckerTimer = timerSUC.subscribe(() => {
      this.selfUpdaterService.checkAndReloadIfNecessary();
    });

    this.slideShowTimer = this.slideTimerSubject
      .pipe(switchMap((period: number) => timer(period)))
      .subscribe(() => this.changeSlide());
    this.setSlideTimer(this.settings.slideInterval);

    this.autoSwitch = false;
    this.router.events
      .pipe(filter(event => event instanceof ActivationStart))
      .subscribe((event: ActivationStart) => this.autoSwitch = !!event.snapshot.data.autoSwitchable);

    this.slideIntervalSubscription = this.settings.slideIntervalChanged.subscribe(
      interval => this.setSlideTimer(interval)
    );
  }

  public ngOnDestroy() {
    this.slideShowTimer.unsubscribe();
    this.selfUpdateCheckerTimer.unsubscribe();
    this.slideIntervalSubscription.unsubscribe();
  }

  private changeSlide() {
    if (this.autoSwitch) {
      this.slideShowService.nextSlide();
    }
    this.setSlideTimer(this.settings.slideInterval);
  }

  public setSlideTimer(delay: number) {
    this.slideTimerSubject.next(delay);
  }
}