import { CHANNEL, CHANNEL_TOKEN, TalyPageDataService } from '@allianz/taly-core';
import { Inject, Injectable, TemplateRef } from '@angular/core';
import { BehaviorSubject, Observable, combineLatest } from 'rxjs';
import { distinctUntilChanged, map, skip, tap } from 'rxjs/operators';
import { TalyFrameLayoutService } from './frame-layout.service';

export type SidebarTemplateSet = Set<TemplateRef<unknown>>;

/**
 * Collect and maintain a list of templates candidates marked by the directive `[pgrSidebar]`
 * somewhere in the application. The templates can be accessed through `templateList$`.
 *
 * The application can set the explicit visibility of the sidebar (`setVisibility`/`show`/`hide`) which gets combined
 * with external factors like the channel (`expert` vs `retail`) and the current active layout (`stacked` or not).
 * That combined status is named `show` and reflects the actual visibility of the sidebar in the sidebar.
 * Accessible through the observable `show$`.
 */
@Injectable()
export class TalyFrameSidebarService {
  private _registeredTemplates: SidebarTemplateSet = new Set();
  private _templatesListSubject = new BehaviorSubject<SidebarTemplateSet>(
    this._registeredTemplates
  );
  private _visibility = false;
  private _visibilitySubject = new BehaviorSubject(this._visibility);
  private _showObservable$!: Observable<boolean>;

  constructor(
    private _talyPageDataService: TalyPageDataService,
    private _frameLayout: TalyFrameLayoutService,
    @Inject(CHANNEL_TOKEN) private _channel: CHANNEL
  ) {
    this.init();
  }

  init() {
    this._talyPageDataService.pageData$
      .pipe(
        skip(1), // skip the first as we subscribe to a behavior subject
        tap(() => this._pageChanged())
      )
      .subscribe();

    const isExpert: boolean = this._channel === CHANNEL.EXPERT;
    const isStacked$ = this._frameLayout.isStackedLayoutObservable;
    const isTooNarrow$ = this._frameLayout.hideSidebarBreakpoint$;

    if (!isExpert) {
      this._showObservable$ = new BehaviorSubject(false).asObservable();
      return;
    }

    this._showObservable$ = combineLatest([isStacked$, isTooNarrow$, this._visibilitySubject]).pipe(
      map(([isStacked, isTooNarrow, showSidebar]) => {
        return showSidebar && !isStacked && !isTooNarrow;
      }),
      distinctUntilChanged()
    );
  }

  registerTemplate(template: TemplateRef<unknown>) {
    this._registeredTemplates.add(template);
    this._update();
  }

  get templateList$() {
    return this._templatesListSubject.asObservable();
  }

  /**
   * combined status of the overall visibility defined by the channel,
   * active layout and the explicitly defined visibility
   */
  get show$() {
    return this._showObservable$;
  }

  setVisibility(value: boolean) {
    if (value) {
      this.show();
    } else {
      this.hide();
    }
  }

  hide() {
    if (this._visibility === true) {
      this._visibility = false;
      this._visibilitySubject.next(this._visibility);
    }
  }

  show() {
    if (this._visibility === false) {
      this._visibility = true;
      this._visibilitySubject.next(this._visibility);
    }
  }

  private _pageChanged() {
    this._registeredTemplates.clear();
    this._update();
  }

  private _update() {
    this._templatesListSubject.next(this._registeredTemplates);
  }
}