core.facade.ts

@Injectable({
  providedIn: 'root'
})
export class CoreFacade {

  public isLoggedIn$ = this._store.select((state: CoreState) => !!state.authToken);
  
  constructor(private _store: CoreStore, private _loginService: LoginService) { }

  public getTrackNumber(): string {
    return this._store.state.trackNumber;
  }

  public generateDeviceId(): void {
    // generate Device-Id just once
    this._store.readDeviceId().then(deviceId => {
      if (!deviceId) {
        this._store.setDeviceId(UUID.next().value)
          .finally(() => console.log('Device-Id has been generated'));
      }
    });
  }
  
  public identifyDevice(trackNumber: string): Observable<boolean> {
    const stream$ = forkJoin([
        ...
        this._store.setTrackNumber(trackNumber)
      ]
    ).pipe(
      switchMap(_ => _loginService.identifyDevice(trackNumber)),
    );

    return stream$;
  }  
}