auth-guard-with-forced-login.service.ts

import { Injectable } from '@angular/core';
import { ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';
import { Observable } from 'rxjs';
import { filter, switchMap, tap } from 'rxjs/operators';

import { AuthService } from './auth.service';

@Injectable()
export class AuthGuardWithForcedLogin {

  constructor(
    private authService: AuthService,
  ) {
  }

  canActivate(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot,
  ): Observable<boolean> {
    return this.authService.isDoneLoading$.pipe(
      filter(isDone => isDone),
      switchMap(_ => this.authService.isAuthenticated$),
      tap(isAuthenticated => isAuthenticated || this.authService.login(state.url)),
    );
  }
}