auth.guard.ts

@Injectable({
  providedIn: 'root',
})
export class AuthGuard implements CanActivate {
  constructor(private router: Router, private authService: AuthService) {}

  canActivate(
    next: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ):
    | Observable<boolean | UrlTree>
    | Promise<boolean | UrlTree>
    | boolean
    | UrlTree {
    return this.authService.user$.pipe(
      map((user) => {
        if (user) {
          return true;
        } else {
          this.router.navigate(['login'], {
            queryParams: { returnUrl: state.url },
          });
          return false;
        }
      })
    );
  }
}