AngularJS interceptor in ES6.js

function authInterceptor($httpProvider) {

	
  $httpProvider.interceptors.push(($timeout, $q, $injector, userStorage) => {
    let $http, $state, $mdDialog, $mdToast, $signin;

    // this trick must be done so that we don't receive
    // `Uncaught Error: [$injector:cdep] Circular dependency found`
    $timeout(() => {
      $signin 		= $injector.get('$signin');
      $http 			= $injector.get('$http');
      $state 			= $injector.get('$state');
      $mdToast    = $injector.get('$mdToast');
      userStorage = $injector.get('userStorage');
			$mdDialog 	= $injector.get('$mdDialog');
    });


    let interceptor = {
      request				: request,      
      responseError	: responseError
    };
		return interceptor;
		
		//intercept request : example to add token :
		function request(config){
			//add autorization to header otherwise server will 401
			config.headers = config.headers || {};
			if (userStorage.isUserLoggedIn()) {
				config.headers.Authorization = 'Bearer ' + userStorage.getUserToken();
			}
			return config; 
		}
		
		//intercept errors
		function responseError(rejection){
			if (rejection.status !== 401 && rejection.status !== 409) return rejection;
			
			let deferred = $q.defer();

			/**
				* case an attenmpt to login, 
				* -> but error : prevent instance a new modal login
				* -> throw a toaster
				*/
			if (rejection.config.url    === '/api/user/login' && 
					rejection.config.method === 'POST') {					    
				deferred.reject('login failed');
			}else{
				let parent = angular.element(document.body);
				let clickOutsideToClose = true;		

						
				$signin.show(parent, clickOutsideToClose)
					.then(() => {
						deferred.resolve( $http(rejection.config) );
					})
					.catch(() => {
						$state.go('home');
						deferred.reject(rejection);
					});          
			}
			return deferred.promise;
		}
  });

}

authInterceptor.$inject = ['$httpProvider'];
export default authInterceptor;