Angular JS HTTP response interceptor

interceptor.js

/**
 * Interceptor
 * Implements functionality to catch various requests and fire events when they happen. This is generally to ensure
 * that responses from the server are handled in a uniform fashion across the application. Also, by firing events
 * it allows to have any number of handlers attach to the response.
 * 
 * @author Kirk Bushell
 * @date 28th March 2013
 */
var module = angular.module('core.interceptor', []);

module.service( 'Messages', [ '$filter', function( $filter ) {
	var service = {
		
		/**
		 * Store all the messages here. The default (base) or the custom messages.
		 *
		 * @type {Object}
		 */
		messages: {
			base: {
				error: {
					create: 'Could not create :resource. Please try again.',
					read:   'Could not load :resource. Please try again.',
					update: 'Could not update :resource. Please try again.',
					'delete': 'Could not delete :resource. Please try again.'
				},
				success: {
					create: ':resource created.',
					read:   'Loaded :resource successfully.',
					update: ':resource saved.',
					'delete': ':resource deleted.'
				}
			},
			
			// Custom messages are stored here.
			custom: {}
		},
		
		get: function( resource , action , type ) {
			resource.split( '-' ).join( ' ' );
			resource = $filter( 'ucfirst' )( resource );
			
			var customResource = get( service.messages.custom[ resource.toLowerCase() ] );
			if ( customResource != null ) {
				var custom = get( customResource[ type ][ action ] );
				if ( custom != null ) return custom;
			}
			
			// Get the default message, if available, and perform the replacement.
			var msg = get( service.messages.base[ type ][ action ] );
			
			if ( msg && msg.length > 0 ) {
				msg = msg.split( ':resource' ).join( resource.singularize() );
			}
			
			return msg;
		},
		
		/**
		 * Registers a resource and all its custom messages.
		 *
		 * @param  {String} resource Resource name
		 * @param  {Object} messages An object with create, read, update, delete keys
		 *
		 * @return {void}
		 */
		register: function( resource , messages ) {
			service.messages.custom[ resource ] = messages;
		}
		
	};
	
	return service;
}]);

module.config(['$httpProvider', function($httpProvider) {
	var interceptor = ['$rootScope', '$q', 'Notify', 'Messages', 'Analytics', function($rootScope, $q, Notify, Messages, Analytics ) {
		
		/**
		 * Parses the resource based on the url that was sent.
		 *
		 * @param  {object} response Response object
		 *
		 * @return {string}
		 */
		var getResourceFromResponse = function( response ) {
			var urlParts = response.config.url.split('?'),
				url      = urlParts[0].replace(/^\/|\/$/g, ''), // strip first and last slash.
				base     = $rootScope.config.app.base.replace(/^\/|\/$/g, ''); // strip first and last slash.
			
			// If there's a base, let's strip it out.
			if ( base.length ) {
				url = url.replace( base , '' );
			}
			
			urlParts = url.split('/');
			url = urlParts[0];
			
			return url;
		}
		
		/**
		 * Extracts an ID from a URL, if it's available.
		 *
		 * @param  {string} resource The name of the resource.
		 * @param  {string} url      The URL to parse.
		 *
		 * @return {mixed}           Returns the extracted ID or null.
		 */
		var getIDFromURL = function( resource , url ) {
			var urlParts   = url.split( resource ),
				possibleID = urlParts[ 1 ],
				id;
			
			// If there is nothing, we know we're creating and not updating.
			// Therefore, there will be no ID to return.
			if ( !possibleID ) return null;
			
			// Remove the first occurance of a slash.
			possibleID = possibleID.replace('/', '');
			
			// Check if there are any more slashes, so we know whether we should split
			// the possible ID variable or just return it.
			if ( possibleID.indexOf('/') === -1 ) {
				return isNaN( possibleID ) ? null : possibleID;
			}
			
			// Since at this point we know that the url still has a slash in it, we will
			// split on that slash and get the first part of the array.
			id = possibleID.split('/')[0];
			
			// Now we want to check if the value is a number or not.
			return isNaN( id ) ? null : id;
		};

		/**
		 * Returns a custom resource action, if it has been supplied in the URL. This is defined
		 * by a string representation AFTER the resource id. Eg.
		 *
		 * /entries/1/submit
		 *
		 * @param string resource
		 * @param string url
		 * @return mixed string on success, null on failure
		 */
		var getActionFromUrl = function( resource, url ) {
			url = url.replace( config.app.base, '' ).split( '/' );
			url.shift();
			
			// Could be dealing with an integer or extra action
			if ( url.length > 1 ) {
				if ( isNaN( url[ 1 ] ) ) {
					// custom action
					return url[ 1 ];
				}

				if ( url.length > 2 && isNaN( url[ 2 ] ) ) {
					return url[ 2 ];
				}
			}

			return null;
		};
		
		/**
		 * Based on the data returned from the server whenever there's a validation error
		 * we will construct a single validation message that is displayed in an alert.
		 *
		 * @param  {Object} data The data object returned from the server.
		 *
		 * @return {String}
		 */
		var getValidationMessages = function( response ) {
			var errors = [];
			
			// Check if the response is empty, meaning there are no validation errors.
			if ( getResponseType(response) != 'validation' || $.isEmptyObject( response.data ) || $.isEmptyObject( response.data.errors ) ) return errors;
			
			// Put all the errors from all the fields into 1 array. Basically flatenning the array.
			angular.forEach( response.data.errors , function( issues ) {
				angular.forEach( issues , function( error ) {
					errors.push( error );
				});
			});
			
			return errors;
		}
		
		var getResponseType = function( response ) {
			return get( response.headers()[ 'x-response-type' ] );
		}
		
		var notificationate = function( response ) {
			var method       = response.config.method.toLowerCase(),
				action       = '',
				status       = response.status,
				type         = 'Error', // notification type. Error, Success, Info or Warning.
				responseType = getResponseType( response ), // custom response type.
				message      = null,
				resource,
				possibleAction;
			
			// Ignore GET requests.
			if ( method == 'get' && status == 200 ) return;
			
			// Any status 200 responses at this point are for successful operations.
			// So we will change the notification type to Success.
			if ( status == 200 ) type = 'Success';
			
			
			// Parse the resource name.
			resource = getResourceFromResponse( response );
			
			// Do not display any message for exceptions.
			if ( resource == 'exceptions' ) return;
			
			// Let's determine what action is taken based on the request method.
			switch ( method ) {
				case 'post':   action = 'create'; break;
				case 'get':    action = 'read';   break;
				case 'put':    action = 'update'; break;
				case 'delete': action = 'delete'; break;
			}
			
			// Check if there's an ID in the URL whenever we send a post request because the action
			// could be update instead of create.
			// This is done because ngResource sends a POST request for updates instead of PUT.
			if ( method == 'post' ) {
				if ( getIDFromURL( resource , response.config.url ) ) {
					action = 'update';
				}
			}

			// Set up our action based on whether or not a custom one has been defined in the URL
			possibleAction = getActionFromUrl( resource, response.config.url );

			if ( possibleAction ) {
				action = possibleAction;
			}
			
			// Based on the response status.
			switch ( status ) {
				case 400:
					if ( responseType == 'validation' ) {
						if ( typeof response.data.message == 'string' ) {
							message = response.data.message;
						}
					}
					else {
						message = response.data;
					}
					break;

				case 401:
					message = 'Your current session has expired. Please log in.';
					break;
				
				case 403:
					message = 'You do not have sufficient permission to access this resource.';
					break;
				
				case 500:
					if ( angular.isString( response.data ) && response.data.length ) {
						message = response.data;
					}
					break;
				
			}
			
			if ( !message ) {
				message = Messages.get( resource , action , type.toLowerCase() );
			}
			
			// Send an update to the validation-errors directive to show/hide validation errors.
			$rootScope.$broadcast( 'validation.errors', getValidationMessages( response ) );
			
			if ( message ) {
				Notify[type]( message );
				
				// Google Analytics event tracking.
				Analytics.trackEvent( resource , type , message );
			}
		}
		
		/**
		 * Broadcasts an event that any part of the app can listen to
		 * and perform custom actions.
		 *
		 * @param  string name     The event name
		 * @param  mixed  response The response that comes back from the server
		 *
		 * @return void
		 */
		var broadcast = function( name , response ) {
			$rootScope.$broadcast( name , response );
			
			notificationate( response );
		}
		
		/**
		 * Successful response handler.
		 *
		 * @param  mixed response The response th at comes back from the server
		 *
		 * @return mixed
		 */
		var success = function( response ) {
			broadcast( 'app.success' , response );
			
			return response;
		}
		
		/**
		 * Invalid response handler.
		 *
		 * @param  mixed response The response th at comes back from the server
		 *
		 * @return mixed
		 */
		var error = function( response ) {
			// This is the default error event to broadcast.
			// It may be overwritten depending on the response status.
			var event = 'app.unknown-error';
			
			switch (response.status) {
				case 400: event = 'app.error'; break; // Bad requests (validation errors.etc.)
				case 401: event = 'app.unauthorised'; break; // Unauthorised, should require login
				case 403: event = 'app.forbidden'; break; // Forbidden, user is simply not allowed access
				case 500: event = 'app.failure'; break; // Critical error on the server, catch and display
			}
			
			broadcast( event , response );
			
			return $q.reject( response );
		}
		
		
		return function(promise) {
			return promise.then( success, error );
		};
	}];
	
	$httpProvider.responseInterceptors.push( interceptor );
}]);