feat(articles): ArticlesService extended $resource (#1266)

Extends the ArticlesService $resource object to include a custom method
for creating, or updating, an Article instance.

Related #1260

modules/articles/client/controllers/articles.client.controller.js

@@ -31,12 +31,10 @@
         return false;
       }
 
-      // TODO: move create/update logic to service
-      if (vm.article._id) {
-        vm.article.$update(successCallback, errorCallback);
-      } else {
-        vm.article.$save(successCallback, errorCallback);
-      }
+      // Create a new article, or update the current instance
+      vm.article.createOrUpdate()
+        .then(successCallback)
+        .catch(errorCallback);
 
       function successCallback(res) {
         $state.go('articles.view', {

modules/articles/client/services/articles.client.service.js

@@ -8,12 +8,46 @@
   ArticlesService.$inject = ['$resource'];
 
   function ArticlesService($resource) {
-    return $resource('api/articles/:articleId', {
+    var Article = $resource('api/articles/:articleId', {
       articleId: '@_id'
     }, {
       update: {
         method: 'PUT'
       }
     });
+
+    angular.extend(Article.prototype, {
+      createOrUpdate: function () {
+        var article = this;
+        return createOrUpdate(article);
+      }
+    });
+
+    return Article;
+
+    function createOrUpdate(article) {
+      if (article._id) {
+        return article.$update(onSuccess, onError);
+      } else {
+        return article.$save(onSuccess, onError);
+      }
+
+      // Handle successful response
+      function onSuccess(article) {
+        // Any required internal processing from inside the service, goes here.
+      }
+
+      // Handle error response
+      function onError(errorResponse) {
+        var error = errorResponse.data;
+        // Handle error internally
+        handleError(error);
+      }
+    }
+
+    function handleError(error) {
+      // Log error
+      console.log(error);
+    }
   }
 }());