Middlewarify dataview endpoint

lib/cartodb/controllers/layergroup.js

@@ -124,7 +124,8 @@ LayergroupController.prototype.register = function(app) {
         userMiddleware,
         allowQueryParams(allowedDataviewQueryParams),
         this.prepareContext,
-        this.dataview.bind(this)
+        this.getMapStoreMapConfigProvider(this.mapStore, this.userLimitsApi),
+        this.getDataview()
     );
 
     app.get(
@@ -133,7 +134,8 @@ LayergroupController.prototype.register = function(app) {
         userMiddleware,
         allowQueryParams(allowedDataviewQueryParams),
         this.prepareContext,
-        this.dataview.bind(this)
+        this.getMapStoreMapConfigProvider(this.mapStore, this.userLimitsApi),
+        this.getDataview()
     );
 
     app.get(
@@ -186,32 +188,31 @@ LayergroupController.prototype.analysisNodeStatus = function(req, res, next) {
     );
 };
 
-LayergroupController.prototype.dataview = function(req, res, next) {
-    var self = this;
+LayergroupController.prototype.getMapStoreMapConfigProvider = function (mapStore, userLimitsApi) {
+    return function getMapStoreMapConfigProviderMiddleware (req, res, next) {
+        const { user } = res.locals;
 
-    step(
-        function retrieveDataview() {
-            var mapConfigProvider = new MapStoreMapConfigProvider(
-                self.mapStore, res.locals.user, self.userLimitsApi, res.locals
-            );
-            self.dataviewBackend.getDataview(
-                mapConfigProvider,
-                res.locals.user,
-                res.locals,
-                this
-            );
-        },
-        function finish(err, dataview, stats) {
+        res.locals.mapConfigProvider = new MapStoreMapConfigProvider(mapStore, user, userLimitsApi, res.locals);
+
+        next();
+    };
+};
+
+LayergroupController.prototype.getDataview = function () {
+    return function getDataviewMiddleware (req, res, next) {
+        const { user, mapConfigProvider } = res.locals;
+
+        this.dataviewBackend.getDataview(mapConfigProvider, user, res.locals, (err, dataview, stats) => {
             req.profiler.add(stats || {});
 
             if (err) {
                 err.label = 'GET DATAVIEW';
-                next(err);
-            } else {
-                self.sendResponse(req, res, dataview, 200);
+                return next(err);
             }
-        }
-    );
+
+            this.sendResponse(req, res, dataview, 200);
+        });
+    }.bind(this);
 };
 
 LayergroupController.prototype.dataviewSearch = function(req, res, next) {