[Framework] First-pass implementation of bundle loader

Begin implementing the bundle loader component of the
framework layer, responsible for taking a list of
included bundles and exposing their contents in a
useful manner. WTD-518.

platform/framework/src/BundleLoader.js

@@ -4,17 +4,89 @@
  * Module defining BundleLoader.js. Created by vwoeltje on 10/31/14.
  */
 define(
-    [],
-    function () {
+    ['./Constants', './Bundle'],
+    function (Constants, Bundle) {
         "use strict";
 
+        var INVALID_ARGUMENT_MESSAGE = "Malformed loadBundles argument; " +
+            "expected string or array",
+            BAD_CONTENTS_PREFIX = "Invalid bundle contents for ",
+            LOAD_ERROR_PREFIX = "Failed to load bundle ";
+
         /**
          *
          * @constructor
+         * @param {object} $http Angular's HTTP requester
+         * @param {object} $log Angular's logging service
          */
-        function BundleLoader() {
-            return {
+        function BundleLoader($http, $log) {
 
+            // Utility function; load contents of JSON file using $http
+            function getJSON(file) {
+                return $http.get(file).then(function (response) {
+                    return response.data;
+                });
+            }
+
+            // Remove bundles which failed to load properly.
+            // These should have been logged when loaded by
+            // loadBundleDefinition, so at this point they are safe
+            // to discard.
+            function filterBundles(array) {
+                return array.map(function (x) { return x !== undefined; });
+            }
+
+            // Convert JSON bundle definitions to Bundle objects.
+            function objectifyBundles(bundleDefinitions) {
+                return bundleDefinitions.map(function (definition) {
+                    return new Bundle()
+                });
+            }
+
+            // Load a definition for a bundle
+            function loadBundleDefinition(bundlePath) {
+                return getJSON(bundlePath + "/" + Constants.BUNDLE_FILE).then(
+                    function (x) {
+                        if (x === null || typeof x !== 'object') {
+                            $log.warn(BAD_CONTENTS_PREFIX + bundlePath);
+                            return undefined;
+                        }
+                        return x;
+                    },
+                    function () {
+                        $log.warn(LOAD_ERROR_PREFIX + bundlePath);
+                        return undefined;
+                    }
+                );
+            }
+
+            function loadBundle(bundlePath) {
+                return loadBundleDefinition(bundlePath).then(function (definition) {
+                    return definition && (new Bundle(bundlePath, definition));
+                });
+            }
+
+            function loadBundlesFromArray(bundleArray) {
+                var bundlePromises = bundleArray.map(loadBundleDefinition);
+
+                return Promise.all(bundlePromises)
+                        .then(filterBundles)
+                        .then(objectifyBundles);
+            }
+
+            function loadBundlesFromFile(listFile) {
+                return getJSON(listFile).then(loadBundlesFromArray);
+            }
+
+            function loadBundles(bundles) {
+                return Array.isArray(bundles) ? loadBundlesFromArray(bundles) :
+                        (typeof bundles === 'string') ? loadBundlesFromFile(bundles) :
+                                Promise.reject(new Error(INVALID_ARGUMENT_MESSAGE));
+            }
+
+
+            return {
+                loadBundles: loadBundles
             };
         }