Add module for choosing/caching featured apps for display

src/dev.html

@@ -38,6 +38,7 @@
     <script src="media/js/worker.js"></script>
     <script src="media/js/pages.js"></script>
     <script src="media/js/apps.js"></script>
+    <script src="media/js/featured.js"></script>
     <script src="media/js/views/search.js"></script>
     <script src="media/js/main.js"></script>
   </body>

src/media/js/featured.js

@@ -0,0 +1,88 @@
+define('featured', ['settings', 'storage', 'log'], function(settings, storage, log) {
+
+  var console = log('featured');
+
+  return {
+
+    all: function() {
+      // This will eventually fetch from the JSON database. For now...
+      var cached = JSON.parse(storage.getItem('all_featured'));
+      if (!cached) {
+        cached = [
+          { name: 'trenta', weight: 10 },
+          { name: 'venti', weight: 8 },
+          { name: 'grande', weight: 6 },
+          { name: 'tall', weight: 4 },
+          { name: 'nessuno', weight: 2 }
+        ];
+        storage.setItem('all_featured', JSON.stringify(cached));
+      }
+      return cached;
+    },
+
+    get: function() {
+      // Retrieve a subset of the featured apps from cache. If the cache has
+      // expired, regenerate a random subset and return the featured apps.
+      var cached = JSON.parse(storage.getItem(this.cacheKey()))
+      if (!cached) {
+        cached = this.regenerate();
+        this.removeYesterday();
+      }
+      return cached;
+    },
+
+    cacheKey: function(date) {
+      // Generate a date-based cache key for the passed Date object (default: today).
+      if(typeof date === 'undefined') {
+        date = new Date();
+      };
+      return 'featured_' + date.toDateString().replace(' ', '_').toLowerCase();
+    },
+
+    regenerate: function() {
+      // From the pool of featured apps, returned a randomized, weighted selection to be
+      // displayed on the homepage. Store 
+      console.log('Generating a new selection of featured apps.');
+      var all = this.all();
+
+      // Create a weighted array of all the available items' indexes in `all`.
+      var weighted_index = [];
+      for (var i = 0; i < all.length; i++) {
+        for (var n = 0; n < Math.ceil(all[i].weight); n++) {
+          weighted_index.push(i);
+        }
+      }
+
+      // Choose the appropriate number of random unique indexes from the weighted array.
+      var chosen_items = [];
+      while (chosen_items.length < settings.numberFeatured) {
+        var random = weighted_index[Math.floor(Math.random() * weighted_index.length)];
+        if (chosen_items.indexOf(random) === -1) {
+          chosen_items.push(random);
+        }
+      }
+
+      // Map the chosen indexes back to their original objects.
+      var featured = [];
+      for (var i = 0; i < chosen_items.length; i++) {
+        featured.push(all[chosen_items[i]]);
+      }
+
+      // Store and return the original objects, removing yesterday's cache.
+      storage.setItem(this.cacheKey(), JSON.stringify(featured));
+      return featured;
+
+    },
+
+    removeYesterday: function() {
+      // Remove the cache for yesterday.
+      console.log('Removing yesterday\'s selection of featured apps.');
+      var date = new Date();
+      date.setDate(date.getDate() - 1);
+      var key = this.cacheKey(date);
+      storage.removeItem(key);
+    }
+
+  };
+
+});

src/media/js/settings.js

@@ -11,7 +11,10 @@ define('settings', ['settings_local', 'utils'], function(settings_local, utils)
 
     // How often (in milliseconds) to check if we have queued apps to install
     // when we return online.
-    offlineInterval: 1000
+    offlineInterval: 1000,
+
+    // Number of apps featured on the homepage.
+    numberFeatured: 6
   });
 
   // The version number for `localStorage` data. Bump when the schema for