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gaia/apps/homescreen/js/settings.js

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+'use strict';
+
+(function(exports) {
+
+  /**
+   * Name of the global home screen settings datastore.
+   */
+  const SETTINGS_STORE = 'homescreen_settings';
+
+  /**
+   * Stored settings version, for use when changing/refactoring settings
+   * storage.
+   */
+  const SETTINGS_VERSION = 0;
+
+  /**
+   * Name of the global home screen columns setting.
+   */
+  const COLUMNS_SETTING = 'grid.cols';
+
+  /**
+   * Name of the global home screen paging setting.
+   */
+  const PAGING_SETTING = 'grid.paging';
+
+  function Settings() {
+    // Initialise default settings
+    this.small = false;
+    this.scrollSnapping = false;
+    this.firstRun = false;
+
+    // Listen to external settings changes
+    if (navigator.getDataStores) {
+      navigator.getDataStores(SETTINGS_STORE).then(stores => {
+        if (stores.length < 1) {
+          return Promise.reject('Settings datastore inaccessible');
+        }
+
+        var signalChange = () => {
+          this.save();
+          window.dispatchEvent(new CustomEvent('settings-changed'));
+        };
+
+        var syncSmallSetting = (signal) => {
+          stores[0].get(COLUMNS_SETTING).then(cols => {
+            var oldSmall = this.small;
+            this.small = cols > 3;
+            if (this.small !== oldSmall) {
+              signalChange();
+            }
+          });
+        };
+
+        var syncPagingSetting = () => {
+          stores[0].get(PAGING_SETTING).then(paging => {
+            var oldSnapping = this.scrollSnapping;
+            this.scrollSnapping = paging || false;
+            if (this.scrollSnapping !== oldSnapping) {
+              signalChange();
+            }
+          });
+        };
+
+        stores[0].addEventListener('change', e => {
+          switch (e.id) {
+            case COLUMNS_SETTING:
+              syncSmallSetting();
+              break;
+            case PAGING_SETTING:
+              syncPagingSetting();
+              break;
+          }
+        });
+
+        syncSmallSetting();
+        syncPagingSetting();
+      }, e => {
+        console.error('Error retrieving home screen settings datastore:', e);
+      });
+    } else {
+      console.error('Datastore API unavailable');
+    }
+
+    // Restore existing settings
+    var settingsString = localStorage.getItem('settings');
+    if (!settingsString) {
+      this.firstRun = true;
+      return;
+    }
+
+    var settings = JSON.parse(settingsString);
+    if (settings.version !== SETTINGS_VERSION) {
+      return;
+    }
+
+    this.small = settings.small || false;
+    this.scrollSnapping = settings.scrollSnapping || false;
+
+    // Monitor global homescreen settings
+    if (!navigator.getDataStores) {
+      console.error('Datastore API unavailable');
+      return;
+    }
+  }
+
+  Settings.prototype = {
+    save: function() {
+      localStorage.setItem('settings', JSON.stringify({
+        version: SETTINGS_VERSION,
+        small: this.small,
+        scrollSnapping: this.scrollSnapping
+      }));
+    }
+  };
+
+  exports.Settings = Settings;
+
+}(window));