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gaia/apps/system/lockscreen/js/settings/settings_cache.js

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+ 'use strict';
+
+/**
+ * A settings getter/setter cache.
+ * Provide as few as possible APIs like the native APIs do.
+ **/
+(function(exports) {
+  var LockScreenSettingsCache = function() {
+    this.cache = {};
+    this.handleSettings = this.handleSettings.bind(this);
+  };
+  LockScreenSettingsCache.prototype.get = function(entry) {
+    if (this.cache[entry]) {
+      return Promise.resolve(this.cache[entry]);
+    }
+
+    var resolve, reject;
+    var promise = new Promise((rev, rej) => {
+      resolve = rev;
+      reject = rej;
+    });
+    var lock = navigator.mozSettings.createLock();
+    var req = lock.get(entry);
+    req.then(() => {
+      this.cache[entry] = req.result;
+      // Once it getted, monitor it to update cache.
+      navigator.mozSettings
+        .addObserver(entry, this.handleSettings);
+      resolve(req.result);
+    }).catch(() => {
+      reject(req.error);
+    });
+    return promise;
+  };
+  LockScreenSettingsCache.prototype.set = function(entry, value) {
+    var resolve, reject;
+    var promise = new Promise((rev, rej) => {
+      resolve = rev;
+      reject = rej;
+    });
+    var lock = navigator.mozSettings.createLock();
+    var reqcontent = {};
+    reqcontent[entry] = value;
+    var req = lock.set(reqcontent);
+    req.then(() => {
+      this.cache[entry] = value;
+      resolve();
+    }).catch(() => {
+      reject();
+    });
+    return promise;
+  };
+  LockScreenSettingsCache.prototype.handleSettings = function(evt) {
+    var { settingsName, settingsValue } = evt;
+    this.cache[settingsName] = settingsValue;
+  };
+  LockScreenSettingsCache.prototype.stop = function() {
+    Object.keys(this.cache).forEach((entry) => {
+      navigator.mozSettings.removeObserver(entry, this.handleSettings);
+    });
+  };
+  exports.LockScreenSettingsCache = LockScreenSettingsCache;
+})(window);
+