Functional prefs implementation

lib/prefs.js

Index: lib/prefs.js
===================================================================
--- a/lib/prefs.js
+++ b/lib/prefs.js
@@ -14,23 +14,114 @@
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 //
 // The values are hardcoded for now.
 //
 
-var Prefs = exports.Prefs = {
+let defaults = {
+  __proto__: null,
   enabled: true,
   patternsfile: "patterns.ini",
   patternsbackups: 5,
   patternsbackupinterval: 24,
   data_directory: "",
   savestats: false,
   privateBrowsing: false,
   subscriptions_fallbackerrors: 5,
   subscriptions_fallbackurl: "https://adblockplus.org/getSubscription?version=%VERSION%&url=%SUBSCRIPTION%&downloadURL=%URL%&error=%ERROR%&channelStatus=%CHANNELSTATUS%&responseStatus=%RESPONSESTATUS%",
   subscriptions_autoupdate: true,
   subscriptions_exceptionsurl: "https://easylist-downloads.adblockplus.org/exceptionrules.txt",
   documentation_link: "https://adblockplus.org/redirect?link=%LINK%&lang=%LANG%",
-  addListener: function() {}
+  update_url_release: "https://updates.adblockplus.org/%NAME%/update.json",
+  update_url_devbuild: "https://adblockplus.org/devbuilds/%s/update.json",
+  last_update: 0
 };
+
+let values = Object.create(defaults);
+let path = _fileSystem.resolve("prefs.json");
+let listeners = [];
+let isDirty = false;
+let isSaving = false;
+
+function defineProperty(key)
+{
+  Prefs.__defineGetter__(key, function() values[key]);
+  Prefs.__defineSetter__(key, function(value)
+  {
+    if (typeof value != typeof defaults[key])
+      throw new Error("Attempt to change preference type");
+
+    if (value == defaults[key])
+      delete values[key];
+    else
+      values[key] = value;
+    save();
+
+    for each (let listener in listeners)
+      listener(key);
+  });
+}
+
+function load()
+{
+  _fileSystem.read(path, function(result)
+  {
+    // prefs.json is expected to be missing, ignore errors reading file
+    if (!result.error)
+    {
+      try
+      {
+        let data = JSON.parse(result.content);
+        for (let key in data)
+          if (key in defaults)
+            values[key] = data[key];
+      }
+      catch (e)
+      {
+        Cu.reportError(e);
+      }
+    }
+
+    if (typeof Prefs._initListener == "function")
+      Prefs._initListener();
+  });
+}
+
+function save()
+{
+  if (isSaving)
+  {
+    isDirty = true;
+    return;
+  }
+
+  isDirty = false;
+  isSaving = true;
+  _fileSystem.write(path, JSON.stringify(values), function()
+  {
+    isSaving = false;
+    if (isDirty)
+      save();
+  });
+}
+
+let Prefs = exports.Prefs = {
+  addListener: function(listener)
+  {
+    if (listeners.indexOf(listener) < 0)
+      listeners.push(listener);
+  },
+
+  removeListener: function(listener)
+  {
+    let index = listeners.indexOf(listener);
+    if (index >= 0)
+      listeners.splice(index, 1);
+  },
+};
+
+for (let key in defaults)
+  defineProperty(key);
+
+load();