Default preferences loader

Thunderbird nightly builds currently do not load default preferences.
They may fix this at some point, but when we convert this add-on to
bootstrapped we'll have to load our own default preferences anyway, so
might as well start doing it now.

chrome.manifest

@@ -1,4 +1,5 @@
 content   FolderPaneSwitcher                 chrome/content/
+content   FolderPaneSwitcher-defaults        defaults/
 locale    FolderPaneSwitcher   en-US         chrome/locale/en-US/
 locale    FolderPaneSwitcher   fr            chrome/locale/fr/
 locale    FolderPaneSwitcher   nl            chrome/locale/nl/

chrome/content/FolderPaneSwitcher.js

@@ -1,5 +1,7 @@
 // -*- js-indent-level: 2 -*-
 Components.utils.import("resource:///modules/gloda/log4moz.js");
+Components.utils.import(
+  "chrome://FolderPaneSwitcher/content/defaultPreferencesLoader.jsm");
 
 // Rules:
 // 
@@ -102,6 +104,22 @@ var FolderPaneSwitcher = {
   },
 
   onLoad: function() {
+    // Current Thunderbird nightly builds do not load default preferences
+    // from overlay add-ons. They're probably going to fix this, but it may go
+    // away again at some point in the future, and in any case we'll need to do
+    // it ourselves when we convert from overlay to bootstrapped, and there
+    // shouldn't be any harm in setting the default values of preferences twice
+    // (i.e., both Thunderbird and our code doing it).
+    // This is in a try/catch because if it fails it's probably because
+    // setStringPref failed, in which case we're running inside an earlier
+    // application version which has already loaded the default preferences
+    // automatically.
+    try {
+        var loader = new DefaultPreferencesLoader();
+        loader.parseUri("chrome://FolderPaneSwitcher-defaults/content/" +
+                        "preferences/prefs.js");
+    } catch (ex) {}
+
     if (! this.logger) {
       this.logger = Log4Moz.getConfiguredLogger("extensions.FolderPaneSwitcher",
 						Log4Moz.Level.Trace,

chrome/content/defaultPreferencesLoader.jsm

@@ -0,0 +1,149 @@
+// https://gist.github.com/oshybystyi/8cf882bc8b0c9a95a116
+
+/**
+ * Working example can be found here
+ * https://github.com/oshybystyi/FireX-Pixel-Perfect/blob/issue-5-make-addon-restartless/content/lib/defaultPreferencesLoader.jsm
+ *
+ * Important this module was tested only with <em:unpack>true</em:unpack>, most
+ * likely it won't work with false value
+ *
+ * A lot of stuff was borrowed from https://github.com/firebug/firebug/blob/master/extension/modules/prefLoader.js
+ */
+
+const { utils: Cu, classes: Cc, interfaces: Ci } = Components;
+
+Cu.import('resource://gre/modules/Services.jsm');
+
+var EXPORTED_SYMBOLS = ['DefaultPreferencesLoader'];
+
+/**
+ * Read defaults/preferences/* and set Services.pref default branch
+ */
+function DefaultPreferencesLoader(installPath, prefDir) {
+    var readFrom = [];
+
+    this.readFrom = readFrom;
+
+    this.defaultBranch = Services.prefs.getDefaultBranch("");
+
+    if (! installPath)
+        // We'll be using parseUri instead of parseDirectory
+        return;
+
+    if (! prefDir)
+        prefDir = 'defaults/preferences';
+
+    // Maybe instead just test if it's a file rather than a directory?
+    // Not sure.
+    if (/\.xpi$/i.test(installPath.path)) {
+        let baseURI = Services.io.newFileURI(installPath);
+        // Packed extension, need to read ZIP to get list of preference files
+        // and then use "jar:" URIs to access them.
+        let zr = Cc['@mozilla.org/libjar/zip-reader;1'].createInstance(
+            Ci.nsIZipReader);
+        zr.open(installPath);
+        let entries = zr.findEntries(prefDir + '/?*');
+        while (entries.hasMore()) {
+            let entry = entries.getNext();
+            readFrom.push('jar:' + baseURI.spec + "!/" + entry);
+        }
+    }
+    else {
+        let dirPath = installPath.clone(); // don't modify the original object
+
+        prefDir.split('/').forEach(function(dir) {
+            dirPath.append(dir);
+        });
+
+        if (dirPath.exists() !== true) {
+            throw new DefaultsDirectoryMissingError(dirPath);
+        }
+
+        let entries = dirPath.directoryEntries;
+
+        while (entries.hasMoreElements()) {
+            let fileURI = Services.io.newFileURI(entries.getNext());
+            readFrom.push(fileURI.spec);
+        }
+    }
+} 
+
+DefaultPreferencesLoader.prototype = {
+    /**
+     * Iterate over files in the default/preferences/*
+     *
+     * @param {function} prefFunc the function that should be used instead of
+     * pref
+     */
+    parseDirectory: function(prefFunc) {
+        this.readFrom.forEach(function(uri) {
+            this.parseUri(uri, prefFunc);
+	});
+    },
+
+    parseUri: function(uri, prefFunc) {
+        prefFunc = prefFunc || this.pref.bind(this);
+	Services.scriptloader.loadSubScript(uri, { pref: prefFunc });
+    },
+
+    /**
+     * Emulates firefox pref function to load default preferences
+     */
+    pref: function(key, value) {
+        switch (typeof value) {
+            case 'boolean':
+                this.defaultBranch.setBoolPref(key, value);
+                break;
+
+            case 'number':
+                this.defaultBranch.setIntPref(key, value);
+                break;
+
+            case 'string':
+                this.defaultBranch.setStringPref(key, value);
+                break;
+
+            default:
+                throw new NotSupportedValueTypeError(key);
+                break;
+        }
+    },
+
+    /**
+     * Clears default preferences according to AMO reviewers reccommendation
+     * This should be invoked on bootstrap::shutdown
+     * @see https://github.com/firebug/firebug/blob/master/extension/modules/prefLoader.js
+     */
+    clearDefaultPrefs: function() {
+        this.parseDirectory(this.prefUnload.bind(this));
+    },
+
+    prefUnload: function(key) {
+        let branch = this.defaultBranch;
+        if (branch.prefHasUserValue(key) !== true) {
+            branch.deleteBranch(key);
+        }
+    }
+
+};
+
+/**
+ * Exception type on missing defaults/preferences folder
+ */
+function DefaultsDirectoryMissingError(installPath) {
+    this.name = 'DefaultsDirectoryMissingError';
+    this.message = '\'' + installPath.path + '\' does no exist';
+}
+
+/** Inherit from Error for error stack and pretty output in terminal **/
+DefaultsDirectoryMissingError.prototype = new Error();
+
+/**
+ * Not supported value type to store by pref
+ */
+function NotSupportedValueTypeError(key) {
+    this.name = 'NotSupportedValueType';
+    this.message = 'Value type for key \'' + key + '\' is not supported';
+}
+
+NotSupportedValueTypeError.prototype = new Error();