1 files changed, 99 insertions, 0 deletions
diff --git a/mailnews/base/src/folderLookupService.js b/mailnews/base/src/folderLookupService.js
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+++ b/mailnews/base/src/folderLookupService.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This module implements the folder lookup service. Presently, this uses RDF as
+ * the backing store, but the intent is that this will eventually become the
+ * authoritative map.
+ */
+
+"use strict";
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cr = Components.results;
+
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+
+function isValidFolder(folder) {
+  // RDF is liable to return folders that don't exist, and we may be working
+  // with a deleted folder but we're still holding on to the reference. For
+  // valid folders, one of two scenarios is true: either the folder has a parent
+  // (the deletion code clears the parent to indicate its nonvalidity), or the
+  // folder is a root folder of some server. Getting the root folder may throw
+  // an exception if we attempted to create a server that doesn't exist, so we
+  // need to guard for that error.
+  try {
+    return folder.parent != null || folder.rootFolder == folder;
+  } catch (e) {
+    return false;
+  }
+}
+
+// This insures that the service is only created once
+var gCreated = false;
+
+function folderLookupService() {
+  if (gCreated)
+    throw Cr.NS_ERROR_ALREADY_INITIALIZED;
+  this._map = new Map();
+  gCreated = true;
+}
+folderLookupService.prototype = {
+  // XPCOM registration stuff
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIFolderLookupService]),
+  classID: Components.ID("{a30be08c-afc8-4fed-9af7-79778a23db23}"),
+
+  // nsIFolderLookupService impl
+  getFolderForURL: function (aUrl) {
+    let folder = null;
+    // First, see if the folder is in our cache.
+    if (this._map.has(aUrl)) {
+      let valid = false;
+      try {
+        folder = this._map.get(aUrl).QueryReferent(Ci.nsIMsgFolder);
+        valid = isValidFolder(folder);
+      } catch (e) {
+        // The object was deleted, so it's not valid
+      }
+
+      if (valid)
+        return folder;
+
+      // Don't keep around invalid folders.
+      this._map.delete(aUrl);
+      folder = null;
+    }
+
+    // If we get here, then the folder was not in our map. It could be that the
+    // folder was created by somebody else, so try to find that folder.
+    // For now, we use the RDF service, since it results in minimal changes. But
+    // RDF has a tendency to create objects without checking to see if they
+    // really exist---use the parent property to see if the folder is a real
+    // folder.
+    if (folder == null) {
+      let rdf = Cc["@mozilla.org/rdf/rdf-service;1"]
+                  .getService(Ci.nsIRDFService);
+      try {
+        folder = rdf.GetResource(aUrl)
+                    .QueryInterface(Ci.nsIMsgFolder);
+      } catch (e) {
+        // If the QI fails, then we somehow picked up an RDF resource that isn't
+        // a folder. Return null in this case.
+        return null;
+      }
+    }
+    if (!isValidFolder(folder))
+      return null;
+
+    // Add the new folder to our map. Store a weak reference instead, so that
+    // the folder can be closed when necessary.
+    let weakRef = folder.QueryInterface(Ci.nsISupportsWeakReference)
+                        .GetWeakReference();
+    this._map.set(aUrl, weakRef);
+    return folder;
+  },
+};
+
+var NSGetFactory = XPCOMUtils.generateNSGetFactory([folderLookupService]);