add support for tracking room tags

lib/models/room.js

@@ -21,6 +21,8 @@ var ContentRepo = require("../content-repo");
  * @prop {string} name The human-readable display name for this room.
  * @prop {Array<MatrixEvent>} timeline The ordered list of message events for
  * this room.
+ * @prop {object} tags Dict of room tags; the keys are the tag name and the values
+ * are any metadata associated with the tag - e.g. { "fav" : { order: 1 } }
  * @prop {RoomState} oldState The state of the room at the time of the oldest
  * event in the timeline.
  * @prop {RoomState} currentState The state of the room at the time of the
@@ -33,6 +35,10 @@ function Room(roomId, storageToken) {
     this.roomId = roomId;
     this.name = roomId;
     this.timeline = [];
+    this.tags = {
+        // $tagname: { $metadata: $value },
+        // $tagname: { $metadata: $value },
+    };
     this.oldState = new RoomState(roomId);
     this.currentState = new RoomState(roomId);
     this.summary = null;
@@ -223,6 +229,9 @@ Room.prototype.addEvents = function(events, duplicateStrategy) {
         else if (events[i].getType() === "m.receipt") {
             this.addReceipt(events[i]);
         }
+        else if (events[i].getType() === "m.tag") {
+            this.addTags(events[i]);
+        }
         else {
             if (duplicateStrategy) {
                 // is there a duplicate?
@@ -401,6 +410,27 @@ Room.prototype.addReceipt = function(event) {
     });
 };
 
+/**
+ * Update the room-tag event for the room.  The previous one is overwritten.
+ * @param {MatrixEvent} event the m.tag event
+ */
+Room.prototype.addTags = function(event) {
+    // event content looks like:
+    // content: {
+    //    tags: {
+    //       $tagname: { $metadata: $value },
+    //       $tagname: { $metadata: $value },
+    //    }
+    // }
+
+    // XXX: we could do a deep-comparison to see if the tags have really
+    // changed - but do we want to bother?
+    this.emit("Room.tags", this);
+
+    // XXX: do we need to deep copy here?
+    this._tags = event.content.tags;
+};
+
 function setEventMetadata(event, stateContext, toStartOfTimeline) {
     // set sender and target properties
     event.sender = stateContext.getSentinelMember(
@@ -527,3 +557,14 @@ module.exports = Room;
  *   var newName = room.name;
  * });
  */
+
+/**
+ * Fires whenever a room's tags are updated.
+ * @event module:client~MatrixClient#"Room.tags"
+ * @param {Room} room The room whose Room.tags was updated.
+ * @example
+ * matrixClient.on("Room.tags", function(room){
+ *   var newTags = room.tags;
+ *   if (newTags["favourite"]) showStar(room);
+ * });
+ */