Remove guest rooms array; replace with a peeking SyncApi

After much discussion, the HS will now behave the same for guests/non-guests
wrt joining a room (you get the entire room state on join). This leave "peeking"
which never triggers a join. This can be implemented for guests by doing a
room initial sync followed by a specific /events poll with a specific room_id.
This means there are 2 sync streams: /sync and the peek /events. Architected
so you can only have 1 peek stream in progress at a time (if this were arbitrary
we'd quickly run into concurrent in-flight browser request limits (5).

lib/client.js

@@ -153,7 +153,7 @@ function MatrixClient(opts) {
     }
     this._syncState = null;
     this._syncingRetry = null;
-    this._guestRooms = null;
+    this._peekSync = null;
     this._isGuest = false;
     this._ongoingScrollbacks = {};
 }
@@ -605,6 +605,7 @@ MatrixClient.prototype.joinRoom = function(roomIdOrAlias, opts, callback) {
     opts = opts || {
         syncRoom: true
     };
+
     var room = this.getRoom(roomIdOrAlias);
     if (room && room.hasMembershipState(this.credentials.userId, "join")) {
         return q(room);
@@ -1939,11 +1940,16 @@ MatrixClient.prototype.registerGuest = function(opts, callback) {
 };
 
 /**
- * Set a list of rooms the Guest is interested in receiving events from.
- * @param {String[]} roomIds A list of room IDs.
+ * Peek into a room and receive updates about the room. This only works if the
+ * history visibility for the room is world_readable.
+ * @param {String} roomId The room to attempt to peek into.
  */
-MatrixClient.prototype.setGuestRooms = function(roomIds) {
-    this._guestRooms = roomIds;
+MatrixClient.prototype.peekInRoom = function(roomId) {
+    if (this._peekSync) {
+        this._peekSync.stopPeeking();
+    }
+    this._peekSync = new SyncApi(this);
+    this._peekSync.peek(roomId);
 };
 
 /**

lib/sync.js

@@ -139,6 +139,23 @@ SyncApi.prototype.syncLeftRooms = function() {
     });
 };
 
+/**
+ * Peek into a room. This will result in the room in question being synced so it
+ * is accessible via getRooms(). Live updates for the room will be provided.
+ * @param {string} roomId The room ID to peek into.
+ */
+SyncApi.prototype.peek = function(roomId) {
+
+};
+
+/**
+ * Stop polling for updates in the peeked room. NOPs if there is no room being
+ * peeked.
+ */
+SyncApi.prototype.stopPeeking = function() {
+
+};
+
 /**
  * Main entry point
  */
@@ -556,7 +573,9 @@ SyncApi.prototype._getGuestFilter = function() {
     }
     return JSON.stringify({
         room: {
-            rooms: guestRooms
+            timeline: {
+                limit: 20
+            }
         }
     });
 };