First working outbound conference calling

This has a number of failings currently: 1) It needs to hide the 1:1 conference
room, 2) Swapping tabs on the outbound call mutes audio (this just seems to be
a vector bug since I can repro this on a normal 1:1 voip call), 3) Needs a big
plinth/etc to say the conf call is in progress.

src/ConferenceHandler.js

@@ -0,0 +1,70 @@
+"use strict";
+var q = require("q");
+var Matrix = require("matrix-js-sdk");
+var Room = Matrix.Room;
+
+var USER_PREFIX = "fs_";
+var DOMAIN = "matrix.org";
+
+function ConferenceHandler(matrixClient, groupChatRoomId) {
+    this.client = matrixClient;
+    this.groupRoomId = groupChatRoomId;
+    // abuse browserify's core node Buffer support (strip padding ='s)
+    this.base64RoomId = new Buffer(this.groupRoomId).toString("base64").replace(/=/g, "");
+    this.confUserId = "@" + USER_PREFIX + this.base64RoomId + ":" + DOMAIN;
+}
+
+ConferenceHandler.prototype.setup = function() {
+    var self = this;
+    return this._joinConferenceUser().then(function() {
+        return self._getConferenceUserRoom();
+    }).then(function(room) {
+        // return a call for *this* room to be placed.
+        return Matrix.createNewMatrixCall(self.client, room.roomId);
+    });
+};
+
+ConferenceHandler.prototype._joinConferenceUser = function() {
+    // Make sure the conference user is in the group chat room
+    var groupRoom = this.client.getRoom(this.groupRoomId);
+    if (!groupRoom) {
+        return q.reject("Bad group room ID");
+    }
+    var members = groupRoom.getJoinedMembers();
+    var confUserExists = false;
+    for (var i = 0; i < members.length; i++) {
+        if (members[i].userId === this.confUserId) {
+            confUserExists = true;
+            break;
+        }
+    }
+    if (confUserExists) {
+        return q();
+    }
+    return this.client.invite(this.groupRoomId, this.confUserId);
+};
+
+ConferenceHandler.prototype._getConferenceUserRoom = function() {
+    // Use an existing 1:1 with the conference user; else make one
+    var rooms = this.client.getRooms();
+    var confRoom = null;
+    for (var i = 0; i < rooms.length; i++) {
+        if (rooms[i].hasMembershipState(this.confUserId, "join") &&
+                rooms[i].getJoinedMembers().length === 2) {
+            confRoom = rooms[i];
+            break;
+        }
+    }
+    if (confRoom) {
+        return q(confRoom);
+    }
+    return this.client.createRoom({
+        preset: "private_chat",
+        invite: [this.confUserId]
+    }).then(function(res) {
+        return new Room(res.room_id);
+    });
+};
+
+module.exports = ConferenceHandler;
+