closes #3997

src/controllers/accounts/chats.js

@@ -65,6 +65,8 @@ chatsController.get = function(req, res, callback) {
 			room.nextStart = recentChats.nextStart;
 			room.title = room.roomName;
 			room.breadcrumbs = helpers.buildBreadcrumbs([{text: '[[pages:chats]]', url: '/chats'}, {text: room.roomName}]);
+			room.maximumUsersInChatRoom = parseInt(meta.config.maximumUsersInChatRoom, 10) || 0;
+			room.showUserInput = !room.maximumUsersInChatRoom || room.maximumUsersInChatRoom > 2;
 
 			res.render('chats', room);
 		});

src/socket.io/modules.js

@@ -125,6 +125,8 @@ SocketModules.chats.loadRoom = function(socket, data, callback) {
 		function (results, next) {
 			results.roomData.users = results.users;
 			results.roomData.isOwner = parseInt(results.roomData.owner, 10) === socket.uid;
+			results.roomData.maximumUsersInChatRoom = parseInt(meta.config.maximumUsersInChatRoom, 10) || 0;
+			results.roomData.showUserInput = !results.roomData.maximumUsersInChatRoom || results.roomData.maximumUsersInChatRoom > 2;
 			next(null, results.roomData);
 		}
 	], callback);
@@ -135,6 +137,16 @@ SocketModules.chats.addUserToRoom = function(socket, data, callback) {
 		return callback(new Error('[[error:invalid-data]]'));
 	}
 	async.waterfall([
+		function (next) {
+			Messaging.getUserCountInRoom(data.roomId, next);
+		},
+		function (userCount, next) {
+			var maxUsers = parseInt(meta.config.maximumUsersInChatRoom, 10) || 0;
+			if (maxUsers && userCount >= maxUsers) {
+				return next(new Error('[[error:cant-add-more-users-to-chat-room]]'));
+			}
+			next();
+		},
 		function (next) {
 			user.getUidByUsername(data.username, next);
 		},

src/views/admin/settings/chat.tpl

@@ -20,6 +20,11 @@
 			<label>Maximum length of chat messages</label>
 			<input type="text" class="form-control" value="1000" data-field="maximumChatMessageLength">
 		</div>
+
+		<div class="form-group">
+			<label>Maximum number of users in chat rooms</label>
+			<input type="text" class="form-control" value="0" data-field="maximumUsersInChatRoom">
+		</div>
 	</div>
 </div>