closes #3983

public/language/en_GB/error.json

@@ -103,6 +103,7 @@
 	"invalid-chat-message": "Invalid chat message",
 	"chat-message-too-long": "Chat message is too long",
 	"cant-edit-chat-message": "You are not allowed to edit this message",
+	"cant-remove-last-user": "You can't remove the last user",
 
 	"reputation-system-disabled": "Reputation system is disabled.",
 	"downvoting-disabled": "Downvoting is disabled",

public/src/client/chats.js

@@ -231,11 +231,22 @@ define('forum/chats', ['components', 'string', 'sounds', 'forum/infinitescroll',
 		});
 
 		tagEl.on('beforeItemRemove', function(event) {
-			event.cancel = !data.isOwner;
+			event.cancel = !data.isOwner || data.users.length < 2;
+			if (!data.owner) {
+				return app.alertError('[[error:not-allowed]]');
+			}
+
+			if (data.users.length < 2) {
+				return app.alertError('[[error:cant-remove-last-user]]');
+			}
 		});
 
 		tagEl.on('itemRemoved', function(event) {
-			socket.emit('modules.chats.removeUserFromRoom', {roomId: data.roomId, username: event.item});
+			socket.emit('modules.chats.removeUserFromRoom', {roomId: data.roomId, username: event.item}, function(err) {
+				if (err) {
+					return app.alertError(err.message);
+				}
+			});
 		});
 
 		var input = $('.users-tag-container').find('.bootstrap-tagsinput input');

src/controllers/accounts/chats.js

@@ -58,7 +58,7 @@ chatsController.get = function(req, res, callback) {
 
 			room.isOwner = parseInt(room.owner, 10) === parseInt(req.uid, 10);
 			room.users = data.users.filter(function(user) {
-				return user && parseInt(user.uid, 10) !== req.uid;
+				return user && parseInt(user.uid, 10) && parseInt(user.uid, 10) !== req.uid;
 			});
 
 			room.usernames = data.users.map(function(user) {

src/messaging/rooms.js

@@ -56,6 +56,10 @@ module.exports = function(Messaging) {
 		db.exists('chat:room:' + roomId + ':uids', callback);
 	};
 
+	Messaging.getUserCountInRoom = function(roomId, callback) {
+		db.sortedSetCard('chat:room:' + roomId + ':uids', callback);
+	};
+
 	Messaging.isRoomOwner = function(uid, roomId, callback) {
 		db.getObjectField('chat:room:' + roomId, 'owner', function(err, owner) {
 			if (err) {
@@ -87,12 +91,19 @@ module.exports = function(Messaging) {
 	Messaging.removeUsersFromRoom = function(uid, uids, roomId, callback) {
 		async.waterfall([
 			function (next) {
-				Messaging.isRoomOwner(uid, roomId, next);
+				async.parallel({
+					isOwner: async.apply(Messaging.isRoomOwner, uid, roomId),
+					userCount: async.apply(Messaging.getUserCountInRoom, roomId)
+				}, next);
 			},
-			function (isOwner, next) {
-				if (!isOwner) {
+			function (results, next) {
+				if (!results.isOwner) {
 					return next(new Error('[[error:cant-add-users-to-chat-room]]'));
 				}
+				if (results.userCount === 2) {
+					return next(new Error('[[error:cant-remove-last-user]]'));
+				}
+
 				db.sortedSetRemove('chat:room:' + roomId + ':uids', uids, next);
 			},
 			function (next) {