Add error message in chat when attempting to use commands

osu.Game/Online/Chat/Channel.cs

@@ -38,9 +38,9 @@ namespace osu.Game.Online.Chat
 
         public event Action<IEnumerable<Message>> NewMessagesArrived;
 
-        public void AddNewMessages(IEnumerable<Message> messages)
+        public void AddNewMessages(params Message[] messages)
         {
-            messages = messages.Except(Messages).ToList();
+            messages = messages.Except(Messages).ToArray();
 
             Messages.AddRange(messages);
 

osu.Game/Online/Chat/ErrorMessage.cs

@@ -0,0 +1,25 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using osu.Game.Users;
+
+namespace osu.Game.Online.Chat
+{
+    public class ErrorMessage : Message
+    {
+        private static int errorId = -1;
+
+        public ErrorMessage(string message) : base(errorId--)
+        {
+            Timestamp = DateTime.Now;
+            Content = message;
+
+            Sender = new User
+            {
+                Username = @"system",
+                Colour = @"ff0000",
+            };
+        }
+    }
+}

osu.Game/Online/Chat/Message.cs

@@ -37,6 +37,11 @@ namespace osu.Game.Online.Chat
         {
         }
 
+        public Message(long id)
+        {
+            Id = id;
+        }
+
         public override bool Equals(object obj)
         {
             var objMessage = obj as Message;

osu.Game/Overlays/ChatOverlay.cs

@@ -306,7 +306,7 @@ namespace osu.Game.Overlays
 
                 //batch messages per channel.
                 foreach (var id in ids)
-                    careChannels.Find(c => c.Id == id)?.AddNewMessages(messages.Where(m => m.TargetId == id));
+                    careChannels.Find(c => c.Id == id)?.AddNewMessages(messages.Where(m => m.TargetId == id).ToArray());
 
                 lastMessageId = messages.LastOrDefault()?.Id ?? lastMessageId;
 
@@ -326,38 +326,45 @@ namespace osu.Game.Overlays
         {
             var postText = textbox.Text;
 
-            if (!string.IsNullOrEmpty(postText) && api.LocalUser.Value != null)
+            if (string.IsNullOrEmpty(postText) || api.LocalUser.Value == null) return;
+
+            if (currentChannel == null) return;
+
+            if (postText[0] == '/')
             {
-                if (currentChannel == null) return;
-
-                var message = new Message
-                {
-                    Sender = api.LocalUser.Value,
-                    Timestamp = DateTimeOffset.Now,
-                    TargetType = TargetType.Channel, //TODO: read this from currentChannel
-                    TargetId = currentChannel.Id,
-                    Content = postText
-                };
-
-                textbox.ReadOnly = true;
-                var req = new PostMessageRequest(message);
-
-                req.Failure += e =>
-                {
-                    textbox.FlashColour(Color4.Red, 1000);
-                    textbox.ReadOnly = false;
-                };
-
-                req.Success += m =>
-                {
-                    currentChannel.AddNewMessages(new[] { m });
-
-                    textbox.ReadOnly = false;
-                    textbox.Text = string.Empty;
-                };
-
-                api.Queue(req);
+                // TODO: handle commands
+                currentChannel.AddNewMessages(new ErrorMessage("Chat commands are not supported yet!"));
+                textbox.Text = string.Empty;
+                return;
             }
+                
+            var message = new Message
+            {
+                Sender = api.LocalUser.Value,
+                Timestamp = DateTimeOffset.Now,
+                TargetType = TargetType.Channel, //TODO: read this from currentChannel
+                TargetId = currentChannel.Id,
+                Content = postText
+            };
+
+            textbox.ReadOnly = true;
+            var req = new PostMessageRequest(message);
+
+            req.Failure += e =>
+            {
+                textbox.FlashColour(Color4.Red, 1000);
+                textbox.ReadOnly = false;
+            };
+
+            req.Success += m =>
+            {
+                currentChannel.AddNewMessages(m);
+
+                textbox.ReadOnly = false;
+                textbox.Text = string.Empty;
+            };
+
+            api.Queue(req);
         }
     }
 }

osu.Game/osu.Game.csproj

@@ -75,6 +75,7 @@
     <Compile Include="Beatmaps\Drawables\BeatmapBackgroundSprite.cs" />
     <Compile Include="Beatmaps\DifficultyCalculator.cs" />
     <Compile Include="Online\API\Requests\PostMessageRequest.cs" />
+    <Compile Include="Online\Chat\ErrorMessage.cs" />
     <Compile Include="Overlays\Chat\ChatTabControl.cs" />
     <Compile Include="Overlays\Music\FilterControl.cs" />
     <Compile Include="Overlays\Music\PlaylistItem.cs" />