Add standalone server chat command "help" and "?"

Source/Common/ChatCommands.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Multiplayer.Common;
 
@@ -18,11 +19,41 @@ public void Handle(IChatSource source, string cmd)
         }
         else
         {
-            source.SendMsg("Invalid command");
+            source.SendMsg("Invalid command. Use help or ? to list available commands.");
         }
     }
 
     public void AddCommandHandler(string name, ChatCmdHandler handler) => handlers[name] = handler;
+
+    public IEnumerable<string> GetCommandNames() => handlers.Keys.OrderBy(name => name);
+
+    public IEnumerable<ChatCmdInfo> GetCommandInfos()
+    {
+        return handlers
+            .GroupBy(entry => entry.Value)
+            .Select(group => new ChatCmdInfo(group.Key, group.Select(entry => entry.Key).ToArray()))
+            .OrderBy(info => info.PrimaryName);
+    }
+
+    public bool TryGetCommandInfo(string name, out ChatCmdInfo info)
+    {
+        if (handlers.TryGetValue(name, out var handler))
+        {
+            info = new ChatCmdInfo(handler, handlers.Where(entry => entry.Value == handler).Select(entry => entry.Key).ToArray());
+            return true;
+        }
+
+        info = null!;
+        return false;
+    }
+}
+
+public sealed class ChatCmdInfo(ChatCmdHandler handler, string[] names)
+{
+    public ChatCmdHandler Handler { get; } = handler;
+    public string[] Names { get; } = names;
+    public string PrimaryName => Names.First();
+    public string DisplayNames => string.Join(", ", Names);
 }
 
 public abstract class ChatCmdHandler
@@ -31,6 +62,9 @@ public abstract class ChatCmdHandler
 
     public MultiplayerServer Server => MultiplayerServer.instance!;
 
+    public virtual string Description => string.Empty;
+    public virtual string Usage => string.Empty;
+
     public abstract void Handle(IChatSource source, string[] args);
 
     public void SendNoPermission(ServerPlayer player)
@@ -46,6 +80,9 @@ public void SendNoPermission(ServerPlayer player)
 
 public class ChatCmdJoinPoint : ChatCmdHandler
 {
+    public override string Description => "Create a fresh join point immediately.";
+    public override string Usage => "joinpoint";
+
     public ChatCmdJoinPoint()
     {
         requiresHost = true;
@@ -58,8 +95,54 @@ public override void Handle(IChatSource source, string[] args)
     }
 }
 
+public class ChatCmdHelp : ChatCmdHandler
+{
+    public override string Description => "Show available commands or detailed help for one command.";
+    public override string Usage => "help [command]";
+
+    public override void Handle(IChatSource source, string[] args)
+    {
+        if (args.Length > 0)
+        {
+            if (Server.chatCmdManager.TryGetCommandInfo(args[0], out var command))
+            {
+                source.SendMsg($"Command: {command.DisplayNames}");
+
+                if (!string.IsNullOrEmpty(command.Handler.Description))
+                    source.SendMsg($"Description: {command.Handler.Description}");
+
+                if (!string.IsNullOrEmpty(command.Handler.Usage))
+                    source.SendMsg($"Usage: {command.Handler.Usage}");
+
+                if (command.Handler.requiresHost)
+                    source.SendMsg("Requires host permissions.");
+
+                return;
+            }
+
+            source.SendMsg($"Unknown command '{args[0]}'. Use help to list available commands.");
+            return;
+        }
+
+        source.SendMsg("Available commands:");
+        foreach (var command in Server.chatCmdManager.GetCommandInfos())
+        {
+            var summary = command.Handler.Description;
+            if (command.Handler.requiresHost)
+                summary = string.IsNullOrEmpty(summary) ? "Requires host permissions." : $"{summary} Requires host permissions.";
+
+            source.SendMsg($"- {command.DisplayNames}: {summary}");
+        }
+
+        source.SendMsg("Use help <command> for detailed usage.");
+    }
+}
+
 public class ChatCmdKick : ChatCmdHandler
 {
+    public override string Description => "Disconnect a player by username.";
+    public override string Usage => "kick <username>";
+
     public ChatCmdKick()
     {
         requiresHost = true;
@@ -92,6 +175,9 @@ public override void Handle(IChatSource source, string[] args)
 
 public class ChatCmdStop : ChatCmdHandler
 {
+    public override string Description => "Stop the standalone server.";
+    public override string Usage => "stop";
+
     public ChatCmdStop()
     {
         requiresHost = true;

Source/Common/MultiplayerServer.cs

@@ -86,6 +86,9 @@ public MultiplayerServer(ServerSettings settings)
             chatCmdManager = new ChatCmdManager();
             playerManager = new PlayerManager(this);
 
+            var helpCmd = new ChatCmdHelp();
+            RegisterChatCmd("help", helpCmd);
+            RegisterChatCmd("?", helpCmd);
             RegisterChatCmd("joinpoint", new ChatCmdJoinPoint());
             RegisterChatCmd("kick", new ChatCmdKick());
             RegisterChatCmd("stop", new ChatCmdStop());