Name adjustments and moved some things to the common lib.

SharpChat/ClientCommands/NickClientCommand.cs

@@ -0,0 +1,63 @@
+using SharpChat.S2CPackets;
+using System.Globalization;
+using System.Text;
+
+namespace SharpChat.ClientCommands {
+    public class NickClientCommand : ClientCommand {
+        private const int MAX_GRAPHEMES = 16;
+        private const int MAX_BYTES = MAX_GRAPHEMES * 10;
+
+        public bool IsMatch(ClientCommandContext ctx) {
+            return ctx.NameEquals("nick");
+        }
+
+        public void Dispatch(ClientCommandContext ctx) {
+            long msgId = ctx.Chat.RandomSnowflake.Next();
+            bool setOthersNick = ctx.User.Can(UserPermissions.SetOthersNickname);
+
+            if(!setOthersNick && !ctx.User.Can(UserPermissions.SetOwnNickname)) {
+                ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.COMMAND_NOT_ALLOWED, true, $"/{ctx.Name}"));
+                return;
+            }
+
+            User? targetUser = null;
+            int offset = 0;
+
+            if(setOthersNick && long.TryParse(ctx.Args.FirstOrDefault(), out long targetUserId) && targetUserId > 0) {
+                targetUser = ctx.Chat.Users.FirstOrDefault(u => u.UserId == targetUserId);
+                ++offset;
+            }
+
+            targetUser ??= ctx.User;
+
+            if(ctx.Args.Length < offset) {
+                ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.COMMAND_FORMAT_ERROR));
+                return;
+            }
+
+            string nickStr = string.Join('_', ctx.Args.Skip(offset))
+                .Replace("\n", string.Empty).Replace("\r", string.Empty)
+                .Replace("\f", string.Empty).Replace("\t", string.Empty)
+                .Replace(' ', '_').Trim();
+
+            if(nickStr == targetUser.UserName)
+                nickStr = string.Empty;
+            else if(string.IsNullOrEmpty(nickStr))
+                nickStr = string.Empty;
+            else {
+                StringInfo nsi = new(nickStr);
+                if(Encoding.UTF8.GetByteCount(nickStr) > MAX_BYTES
+                    || nsi.LengthInTextElements > MAX_GRAPHEMES)
+                    nickStr = nsi.SubstringByTextElements(0, Math.Min(nsi.LengthInTextElements, MAX_GRAPHEMES)).Trim();
+            }
+
+            if(!string.IsNullOrWhiteSpace(nickStr) && ctx.Chat.Users.Any(u => u.NameEquals(nickStr))) {
+                ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.NAME_IN_USE, true, nickStr));
+                return;
+            }
+
+            string? previousName = targetUser.UserId == ctx.User.UserId ? (targetUser.NickName ?? targetUser.UserName) : null;
+            ctx.Chat.UpdateUser(targetUser, nickName: nickStr, silent: previousName == null);
+        }
+    }
+}