detect fucked up user names

CompatBot/EventHandlers/UsernameZalgoMonitor.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using CompatApiClient.Utils;
+using CompatBot.Utils;
+using DSharpPlus;
+using DSharpPlus.Entities;
+using DSharpPlus.EventArgs;
+using HomoglyphConverter;
+using Microsoft.Extensions.Caching.Memory;
+
+namespace CompatBot.EventHandlers
+{
+    internal static class UsernameZalgoMonitor
+    {
+        public static async Task OnUserUpdated(UserUpdateEventArgs args)
+        {
+            var m = args.Client.GetMember(args.UserAfter);
+            if (NeedsRename(m.DisplayName))
+                await args.Client.ReportAsync("Potential display name issue",
+                    $"User {m.GetMentionWithNickname()} has changed their __username__ from " +
+                    $"**{args.UserBefore.Username.Sanitize()}#{args.UserBefore.Discriminator}** to " +
+                    $"**{args.UserAfter.Username.Sanitize()}#{args.UserAfter.Discriminator}**",
+                    null,
+                    ReportSeverity.Medium);
+        }
+
+        public static async Task OnMemberUpdated(GuildMemberUpdateEventArgs args)
+        {
+            if (NeedsRename(args.NicknameAfter))
+                await args.Client.ReportAsync("Potential display name issue",
+                    $"Member {args.Member.GetMentionWithNickname()} has changed their __display name__ from " +
+                    $"**{(args.NicknameBefore ?? args.Member.Username).Sanitize()}** to " +
+                    $"**{args.Member.DisplayName.Sanitize()}**",
+                    null,
+                    ReportSeverity.Medium);
+        }
+
+        public static async Task OnMemberAdded(GuildMemberAddEventArgs args)
+        {
+            if (NeedsRename(args.Member.DisplayName))
+                await args.Client.ReportAsync("Potential display name issue",
+                    $"New member joined the server: {args.Member.GetMentionWithNickname()}",
+                    null,
+                    ReportSeverity.Medium);
+        }
+
+        private static bool NeedsRename(string displayName)
+        {
+            displayName = displayName?.Normalize().TrimEager();
+            if (string.IsNullOrEmpty(displayName))
+                return true;
+
+            var consecutiveCombiningCharacters = 0;
+            foreach (var c in displayName)
+            {
+                switch (char.GetUnicodeCategory(c))
+                {
+                    case UnicodeCategory.ModifierLetter:
+                    case UnicodeCategory.ModifierSymbol:
+                    case UnicodeCategory.NonSpacingMark:
+                        if (++consecutiveCombiningCharacters > 1)
+                            return true;
+                        break;
+
+                    case UnicodeCategory.Control:
+                    case UnicodeCategory.Format:
+                        break;
+
+                    default:
+                        consecutiveCombiningCharacters = 0;
+                        break;
+                }
+            }
+            return false;
+        }
+    }
+}

CompatBot/Program.cs

@@ -185,9 +185,14 @@ namespace CompatBot
                     client.MessageDeleted += ThumbnailCacheMonitor.OnMessageDeleted;
 
                     client.UserUpdated += UsernameSpoofMonitor.OnUserUpdated;
+                    client.UserUpdated += UsernameZalgoMonitor.OnUserUpdated;
+
                     client.GuildMemberAdded += Greeter.OnMemberAdded;
                     client.GuildMemberAdded += UsernameSpoofMonitor.OnMemberAdded;
+                    client.GuildMemberAdded += UsernameZalgoMonitor.OnMemberAdded;
+
                     client.GuildMemberUpdated += UsernameSpoofMonitor.OnMemberUpdated;
+                    client.GuildMemberUpdated += UsernameZalgoMonitor.OnMemberUpdated;
 
                     client.DebugLogger.LogMessageReceived += (sender, eventArgs) =>
                     {

CompatBot/Utils/DiscordClientExtensions.cs

@@ -127,14 +127,16 @@ namespace CompatBot.Utils
             return await logChannel.SendMessageAsync(embed: embedBuilder.Build()).ConfigureAwait(false);
         }
 
-        public static async Task<DiscordMessage> ReportAsync(this DiscordClient client, string infraction, string description, IEnumerable<DiscordMember> potentialVictims, ReportSeverity severity)
+        public static async Task<DiscordMessage> ReportAsync(this DiscordClient client, string infraction, string description, ICollection<DiscordMember> potentialVictims, ReportSeverity severity)
         {
             var result = new DiscordEmbedBuilder
             {
                 Title = infraction,
                 Color = GetColor(severity),
                 Description = description.Trim(EmbedPager.MaxDescriptionLength),
-            }.AddField("Potential Targets", string.Join(Environment.NewLine, potentialVictims.Select(GetMentionWithNickname)).Trim(EmbedPager.MaxFieldLength));
+            };
+            if (potentialVictims?.Count > 0)
+                result.AddField("Potential Targets", string.Join(Environment.NewLine, potentialVictims.Select(GetMentionWithNickname)).Trim(EmbedPager.MaxFieldLength));
             var logChannel = await client.GetChannelAsync(Config.BotLogId).ConfigureAwait(false);
             return await logChannel.SendMessageAsync(embed: result.Build()).ConfigureAwait(false);
         }