From 2f6081a62c918af627c18f006eccca63ceccf97f Mon Sep 17 00:00:00 2001
From: mathiascode <mail@mathias.is>
Date: Sun, 22 Dec 2019 21:19:01 +0200
Subject: [PATCH] Don't allow players with identical usernnames to join

---
 .../pw/kaboom/extras/commands/CommandUsername.java     | 10 ++++++++++
 .../kaboom/extras/modules/player/PlayerConnection.java |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/src/main/java/pw/kaboom/extras/commands/CommandUsername.java b/src/main/java/pw/kaboom/extras/commands/CommandUsername.java
index 7478a5f..b7ce5e1 100644
--- a/src/main/java/pw/kaboom/extras/commands/CommandUsername.java
+++ b/src/main/java/pw/kaboom/extras/commands/CommandUsername.java
@@ -1,5 +1,6 @@
 package pw.kaboom.extras.commands;
 
+import org.bukkit.Bukkit;
 import org.bukkit.ChatColor;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
@@ -7,6 +8,7 @@ import org.bukkit.command.CommandSender;
 import org.bukkit.command.ConsoleCommandSender;
 import org.bukkit.entity.Player;
 
+import org.bukkit.event.player.AsyncPlayerPreLoginEvent;
 import pw.kaboom.extras.Main;
 import pw.kaboom.extras.helpers.SkinDownloader;
 
@@ -23,6 +25,14 @@ public final class CommandUsername implements CommandExecutor {
 			} else if (!SkinDownloader.skinInProgress.contains(player.getUniqueId())) {
 				final String nameColor = ChatColor.translateAlternateColorCodes('&', String.join(" ", args));
 				final String name = nameColor.substring(0, Math.min(16, nameColor.length()));
+
+				for (Player onlinePlayer : Bukkit.getOnlinePlayers()) {
+					if (onlinePlayer.getName().equals(name)) {
+						player.sendMessage("A player with that username is already logged in");
+						return true;
+					}
+				}
+
 				final boolean shouldChangeUsername = true;
 				final boolean shouldSendMessage = true;
 
diff --git a/src/main/java/pw/kaboom/extras/modules/player/PlayerConnection.java b/src/main/java/pw/kaboom/extras/modules/player/PlayerConnection.java
index 1cd31bd..ce5efe1 100644
--- a/src/main/java/pw/kaboom/extras/modules/player/PlayerConnection.java
+++ b/src/main/java/pw/kaboom/extras/modules/player/PlayerConnection.java
@@ -1,5 +1,6 @@
 package pw.kaboom.extras.modules.player;
 
+import org.bukkit.Bukkit;
 import org.bukkit.Chunk;
 import org.bukkit.World;
 import org.bukkit.block.BlockState;
@@ -22,6 +23,12 @@ public final class PlayerConnection implements Listener {
 	void onAsyncPlayerPreLogin(final AsyncPlayerPreLoginEvent event) {
 		if (event.getName().length() > 16) {
 			event.disallow(AsyncPlayerPreLoginEvent.Result.KICK_OTHER, "Your username can't be longer than 16 characters");
+		} else {
+			for (Player player : Bukkit.getOnlinePlayers()) {
+				if (player.getName().equals(event.getName())) {
+					event.disallow(AsyncPlayerPreLoginEvent.Result.KICK_OTHER, "A player with that username is already logged in");
+				}
+			}
 		}
 	}