From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: BillyGalbreath <blake.galbreath@gmail.com>
Date: Sat, 1 Jan 2022 18:38:58 -0600
Subject: [PATCH] Configurable valid characters for usernames


diff --git a/src/main/java/net/minecraft/world/entity/player/Player.java b/src/main/java/net/minecraft/world/entity/player/Player.java
index fd67cefb971b394042c0fdd845c20cf55d8efc2f..fab644c79287a444fd58c43547beba3e06e9e7ff 100644
--- a/src/main/java/net/minecraft/world/entity/player/Player.java
+++ b/src/main/java/net/minecraft/world/entity/player/Player.java
@@ -2404,6 +2404,7 @@ public abstract class Player extends LivingEntity {
     }
 
     public static boolean isValidUsername(String name) {
+        if (true) return org.purpurmc.purpur.PurpurConfig.usernameValidCharactersPattern.matcher(name).matches(); // Purpur
         // Paper start
         if (name == null || name.isEmpty() || name.length() > 16) {
             return false;
diff --git a/src/main/java/org/purpurmc/purpur/PurpurConfig.java b/src/main/java/org/purpurmc/purpur/PurpurConfig.java
index f562729f543ef2b5998c6c38c0a08b3ae4dab1bf..d56c2776d08306245618dca04cd39891bb61c1bd 100644
--- a/src/main/java/org/purpurmc/purpur/PurpurConfig.java
+++ b/src/main/java/org/purpurmc/purpur/PurpurConfig.java
@@ -452,4 +452,11 @@ public class PurpurConfig {
     private static void networkSettings() {
         useUPnP = getBoolean("settings.network.upnp-port-forwarding", useUPnP);
     }
+
+    public static java.util.regex.Pattern usernameValidCharactersPattern;
+    private static void usernameValidationSettings() {
+        String defaultPattern = "^[a-zA-Z0-9_.]*$";
+        String setPattern = getString("settings.username-valid-characters", defaultPattern);
+        usernameValidCharactersPattern = java.util.regex.Pattern.compile(setPattern == null || setPattern.isBlank() ? defaultPattern : setPattern);
+    }
 }