From 7ca0689989951d62003b29e8f011f1bf17f98085 Mon Sep 17 00:00:00 2001
From: Adrian <68704415+4drian3d@users.noreply.github.com>
Date: Thu, 22 Feb 2024 12:48:36 -0500
Subject: [PATCH] Fixed duplicate sending of resource packs responses to
 backend server (#1249)

Also fixes the sending of SUCCESSFUL responses to the backend server that will apply a resource pack in case Velocity has already applied one or more resource packs to the player
---
 .../client/ClientConfigSessionHandler.java           |  3 ---
 .../resourcepack/ModernResourcePackHandler.java      | 12 +++++++++++-
 .../player/resourcepack/ResourcePackHandler.java     | 12 ++++++++----
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java b/proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java
index 99a916242..48ea03c41 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java
@@ -95,9 +95,6 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(ResourcePackResponsePacket packet) {
-    if (player.getConnectionInFlight() != null) {
-      player.getConnectionInFlight().ensureConnected().write(packet);
-    }
     return player.resourcePackHandler().onResourcePackResponse(
         new ResourcePackResponseBundle(packet.getId(),
             packet.getHash(),
diff --git a/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ModernResourcePackHandler.java b/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ModernResourcePackHandler.java
index 640c7ed55..5ba74a273 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ModernResourcePackHandler.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ModernResourcePackHandler.java
@@ -146,10 +146,20 @@ public final class ModernResourcePackHandler extends ResourcePackHandler {
       }
       // The resource pack has been applied correctly.
       case SUCCESSFUL -> {
+        pendingResourcePacks.remove(uuid);
         if (queued != null) {
           appliedResourcePacks.put(uuid, queued);
+        } else {
+          // When transitioning to another server that has a resource pack to apply,
+          // if one or more resource packs have already been applied from Velocity,
+          // the player sends more than 1 SUCCESSFUL response to the backend server,
+          // which results in the server receiving more resource pack responses
+          // than the server has sent requests to the player
+          final ResourcePackInfo appliedPack = appliedResourcePacks.get(uuid);
+          if (appliedPack != null) {
+            return handleResponseResult(appliedPack, bundle);
+          }
         }
-        pendingResourcePacks.remove(uuid);
       }
       // An error occurred while trying to download the resource pack to the client,
       // so the resource pack cannot be applied.
diff --git a/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackHandler.java b/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackHandler.java
index 68640fb89..e2160f8ec 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackHandler.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackHandler.java
@@ -20,6 +20,7 @@ package com.velocitypowered.proxy.connection.player.resourcepack;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
 import com.velocitypowered.proxy.VelocityServer;
+import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
@@ -147,12 +148,15 @@ public abstract sealed class ResourcePackHandler
           final @Nullable ResourcePackInfo queued,
           final @NotNull ResourcePackResponseBundle bundle
   ) {
+    // If Velocity, through a plugin, has sent a resource pack to the client,
+    // there is no need to report the status of the response to the server
+    // since it has no information that a resource pack has been sent
     final boolean handled = queued != null
-            && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
+            && queued.getOriginalOrigin() == ResourcePackInfo.Origin.PLUGIN_ON_PROXY;
     if (!handled) {
-      if (player.getConnectionInFlight() != null
-              && player.getConnectionInFlight().getConnection() != null) {
-        player.getConnectionInFlight().getConnection().write(new ResourcePackResponsePacket(
+      final VelocityServerConnection connectionInFlight = player.getConnectionInFlight();
+      if (connectionInFlight != null && connectionInFlight.getConnection() != null) {
+        connectionInFlight.getConnection().write(new ResourcePackResponsePacket(
                 bundle.uuid(), bundle.hash(), bundle.status()));
       }
     }