Refactor ResourcePacks handling (#1225)

* Initial ResourcePack refactor

* Implement sendResourcePacks method

* Initializes the ResourcePackHandler at player initialization

* Move adventure to velocity resource pack conversion to the same class

* Added some internal resource pack documentation

* Refactored Modern ResourcePack handling

* Handle RemoveResourcePackPacket from backend server

* Fixed license

* Use removeIf instead of manual iteration

* Improve ModernResourcePackHandler

* fix hash conversion

* bundle resource packs

* keep old constructors of PlayerResourcePackStatusEvent

* add @Nullable to PlayerResourcePackStatusEvent#getPackId

* Use a single instance of BundleDelimiterPacket

* Throw UnSupportedOperationException on operations not supported by LegacyResourcePackHandler

* Use a single instance on empty packets

* Handle active packet bundle sending from backend server in case of sending a packet bundle of resource packs

* Improve packet bundling

* Fixed login for players with version 1.20.2

---------

Co-authored-by: Gero <gecam59@gmail.com>

api/src/main/java/com/velocitypowered/api/event/player/PlayerResourcePackStatusEvent.java

@@ -12,6 +12,7 @@ import com.velocitypowered.api.event.annotation.AwaitingEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
+import java.util.UUID;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
@@ -24,6 +25,7 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 public class PlayerResourcePackStatusEvent {
 
   private final Player player;
+  private final @MonotonicNonNull UUID packId;
   private final Status status;
   private final @MonotonicNonNull ResourcePackInfo packInfo;
   private boolean overwriteKick;
@@ -32,20 +34,31 @@ public class PlayerResourcePackStatusEvent {
    * Instantiates this event.
    *
    * @deprecated Use {@link PlayerResourcePackStatusEvent#PlayerResourcePackStatusEvent
-   *             (Player, Status, ResourcePackInfo)} instead.
+   *             (Player, UUID, Status, ResourcePackInfo)} instead.
    */
   @Deprecated
   public PlayerResourcePackStatusEvent(Player player, Status status) {
-    this.player = Preconditions.checkNotNull(player, "player");
+    this(player, null, status, null);
-    this.status = Preconditions.checkNotNull(status, "status");
+  }
-    this.packInfo = null;
+
+  /**
+   * Instantiates this event.
+   *
+   * @deprecated Use {@link PlayerResourcePackStatusEvent#PlayerResourcePackStatusEvent
+   *             (Player, UUID, Status, ResourcePackInfo)} instead.
+   */
+  @Deprecated
+  public PlayerResourcePackStatusEvent(Player player, Status status, ResourcePackInfo packInfo) {
+    this(player, null, status, packInfo);
   }
 
   /**
    * Instantiates this event.
    */
-  public PlayerResourcePackStatusEvent(Player player, Status status, ResourcePackInfo packInfo) {
+  public PlayerResourcePackStatusEvent(
+          Player player, UUID packId, Status status, ResourcePackInfo packInfo) {
     this.player = Preconditions.checkNotNull(player, "player");
+    this.packId = packId == null ? packInfo == null ? null : packInfo.getId() : packId;
     this.status = Preconditions.checkNotNull(status, "status");
     this.packInfo = packInfo;
   }
@@ -59,6 +72,16 @@ public class PlayerResourcePackStatusEvent {
     return player;
   }
 
+  /**
+   * Returns the id of the resource pack.
+   *
+   * @return the id
+   */
+  @Nullable
+  public UUID getPackId() {
+    return packId;
+  }
+
   /**
    * Returns the new status for the resource pack.
    *

api/src/main/java/com/velocitypowered/api/proxy/player/ResourcePackInfo.java

@@ -8,13 +8,14 @@
 package com.velocitypowered.api.proxy.player;
 
 import java.util.UUID;
+import net.kyori.adventure.resource.ResourcePackRequestLike;
 import net.kyori.adventure.text.Component;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * Represents the information for a resource pack to apply that can be sent to the client.
  */
-public interface ResourcePackInfo {
+public interface ResourcePackInfo extends ResourcePackRequestLike {
 
   /**
    * Gets the id of this resource-pack.

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftSessionHandler.java

@@ -20,6 +20,7 @@ package com.velocitypowered.proxy.connection;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.packet.AvailableCommandsPacket;
 import com.velocitypowered.proxy.protocol.packet.BossBarPacket;
+import com.velocitypowered.proxy.protocol.packet.BundleDelimiterPacket;
 import com.velocitypowered.proxy.protocol.packet.ClientSettingsPacket;
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 import com.velocitypowered.proxy.protocol.packet.EncryptionRequestPacket;
@@ -324,4 +325,8 @@ public interface MinecraftSessionHandler {
   default boolean handle(ChatAcknowledgementPacket chatAcknowledgement) {
     return false;
   }
+
+  default boolean handle(BundleDelimiterPacket bundleDelimiterPacket) {
+    return false;
+  }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -35,13 +35,16 @@ import com.velocitypowered.proxy.command.CommandGraphInjector;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.client.ClientPlaySessionHandler;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackHandler;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.netty.MinecraftDecoder;
 import com.velocitypowered.proxy.protocol.packet.AvailableCommandsPacket;
 import com.velocitypowered.proxy.protocol.packet.BossBarPacket;
+import com.velocitypowered.proxy.protocol.packet.BundleDelimiterPacket;
 import com.velocitypowered.proxy.protocol.packet.ClientSettingsPacket;
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
@@ -125,6 +128,12 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
     return false;
   }
 
+  @Override
+  public boolean handle(BundleDelimiterPacket bundleDelimiterPacket) {
+    serverConn.getPlayer().getBundleHandler().toggleBundleSession();
+    return false;
+  }
+
   @Override
   public boolean handle(StartUpdatePacket packet) {
     MinecraftConnection smc = serverConn.ensureConnected();
@@ -188,13 +197,13 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
         return;
       }
       if (serverResourcePackSendEvent.getResult().isAllowed()) {
-        ResourcePackInfo toSend = serverResourcePackSendEvent.getProvidedResourcePack();
+        final ResourcePackInfo toSend = serverResourcePackSendEvent.getProvidedResourcePack();
         if (toSend != serverResourcePackSendEvent.getReceivedResourcePack()) {
           ((VelocityResourcePackInfo) toSend)
               .setOriginalOrigin(ResourcePackInfo.Origin.DOWNSTREAM_SERVER);
         }
 
-        serverConn.getPlayer().queueResourcePack(toSend);
+        serverConn.getPlayer().resourcePackHandler().queueResourcePack(toSend);
       } else if (serverConn.getConnection() != null) {
         serverConn.getConnection().write(new ResourcePackResponsePacket(
             packet.getId(),
@@ -219,7 +228,15 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(RemoveResourcePackPacket packet) {
-    return false; //TODO
+    final ConnectedPlayer player = serverConn.getPlayer();
+    final ResourcePackHandler handler = player.resourcePackHandler();
+    if (packet.getId() != null) {
+      handler.remove(packet.getId());
+    } else {
+      handler.clearAppliedResourcePacks();
+    }
+    playerConnection.write(packet);
+    return true;
   }
 
   @Override

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/ConfigSessionHandler.java

@@ -84,8 +84,8 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
   public void activated() {
     ConnectedPlayer player = serverConn.getPlayer();
     if (player.getProtocolVersion() == ProtocolVersion.MINECRAFT_1_20_2) {
-      resourcePackToApply = player.getAppliedResourcePack();
+      resourcePackToApply = player.resourcePackHandler().getFirstAppliedPack();
-      player.clearAppliedResourcePack();
+      player.resourcePackHandler().clearAppliedResourcePacks();
     }
   }
 
@@ -136,7 +136,7 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
         }
 
         resourcePackToApply = null;
-        serverConn.getPlayer().queueResourcePack(toSend);
+        serverConn.getPlayer().resourcePackHandler().queueResourcePack(toSend);
       } else if (serverConn.getConnection() != null) {
         serverConn.getConnection().write(new ResourcePackResponsePacket(
                 packet.getId(), packet.getHash(), PlayerResourcePackStatusEvent.Status.DECLINED));
@@ -174,8 +174,9 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
         smc.setActiveSessionHandler(StateRegistry.PLAY,
             new TransitionSessionHandler(server, serverConn, resultFuture));
       }
-      if (player.getAppliedResourcePack() == null && resourcePackToApply != null) {
+      if (player.resourcePackHandler().getFirstAppliedPack() == null
-        player.queueResourcePack(resourcePackToApply);
+              && resourcePackToApply != null) {
+        player.resourcePackHandler().queueResourcePack(resourcePackToApply);
       }
       smc.setAutoReading(true);
     }, smc.eventLoop());
@@ -228,7 +229,7 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
   /**
    * Represents the state of the configuration stage.
    */
-  public static enum State {
+  public enum State {
     START, NEGOTIATING, PLUGIN_MESSAGE_INTERRUPT, RESOURCE_PACK_INTERRUPT, COMPLETE
   }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/AuthSessionHandler.java

@@ -142,10 +142,9 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
     }
 
     if (player.getIdentifiedKey() != null) {
-      IdentifiedKey playerKey = player.getIdentifiedKey();
+      final IdentifiedKey playerKey = player.getIdentifiedKey();
       if (playerKey.getSignatureHolder() == null) {
-        if (playerKey instanceof IdentifiedKeyImpl) {
+        if (playerKey instanceof IdentifiedKeyImpl unlinkedKey) {
-          IdentifiedKeyImpl unlinkedKey = (IdentifiedKeyImpl) playerKey;
           // Failsafe
           if (!unlinkedKey.internalAddHolder(player.getUniqueId())) {
             if (onlineMode) {
@@ -153,7 +152,7 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
                   Component.translatable("multiplayer.disconnect.invalid_public_key"));
               return;
             } else {
-              logger.warn("Key for player " + player.getUsername() + " could not be verified!");
+              logger.warn("Key for player {} could not be verified!", player.getUsername());
             }
           }
         } else {
@@ -161,8 +160,9 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
         }
       } else {
         if (!Objects.equals(playerKey.getSignatureHolder(), playerUniqueId)) {
-          logger.warn("UUID for Player " + player.getUsername() + " mismatches! "
+          logger.warn("UUID for Player {} mismatches! "
-              + "Chat/Commands signatures will not work correctly for this player!");
+              + "Chat/Commands signatures will not work correctly for this player!",
+                  player.getUsername());
         }
       }
     }
@@ -240,7 +240,7 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
 
     return server.getEventManager().fire(event).thenRunAsync(() -> {
       Optional<RegisteredServer> toTry = event.getInitialServer();
-      if (!toTry.isPresent()) {
+      if (toTry.isEmpty()) {
         player.disconnect0(
             Component.translatable("velocity.error.no-available-servers", NamedTextColor.RED),
             true);
@@ -263,7 +263,7 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
     this.inbound.cleanup();
   }
 
-  static enum State {
+  enum State {
     START, SUCCESS_SENT, ACKNOWLEDGED
   }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/BundleDelimiterHandler.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.client;
+
+import com.velocitypowered.proxy.connection.MinecraftConnection;
+import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
+import com.velocitypowered.proxy.protocol.StateRegistry;
+import com.velocitypowered.proxy.protocol.packet.BundleDelimiterPacket;
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * BundleDelimiterHandler.
+ */
+public final class BundleDelimiterHandler {
+  private final ConnectedPlayer player;
+  private boolean inBundleSession = false;
+  private CompletableFuture<Void> finishedBundleSessionFuture;
+
+  public BundleDelimiterHandler(ConnectedPlayer player) {
+    this.player = player;
+  }
+
+  public boolean isInBundleSession() {
+    return this.inBundleSession;
+  }
+
+  /**
+   * Toggles the player to be in the process of receiving multiple packets
+   * from the backend server via a packet bundle.
+   */
+  public void toggleBundleSession() {
+    if (this.inBundleSession) {
+      this.finishedBundleSessionFuture.complete(null);
+      this.finishedBundleSessionFuture = null;
+    } else {
+      this.finishedBundleSessionFuture = new CompletableFuture<>();
+    }
+    this.inBundleSession = !this.inBundleSession;
+  }
+
+  /**
+   * Bundles all packets sent in the given Runnable.
+   */
+  public CompletableFuture<Void> bundlePackets(final Runnable sendPackets) {
+    VelocityServerConnection connectedServer = player.getConnectedServer();
+    MinecraftConnection connection = connectedServer == null
+        ? null : connectedServer.getConnection();
+    if (connection == null) {
+      sendPackets(sendPackets);
+      return CompletableFuture.completedFuture(null);
+    }
+    CompletableFuture<Void> future = new CompletableFuture<>();
+    connection.eventLoop().execute(() -> {
+      if (inBundleSession) {
+        finishedBundleSessionFuture.thenRun(() -> {
+          sendPackets(sendPackets);
+          future.complete(null);
+        });
+      } else {
+        if (connection.getState() == StateRegistry.PLAY) {
+          sendPackets(sendPackets);
+        } else {
+          sendPackets.run();
+        }
+        future.complete(null);
+      }
+    });
+    return future;
+  }
+
+  private void sendPackets(Runnable sendPackets) {
+    player.getConnection().write(BundleDelimiterPacket.INSTANCE);
+    try {
+      sendPackets.run();
+    } finally {
+      player.getConnection().write(BundleDelimiterPacket.INSTANCE);
+    }
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java

@@ -22,6 +22,7 @@ import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
+import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackResponseBundle;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.StateRegistry;
@@ -70,17 +71,13 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
     configSwitchFuture = new CompletableFuture<>();
   }
 
-  @Override
-  public void deactivated() {
-  }
-
   @Override
   public boolean handle(KeepAlivePacket packet) {
-    VelocityServerConnection serverConnection = player.getConnectedServer();
+    final VelocityServerConnection serverConnection = player.getConnectedServer();
     if (serverConnection != null) {
-      Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
+      final Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
       if (sentTime != null) {
-        MinecraftConnection smc = serverConnection.getConnection();
+        final MinecraftConnection smc = serverConnection.getConnection();
         if (smc != null) {
           player.setPing(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - sentTime));
           smc.write(packet);
@@ -101,7 +98,9 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
     if (player.getConnectionInFlight() != null) {
       player.getConnectionInFlight().ensureConnected().write(packet);
     }
-    return player.onResourcePackResponse(packet.getStatus());
+    return player.resourcePackHandler().onResourcePackResponse(
+            new ResourcePackResponseBundle(packet.getId(), packet.getStatus())
+    );
   }
 
   @Override
@@ -196,9 +195,9 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
       smc.write(brandPacket);
     }
 
-    player.getConnection().write(new FinishedUpdatePacket());
+    player.getConnection().write(FinishedUpdatePacket.INSTANCE);
 
-    smc.write(new FinishedUpdatePacket());
+    smc.write(FinishedUpdatePacket.INSTANCE);
     smc.getChannel().pipeline().get(MinecraftEncoder.class).setState(StateRegistry.PLAY);
 
     return configSwitchFuture;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -38,6 +38,7 @@ import com.velocitypowered.proxy.connection.backend.BackendConnectionPhases;
 import com.velocitypowered.proxy.connection.backend.BungeeCordMessageResponder;
 import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants;
+import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackResponseBundle;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.packet.BossBarPacket;
@@ -172,11 +173,11 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(KeepAlivePacket packet) {
-    VelocityServerConnection serverConnection = player.getConnectedServer();
+    final VelocityServerConnection serverConnection = player.getConnectedServer();
     if (serverConnection != null) {
-      Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
+      final Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
       if (sentTime != null) {
-        MinecraftConnection smc = serverConnection.getConnection();
+        final MinecraftConnection smc = serverConnection.getConnection();
         if (smc != null) {
           player.setPing(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - sentTime));
           smc.write(packet);
@@ -204,7 +205,6 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
       return true;
     }
 
-
     if (!updateTimeKeeper(packet.getTimeStamp())) {
       return true;
     }
@@ -392,7 +392,8 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(ResourcePackResponsePacket packet) {
-    return player.onResourcePackResponse(packet.getStatus());
+    return player.resourcePackHandler().onResourcePackResponse(
+            new ResourcePackResponseBundle(packet.getId(), packet.getStatus()));
   }
 
   @Override

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -31,7 +31,6 @@ import com.velocitypowered.api.event.player.KickedFromServerEvent.Notify;
 import com.velocitypowered.api.event.player.KickedFromServerEvent.RedirectPlayer;
 import com.velocitypowered.api.event.player.KickedFromServerEvent.ServerKickResult;
 import com.velocitypowered.api.event.player.PlayerModInfoEvent;
-import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
 import com.velocitypowered.api.event.player.PlayerSettingsChangedEvent;
 import com.velocitypowered.api.event.player.ServerPreConnectEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
@@ -55,6 +54,7 @@ import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftConnectionAssociation;
 import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackHandler;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
 import com.velocitypowered.proxy.connection.util.VelocityInboundConnection;
@@ -66,7 +66,6 @@ import com.velocitypowered.proxy.protocol.packet.HeaderAndFooterPacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.RemoveResourcePackPacket;
-import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatQueue;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatType;
 import com.velocitypowered.proxy.protocol.packet.chat.ComponentHolder;
@@ -82,19 +81,14 @@ import com.velocitypowered.proxy.tablist.VelocityTabListLegacy;
 import com.velocitypowered.proxy.util.ClosestLocaleMatcher;
 import com.velocitypowered.proxy.util.DurationUtils;
 import com.velocitypowered.proxy.util.TranslatableMapper;
-import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import java.net.InetSocketAddress;
-import java.util.ArrayDeque;
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Optional;
-import java.util.Queue;
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
@@ -129,7 +123,6 @@ import org.jetbrains.annotations.NotNull;
 public class ConnectedPlayer implements MinecraftConnectionAssociation, Player, KeyIdentifiable,
     VelocityInboundConnection {
 
-  private static final int MAX_PLUGIN_CHANNELS = 1024;
   private static final PlainTextComponentSerializer PASS_THRU_TRANSLATE =
       PlainTextComponentSerializer.builder().flattener(TranslatableMapper.FLATTENER).build();
   static final PermissionProvider DEFAULT_PERMISSIONS = s -> PermissionFunction.ALWAYS_UNDEFINED;
@@ -159,14 +152,12 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   private ClientConnectionPhase connectionPhase;
   private final CompletableFuture<Void> teardownFuture = new CompletableFuture<>();
   private @MonotonicNonNull List<String> serversToTry = null;
-  private @MonotonicNonNull Boolean previousResourceResponse;
+  private final ResourcePackHandler resourcePackHandler;
-  private final Queue<ResourcePackInfo> outstandingResourcePacks = new ArrayDeque<>();
+  private final BundleDelimiterHandler bundleHandler = new BundleDelimiterHandler(this);
-  private @Nullable ResourcePackInfo pendingResourcePack;
+
-  private @Nullable ResourcePackInfo appliedResourcePack;
-  private @NotNull List<ResourcePackInfo> pendingResourcePacks = new ArrayList<>();
-  private @NotNull List<ResourcePackInfo> appliedResourcePacks = new ArrayList<>();
   private final @NotNull Pointers pointers =
-      Player.super.pointers().toBuilder().withDynamic(Identity.UUID, this::getUniqueId)
+      Player.super.pointers().toBuilder()
+          .withDynamic(Identity.UUID, this::getUniqueId)
           .withDynamic(Identity.NAME, this::getUsername)
           .withDynamic(Identity.DISPLAY_NAME, () -> Component.text(this.getUsername()))
           .withDynamic(Identity.LOCALE, this::getEffectiveLocale)
@@ -174,7 +165,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
           .withStatic(FacetPointers.TYPE, Type.PLAYER).build();
   private @Nullable String clientBrand;
   private @Nullable Locale effectiveLocale;
-  private @Nullable IdentifiedKey playerKey;
+  private final @Nullable IdentifiedKey playerKey;
   private @Nullable ClientSettingsPacket clientSettingsPacket;
   private final ChatQueue chatQueue;
   private final ChatBuilderFactory chatBuilderFactory;
@@ -200,6 +191,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     this.playerKey = playerKey;
     this.chatQueue = new ChatQueue(this);
     this.chatBuilderFactory = new ChatBuilderFactory(this.getProtocolVersion());
+    this.resourcePackHandler = ResourcePackHandler.create(this, server);
   }
 
   /**
@@ -219,6 +211,10 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     return chatQueue;
   }
 
+  public BundleDelimiterHandler getBundleHandler() {
+    return this.bundleHandler;
+  }
+
   @Override
   public @NonNull Identity identity() {
     return this.identity;
@@ -238,7 +234,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   @Override
-  public void setEffectiveLocale(Locale locale) {
+  public void setEffectiveLocale(final @Nullable Locale locale) {
     effectiveLocale = locale;
   }
 
@@ -293,6 +289,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     return settings == null ? ClientSettingsWrapper.DEFAULT : this.settings;
   }
 
+  @Nullable
   public ClientSettingsPacket getClientSettingsPacket() {
     return clientSettingsPacket;
   }
@@ -367,7 +364,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   @Override
   public void sendMessage(@NonNull Identity identity, @NonNull Component message) {
-    Component translated = translateMessage(message);
+    final Component translated = translateMessage(message);
 
     connection.write(getChatBuilderFactory().builder()
         .component(translated).forIdentity(identity).toClient());
@@ -432,7 +429,8 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   @Override
-  public void sendPlayerListHeaderAndFooter(final Component header, final Component footer) {
+  public void sendPlayerListHeaderAndFooter(final @NotNull Component header,
+                                            final @NotNull Component footer) {
     Component translatedHeader = translateMessage(header);
     Component translatedFooter = translateMessage(footer);
     this.playerListHeader = translatedHeader;
@@ -472,6 +470,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
   }
 
+  @SuppressWarnings("ConstantValue")
   @Override
   public <T> void sendTitlePart(@NotNull TitlePart<T> part, @NotNull T value) {
     if (part == null) {
@@ -744,11 +743,9 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
         return;
       }
 
-      if (event.getResult() instanceof DisconnectPlayer) {
+      if (event.getResult() instanceof final DisconnectPlayer res) {
-        DisconnectPlayer res = (DisconnectPlayer) event.getResult();
         disconnect(res.getReasonComponent());
-      } else if (event.getResult() instanceof RedirectPlayer) {
+      } else if (event.getResult() instanceof final RedirectPlayer res) {
-        RedirectPlayer res = (RedirectPlayer) event.getResult();
         createConnectionRequest(res.getServer(), previousConnection).connect()
             .whenCompleteAsync((status, throwable) -> {
               if (throwable != null) {
@@ -794,8 +791,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
                   break;
               }
             }, connection.eventLoop());
-      } else if (event.getResult() instanceof Notify) {
+      } else if (event.getResult() instanceof final Notify res) {
-        Notify res = (Notify) event.getResult();
         if (event.kickedDuringServerConnect() && previousConnection != null) {
           sendMessage(Identity.nil(), res.getMessageComponent());
         } else {
@@ -906,7 +902,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
     DisconnectEvent.LoginStatus status;
     if (connectedPlayer.isPresent()) {
-      if (!connectedPlayer.get().getCurrentServer().isPresent()) {
+      if (connectedPlayer.get().getCurrentServer().isEmpty()) {
         status = LoginStatus.PRE_SERVER_JOIN;
       } else {
         status = connectedPlayer.get() == this ? LoginStatus.SUCCESSFUL_LOGIN
@@ -933,9 +929,9 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
 
   @Override
   public String toString() {
-    boolean isPlayerAddressLoggingEnabled = server.getConfiguration()
+    final boolean isPlayerAddressLoggingEnabled = server.getConfiguration()
         .isPlayerAddressLoggingEnabled();
-    String playerIp =
+    final String playerIp =
         isPlayerAddressLoggingEnabled ? getRemoteAddress().toString() : "<ip address withheld>";
     return "[connected player] " + profile.getName() + " (" + playerIp + ")";
   }
@@ -956,11 +952,12 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   }
 
   @Override
+  @Nullable
   public String getClientBrand() {
     return clientBrand;
   }
 
-  void setClientBrand(String clientBrand) {
+  void setClientBrand(final @Nullable String clientBrand) {
     this.clientBrand = clientBrand;
   }
 
@@ -981,6 +978,15 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
   }
 
+  /**
+   * Get the ResourcePackHandler corresponding to the player's version.
+   *
+   * @return the ResourcePackHandler of this player
+   */
+  public ResourcePackHandler resourcePackHandler() {
+    return this.resourcePackHandler;
+  }
+
   @Override
   @Deprecated
   public void sendResourcePack(String url) {
@@ -997,7 +1003,15 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public void sendResourcePackOffer(ResourcePackInfo packInfo) {
     if (this.getProtocolVersion().noLessThan(ProtocolVersion.MINECRAFT_1_8)) {
       Preconditions.checkNotNull(packInfo, "packInfo");
-      queueResourcePack(packInfo);
+      this.resourcePackHandler.queueResourcePack(packInfo);
+    }
+  }
+
+  @Override
+  public void sendResourcePacks(@NotNull ResourcePackRequest request) {
+    if (this.getProtocolVersion().noLessThan(ProtocolVersion.MINECRAFT_1_8)) {
+      Preconditions.checkNotNull(request, "packRequest");
+      this.resourcePackHandler.queueResourcePack(request);
     }
   }
 
@@ -1005,15 +1019,21 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public void clearResourcePacks() {
     if (this.getProtocolVersion().noLessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
       connection.write(new RemoveResourcePackPacket());
+      this.resourcePackHandler.clearAppliedResourcePacks();
     }
   }
 
   @Override
   public void removeResourcePacks(@NotNull UUID id, @NotNull UUID @NotNull ... others) {
     if (this.getProtocolVersion().noLessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
-      connection.write(new RemoveResourcePackPacket(id));
+      Preconditions.checkNotNull(id, "packUUID");
+      if (this.resourcePackHandler.remove(id)) {
+        connection.write(new RemoveResourcePackPacket(id));
+      }
       for (final UUID other : others) {
-        connection.write(new RemoveResourcePackPacket(other));
+        if (this.resourcePackHandler.remove(other)) {
+          connection.write(new RemoveResourcePackPacket(other));
+        }
       }
     }
   }
@@ -1039,174 +1059,26 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
   }
 
-  /**
-   * Queues a resource-pack for sending to the player and sends it immediately if the queue is
-   * empty.
-   */
-  public void queueResourcePack(ResourcePackInfo info) {
-    outstandingResourcePacks.add(info);
-    if (outstandingResourcePacks.size() == 1) {
-      tickResourcePackQueue();
-    }
-  }
-
-  private void tickResourcePackQueue() {
-    ResourcePackInfo queued = outstandingResourcePacks.peek();
-
-    if (queued != null) {
-      // Check if the player declined a resource pack once already
-      if (previousResourceResponse != null && !previousResourceResponse) {
-        // If that happened we can flush the queue right away.
-        // Unless its 1.17+ and forced it will come back denied anyway
-        while (!outstandingResourcePacks.isEmpty()) {
-          queued = outstandingResourcePacks.peek();
-          if (queued.getShouldForce() && getProtocolVersion()
-              .noLessThan(ProtocolVersion.MINECRAFT_1_17)) {
-            break;
-          }
-          onResourcePackResponse(PlayerResourcePackStatusEvent.Status.DECLINED);
-          queued = null;
-        }
-        if (queued == null) {
-          // Exit as the queue was cleared
-          return;
-        }
-      }
-
-      ResourcePackRequestPacket request = new ResourcePackRequestPacket();
-      request.setId(queued.getId());
-      request.setUrl(queued.getUrl());
-      if (queued.getHash() != null) {
-        request.setHash(ByteBufUtil.hexDump(queued.getHash()));
-      } else {
-        request.setHash("");
-      }
-      request.setRequired(queued.getShouldForce());
-      request.setPrompt(queued.getPrompt() == null ? null :
-          new ComponentHolder(getProtocolVersion(), queued.getPrompt()));
-
-      connection.write(request);
-    }
-  }
-
   @Override
   @Deprecated
   public @Nullable ResourcePackInfo getAppliedResourcePack() {
-    return appliedResourcePack;
+    return this.resourcePackHandler.getFirstAppliedPack();
   }
 
   @Override
   @Deprecated
   public @Nullable ResourcePackInfo getPendingResourcePack() {
-    return pendingResourcePack;
+    return this.resourcePackHandler.getFirstPendingPack();
   }
 
   @Override
   public Collection<ResourcePackInfo> getAppliedResourcePacks() {
-    return new ArrayList<>(appliedResourcePacks);
+    return this.resourcePackHandler.getAppliedResourcePacks();
   }
 
   @Override
   public Collection<ResourcePackInfo> getPendingResourcePacks() {
-    return new ArrayList<>(pendingResourcePacks);
+    return this.resourcePackHandler.getPendingResourcePacks();
-  }
-
-  /**
-   * Clears the applied resource pack field.
-   */
-  public void clearAppliedResourcePack() {
-    appliedResourcePack = null;
-  }
-
-  /**
-   * Processes a client response to a sent resource-pack.
-   */
-  public boolean onResourcePackResponse(PlayerResourcePackStatusEvent.Status status) {
-    final boolean peek = status.isIntermediate();
-    final ResourcePackInfo queued = peek
-        ? outstandingResourcePacks.peek() : outstandingResourcePacks.poll();
-
-    server.getEventManager().fire(new PlayerResourcePackStatusEvent(this, status, queued))
-        .thenAcceptAsync(event -> {
-          if (event.getStatus() == PlayerResourcePackStatusEvent.Status.DECLINED
-              && event.getPackInfo() != null && event.getPackInfo().getShouldForce()
-              && (!event.isOverwriteKick() || event.getPlayer()
-              .getProtocolVersion().noLessThan(ProtocolVersion.MINECRAFT_1_17))
-          ) {
-            event.getPlayer().disconnect(Component
-                .translatable("multiplayer.requiredTexturePrompt.disconnect"));
-          }
-        });
-
-    switch (status) {
-      case ACCEPTED:
-        previousResourceResponse = true;
-        pendingResourcePack = queued;
-        if (this.getProtocolVersion().lessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
-          pendingResourcePacks.clear();
-        }
-        pendingResourcePacks.add(queued);
-        break;
-      case DECLINED:
-        previousResourceResponse = false;
-        break;
-      case SUCCESSFUL:
-        appliedResourcePack = queued;
-        pendingResourcePack = null;
-        appliedResourcePacks.add(queued);
-        if (this.getProtocolVersion().lessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
-          pendingResourcePacks.clear();
-        }
-        if (queued != null) {
-          pendingResourcePacks.removeIf(resourcePackInfo -> {
-            if (resourcePackInfo.getId() == null) {
-              return resourcePackInfo.getUrl().equals(queued.getUrl())
-                      && Arrays.equals(resourcePackInfo.getHash(), queued.getHash());
-            }
-            return resourcePackInfo.getId().equals(queued.getId());
-          });
-        }
-        break;
-      case FAILED_DOWNLOAD:
-        pendingResourcePack = null;
-        if (this.getProtocolVersion().lessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
-          pendingResourcePacks.clear();
-        }
-        if (queued != null) {
-          pendingResourcePacks.removeIf(resourcePackInfo -> {
-            if (resourcePackInfo.getId() == null) {
-              return resourcePackInfo.getUrl().equals(queued.getUrl())
-                      && Arrays.equals(resourcePackInfo.getHash(), queued.getHash());
-            }
-            return resourcePackInfo.getId().equals(queued.getId());
-          });
-        }
-        break;
-      case DISCARDED:
-        if (queued != null && queued.getId() != null) {
-          appliedResourcePacks.removeIf(resourcePackInfo -> {
-            return queued.getId().equals(resourcePackInfo.getId());
-          });
-        }
-        break;
-      default:
-        break;
-    }
-
-    if (!peek) {
-      connection.eventLoop().execute(this::tickResourcePackQueue);
-    }
-
-    return queued != null
-        && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
-  }
-
-  /**
-   * Gives an indication about the previous resource pack responses.
-   */
-  public @Nullable Boolean getPreviousResourceResponse() {
-    //TODO can probably be removed
-    return previousResourceResponse;
   }
 
   /**
@@ -1228,7 +1100,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
    */
   public void switchToConfigState() {
     CompletableFuture.runAsync(() -> {
-      connection.write(new StartUpdatePacket());
+      connection.write(StartUpdatePacket.INSTANCE);
       connection.getChannel().pipeline()
           .get(MinecraftEncoder.class).setState(StateRegistry.CONFIG);
       // Make sure we don't send any play packets to the player after update start
@@ -1271,7 +1143,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
   }
 
-  private class ConnectionRequestBuilderImpl implements ConnectionRequestBuilder {
+  private final class ConnectionRequestBuilderImpl implements ConnectionRequestBuilder {
 
     private final RegisteredServer toConnect;
     private final @Nullable VelocityRegisteredServer previousServer;
@@ -1315,7 +1187,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
             new ServerPreConnectEvent(ConnectedPlayer.this, toConnect, previousServer);
         return server.getEventManager().fire(event).thenComposeAsync(newEvent -> {
           Optional<RegisteredServer> newDest = newEvent.getResult().getServer();
-          if (!newDest.isPresent()) {
+          if (newDest.isEmpty()) {
             return completedFuture(
                 plainResult(ConnectionRequestBuilder.Status.CONNECTION_CANCELLED, toConnect));
           }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/HandshakeSessionHandler.java

@@ -67,7 +67,7 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
   @Override
   public boolean handle(LegacyPingPacket packet) {
     connection.setProtocolVersion(ProtocolVersion.LEGACY);
-    StatusSessionHandler handler =
+    final StatusSessionHandler handler =
         new StatusSessionHandler(server, new LegacyInboundConnection(connection, packet));
     connection.setActiveSessionHandler(StateRegistry.STATUS, handler);
     handler.handle(packet);
@@ -85,9 +85,9 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(HandshakePacket handshake) {
-    InitialInboundConnection ic = new InitialInboundConnection(connection,
+    final InitialInboundConnection ic = new InitialInboundConnection(connection,
         cleanVhost(handshake.getServerAddress()), handshake);
-    StateRegistry nextState = getStateForProtocol(handshake.getNextStatus());
+    final StateRegistry nextState = getStateForProtocol(handshake.getNextStatus());
     if (nextState == null) {
       LOGGER.error("{} provided invalid protocol {}", ic, handshake.getNextStatus());
       connection.close(true);
@@ -96,14 +96,10 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
       connection.setAssociation(ic);
 
       switch (nextState) {
-        case STATUS:
+        case STATUS -> connection.setActiveSessionHandler(StateRegistry.STATUS,
-          connection.setActiveSessionHandler(StateRegistry.STATUS,
               new StatusSessionHandler(server, ic));
-          break;
+        case LOGIN -> this.handleLogin(handshake, ic);
-        case LOGIN:
+        default ->
-          this.handleLogin(handshake, ic);
-          break;
-        default:
           // If you get this, it's a bug in Velocity.
           throw new AssertionError("getStateForProtocol provided invalid state!");
       }
@@ -113,24 +109,23 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
   }
 
   private static @Nullable StateRegistry getStateForProtocol(int status) {
-    switch (status) {
+    return switch (status) {
-      case StateRegistry.STATUS_ID:
+      case StateRegistry.STATUS_ID -> StateRegistry.STATUS;
-        return StateRegistry.STATUS;
+      case StateRegistry.LOGIN_ID -> StateRegistry.LOGIN;
-      case StateRegistry.LOGIN_ID:
+      default -> null;
-        return StateRegistry.LOGIN;
+    };
-      default:
-        return null;
-    }
   }
 
   private void handleLogin(HandshakePacket handshake, InitialInboundConnection ic) {
     if (!ProtocolVersion.isSupported(handshake.getProtocolVersion())) {
-      ic.disconnectQuietly(Component.translatable("multiplayer.disconnect.outdated_client")
+      ic.disconnectQuietly(Component.translatable()
-          .args(Component.text(ProtocolVersion.SUPPORTED_VERSION_STRING)));
+              .key("multiplayer.disconnect.outdated_client")
+              .arguments(Component.text(ProtocolVersion.SUPPORTED_VERSION_STRING))
+              .build());
       return;
     }
 
-    InetAddress address = ((InetSocketAddress) connection.getRemoteAddress()).getAddress();
+    final InetAddress address = ((InetSocketAddress) connection.getRemoteAddress()).getAddress();
     if (!server.getIpAttemptLimiter().attempt(address)) {
       // Bump connection into correct protocol state so that we can send the disconnect packet.
       connection.setState(StateRegistry.LOGIN);
@@ -151,7 +146,7 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
       return;
     }
 
-    LoginInboundConnection lic = new LoginInboundConnection(ic);
+    final LoginInboundConnection lic = new LoginInboundConnection(ic);
     server.getEventManager().fireAndForget(new ConnectionHandshakeEvent(lic));
     connection.setActiveSessionHandler(StateRegistry.LOGIN,
         new InitialLoginSessionHandler(server, connection, lic));
@@ -213,16 +208,10 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
     connection.close(true);
   }
 
-  private static class LegacyInboundConnection implements VelocityInboundConnection {
+  private record LegacyInboundConnection(
-
+          MinecraftConnection connection,
-    private final MinecraftConnection connection;
+          LegacyPingPacket ping
-    private final LegacyPingPacket ping;
+  ) implements VelocityInboundConnection {
-
-    private LegacyInboundConnection(MinecraftConnection connection,
-        LegacyPingPacket ping) {
-      this.connection = connection;
-      this.ping = ping;
-    }
 
     @Override
     public InetSocketAddress getRemoteAddress() {

proxy/src/main/java/com/velocitypowered/proxy/connection/client/InitialInboundConnection.java

@@ -74,9 +74,9 @@ public final class InitialInboundConnection implements VelocityInboundConnection
 
   @Override
   public String toString() {
-    boolean isPlayerAddressLoggingEnabled = connection.server.getConfiguration()
+    final boolean isPlayerAddressLoggingEnabled = connection.server.getConfiguration()
         .isPlayerAddressLoggingEnabled();
-    String playerIp =
+    final String playerIp =
         isPlayerAddressLoggingEnabled
             ? connection.getRemoteAddress().toString() : "<ip address withheld>";
     return "[initial connection] " + playerIp;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/StatusSessionHandler.java

@@ -95,7 +95,7 @@ public class StatusSessionHandler implements MinecraftSessionHandler {
         .thenCompose(ping -> server.getEventManager().fire(new ProxyPingEvent(inbound, ping)))
         .thenAcceptAsync(
             (event) -> {
-              StringBuilder json = new StringBuilder();
+              final StringBuilder json = new StringBuilder();
               VelocityServer.getPingGsonInstance(connection.getProtocolVersion())
                   .toJson(event.getPing(), json);
               connection.write(new StatusResponsePacket(json));

proxy/src/main/java/com/velocitypowered/proxy/connection/player/VelocityResourcePackInfo.java

@@ -19,10 +19,14 @@ package com.velocitypowered.proxy.connection.player;
 
 import com.google.common.base.Preconditions;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
+import io.netty.buffer.ByteBufUtil;
+import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.util.UUID;
+import net.kyori.adventure.resource.ResourcePackRequest;
 import net.kyori.adventure.text.Component;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Implements {@link ResourcePackInfo}.
@@ -31,13 +35,13 @@ public final class VelocityResourcePackInfo implements ResourcePackInfo {
 
   private final UUID id;
   private final String url;
-  private final @Nullable byte[] hash;
+  private final byte @Nullable [] hash;
   private final boolean shouldForce;
   private final @Nullable Component prompt; // 1.17+ only
   private final Origin origin;
   private Origin originalOrigin;
 
-  private VelocityResourcePackInfo(UUID id, String url, @Nullable byte[] hash, boolean shouldForce,
+  private VelocityResourcePackInfo(UUID id, String url, byte @Nullable [] hash, boolean shouldForce,
                                    @Nullable Component prompt, Origin origin) {
     this.id = id;
     this.url = url;
@@ -69,7 +73,7 @@ public final class VelocityResourcePackInfo implements ResourcePackInfo {
   }
 
   @Override
-  public @Nullable byte[] getHash() {
+  public byte @Nullable[] getHash() {
     return hash == null ? null : hash.clone(); // Thanks spotbugs, very helpful.
   }
 
@@ -105,6 +109,32 @@ public final class VelocityResourcePackInfo implements ResourcePackInfo {
         .setPrompt(prompt);
   }
 
+  @Override
+  public @NotNull ResourcePackRequest asResourcePackRequest() {
+    return ResourcePackRequest.resourcePackRequest()
+            .packs(net.kyori.adventure.resource.ResourcePackInfo.resourcePackInfo()
+                    .id(this.id)
+                    .uri(URI.create(this.url))
+                    .hash(this.hash == null ? "" : ByteBufUtil.hexDump(this.hash))
+                    .build())
+            .required(this.shouldForce)
+            .prompt(this.prompt)
+            .build();
+  }
+
+  @SuppressWarnings("checkstyle:MissingJavadocMethod")
+  public static ResourcePackInfo fromAdventureRequest(
+          final ResourcePackRequest request,
+          final net.kyori.adventure.resource.ResourcePackInfo pack
+  ) {
+    return new BuilderImpl(pack.uri().toString())
+            .setHash(pack.hash().isEmpty() ? null : ByteBufUtil.decodeHexDump(pack.hash()))
+            .setId(pack.id())
+            .setShouldForce(request.required())
+            .setPrompt(request.prompt())
+            .build();
+  }
+
   /**
    * Implements the builder for {@link ResourcePackInfo} instances.
    */
@@ -113,7 +143,7 @@ public final class VelocityResourcePackInfo implements ResourcePackInfo {
     private UUID id;
     private final String url;
     private boolean shouldForce;
-    private @Nullable byte[] hash;
+    private byte @Nullable [] hash;
     private @Nullable Component prompt;
     private Origin origin = Origin.PLUGIN_ON_PROXY;
 
@@ -135,7 +165,7 @@ public final class VelocityResourcePackInfo implements ResourcePackInfo {
     }
 
     @Override
-    public BuilderImpl setHash(@Nullable byte[] hash) {
+    public BuilderImpl setHash(final byte @Nullable [] hash) {
       if (hash != null) {
         Preconditions.checkArgument(hash.length == 20, "Hash length is not 20");
         this.hash = hash.clone(); // Thanks spotbugs, very helpful.

proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/Legacy117ResourcePackHandler.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.player.resourcepack;
+
+import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.proxy.VelocityServer;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+
+/**
+ * Legacy (Minecraft 1.17-1.20.2) ResourcePackHandler.
+ */
+public final class Legacy117ResourcePackHandler extends LegacyResourcePackHandler {
+  Legacy117ResourcePackHandler(final ConnectedPlayer player, final VelocityServer server) {
+    super(player, server);
+  }
+
+  @Override
+  protected boolean shouldDisconnectForForcePack(final PlayerResourcePackStatusEvent event) {
+    return super.shouldDisconnectForForcePack(event) && !event.isOverwriteKick();
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/LegacyResourcePackHandler.java

@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.player.resourcepack;
+
+import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.network.ProtocolVersion;
+import com.velocitypowered.api.proxy.player.ResourcePackInfo;
+import com.velocitypowered.proxy.VelocityServer;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import java.util.ArrayDeque;
+import java.util.Collection;
+import java.util.List;
+import java.util.Queue;
+import java.util.UUID;
+import net.kyori.adventure.text.Component;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Legacy (Minecraft <1.17) ResourcePackHandler.
+ */
+public sealed class LegacyResourcePackHandler extends ResourcePackHandler
+        permits Legacy117ResourcePackHandler {
+  protected @MonotonicNonNull Boolean previousResourceResponse;
+  protected final Queue<ResourcePackInfo> outstandingResourcePacks = new ArrayDeque<>();
+  private @Nullable ResourcePackInfo pendingResourcePack;
+  private @Nullable ResourcePackInfo appliedResourcePack;
+
+  LegacyResourcePackHandler(final ConnectedPlayer player, final VelocityServer server) {
+    super(player, server);
+  }
+
+  @Override
+  @Nullable
+  public ResourcePackInfo getFirstAppliedPack() {
+    return appliedResourcePack;
+  }
+
+  @Override
+  @Nullable
+  public ResourcePackInfo getFirstPendingPack() {
+    return pendingResourcePack;
+  }
+
+  @Override
+  public @NotNull Collection<ResourcePackInfo> getAppliedResourcePacks() {
+    if (appliedResourcePack == null) {
+      return List.of();
+    }
+    return List.of(appliedResourcePack);
+  }
+
+  @Override
+  public @NotNull Collection<ResourcePackInfo> getPendingResourcePacks() {
+    if (pendingResourcePack == null) {
+      return List.of();
+    }
+    return List.of(pendingResourcePack);
+  }
+
+  @Override
+  public void clearAppliedResourcePacks() {
+    // This is valid only for players with 1.20.2 versions
+    this.appliedResourcePack = null;
+  }
+
+  @Override
+  public boolean remove(final @NotNull UUID id) throws UnsupportedOperationException {
+    throw new UnsupportedOperationException("Cannot remove a ResourcePack from a legacy client");
+  }
+
+  @Override
+  public void queueResourcePack(@NotNull ResourcePackInfo info) {
+    outstandingResourcePacks.add(info);
+    if (outstandingResourcePacks.size() == 1) {
+      tickResourcePackQueue();
+    }
+  }
+
+  private void tickResourcePackQueue() {
+    ResourcePackInfo queued = outstandingResourcePacks.peek();
+
+    if (queued != null) {
+      // Check if the player declined a resource pack once already
+      if (previousResourceResponse != null && !previousResourceResponse) {
+        // If that happened we can flush the queue right away.
+        // Unless its 1.17+ and forced it will come back denied anyway
+        while (!outstandingResourcePacks.isEmpty()) {
+          queued = outstandingResourcePacks.peek();
+          if (queued.getShouldForce() && player.getProtocolVersion()
+                  .noLessThan(ProtocolVersion.MINECRAFT_1_17)) {
+            break;
+          }
+          onResourcePackResponse(new ResourcePackResponseBundle(queued.getId(),
+                  PlayerResourcePackStatusEvent.Status.DECLINED));
+          queued = null;
+        }
+        if (queued == null) {
+          // Exit as the queue was cleared
+          return;
+        }
+      }
+
+      sendResourcePackRequestPacket(queued);
+    }
+  }
+
+  @Override
+  public boolean onResourcePackResponse(
+          final @NotNull ResourcePackResponseBundle bundle
+  ) {
+    final boolean peek = bundle.status().isIntermediate();
+    final ResourcePackInfo queued = peek
+            ? outstandingResourcePacks.peek() : outstandingResourcePacks.poll();
+
+    server.getEventManager()
+            .fire(new PlayerResourcePackStatusEvent(
+                this.player, bundle.uuid(), bundle.status(), queued))
+            .thenAcceptAsync(event -> {
+              if (shouldDisconnectForForcePack(event)) {
+                event.getPlayer().disconnect(Component
+                        .translatable("multiplayer.requiredTexturePrompt.disconnect"));
+              }
+            });
+
+    switch (bundle.status()) {
+      case ACCEPTED -> {
+        previousResourceResponse = true;
+        pendingResourcePack = queued;
+      }
+      case DECLINED -> previousResourceResponse = false;
+      case SUCCESSFUL -> {
+        appliedResourcePack = queued;
+        pendingResourcePack = null;
+      }
+      case FAILED_DOWNLOAD -> pendingResourcePack = null;
+      case DISCARDED -> {
+        if (queued != null && queued.getId() != null
+                && appliedResourcePack != null
+                && appliedResourcePack.getId().equals(queued.getId())) {
+          appliedResourcePack = null;
+        }
+      }
+      default -> {
+      }
+    }
+
+    if (!peek) {
+      player.getConnection().eventLoop().execute(this::tickResourcePackQueue);
+    }
+
+    return queued != null
+            && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
+  }
+
+  protected boolean shouldDisconnectForForcePack(final PlayerResourcePackStatusEvent event) {
+    return event.getStatus() == PlayerResourcePackStatusEvent.Status.DECLINED
+            && event.getPackInfo() != null && event.getPackInfo().getShouldForce();
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ModernResourcePackHandler.java

@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.player.resourcepack;
+
+import com.google.common.collect.ListMultimap;
+import com.google.common.collect.Multimaps;
+import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.proxy.player.ResourcePackInfo;
+import com.velocitypowered.proxy.VelocityServer;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+import net.kyori.adventure.resource.ResourcePackRequest;
+import net.kyori.adventure.text.Component;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Modern (Minecraft 1.20.3+) ResourcePackHandler
+ */
+public final class ModernResourcePackHandler extends ResourcePackHandler {
+  private static final Logger LOGGER = LoggerFactory.getLogger(ModernResourcePackHandler.class);
+  private final ListMultimap<UUID, ResourcePackInfo> outstandingResourcePacks =
+      Multimaps.newListMultimap(new ConcurrentHashMap<>(), LinkedList::new);
+  private final Map<UUID, ResourcePackInfo> pendingResourcePacks = new ConcurrentHashMap<>();
+  private final Map<UUID, ResourcePackInfo> appliedResourcePacks = new ConcurrentHashMap<>();
+
+  ModernResourcePackHandler(final ConnectedPlayer player, final VelocityServer server) {
+    super(player, server);
+  }
+
+  @Override
+  public @Nullable ResourcePackInfo getFirstAppliedPack() {
+    if (appliedResourcePacks.isEmpty()) {
+      return null;
+    }
+    return appliedResourcePacks.values().iterator().next();
+  }
+
+  @Override
+  public @Nullable ResourcePackInfo getFirstPendingPack() {
+    if (pendingResourcePacks.isEmpty()) {
+      return null;
+    }
+    return pendingResourcePacks.values().iterator().next();
+  }
+
+  @Override
+  public @NotNull Collection<ResourcePackInfo> getAppliedResourcePacks() {
+    return List.copyOf(appliedResourcePacks.values());
+  }
+
+  @Override
+  public @NotNull Collection<ResourcePackInfo> getPendingResourcePacks() {
+    return List.copyOf(pendingResourcePacks.values());
+  }
+
+  @Override
+  public void clearAppliedResourcePacks() {
+    this.outstandingResourcePacks.clear();
+    this.pendingResourcePacks.clear();
+    this.appliedResourcePacks.clear();
+  }
+
+  @Override
+  public boolean remove(final @NotNull UUID uuid) {
+    outstandingResourcePacks.removeAll(uuid);
+    return appliedResourcePacks.remove(uuid) != null | pendingResourcePacks.remove(uuid) != null;
+  }
+
+  @Override
+  public void queueResourcePack(final @NotNull ResourcePackInfo info) {
+    final List<ResourcePackInfo> outstandingResourcePacks =
+        this.outstandingResourcePacks.get(info.getId());
+    outstandingResourcePacks.add(info);
+    if (outstandingResourcePacks.size() == 1) {
+      tickResourcePackQueue(outstandingResourcePacks.get(0).getId());
+    }
+  }
+
+  @Override
+  public void queueResourcePack(final @NotNull ResourcePackRequest request) {
+    if (request.packs().size() > 1) {
+      player.getBundleHandler().bundlePackets(() -> {
+        super.queueResourcePack(request);
+      });
+    } else {
+      super.queueResourcePack(request);
+    }
+  }
+
+  private void tickResourcePackQueue(final @NotNull UUID uuid) {
+    final List<ResourcePackInfo> outstandingResourcePacks =
+        this.outstandingResourcePacks.get(uuid);
+    if (!outstandingResourcePacks.isEmpty()) {
+      sendResourcePackRequestPacket(outstandingResourcePacks.get(0));
+    }
+  }
+
+  @Override
+  public boolean onResourcePackResponse(
+          final @NotNull ResourcePackResponseBundle bundle
+  ) {
+    final UUID uuid = bundle.uuid();
+    final List<ResourcePackInfo> outstandingResourcePacks =
+        this.outstandingResourcePacks.get(uuid);
+    final boolean peek = bundle.status().isIntermediate();
+    final ResourcePackInfo queued = outstandingResourcePacks.isEmpty() ? null :
+        peek ? outstandingResourcePacks.get(0) : outstandingResourcePacks.remove(0);
+
+    server.getEventManager()
+            .fire(new PlayerResourcePackStatusEvent(this.player, uuid, bundle.status(), queued))
+            .thenAcceptAsync(event -> {
+              if (event.getStatus() == PlayerResourcePackStatusEvent.Status.DECLINED
+                      && event.getPackInfo() != null && event.getPackInfo().getShouldForce()
+                      && !event.isOverwriteKick()
+              ) {
+                player.disconnect(Component
+                        .translatable("multiplayer.requiredTexturePrompt.disconnect"));
+              }
+            });
+
+    switch (bundle.status()) {
+      // The player has accepted the resource pack and will proceed to download it.
+      case ACCEPTED -> {
+        if (queued != null) {
+          pendingResourcePacks.put(uuid, queued);
+        }
+      }
+      // The resource pack has been applied correctly.
+      case SUCCESSFUL -> {
+        if (queued != null) {
+          appliedResourcePacks.put(uuid, queued);
+        }
+        pendingResourcePacks.remove(uuid);
+      }
+      // An error occurred while trying to download the resource pack to the client,
+      // so the resource pack cannot be applied.
+      case DISCARDED, DECLINED, FAILED_RELOAD, FAILED_DOWNLOAD, INVALID_URL -> {
+        pendingResourcePacks.remove(uuid);
+        appliedResourcePacks.remove(uuid);
+      }
+      // The other cases in which no action is taken are documented in the javadocs.
+      default -> {
+      }
+    }
+
+    if (!peek) {
+      player.getConnection().eventLoop().execute(() -> tickResourcePackQueue(uuid));
+    }
+
+    return queued != null
+            && queued.getOriginalOrigin() != ResourcePackInfo.Origin.DOWNSTREAM_SERVER;
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackHandler.java

@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+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.client.ConnectedPlayer;
+import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
+import com.velocitypowered.proxy.protocol.packet.chat.ComponentHolder;
+import io.netty.buffer.ByteBufUtil;
+import java.util.Collection;
+import java.util.UUID;
+import net.kyori.adventure.resource.ResourcePackRequest;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * ResourcePackHandler.
+ */
+public abstract sealed class ResourcePackHandler
+        permits LegacyResourcePackHandler, ModernResourcePackHandler {
+  protected final ConnectedPlayer player;
+  protected final VelocityServer server;
+
+  protected ResourcePackHandler(final ConnectedPlayer player, final VelocityServer server) {
+    this.player = player;
+    this.server = server;
+  }
+
+  /**
+   * Creates a new ResourcePackHandler.
+   *
+   * @param player the player.
+   * @param server the velocity server
+   *
+   * @return a new ResourcePackHandler
+   */
+  public static @NotNull ResourcePackHandler create(final ConnectedPlayer player,
+                                           final VelocityServer server) {
+    final ProtocolVersion protocolVersion = player.getProtocolVersion();
+    if (protocolVersion.lessThan(ProtocolVersion.MINECRAFT_1_17)) {
+      return new LegacyResourcePackHandler(player, server);
+    }
+    if (protocolVersion.lessThan(ProtocolVersion.MINECRAFT_1_20_3)) {
+      return new Legacy117ResourcePackHandler(player, server);
+    }
+    return new ModernResourcePackHandler(player, server);
+  }
+
+  public abstract @Nullable ResourcePackInfo getFirstAppliedPack();
+
+  public abstract @Nullable ResourcePackInfo getFirstPendingPack();
+
+  public abstract @NotNull Collection<ResourcePackInfo> getAppliedResourcePacks();
+
+  public abstract @NotNull Collection<ResourcePackInfo> getPendingResourcePacks();
+
+  /**
+   * Clears the applied resource pack field.
+   */
+  public abstract void clearAppliedResourcePacks();
+
+  public abstract boolean remove(final UUID id);
+
+  /**
+   * Queues a resource-pack for sending to the player and sends it immediately if the queue is
+   * empty.
+   */
+  public abstract void queueResourcePack(final @NotNull ResourcePackInfo info);
+
+  /**
+   * Queues a resource-request for sending to the player and sends it immediately if the queue is
+   * empty.
+   */
+  public void queueResourcePack(final @NotNull ResourcePackRequest request) {
+    for (final net.kyori.adventure.resource.ResourcePackInfo pack : request.packs()) {
+      queueResourcePack(VelocityResourcePackInfo.fromAdventureRequest(request, pack));
+    }
+  }
+
+  protected void sendResourcePackRequestPacket(final @NotNull ResourcePackInfo queued) {
+    final ResourcePackRequestPacket request = new ResourcePackRequestPacket();
+    request.setId(queued.getId());
+    request.setUrl(queued.getUrl());
+    if (queued.getHash() != null) {
+      request.setHash(ByteBufUtil.hexDump(queued.getHash()));
+    } else {
+      request.setHash("");
+    }
+    request.setRequired(queued.getShouldForce());
+    request.setPrompt(queued.getPrompt() == null ? null :
+            new ComponentHolder(player.getProtocolVersion(), queued.getPrompt()));
+
+    player.getConnection().write(request);
+  }
+
+  /**
+   * Processes a client response to a sent resource-pack.
+   * <ul>
+   * <p>Cases in which no action will be taken:</p>
+   *
+   * <br><li><b>DOWNLOADED</b>
+   * <p>In this case the resource pack is downloaded and will be applied to the client,
+   * no action is required in Velocity.</p>
+   *
+   * <br><li><b>INVALID_URL</b>
+   * <p>In this case, the client has received a resource pack request
+   * and the first check it performs is if the URL is valid, if not,
+   * it will return this value</p>
+   *
+   * <br><li><b>FAILED_RELOAD</b>
+   * <p>In this case, when trying to reload the client's resources,
+   * an error occurred while reloading a resource pack</p>
+   * </ul>
+   *
+   * <br><li><b>DECLINED</b>
+   * <p>Only in modern versions, as the resource pack has already been rejected,
+   * there is nothing to do, if the resource pack is required,
+   * the client will be kicked out of the server.</p>
+   *
+   * @param bundle the resource pack response bundle
+   */
+  public abstract boolean onResourcePackResponse(
+          final @NotNull ResourcePackResponseBundle bundle);
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/player/resourcepack/ResourcePackResponseBundle.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.player.resourcepack;
+
+import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import java.util.UUID;
+
+@SuppressWarnings("checkstyle:MissingJavadocType")
+public record ResourcePackResponseBundle(UUID uuid, PlayerResourcePackStatusEvent.Status status) {
+}

proxy/src/main/java/com/velocitypowered/proxy/crypto/IdentifiedKeyImpl.java

@@ -119,7 +119,7 @@ public class IdentifiedKeyImpl implements IdentifiedKey {
     if (revision == Revision.GENERIC_V1) {
       String pemKey = EncryptionUtils.pemEncodeRsaKey(publicKey);
       long expires = expiryTemporal.toEpochMilli();
-      byte[] toVerify = ("" + expires + pemKey).getBytes(StandardCharsets.US_ASCII);
+      byte[] toVerify = (expires + pemKey).getBytes(StandardCharsets.US_ASCII);
       return EncryptionUtils.verifySignature(
           EncryptionUtils.SHA1_WITH_RSA, EncryptionUtils.getYggdrasilSessionKey(), signature,
           toVerify);
@@ -166,12 +166,10 @@ public class IdentifiedKeyImpl implements IdentifiedKey {
     if (this == o) {
       return true;
     }
-    if (!(o instanceof IdentifiedKey)) {
+    if (!(o instanceof final IdentifiedKey that)) {
       return false;
     }
 
-    IdentifiedKey that = (IdentifiedKey) o;
-
     return Objects.equal(this.getSignedPublicKey(), that.getSignedPublicKey())
         && Objects.equal(this.getExpiryTemporal(), that.getExpiryTemporal())
         && Arrays.equals(this.getSignature(), that.getSignature())

proxy/src/main/java/com/velocitypowered/proxy/protocol/StateRegistry.java

@@ -48,6 +48,7 @@ import static com.velocitypowered.proxy.protocol.ProtocolUtils.Direction.SERVERB
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.proxy.protocol.packet.AvailableCommandsPacket;
 import com.velocitypowered.proxy.protocol.packet.BossBarPacket;
+import com.velocitypowered.proxy.protocol.packet.BundleDelimiterPacket;
 import com.velocitypowered.proxy.protocol.packet.ClientSettingsPacket;
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 import com.velocitypowered.proxy.protocol.packet.EncryptionRequestPacket;
@@ -144,7 +145,7 @@ public enum StateRegistry {
           PluginMessagePacket.class, PluginMessagePacket::new,
           map(0x01, MINECRAFT_1_20_2, false));
       serverbound.register(
-          FinishedUpdatePacket.class, FinishedUpdatePacket::new,
+          FinishedUpdatePacket.class, () -> FinishedUpdatePacket.INSTANCE,
           map(0x02, MINECRAFT_1_20_2, false));
       serverbound.register(KeepAlivePacket.class, KeepAlivePacket::new,
           map(0x03, MINECRAFT_1_20_2, false));
@@ -163,7 +164,7 @@ public enum StateRegistry {
           DisconnectPacket.class, () -> new DisconnectPacket(false),
           map(0x01, MINECRAFT_1_20_2, false));
       clientbound.register(
-          FinishedUpdatePacket.class, FinishedUpdatePacket::new,
+          FinishedUpdatePacket.class, () -> FinishedUpdatePacket.INSTANCE,
           map(0x02, MINECRAFT_1_20_2, false));
       clientbound.register(KeepAlivePacket.class, KeepAlivePacket::new,
           map(0x03, MINECRAFT_1_20_2, false));
@@ -289,7 +290,7 @@ public enum StateRegistry {
           map(0x27, MINECRAFT_1_20_2, false),
           map(0x28, MINECRAFT_1_20_3, false));
       serverbound.register(
-          FinishedUpdatePacket.class, FinishedUpdatePacket::new,
+          FinishedUpdatePacket.class, () -> FinishedUpdatePacket.INSTANCE,
           map(0x0B, MINECRAFT_1_20_2, false));
 
       clientbound.register(
@@ -569,9 +570,13 @@ public enum StateRegistry {
           map(0x49, MINECRAFT_1_20_3, false));
       clientbound.register(
           StartUpdatePacket.class,
-          StartUpdatePacket::new,
+          () -> StartUpdatePacket.INSTANCE,
           map(0x65, MINECRAFT_1_20_2, false),
           map(0x67, MINECRAFT_1_20_3, false));
+      clientbound.register(
+          BundleDelimiterPacket.class,
+          () -> BundleDelimiterPacket.INSTANCE,
+          map(0x00, MINECRAFT_1_19_4, false));
     }
   },
   LOGIN {

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/LegacyPingEncoder.java

@@ -39,7 +39,7 @@ public class LegacyPingEncoder extends MessageToByteEncoder<LegacyDisconnect> {
   protected void encode(ChannelHandlerContext ctx, LegacyDisconnect msg, ByteBuf out)
       throws Exception {
     out.writeByte(0xff);
-    writeLegacyString(out, msg.getReason());
+    writeLegacyString(out, msg.reason());
   }
 
   private static void writeLegacyString(ByteBuf out, String string) {

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/BundleDelimiterPacket.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2018-2021 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.protocol.packet;
+
+import com.velocitypowered.api.network.ProtocolVersion;
+import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
+import com.velocitypowered.proxy.protocol.MinecraftPacket;
+import com.velocitypowered.proxy.protocol.ProtocolUtils;
+import io.netty.buffer.ByteBuf;
+
+public final class BundleDelimiterPacket implements MinecraftPacket {
+  public static final BundleDelimiterPacket INSTANCE = new BundleDelimiterPacket();
+
+  private BundleDelimiterPacket() {
+  }
+
+  @Override
+  public void decode(ByteBuf buf, ProtocolUtils.Direction direction, ProtocolVersion version) {
+
+  }
+
+  @Override
+  public void encode(ByteBuf buf, ProtocolUtils.Direction direction, ProtocolVersion version) {
+
+  }
+
+  @Override
+  public boolean handle(MinecraftSessionHandler handler) {
+    return handler.handle(this);
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/LegacyDisconnect.java

@@ -25,19 +25,14 @@ import net.kyori.adventure.text.TextComponent;
 import net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer;
 import net.kyori.adventure.text.serializer.plain.PlainTextComponentSerializer;
 
-public class LegacyDisconnect {
+@SuppressWarnings("checkstyle:MissingJavadocType")
+public record LegacyDisconnect(String reason) {
 
   private static final ServerPing.Players FAKE_PLAYERS = new ServerPing.Players(0, 0,
       ImmutableList.of());
   private static final String LEGACY_COLOR_CODE = Character
       .toString(LegacyComponentSerializer.SECTION_CHAR);
 
-  private final String reason;
-
-  private LegacyDisconnect(String reason) {
-    this.reason = reason;
-  }
-
   /**
    * Converts a modern server list ping response into an legacy disconnect packet.
    *
@@ -47,22 +42,21 @@ public class LegacyDisconnect {
    */
   public static LegacyDisconnect fromServerPing(ServerPing response,
       LegacyMinecraftPingVersion version) {
-    Players players = response.getPlayers().orElse(FAKE_PLAYERS);
+    final Players players = response.getPlayers().orElse(FAKE_PLAYERS);
 
-    switch (version) {
+    return switch (version) {
-      case MINECRAFT_1_3:
+      case MINECRAFT_1_3 ->
         // Minecraft 1.3 and below use the section symbol as a delimiter. Accordingly, we must
         // remove all section symbols, along with fetching just the first line of an (unformatted)
         // MOTD.
-        return new LegacyDisconnect(String.join(LEGACY_COLOR_CODE,
+        new LegacyDisconnect(String.join(LEGACY_COLOR_CODE,
             cleanSectionSymbol(getFirstLine(PlainTextComponentSerializer.plainText().serialize(
                 response.getDescriptionComponent()))),
             Integer.toString(players.getOnline()),
             Integer.toString(players.getMax())));
-      case MINECRAFT_1_4:
+      case MINECRAFT_1_4, MINECRAFT_1_6 ->
-      case MINECRAFT_1_6:
         // Minecraft 1.4-1.6 provide support for more fields, and additionally support color codes.
-        return new LegacyDisconnect(String.join("\0",
+        new LegacyDisconnect(String.join("\0",
             LEGACY_COLOR_CODE + "1",
             Integer.toString(response.getVersion().getProtocol()),
             response.getVersion().getName(),
@@ -71,9 +65,8 @@ public class LegacyDisconnect {
             Integer.toString(players.getOnline()),
             Integer.toString(players.getMax())
         ));
-      default:
+      default -> throw new IllegalArgumentException("Unknown version " + version);
-        throw new IllegalArgumentException("Unknown version " + version);
+    };
-    }
   }
 
   private static String cleanSectionSymbol(String string) {
@@ -81,7 +74,7 @@ public class LegacyDisconnect {
   }
 
   private static String getFirstLine(String legacyMotd) {
-    int newline = legacyMotd.indexOf('\n');
+    final int newline = legacyMotd.indexOf('\n');
     return newline == -1 ? legacyMotd : legacyMotd.substring(0, newline);
   }
 
@@ -93,11 +86,7 @@ public class LegacyDisconnect {
    */
   public static LegacyDisconnect from(TextComponent component) {
     // We intentionally use the legacy serializers, because the old clients can't understand JSON.
-    String serialized = LegacyComponentSerializer.legacySection().serialize(component);
+    final String serialized = LegacyComponentSerializer.legacySection().serialize(component);
     return new LegacyDisconnect(serialized);
   }
-
-  public String getReason() {
-    return reason;
-  }
 }

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/RemoveResourcePackPacket.java

@@ -23,7 +23,6 @@ import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.ProtocolUtils.Direction;
 import io.netty.buffer.ByteBuf;
-
 import java.util.UUID;
 
 public class RemoveResourcePackPacket implements MinecraftPacket {
@@ -37,6 +36,10 @@ public class RemoveResourcePackPacket implements MinecraftPacket {
     this.id = id;
   }
 
+  public UUID getId() {
+    return id;
+  }
+
   @Override
   public void decode(ByteBuf buf, Direction direction, ProtocolVersion protocolVersion) {
     if (buf.readBoolean()) {

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/ResourcePackRequestPacket.java

@@ -28,11 +28,10 @@ import com.velocitypowered.proxy.protocol.ProtocolUtils.Direction;
 import com.velocitypowered.proxy.protocol.packet.chat.ComponentHolder;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
-import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
-import org.checkerframework.checker.nullness.qual.Nullable;
-
 import java.util.UUID;
 import java.util.regex.Pattern;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class ResourcePackRequestPacket implements MinecraftPacket {
 
@@ -80,7 +79,7 @@ public class ResourcePackRequestPacket implements MinecraftPacket {
     return prompt;
   }
 
-  public void setPrompt(ComponentHolder prompt) {
+  public void setPrompt(@Nullable ComponentHolder prompt) {
     this.prompt = prompt;
   }
 
@@ -126,7 +125,7 @@ public class ResourcePackRequestPacket implements MinecraftPacket {
   }
 
   public VelocityResourcePackInfo toServerPromptedPack() {
-    ResourcePackInfo.Builder builder =
+    final ResourcePackInfo.Builder builder =
         new VelocityResourcePackInfo.BuilderImpl(Preconditions.checkNotNull(url))
             .setId(id).setPrompt(prompt == null ? null : prompt.getComponent())
             .setShouldForce(isRequired).setOrigin(ResourcePackInfo.Origin.DOWNSTREAM_SERVER);

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/ResourcePackResponsePacket.java

@@ -54,6 +54,10 @@ public class ResourcePackResponsePacket implements MinecraftPacket {
     return hash;
   }
 
+  public UUID getId() {
+    return id;
+  }
+
   @Override
   public void decode(ByteBuf buf, Direction direction, ProtocolVersion protocolVersion) {
     if (protocolVersion.noLessThan(ProtocolVersion.MINECRAFT_1_20_3)) {

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/config/FinishedUpdatePacket.java

@@ -24,6 +24,10 @@ import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
 
 public class FinishedUpdatePacket implements MinecraftPacket {
+  public static final FinishedUpdatePacket INSTANCE = new FinishedUpdatePacket();
+
+  private FinishedUpdatePacket() {
+  }
 
   @Override
   public void decode(ByteBuf buf, ProtocolUtils.Direction direction,

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/config/StartUpdatePacket.java

@@ -24,6 +24,10 @@ import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
 
 public class StartUpdatePacket implements MinecraftPacket {
+  public static final StartUpdatePacket INSTANCE = new StartUpdatePacket();
+
+  private StartUpdatePacket() {
+  }
 
   @Override
   public void decode(ByteBuf buf, ProtocolUtils.Direction direction,

proxy/src/main/java/com/velocitypowered/proxy/util/TranslatableMapper.java

@@ -44,8 +44,8 @@ public enum TranslatableMapper implements BiConsumer<TranslatableComponent, Cons
           final Consumer<Component> componentConsumer
   ) {
     for (final Translator source : GlobalTranslator.translator().sources()) {
-      if (source instanceof TranslationRegistry
+      if (source instanceof TranslationRegistry registry
-              && ((TranslationRegistry) source).contains(translatableComponent.key())) {
+              && registry.contains(translatableComponent.key())) {
         componentConsumer.accept(GlobalTranslator.render(translatableComponent,
                 ClosestLocaleMatcher.INSTANCE.lookupClosest(Locale.getDefault())));
         return;
@@ -56,8 +56,7 @@ public enum TranslatableMapper implements BiConsumer<TranslatableComponent, Cons
       return;
     }
     for (final Translator source : GlobalTranslator.translator().sources()) {
-      if (source instanceof TranslationRegistry
+      if (source instanceof TranslationRegistry registry && registry.contains(fallback)) {
-              && ((TranslationRegistry) source).contains(fallback)) {
         componentConsumer.accept(
                 GlobalTranslator.render(Component.translatable(fallback),
                         ClosestLocaleMatcher.INSTANCE.lookupClosest(Locale.getDefault())));