Add ServerResourcePackRemoveEvent (#1379)

* Add ServerResourcePackRemoveEvent

* Add nonnull check

* Fix indentation

* Fix import code style

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

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2018-2023 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.event.ResultedEvent;
+import com.velocitypowered.api.event.annotation.AwaitingEvent;
+import com.velocitypowered.api.proxy.ServerConnection;
+import java.util.UUID;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This event is fired when the downstream server tries to remove a resource pack from player
+ * or clear all of them. The proxy will wait on this event to finish before forwarding the
+ * action to the user. If this event is denied, no resource packs will be removed from player.
+ */
+@AwaitingEvent
+public class ServerResourcePackRemoveEvent implements ResultedEvent<ResultedEvent.GenericResult> {
+
+  private GenericResult result;
+  private final @MonotonicNonNull UUID packId;
+  private final ServerConnection serverConnection;
+
+  /**
+   * Instantiates this event.
+   */
+  public ServerResourcePackRemoveEvent(UUID packId, ServerConnection serverConnection) {
+    this.result = ResultedEvent.GenericResult.allowed();
+    this.packId = packId;
+    this.serverConnection = serverConnection;
+  }
+
+  /**
+   * Returns the id of the resource pack, if it's null all the resource packs
+   * from player will be cleared.
+   *
+   * @return the id
+   */
+  @Nullable
+  public UUID getPackId() {
+    return packId;
+  }
+
+  /**
+   * Returns the server that tries to remove a resource pack from player or clear all of them.
+   *
+   * @return the server connection
+   */
+  public ServerConnection getServerConnection() {
+    return serverConnection;
+  }
+
+  @Override
+  public GenericResult getResult() {
+    return this.result;
+  }
+
+  @Override
+  public void setResult(GenericResult result) {
+    this.result = Preconditions.checkNotNull(result, "result");
+  }
+}

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

@@ -29,6 +29,7 @@ import com.velocitypowered.api.event.connection.PreTransferEvent;
 import com.velocitypowered.api.event.player.CookieRequestEvent;
 import com.velocitypowered.api.event.player.CookieStoreEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.event.player.ServerResourcePackRemoveEvent;
 import com.velocitypowered.api.event.player.ServerResourcePackSendEvent;
 import com.velocitypowered.api.event.proxy.ProxyPingEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
@@ -258,14 +259,26 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(RemoveResourcePackPacket packet) {
-    final ConnectedPlayer player = serverConn.getPlayer();
-    final ResourcePackHandler handler = player.resourcePackHandler();
-    if (packet.getId() != null) {
-      handler.remove(packet.getId());
-    } else {
-      handler.clearAppliedResourcePacks();
-    }
-    playerConnection.write(packet);
+    final ServerResourcePackRemoveEvent event = new ServerResourcePackRemoveEvent(
+            packet.getId(), this.serverConn);
+    server.getEventManager().fire(event).thenAcceptAsync(serverResourcePackRemoveEvent -> {
+      if (playerConnection.isClosed()) {
+        return;
+      }
+      if (serverResourcePackRemoveEvent.getResult().isAllowed()) {
+        final ConnectedPlayer player = serverConn.getPlayer();
+        final ResourcePackHandler handler = player.resourcePackHandler();
+        if (packet.getId() != null) {
+          handler.remove(packet.getId());
+        } else {
+          handler.clearAppliedResourcePacks();
+        }
+        playerConnection.write(packet);
+      }
+    }, playerConnection.eventLoop()).exceptionally((ex) -> {
+      logger.error("Exception while handling resource pack remove for {}", playerConnection, ex);
+      return null;
+    });
     return true;
   }
 

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

@@ -21,6 +21,7 @@ import com.velocitypowered.api.event.connection.PreTransferEvent;
 import com.velocitypowered.api.event.player.CookieRequestEvent;
 import com.velocitypowered.api.event.player.CookieStoreEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.event.player.ServerResourcePackRemoveEvent;
 import com.velocitypowered.api.event.player.ServerResourcePackSendEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
@@ -30,6 +31,7 @@ import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.client.ClientConfigSessionHandler;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.connection.player.resourcepack.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.handler.ResourcePackHandler;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
@@ -41,6 +43,7 @@ import com.velocitypowered.proxy.protocol.packet.ClientboundStoreCookiePacket;
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 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.ResourcePackResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TransferPacket;
@@ -192,6 +195,33 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
     return true;
   }
 
+  @Override
+  public boolean handle(RemoveResourcePackPacket packet) {
+    final MinecraftConnection playerConnection = this.serverConn.getPlayer().getConnection();
+
+    final ServerResourcePackRemoveEvent event = new ServerResourcePackRemoveEvent(
+            packet.getId(), this.serverConn);
+    server.getEventManager().fire(event).thenAcceptAsync(serverResourcePackRemoveEvent -> {
+      if (playerConnection.isClosed()) {
+        return;
+      }
+      if (serverResourcePackRemoveEvent.getResult().isAllowed()) {
+        final ConnectedPlayer player = serverConn.getPlayer();
+        final ResourcePackHandler handler = player.resourcePackHandler();
+        if (packet.getId() != null) {
+          handler.remove(packet.getId());
+        } else {
+          handler.clearAppliedResourcePacks();
+        }
+        playerConnection.write(packet);
+      }
+    }, playerConnection.eventLoop()).exceptionally((ex) -> {
+      logger.error("Exception while handling resource pack remove for {}", playerConnection, ex);
+      return null;
+    });
+    return true;
+  }
+
   @Override
   public boolean handle(FinishedUpdatePacket packet) {
     final MinecraftConnection smc = serverConn.ensureConnected();