Improved PluginMessaging API (#1254)

* Improved PluginMessaging API by adding a method to easily encode the data to be sent

* Added javadocs

* Implement PluginMessageEncoder

api/src/main/java/com/velocitypowered/api/proxy/Player.java

@@ -13,6 +13,7 @@ import com.velocitypowered.api.proxy.crypto.KeyIdentifiable;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
 import com.velocitypowered.api.proxy.messages.ChannelMessageSink;
 import com.velocitypowered.api.proxy.messages.ChannelMessageSource;
+import com.velocitypowered.api.proxy.messages.PluginMessageEncoder;
 import com.velocitypowered.api.proxy.player.PlayerSettings;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
 import com.velocitypowered.api.proxy.player.TabList;
@@ -282,16 +283,42 @@ public interface Player extends
   @NotNull Collection<ResourcePackInfo> getPendingResourcePacks();
 
   /**
-   * <strong>Note that this method does not send a plugin message to the server the player
+   * {@inheritDoc}
+   *
+   * <p><strong>Note that this method does not send a plugin message to the server the player
    * is connected to.</strong> You should only use this method if you are trying to communicate
-   * with a mod that is installed on the player's client. To send a plugin message to the server
+   * with a mod that is installed on the player's client.</p>
+   *
+   * <p>To send a plugin message to the server
    * from the player, you should use the equivalent method on the instance returned by
    * {@link #getCurrentServer()}.
    *
-   * @inheritDoc
+   * <pre>
+   *    final ChannelIdentifier identifier;
+   *    final Player player;
+   *    player.getCurrentServer()
+   *          .map(ServerConnection::getServer)
+   *          .ifPresent((RegisteredServer server) -> {
+   *            server.sendPluginMessage(identifier, data);
+   *          });
+   *  </pre>
+   *
    */
   @Override
-  boolean sendPluginMessage(@NotNull ChannelIdentifier identifier, byte @NotNull[] data);
+  boolean sendPluginMessage(@NotNull ChannelIdentifier identifier, byte @NotNull [] data);
+
+  /**
+   * {@inheritDoc}
+   * <p><strong>Note that this method does not send a plugin message to the server the player
+   * is connected to.</strong> You should only use this method if you are trying to communicate
+   * with a mod that is installed on the player's client.</p>
+   *
+   * <p>To send a plugin message to the server
+   * from the player, you should use the equivalent method on the instance returned by
+   * {@link #getCurrentServer()}.
+   */
+  @Override
+  boolean sendPluginMessage(@NotNull ChannelIdentifier identifier, @NotNull PluginMessageEncoder dataEncoder);
 
   @Override
   default @NotNull Key key() {

api/src/main/java/com/velocitypowered/api/proxy/messages/ChannelMessageSink.java

@@ -7,6 +7,9 @@
 
 package com.velocitypowered.api.proxy.messages;
 
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+
 /**
  * Represents something that can be sent plugin messages.
  */
@@ -19,5 +22,26 @@ public interface ChannelMessageSink {
    * @param data the data to send
    * @return whether or not the message could be sent
    */
-  boolean sendPluginMessage(ChannelIdentifier identifier, byte[] data);
+  boolean sendPluginMessage(@NotNull ChannelIdentifier identifier, byte @NotNull[] data);
+
+  /**
+   * Sends a plugin message to this target.
+   *
+   * <pre>
+   *   final ChannelMessageSink target;
+   *   final ChannelIdentifier identifier;
+   *   final boolean result = target.sendPluginMessage(identifier, (output) -> {
+   *     output.writeUTF("some input");
+   *     output.writeInt(1);
+   *   });
+   * </pre>
+   *
+   * @param identifier the channel identifier to send the message on
+   * @param dataEncoder the encoder of the data to be sent
+   * @return whether the message could be sent
+   */
+  @ApiStatus.Experimental
+  boolean sendPluginMessage(
+          @NotNull ChannelIdentifier identifier,
+          @NotNull PluginMessageEncoder dataEncoder);
 }

api/src/main/java/com/velocitypowered/api/proxy/messages/PluginMessageEncoder.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2024 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.proxy.messages;
+
+import com.google.common.io.ByteArrayDataOutput;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * A data encoder to be sent via a plugin message.
+ *
+ * @since 3.3.0
+ */
+@FunctionalInterface
+@ApiStatus.Experimental
+public interface PluginMessageEncoder {
+
+  /**
+   * Encodes data into a {@link ByteArrayDataOutput} to be transmitted by plugin messages.
+   *
+   * @param output the {@link ByteArrayDataOutput} provided
+   */
+  void encode(@NotNull ByteArrayDataOutput output);
+}

proxy/src/main/java/com/velocitypowered/proxy/adventure/ComponentLoggerProviderImpl.java

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package com.velocitypowered.proxy.provider;
+package com.velocitypowered.proxy.adventure;
 
 import com.google.auto.service.AutoService;
 import com.velocitypowered.proxy.util.TranslatableMapper;

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

@@ -19,11 +19,13 @@ package com.velocitypowered.proxy.connection.backend;
 
 import static com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants.HANDSHAKE_HOSTNAME_TOKEN;
 import static com.velocitypowered.proxy.network.Connections.HANDLER;
+import static java.util.Objects.requireNonNull;
 
 import com.google.common.base.Preconditions;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.ServerConnection;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
+import com.velocitypowered.api.proxy.messages.PluginMessageEncoder;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.proxy.server.ServerInfo;
 import com.velocitypowered.proxy.VelocityServer;
@@ -41,6 +43,7 @@ import com.velocitypowered.proxy.protocol.packet.HandshakePacket;
 import com.velocitypowered.proxy.protocol.packet.JoinGamePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.ServerLoginPacket;
+import com.velocitypowered.proxy.protocol.util.ByteBufDataOutput;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
@@ -52,6 +55,7 @@ import java.util.concurrent.CompletableFuture;
 import net.kyori.adventure.nbt.CompoundBinaryTag;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Handles a connection from the proxy to some backend server.
@@ -255,10 +259,31 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
   }
 
   @Override
-  public boolean sendPluginMessage(ChannelIdentifier identifier, byte[] data) {
+  public boolean sendPluginMessage(
+          final @NotNull ChannelIdentifier identifier,
+          final byte @NotNull [] data
+  ) {
     return sendPluginMessage(identifier, Unpooled.wrappedBuffer(data));
   }
 
+  @Override
+  public boolean sendPluginMessage(
+          final @NotNull ChannelIdentifier identifier,
+          final @NotNull PluginMessageEncoder dataEncoder
+  ) {
+    requireNonNull(identifier);
+    requireNonNull(dataEncoder);
+    final ByteBuf buf = Unpooled.buffer();
+    final ByteBufDataOutput dataOutput = new ByteBufDataOutput(buf);
+    dataEncoder.encode(dataOutput);
+    if (buf.isReadable()) {
+      return sendPluginMessage(identifier, buf);
+    } else {
+      buf.release();
+      return false;
+    }
+  }
+
   /**
    * Sends a plugin message to the server through this connection.
    *
@@ -270,9 +295,9 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
     Preconditions.checkNotNull(identifier, "identifier");
     Preconditions.checkNotNull(data, "data");
 
-    MinecraftConnection mc = ensureConnected();
+    final MinecraftConnection mc = ensureConnected();
 
-    PluginMessagePacket message = new PluginMessagePacket(identifier.getId(), data);
+    final PluginMessagePacket message = new PluginMessagePacket(identifier.getId(), data);
     mc.write(message);
     return true;
   }

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

@@ -19,6 +19,7 @@ package com.velocitypowered.proxy.connection.client;
 
 import static com.velocitypowered.api.proxy.ConnectionRequestBuilder.Status.ALREADY_CONNECTED;
 import static com.velocitypowered.proxy.connection.util.ConnectionRequestResults.plainResult;
+import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.CompletableFuture.completedFuture;
 
 import com.google.common.base.Preconditions;
@@ -44,6 +45,7 @@ import com.velocitypowered.api.proxy.ServerConnection;
 import com.velocitypowered.api.proxy.crypto.IdentifiedKey;
 import com.velocitypowered.api.proxy.crypto.KeyIdentifiable;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
+import com.velocitypowered.api.proxy.messages.PluginMessageEncoder;
 import com.velocitypowered.api.proxy.player.PlayerSettings;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
@@ -75,6 +77,7 @@ import com.velocitypowered.proxy.protocol.packet.chat.builder.ChatBuilderFactory
 import com.velocitypowered.proxy.protocol.packet.chat.legacy.LegacyChatPacket;
 import com.velocitypowered.proxy.protocol.packet.config.StartUpdatePacket;
 import com.velocitypowered.proxy.protocol.packet.title.GenericTitlePacket;
+import com.velocitypowered.proxy.protocol.util.ByteBufDataOutput;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
 import com.velocitypowered.proxy.tablist.InternalTabList;
 import com.velocitypowered.proxy.tablist.KeyedVelocityTabList;
@@ -83,6 +86,7 @@ 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.ByteBuf;
 import io.netty.buffer.Unpooled;
 import java.net.InetSocketAddress;
 import java.util.Collection;
@@ -947,12 +951,32 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   public boolean sendPluginMessage(@NotNull ChannelIdentifier identifier, byte @NotNull [] data) {
     Preconditions.checkNotNull(identifier, "identifier");
     Preconditions.checkNotNull(data, "data");
-    PluginMessagePacket message = new PluginMessagePacket(identifier.getId(),
+    final PluginMessagePacket message = new PluginMessagePacket(identifier.getId(),
             Unpooled.wrappedBuffer(data));
     connection.write(message);
     return true;
   }
 
+  @Override
+  public boolean sendPluginMessage(
+          final @NotNull ChannelIdentifier identifier,
+          final @NotNull PluginMessageEncoder dataEncoder
+  ) {
+    requireNonNull(identifier);
+    requireNonNull(dataEncoder);
+    final ByteBuf buf = Unpooled.buffer();
+    final ByteBufDataOutput dataOutput = new ByteBufDataOutput(buf);
+    dataEncoder.encode(dataOutput);
+    if (buf.isReadable()) {
+      final PluginMessagePacket message = new PluginMessagePacket(identifier.getId(), buf);
+      connection.write(message);
+      return true;
+    } else {
+      buf.release();
+      return false;
+    }
+  }
+
   @Override
   @Nullable
   public String getClientBrand() {

proxy/src/main/java/com/velocitypowered/proxy/server/VelocityRegisteredServer.java

@@ -23,11 +23,13 @@ import static com.velocitypowered.proxy.network.Connections.HANDLER;
 import static com.velocitypowered.proxy.network.Connections.MINECRAFT_DECODER;
 import static com.velocitypowered.proxy.network.Connections.MINECRAFT_ENCODER;
 import static com.velocitypowered.proxy.network.Connections.READ_TIMEOUT;
+import static java.util.Objects.requireNonNull;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.velocitypowered.api.proxy.Player;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
+import com.velocitypowered.api.proxy.messages.PluginMessageEncoder;
 import com.velocitypowered.api.proxy.server.PingOptions;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.proxy.server.ServerInfo;
@@ -42,6 +44,7 @@ import com.velocitypowered.proxy.protocol.netty.MinecraftDecoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftEncoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftVarintFrameDecoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftVarintLengthEncoder;
+import com.velocitypowered.proxy.protocol.util.ByteBufDataOutput;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.Channel;
@@ -59,6 +62,7 @@ import net.kyori.adventure.audience.Audience;
 import net.kyori.adventure.audience.ForwardingAudience;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Represents a server registered on the proxy.
@@ -107,9 +111,9 @@ public class VelocityRegisteredServer implements RegisteredServer, ForwardingAud
       throw new IllegalStateException("No Velocity proxy instance available");
     }
     CompletableFuture<ServerPing> pingFuture = new CompletableFuture<>();
-    server.createBootstrap(loop).handler(new ChannelInitializer<Channel>() {
+    server.createBootstrap(loop).handler(new ChannelInitializer<>() {
       @Override
-      protected void initChannel(Channel ch) throws Exception {
+      protected void initChannel(Channel ch) {
         ch.pipeline().addLast(FRAME_DECODER, new MinecraftVarintFrameDecoder())
             .addLast(READ_TIMEOUT, new ReadTimeoutHandler(
                 pingOptions.getTimeout() == 0
@@ -143,10 +147,30 @@ public class VelocityRegisteredServer implements RegisteredServer, ForwardingAud
   }
 
   @Override
-  public boolean sendPluginMessage(ChannelIdentifier identifier, byte[] data) {
+  public boolean sendPluginMessage(final @NotNull ChannelIdentifier identifier, final byte @NotNull [] data) {
+    requireNonNull(identifier);
+    requireNonNull(data);
     return sendPluginMessage(identifier, Unpooled.wrappedBuffer(data));
   }
 
+  @Override
+  public boolean sendPluginMessage(
+          final @NotNull ChannelIdentifier identifier,
+          final @NotNull PluginMessageEncoder dataEncoder
+  ) {
+    requireNonNull(identifier);
+    requireNonNull(dataEncoder);
+    final ByteBuf buf = Unpooled.buffer();
+    final ByteBufDataOutput dataInput = new ByteBufDataOutput(buf);
+    dataEncoder.encode(dataInput);
+    if (buf.isReadable()) {
+      return sendPluginMessage(identifier, buf);
+    } else {
+      buf.release();
+      return false;
+    }
+  }
+
   /**
    * Sends a plugin message to the server through this connection. The message will be released
    * afterwards.
@@ -156,8 +180,8 @@ public class VelocityRegisteredServer implements RegisteredServer, ForwardingAud
    * @return whether or not the message was sent
    */
   public boolean sendPluginMessage(ChannelIdentifier identifier, ByteBuf data) {
-    for (ConnectedPlayer player : players.values()) {
-      VelocityServerConnection serverConnection = player.getConnectedServer();
+    for (final ConnectedPlayer player : players.values()) {
+      final VelocityServerConnection serverConnection = player.getConnectedServer();
       if (serverConnection != null && serverConnection.getConnection() != null
               && serverConnection.getServer() == this) {
         return serverConnection.sendPluginMessage(identifier, data);