Fix Velocity compatibility (requires Velocity 3.0.0)

This finally removes the hacky reorder fix on Velocity; it added a few more events that could benefit us, but this is the most important right now.

velocity/src/main/java/com/viaversion/viaversion/VelocityPlugin.java

@@ -39,11 +39,11 @@ import com.viaversion.viaversion.util.GsonUtil;
 import com.viaversion.viaversion.util.VersionInfo;
 import com.viaversion.viaversion.velocity.command.VelocityCommandHandler;
 import com.viaversion.viaversion.velocity.command.VelocityCommandSender;
-import com.viaversion.viaversion.velocity.platform.VelocityViaTask;
 import com.viaversion.viaversion.velocity.platform.VelocityViaAPI;
 import com.viaversion.viaversion.velocity.platform.VelocityViaConfig;
 import com.viaversion.viaversion.velocity.platform.VelocityViaInjector;
 import com.viaversion.viaversion.velocity.platform.VelocityViaLoader;
+import com.viaversion.viaversion.velocity.platform.VelocityViaTask;
 import com.viaversion.viaversion.velocity.service.ProtocolDetectorService;
 import com.viaversion.viaversion.velocity.util.LoggerWrapper;
 import net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer;

velocity/src/main/java/com/viaversion/viaversion/velocity/handlers/VelocityChannelInitializer.java

@@ -26,33 +26,42 @@ import io.netty.channel.ChannelInitializer;
 import java.lang.reflect.Method;
 
 public class VelocityChannelInitializer extends ChannelInitializer<Channel> {
+    public static final String MINECRAFT_ENCODER = "minecraft-encoder";
+    public static final String MINECRAFT_DECODER = "minecraft-decoder";
+    public static final String VIA_ENCODER = "via-encoder";
+    public static final String VIA_DECODER = "via-decoder";
+    public static final Object COMPRESSION_ENABLED_EVENT;
+    private static final Method INIT_CHANNEL;
+
     private final ChannelInitializer<?> original;
     private final boolean clientSide;
-    private static Method initChannel;
+
+    static {
+        try {
+            INIT_CHANNEL = ChannelInitializer.class.getDeclaredMethod("initChannel", Channel.class);
+            INIT_CHANNEL.setAccessible(true);
+
+            Class<?> eventClass = Class.forName("com.velocitypowered.proxy.protocol.VelocityConnectionEvent");
+            COMPRESSION_ENABLED_EVENT = eventClass.getDeclaredField("COMPRESSION_ENABLED").get(null);
+        } catch (ReflectiveOperationException e) {
+            throw new RuntimeException(e);
+        }
+    }
 
     public VelocityChannelInitializer(ChannelInitializer<?> original, boolean clientSide) {
         this.original = original;
         this.clientSide = clientSide;
     }
 
-    static {
-        try {
-            initChannel = ChannelInitializer.class.getDeclaredMethod("initChannel", Channel.class);
-            initChannel.setAccessible(true);
-        } catch (NoSuchMethodException e) {
-            e.printStackTrace();
-        }
-    }
-
     @Override
     protected void initChannel(Channel channel) throws Exception {
-        initChannel.invoke(original, channel);
+        INIT_CHANNEL.invoke(original, channel);
 
         UserConnection user = new UserConnectionImpl(channel, clientSide);
         new ProtocolPipelineImpl(user);
 
         // We need to add a separated handler because Velocity uses pipeline().get(MINECRAFT_DECODER)
-        channel.pipeline().addBefore("minecraft-encoder", "via-encoder", new VelocityEncodeHandler(user));
+        channel.pipeline().addBefore(MINECRAFT_ENCODER, VIA_ENCODER, new VelocityEncodeHandler(user));
-        channel.pipeline().addBefore("minecraft-decoder", "via-decoder", new VelocityDecodeHandler(user));
+        channel.pipeline().addBefore(MINECRAFT_DECODER, VIA_DECODER, new VelocityDecodeHandler(user));
     }
 }

velocity/src/main/java/com/viaversion/viaversion/velocity/handlers/VelocityDecodeHandler.java

@@ -20,21 +20,17 @@ package com.viaversion.viaversion.velocity.handlers;
 import com.viaversion.viaversion.api.connection.UserConnection;
 import com.viaversion.viaversion.exception.CancelCodecException;
 import com.viaversion.viaversion.exception.CancelDecoderException;
-import com.viaversion.viaversion.util.PipelineUtil;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.MessageToByteEncoder;
+import io.netty.channel.ChannelPipeline;
 import io.netty.handler.codec.MessageToMessageDecoder;
 
-import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 
 @ChannelHandler.Sharable
 public class VelocityDecodeHandler extends MessageToMessageDecoder<ByteBuf> {
     private final UserConnection info;
-    private boolean handledCompression;
-    private boolean skipDoubleTransform;
 
     public VelocityDecodeHandler(UserConnection info) {
         this.info = info;
@@ -42,12 +38,6 @@ public class VelocityDecodeHandler extends MessageToMessageDecoder<ByteBuf> {
 
     @Override
     protected void decode(ChannelHandlerContext ctx, ByteBuf bytebuf, List<Object> out) throws Exception {
-        if (skipDoubleTransform) {
-            skipDoubleTransform = false;
-            out.add(bytebuf.retain());
-            return;
-        }
-
         if (!info.checkIncomingPacket()) throw CancelDecoderException.generate(null);
         if (!info.shouldTransformPacket()) {
             out.add(bytebuf.retain());
@@ -56,58 +46,39 @@ public class VelocityDecodeHandler extends MessageToMessageDecoder<ByteBuf> {
 
         ByteBuf transformedBuf = ctx.alloc().buffer().writeBytes(bytebuf);
         try {
-            boolean needsCompress = handleCompressionOrder(ctx, transformedBuf);
-
             info.transformIncoming(transformedBuf, CancelDecoderException::generate);
-
-            if (needsCompress) {
-                recompress(ctx, transformedBuf);
-                skipDoubleTransform = true;
-            }
             out.add(transformedBuf.retain());
         } finally {
             transformedBuf.release();
         }
     }
 
-    private boolean handleCompressionOrder(ChannelHandlerContext ctx, ByteBuf buf) throws InvocationTargetException {
-        if (handledCompression) return false;
-
-        int decoderIndex = ctx.pipeline().names().indexOf("compression-decoder");
-        if (decoderIndex == -1) return false;
-        handledCompression = true;
-        if (decoderIndex > ctx.pipeline().names().indexOf("via-decoder")) {
-            // Need to decompress this packet due to bad order
-            ByteBuf decompressed = (ByteBuf) PipelineUtil.callDecode((MessageToMessageDecoder<?>) ctx.pipeline().get("compression-decoder"), ctx, buf).get(0);
-            try {
-                buf.clear().writeBytes(decompressed);
-            } finally {
-                decompressed.release();
-            }
-            ChannelHandler encoder = ctx.pipeline().get("via-encoder");
-            ChannelHandler decoder = ctx.pipeline().get("via-decoder");
-            ctx.pipeline().remove(encoder);
-            ctx.pipeline().remove(decoder);
-            ctx.pipeline().addAfter("compression-encoder", "via-encoder", encoder);
-            ctx.pipeline().addAfter("compression-decoder", "via-decoder", decoder);
-            return true;
-        }
-        return false;
-    }
-
-    private void recompress(ChannelHandlerContext ctx, ByteBuf buf) throws Exception {
-        ByteBuf compressed = ctx.alloc().buffer();
-        try {
-            PipelineUtil.callEncode((MessageToByteEncoder<?>) ctx.pipeline().get("compression-encoder"), ctx, buf, compressed);
-            buf.clear().writeBytes(compressed);
-        } finally {
-            compressed.release();
-        }
-    }
-
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         if (cause instanceof CancelCodecException) return;
         super.exceptionCaught(ctx, cause);
     }
+
+    // Abuse decoder handler to catch events
+    @Override
+    public void userEventTriggered(ChannelHandlerContext ctx, Object event) throws Exception {
+        if (event != VelocityChannelInitializer.COMPRESSION_ENABLED_EVENT) {
+            super.userEventTriggered(ctx, event);
+            return;
+        }
+
+        // When Velocity adds the compression handlers, the order becomes Minecraft Encoder -> Compressor -> Via Encoder
+        // Move Via codec handlers back to right position
+        ChannelPipeline pipeline = ctx.pipeline();
+
+        ChannelHandler encoder = pipeline.get(VelocityChannelInitializer.VIA_ENCODER);
+        pipeline.remove(encoder);
+        pipeline.addBefore(VelocityChannelInitializer.MINECRAFT_ENCODER, VelocityChannelInitializer.VIA_ENCODER, encoder);
+
+        ChannelHandler decoder = pipeline.get(VelocityChannelInitializer.VIA_DECODER);
+        pipeline.remove(decoder);
+        pipeline.addBefore(VelocityChannelInitializer.MINECRAFT_DECODER, VelocityChannelInitializer.VIA_DECODER, decoder);
+
+        super.userEventTriggered(ctx, event);
+    }
 }

velocity/src/main/java/com/viaversion/viaversion/velocity/handlers/VelocityEncodeHandler.java

@@ -20,21 +20,16 @@ package com.viaversion.viaversion.velocity.handlers;
 import com.viaversion.viaversion.api.connection.UserConnection;
 import com.viaversion.viaversion.exception.CancelCodecException;
 import com.viaversion.viaversion.exception.CancelEncoderException;
-import com.viaversion.viaversion.util.PipelineUtil;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.MessageToByteEncoder;
-import io.netty.handler.codec.MessageToMessageDecoder;
 import io.netty.handler.codec.MessageToMessageEncoder;
 
-import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 
 @ChannelHandler.Sharable
 public class VelocityEncodeHandler extends MessageToMessageEncoder<ByteBuf> {
     private final UserConnection info;
-    private boolean handledCompression;
 
     public VelocityEncodeHandler(UserConnection info) {
         this.info = info;
@@ -50,54 +45,13 @@ public class VelocityEncodeHandler extends MessageToMessageEncoder<ByteBuf> {
 
         ByteBuf transformedBuf = ctx.alloc().buffer().writeBytes(bytebuf);
         try {
-            boolean needsCompress = handleCompressionOrder(ctx, transformedBuf);
-
             info.transformOutgoing(transformedBuf, CancelEncoderException::generate);
-
-            if (needsCompress) {
-                recompress(ctx, transformedBuf);
-            }
             out.add(transformedBuf.retain());
         } finally {
             transformedBuf.release();
         }
     }
 
-    private boolean handleCompressionOrder(ChannelHandlerContext ctx, ByteBuf buf) throws InvocationTargetException {
-        if (handledCompression) return false;
-
-        int encoderIndex = ctx.pipeline().names().indexOf("compression-encoder");
-        if (encoderIndex == -1) return false;
-        handledCompression = true;
-        if (encoderIndex > ctx.pipeline().names().indexOf("via-encoder")) {
-            // Need to decompress this packet due to bad order
-            ByteBuf decompressed = (ByteBuf) PipelineUtil.callDecode((MessageToMessageDecoder<?>) ctx.pipeline().get("compression-decoder"), ctx, buf).get(0);
-            try {
-                buf.clear().writeBytes(decompressed);
-            } finally {
-                decompressed.release();
-            }
-            ChannelHandler encoder = ctx.pipeline().get("via-encoder");
-            ChannelHandler decoder = ctx.pipeline().get("via-decoder");
-            ctx.pipeline().remove(encoder);
-            ctx.pipeline().remove(decoder);
-            ctx.pipeline().addAfter("compression-encoder", "via-encoder", encoder);
-            ctx.pipeline().addAfter("compression-decoder", "via-decoder", decoder);
-            return true;
-        }
-        return false;
-    }
-
-    private void recompress(ChannelHandlerContext ctx, ByteBuf buf) throws InvocationTargetException {
-        ByteBuf compressed = ctx.alloc().buffer();
-        try {
-            PipelineUtil.callEncode((MessageToByteEncoder<?>) ctx.pipeline().get("compression-encoder"), ctx, buf, compressed);
-            buf.clear().writeBytes(compressed);
-        } finally {
-            compressed.release();
-        }
-    }
-
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         if (cause instanceof CancelCodecException) return;

velocity/src/main/java/com/viaversion/viaversion/velocity/providers/VelocityVersionProvider.java

@@ -48,6 +48,7 @@ public class VelocityVersionProvider extends BaseVersionProvider {
     }
 
     private int getBackProtocol(UserConnection user) throws Exception {
+        //TODO use newly added Velocity netty event
         ChannelHandler mcHandler = user.getChannel().pipeline().get("handler");
         return ProtocolDetectorService.getProtocolId(
                 ((ServerConnection) getAssociation.invoke(mcHandler)).getServerInfo().getName());