[BREAKING] PluginMessageEvent instead

api/src/main/java/com/velocitypowered/api/event/connection/PluginMessageEvent.java

@@ -0,0 +1,94 @@
+package com.velocitypowered.api.event.connection;
+
+import com.google.common.base.Preconditions;
+import com.google.common.io.ByteArrayDataInput;
+import com.google.common.io.ByteStreams;
+import com.velocitypowered.api.event.ResultedEvent;
+import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
+import com.velocitypowered.api.proxy.messages.ChannelMessageSink;
+import com.velocitypowered.api.proxy.messages.ChannelMessageSource;
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.util.Arrays;
+
+/**
+ * This event is fired when a plugin message is sent to the proxy, either from a client ({@link com.velocitypowered.api.proxy.Player})
+ * or a server ({@link com.velocitypowered.api.proxy.ServerConnection}).
+ */
+public class PluginMessageEvent implements ResultedEvent<PluginMessageEvent.ForwardResult> {
+    private final ChannelMessageSource source;
+    private final ChannelMessageSink target;
+    private final ChannelIdentifier identifier;
+    private final byte[] data;
+    private ForwardResult result;
+
+    public PluginMessageEvent(ChannelMessageSource source, ChannelMessageSink target, ChannelIdentifier identifier, byte[] data) {
+        this.source = Preconditions.checkNotNull(source, "source");
+        this.target = Preconditions.checkNotNull(target, "target");
+        this.identifier = Preconditions.checkNotNull(identifier, "identifier");
+        this.data = Preconditions.checkNotNull(data, "data");
+        this.result = ForwardResult.forward();
+    }
+
+    @Override
+    public ForwardResult getResult() {
+        return result;
+    }
+
+    @Override
+    public void setResult(@NonNull ForwardResult result) {
+        this.result = Preconditions.checkNotNull(result, "result");
+    }
+
+    public ChannelMessageSource getSource() {
+        return source;
+    }
+
+    public ChannelMessageSink getTarget() {
+        return target;
+    }
+
+    public ChannelIdentifier getIdentifier() {
+        return identifier;
+    }
+
+    public byte[] getData() {
+        return Arrays.copyOf(data, data.length);
+    }
+
+    public ByteArrayDataInput dataAsDataStream() {
+        return ByteStreams.newDataInput(data);
+    }
+
+    /**
+     * A result determining whether or not to forward this message on.
+     */
+    public static class ForwardResult implements ResultedEvent.Result {
+        private static final ForwardResult ALLOWED = new ForwardResult(true);
+        private static final ForwardResult DENIED = new ForwardResult(false);
+
+        private final boolean allowed;
+
+        private ForwardResult(boolean b) {
+            this.allowed = b;
+        }
+
+        @Override
+        public boolean isAllowed() {
+            return allowed;
+        }
+
+        @Override
+        public String toString() {
+            return allowed ? "forward to sink" : "handled message at proxy";
+        }
+
+        public static ForwardResult forward() {
+            return ALLOWED;
+        }
+
+        public static ForwardResult handled() {
+            return DENIED;
+        }
+    }
+}

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

@@ -1,16 +1,14 @@
 package com.velocitypowered.api.proxy.messages;
 
 /**
- * Represents an interface to register and unregister {@link MessageHandler} instances for handling plugin messages from
- * the client or the server.
+ * Represents an interface to register and unregister {@link ChannelIdentifier}s for the proxy to listen on.
  */
 public interface ChannelRegistrar {
     /**
-     * Registers the specified message handler to listen for plugin messages on the specified channels.
-     * @param handler the handler to register
+     * Registers the specified message identifiers to listen on for the
      * @param identifiers the channel identifiers to register
      */
-    void register(MessageHandler handler, ChannelIdentifier... identifiers);
+    void register(ChannelIdentifier... identifiers);
 
     /**
      * Unregisters the handler for the specified channel.

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

@@ -1,15 +0,0 @@
-package com.velocitypowered.api.proxy.messages;
-
-/**
- * Represents from "which side" of the proxy the plugin message came from.
- */
-public enum ChannelSide {
-    /**
-     * The plugin message came from a server that a client was connected to.
-     */
-    FROM_SERVER,
-    /**
-     * The plugin message came from the client.
-     */
-    FROM_CLIENT
-}

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

@@ -1,28 +0,0 @@
-package com.velocitypowered.api.proxy.messages;
-
-/**
- * Represents a handler for handling plugin messages.
- */
-public interface MessageHandler {
-    /**
-     * Handles an incoming plugin message.
-     * @param source the source of the plugin message
-     * @param side from where the plugin message originated
-     * @param identifier the channel on which the message was sent
-     * @param data the data inside the plugin message
-     * @return a {@link ForwardStatus} indicating whether or not to forward this plugin message on
-     */
-    ForwardStatus handle(ChannelMessageSource source, ChannelSide side, ChannelIdentifier identifier, byte[] data);
-
-    enum ForwardStatus {
-        /**
-         * Forwards this plugin message on to the client or server, depending on the {@link ChannelSide} it originated
-         * from.
-         */
-        FORWARD,
-        /**
-         * Discard the plugin message and do not forward it on.
-         */
-        HANDLED
-    }
-}

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

@@ -1,8 +1,7 @@
 package com.velocitypowered.proxy.connection.backend;
 
+import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.api.event.player.ServerConnectedEvent;
-import com.velocitypowered.api.proxy.messages.ChannelSide;
-import com.velocitypowered.api.proxy.messages.MessageHandler;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.client.ClientPlaySessionHandler;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
@@ -68,11 +67,14 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
                 return;
             }
 
-            MessageHandler.ForwardStatus status = server.getChannelRegistrar().handlePluginMessage(connection,
-                    ChannelSide.FROM_SERVER, pm);
-            if (status == MessageHandler.ForwardStatus.FORWARD) {
-                connection.getPlayer().getConnection().write(pm);
-            }
+            PluginMessageEvent event = new PluginMessageEvent(connection, connection.getPlayer(), server.getChannelRegistrar().getFromId(pm.getChannel()),
+                    pm.getData());
+            server.getEventManager().fire(event)
+                    .thenAcceptAsync(pme -> {
+                        if (pme.getResult().isAllowed()) {
+                            connection.getPlayer().getConnection().write(pm);
+                        }
+                    }, connection.getMinecraftConnection().getChannel().eventLoop());
         } else {
             // Just forward the packet on. We don't have anything to handle at this time.
             connection.getPlayer().getConnection().write(packet);

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

@@ -1,8 +1,7 @@
 package com.velocitypowered.proxy.connection.client;
 
 import com.velocitypowered.api.event.connection.DisconnectEvent;
-import com.velocitypowered.api.proxy.messages.ChannelSide;
-import com.velocitypowered.api.proxy.messages.MessageHandler;
+import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
@@ -235,12 +234,14 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
             return;
         }
 
-        MessageHandler.ForwardStatus status = server.getChannelRegistrar().handlePluginMessage(player,
-                ChannelSide.FROM_CLIENT, packet);
-        if (status == MessageHandler.ForwardStatus.FORWARD) {
-            // We're going to forward on the original packet.
-            player.getConnectedServer().getMinecraftConnection().write(packet);
-        }
+        PluginMessageEvent event = new PluginMessageEvent(player, player.getConnectedServer(),
+                server.getChannelRegistrar().getFromId(packet.getChannel()), packet.getData());
+        server.getEventManager().fire(event)
+                .thenAcceptAsync(pme -> {
+                    if (pme.getResult().isAllowed()) {
+                        player.getConnectedServer().getMinecraftConnection().write(packet);
+                    }
+                }, player.getConnectedServer().getMinecraftConnection().getChannel().eventLoop());
     }
 
     public Set<String> getClientPluginMsgChannels() {

proxy/src/main/java/com/velocitypowered/proxy/messages/VelocityChannelRegistrar.java

@@ -3,9 +3,6 @@ package com.velocitypowered.proxy.messages;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.velocitypowered.api.proxy.messages.*;
-import com.velocitypowered.proxy.protocol.packet.PluginMessage;
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
 
 import java.util.Collection;
 import java.util.Map;
@@ -13,39 +10,20 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
 public class VelocityChannelRegistrar implements ChannelRegistrar {
-    private static final Logger logger = LogManager.getLogger(VelocityChannelRegistrar.class);
-    private final Map<String, MessageHandler> handlers = new ConcurrentHashMap<>();
     private final Map<String, ChannelIdentifier> identifierMap = new ConcurrentHashMap<>();
 
     @Override
-    public void register(MessageHandler handler, ChannelIdentifier... identifiers) {
+    public void register(ChannelIdentifier... identifiers) {
         for (ChannelIdentifier identifier : identifiers) {
             Preconditions.checkArgument(identifier instanceof LegacyChannelIdentifier || identifier instanceof MinecraftChannelIdentifier,
                     "identifier is unknown");
         }
 
         for (ChannelIdentifier identifier : identifiers) {
-            handlers.put(identifier.getId(), handler);
             identifierMap.put(identifier.getId(), identifier);
         }
     }
 
-    public MessageHandler.ForwardStatus handlePluginMessage(ChannelMessageSource source, ChannelSide side, PluginMessage message) {
-        MessageHandler handler = handlers.get(message.getChannel());
-        ChannelIdentifier identifier = identifierMap.get(message.getChannel());
-        if (handler == null || identifier == null) {
-            return MessageHandler.ForwardStatus.FORWARD;
-        }
-
-        try {
-            return handler.handle(source, side, identifier, message.getData());
-        } catch (Exception e) {
-            logger.info("Unable to handle plugin message on channel {} for {}", message.getChannel(), source);
-            // In case of doubt, do not forward the message on.
-            return MessageHandler.ForwardStatus.HANDLED;
-        }
-    }
-
     @Override
     public void unregister(ChannelIdentifier... identifiers) {
         for (ChannelIdentifier identifier : identifiers) {
@@ -54,7 +32,6 @@ public class VelocityChannelRegistrar implements ChannelRegistrar {
         }
 
         for (ChannelIdentifier identifier : identifiers) {
-            handlers.remove(identifier.getId());
             identifierMap.remove(identifier.getId());
         }
     }
@@ -73,4 +50,8 @@ public class VelocityChannelRegistrar implements ChannelRegistrar {
     public boolean registered(String id) {
         return identifierMap.containsKey(id);
     }
+
+    public ChannelIdentifier getFromId(String id) {
+        return identifierMap.get(id);
+    }
 }