Merge branch 'plugin-messages'

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

@@ -1,6 +1,7 @@
 package com.velocitypowered.api.proxy;
 
 import com.velocitypowered.api.command.CommandSource;
+import com.velocitypowered.api.proxy.messages.ChannelMessageSource;
 import com.velocitypowered.api.server.ServerInfo;
 import com.velocitypowered.api.util.MessagePosition;
 import net.kyori.text.Component;
@@ -12,7 +13,7 @@ import java.util.UUID;
 /**
  * Represents a player who is connected to the proxy.
  */
-public interface Player extends CommandSource, InboundConnection {
+public interface Player extends CommandSource, InboundConnection, ChannelMessageSource {
     /**
      * Returns the player's current username.
      * @return the username

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

@@ -4,6 +4,7 @@ import com.velocitypowered.api.command.CommandSource;
 import com.velocitypowered.api.command.CommandManager;
 import com.velocitypowered.api.event.EventManager;
 import com.velocitypowered.api.plugin.PluginManager;
+import com.velocitypowered.api.proxy.messages.ChannelRegistrar;
 import com.velocitypowered.api.scheduler.Scheduler;
 import com.velocitypowered.api.server.ServerInfo;
 
@@ -101,4 +102,10 @@ public interface ProxyServer {
      * @return the scheduler instance
      */
     Scheduler getScheduler();
+
+    /**
+     * Gets the {@link ChannelRegistrar} instance.
+     * @return the channel registrar
+     */
+    ChannelRegistrar getChannelRegistrar();
 }

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

@@ -1,11 +1,12 @@
 package com.velocitypowered.api.proxy;
 
+import com.velocitypowered.api.proxy.messages.ChannelMessageSource;
 import com.velocitypowered.api.server.ServerInfo;
 
 /**
  * Represents a connection to a backend server from the proxy for a client.
  */
-public interface ServerConnection {
+public interface ServerConnection extends ChannelMessageSource {
     ServerInfo getServerInfo();
 
     Player getPlayer();

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

@@ -0,0 +1,8 @@
+package com.velocitypowered.api.proxy.messages;
+
+/**
+ * Represents a kind of channel identifier.
+ */
+public interface ChannelIdentifier {
+    String getId();
+}

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

@@ -0,0 +1,4 @@
+package com.velocitypowered.api.proxy.messages;
+
+public interface ChannelMessageSource {
+}

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

@@ -0,0 +1,11 @@
+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.
+ */
+public interface ChannelRegistrar {
+    void register(MessageHandler handler, ChannelIdentifier... identifiers);
+
+    void unregister(ChannelIdentifier... identifiers);
+}

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

@@ -0,0 +1,6 @@
+package com.velocitypowered.api.proxy.messages;
+
+public enum ChannelSide {
+    FROM_SERVER,
+    FROM_CLIENT
+}

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

@@ -0,0 +1,48 @@
+package com.velocitypowered.api.proxy.messages;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
+
+import java.util.Objects;
+
+/**
+ * Reperesents a legacy channel identifier (for Minecraft 1.12 and below). For modern 1.13 plugin messages, please see
+ * {@link MinecraftChannelIdentifier}. This class is immutable and safe for multi-threaded use.
+ */
+public final class LegacyChannelIdentifier implements ChannelIdentifier {
+    private final String name;
+
+    public LegacyChannelIdentifier(String name) {
+        Preconditions.checkArgument(!Strings.isNullOrEmpty(name), "provided name is empty");
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public String toString() {
+        return "LegacyChannelIdentifier{" +
+                "name='" + name + '\'' +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        LegacyChannelIdentifier that = (LegacyChannelIdentifier) o;
+        return Objects.equals(name, that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name);
+    }
+
+    @Override
+    public String getId() {
+        return name;
+    }
+}

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

@@ -0,0 +1,10 @@
+package com.velocitypowered.api.proxy.messages;
+
+public interface MessageHandler {
+    ForwardStatus handle(ChannelMessageSource source, ChannelSide side, byte[] data);
+
+    enum ForwardStatus {
+        FORWARD,
+        HANDLED
+    }
+}

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

@@ -0,0 +1,69 @@
+package com.velocitypowered.api.proxy.messages;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
+
+import java.util.Objects;
+import java.util.regex.Pattern;
+
+/**
+ * Represents a Minecraft 1.13+ channel identifier. This class is immutable and safe for multi-threaded use.
+ */
+public final class MinecraftChannelIdentifier implements ChannelIdentifier {
+    private static final Pattern VALID_IDENTIFIER_REGEX = Pattern.compile("[a-z0-9\\-_]+");
+
+    private final String namespace;
+    private final String name;
+
+    private MinecraftChannelIdentifier(String namespace, String name) {
+        this.namespace = namespace;
+        this.name = name;
+    }
+
+    public static MinecraftChannelIdentifier forDefaultNamespace(String name) {
+        return new MinecraftChannelIdentifier("minecraft", name);
+    }
+
+    public static MinecraftChannelIdentifier create(String namespace, String name) {
+        Preconditions.checkArgument(!Strings.isNullOrEmpty(namespace), "namespace is null or empty");
+        Preconditions.checkArgument(!Strings.isNullOrEmpty(name), "namespace is null or empty");
+        Preconditions.checkArgument(VALID_IDENTIFIER_REGEX.matcher(namespace).matches(), "namespace is not valid");
+        Preconditions.checkArgument(VALID_IDENTIFIER_REGEX.matcher(name).matches(), "name is not valid");
+        return new MinecraftChannelIdentifier(namespace, name);
+    }
+
+    public String getNamespace() {
+        return namespace;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public String toString() {
+        return "MinecraftChannelIdentifier{" +
+                "namespace='" + namespace + '\'' +
+                ", name='" + name + '\'' +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        MinecraftChannelIdentifier that = (MinecraftChannelIdentifier) o;
+        return Objects.equals(namespace, that.namespace) &&
+                Objects.equals(name, that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(namespace, name);
+    }
+
+    @Override
+    public String getId() {
+        return namespace + ":" + name;
+    }
+}

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -21,6 +21,7 @@ import com.velocitypowered.proxy.config.VelocityConfiguration;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.connection.http.NettyHttpClient;
 import com.velocitypowered.proxy.command.VelocityCommandManager;
+import com.velocitypowered.proxy.messages.VelocityChannelRegistrar;
 import com.velocitypowered.proxy.plugin.VelocityEventManager;
 import com.velocitypowered.proxy.protocol.util.FaviconSerializer;
 import com.velocitypowered.proxy.plugin.VelocityPluginManager;
@@ -84,6 +85,7 @@ public class VelocityServer implements ProxyServer {
     private Ratelimiter ipAttemptLimiter;
     private VelocityEventManager eventManager;
     private VelocityScheduler scheduler;
+    private VelocityChannelRegistrar channelRegistrar;
 
     private VelocityServer() {
         commandManager.register(new VelocityCommand(), "velocity");
@@ -137,6 +139,7 @@ public class VelocityServer implements ProxyServer {
         httpClient = new NettyHttpClient(this);
         eventManager = new VelocityEventManager(pluginManager);
         scheduler = new VelocityScheduler(pluginManager, Sleeper.SYSTEM);
+        channelRegistrar = new VelocityChannelRegistrar();
         loadPlugins();
 
         try {
@@ -304,4 +307,9 @@ public class VelocityServer implements ProxyServer {
     public VelocityScheduler getScheduler() {
         return scheduler;
     }
+
+    @Override
+    public VelocityChannelRegistrar getChannelRegistrar() {
+        return channelRegistrar;
+    }
 }

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

@@ -1,6 +1,8 @@
 package com.velocitypowered.proxy.connection.backend;
 
 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;
@@ -65,7 +67,11 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
                 return;
             }
 
-            connection.getPlayer().getConnection().write(pm);
+            MessageHandler.ForwardStatus status = VelocityServer.getServer().getChannelRegistrar().handlePluginMessage(
+                    connection, ChannelSide.FROM_SERVER, pm);
+            if (status == MessageHandler.ForwardStatus.FORWARD) {
+                connection.getPlayer().getConnection().write(pm);
+            }
         } 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

@@ -1,6 +1,8 @@
 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.proxy.VelocityServer;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
@@ -220,8 +222,12 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
             return;
         }
 
-        // We're going to forward on the original packet.
-        player.getConnectedServer().getMinecraftConnection().write(packet);
+        MessageHandler.ForwardStatus status = VelocityServer.getServer().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);
+        }
     }
 
     public Set<String> getClientPluginMsgChannels() {

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

@@ -0,0 +1,48 @@
+package com.velocitypowered.proxy.messages;
+
+import com.google.common.base.Preconditions;
+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.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class VelocityChannelRegistrar implements ChannelRegistrar {
+    private static final Logger logger = LogManager.getLogger(VelocityChannelRegistrar.class);
+    private final Map<String, MessageHandler> handlers = new ConcurrentHashMap<>();
+
+    @Override
+    public void register(MessageHandler handler, 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);
+        }
+    }
+
+    public MessageHandler.ForwardStatus handlePluginMessage(ChannelMessageSource source, ChannelSide side, PluginMessage message) {
+        MessageHandler handler = handlers.get(message.getChannel());
+        if (handler == null) {
+            // Nothing we can do.
+            return MessageHandler.ForwardStatus.FORWARD;
+        }
+
+        try {
+            return handler.handle(source, side, 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) {
+
+    }
+}