From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Nassim Jahnke <nassim@njahnke.dev>
Date: Thu, 29 Apr 2021 21:19:33 +0200
Subject: [PATCH] Add Channel initialization listeners


diff --git a/src/main/java/io/papermc/paper/network/ChannelInitializeListener.java b/src/main/java/io/papermc/paper/network/ChannelInitializeListener.java
new file mode 100644
index 0000000000000000000000000000000000000000..88099df34c2d74daba9645aadf65b446ca795a91
--- /dev/null
+++ b/src/main/java/io/papermc/paper/network/ChannelInitializeListener.java
@@ -0,0 +1,15 @@
+package io.papermc.paper.network;
+
+import io.netty.channel.Channel;
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+/**
+ * Internal API to register channel initialization listeners.
+ * <p>
+ * This is not officially supported API and we make no guarantees to the existence or state of this interface.
+ */
+@FunctionalInterface
+public interface ChannelInitializeListener {
+
+    void afterInitChannel(@NonNull Channel channel);
+}
diff --git a/src/main/java/io/papermc/paper/network/ChannelInitializeListenerHolder.java b/src/main/java/io/papermc/paper/network/ChannelInitializeListenerHolder.java
new file mode 100644
index 0000000000000000000000000000000000000000..30e62719e0a83525daa33cf41cb61df360c0e046
--- /dev/null
+++ b/src/main/java/io/papermc/paper/network/ChannelInitializeListenerHolder.java
@@ -0,0 +1,74 @@
+package io.papermc.paper.network;
+
+import io.netty.channel.Channel;
+import net.kyori.adventure.key.Key;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Internal API to register channel initialization listeners.
+ * <p>
+ * This is not officially supported API and we make no guarantees to the existence or state of this class.
+ */
+public final class ChannelInitializeListenerHolder {
+
+    private static final Map<Key, ChannelInitializeListener> LISTENERS = new HashMap<>();
+    private static final Map<Key, ChannelInitializeListener> IMMUTABLE_VIEW = Collections.unmodifiableMap(LISTENERS);
+
+    private ChannelInitializeListenerHolder() {
+    }
+
+    /**
+     * Registers whether an initialization listener is registered under the given key.
+     *
+     * @param key key
+     * @return whether an initialization listener is registered under the given key
+     */
+    public static boolean hasListener(@NonNull Key key) {
+        return LISTENERS.containsKey(key);
+    }
+
+    /**
+     * Registers a channel initialization listener called after ServerConnection is initialized.
+     *
+     * @param key      key
+     * @param listener initialization listeners
+     */
+    public static void addListener(@NonNull Key key, @NonNull ChannelInitializeListener listener) {
+        LISTENERS.put(key, listener);
+    }
+
+    /**
+     * Removes and returns an initialization listener registered by the given key if present.
+     *
+     * @param key key
+     * @return removed initialization listener if present
+     */
+    public static @Nullable ChannelInitializeListener removeListener(@NonNull Key key) {
+        return LISTENERS.remove(key);
+    }
+
+    /**
+     * Returns an immutable map of registered initialization listeners.
+     *
+     * @return immutable map of registered initialization listeners
+     */
+    public static @NonNull Map<Key, ChannelInitializeListener> getListeners() {
+        return IMMUTABLE_VIEW;
+    }
+
+    /**
+     * Calls the registered listeners with the given channel.
+     *
+     * @param channel channel
+     */
+    public static void callListeners(@NonNull Channel channel) {
+        for (ChannelInitializeListener listener : LISTENERS.values()) {
+            listener.afterInitChannel(channel);
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/network/ConnectionEvent.java b/src/main/java/io/papermc/paper/network/ConnectionEvent.java
new file mode 100644
index 0000000000000000000000000000000000000000..0d7e7db9e37ef0183c32b217bd944fb4f41ab83a
--- /dev/null
+++ b/src/main/java/io/papermc/paper/network/ConnectionEvent.java
@@ -0,0 +1,10 @@
+package io.papermc.paper.network;
+
+/**
+ * Internal connection pipeline events.
+ */
+public enum ConnectionEvent {
+
+    COMPRESSION_THRESHOLD_SET,
+    COMPRESSION_DISABLED
+}
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index fe89e8f509f3972ceb71c9aa6277524baa39985b..6c30eb3750f434341ecec0bf8e9054bb331f9757 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -668,6 +668,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             } else {
                 this.channel.pipeline().addAfter("prepender", "compress", new CompressionEncoder(compressionThreshold));
             }
+            this.channel.pipeline().fireUserEventTriggered(io.papermc.paper.network.ConnectionEvent.COMPRESSION_THRESHOLD_SET); // Paper - Add Channel initialization listeners
         } else {
             if (this.channel.pipeline().get("decompress") instanceof CompressionDecoder) {
                 this.channel.pipeline().remove("decompress");
@@ -676,6 +677,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             if (this.channel.pipeline().get("compress") instanceof CompressionEncoder) {
                 this.channel.pipeline().remove("compress");
             }
+            this.channel.pipeline().fireUserEventTriggered(io.papermc.paper.network.ConnectionEvent.COMPRESSION_DISABLED); // Paper - Add Channel initialization listeners
         }
 
     }
diff --git a/src/main/java/net/minecraft/server/network/ServerConnectionListener.java b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
index 64119f2188f8958b8a5913fec82ac5bba1b74b2a..d6d7f1c446ba5507f67038ff27775ba75156f4a7 100644
--- a/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
+++ b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
@@ -115,6 +115,7 @@ public class ServerConnectionListener {
                     pending.add(object); // Paper - prevent blocking on adding a new connection while the server is ticking
                     ((Connection) object).configurePacketHandler(channelpipeline);
                     ((Connection) object).setListenerForServerboundHandshake(new ServerHandshakePacketListenerImpl(ServerConnectionListener.this.server, (Connection) object));
+                    io.papermc.paper.network.ChannelInitializeListenerHolder.callListeners(channel); // Paper - Add Channel initialization listeners
                 }
             }).group(eventloopgroup).localAddress(address, port)).option(ChannelOption.AUTO_READ, false).bind().syncUninterruptibly()); // CraftBukkit
         }