#3776: Expose ChannelInitializerHolder in protocol module

protocol/src/main/java/net/md_5/bungee/protocol/channel/BungeeChannelInitializer.java

@@ -0,0 +1,54 @@
+package net.md_5.bungee.protocol.channel;
+
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+/**
+ * This class hold a netty channel initializer that calls the given {@link ChannelAcceptor}.
+ * Use {@link BungeeChannelInitializer#create(ChannelAcceptor)} to create a new instance.
+ * <p>
+ * Please note that this API is unsafe and doesn't provide any guarantees about
+ * the stability of the channel pipeline or the API itself. Use at your own
+ * risk.
+ */
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public abstract class BungeeChannelInitializer
+{
+
+    public abstract ChannelAcceptor getChannelAcceptor();
+
+    public abstract ChannelInitializer<Channel> getChannelInitializer();
+
+    /**
+     * Creates a new instance of BungeeChannelInitializer
+     *
+     * @param acceptor the {@link ChannelAcceptor} that will accept the channel
+     * and initializer the pipeline
+     * @return {@link BungeeChannelInitializer} containing a cached
+     * {@link ChannelInitializer} that will call the acceptor
+     */
+    public static BungeeChannelInitializer create(ChannelAcceptor acceptor)
+    {
+        return new BungeeChannelInitializer()
+        {
+            @Getter
+            private final ChannelAcceptor channelAcceptor = acceptor;
+
+            @Getter // cache the ChannelInitializer
+            private final ChannelInitializer<Channel> channelInitializer = new ChannelInitializer<Channel>()
+            {
+                @Override
+                protected void initChannel(Channel channel) throws Exception
+                {
+                    if ( !getChannelAcceptor().accept( channel ) )
+                    {
+                        channel.close();
+                    }
+                }
+            };
+        };
+    }
+}

protocol/src/main/java/net/md_5/bungee/protocol/channel/ChannelAcceptor.java

@@ -0,0 +1,16 @@
+package net.md_5.bungee.protocol.channel;
+
+import io.netty.channel.Channel;
+
+@FunctionalInterface
+public interface ChannelAcceptor
+{
+
+    /**
+     * Inside this method the pipeline should be initialized.
+     *
+     * @param channel the channel to be accepted and initialized
+     * @return if the channel was accepted
+     */
+    boolean accept(Channel channel);
+}