/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.example.proxy;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOption;

public class HexDumpProxyFrontendHandler implements ChannelHandler {

    private final String remoteHost;
    private final int remotePort;

    // As we use inboundChannel.eventLoop() when building the Bootstrap this does not need to be volatile as
    // the outboundChannel will use the same EventLoop (and therefore Thread) as the inboundChannel.
    private Channel outboundChannel;

    public HexDumpProxyFrontendHandler(String remoteHost, int remotePort) {
        this.remoteHost = remoteHost;
        this.remotePort = remotePort;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        final Channel inboundChannel = ctx.channel();

        // Start the connection attempt.
        Bootstrap b = new Bootstrap();
        b.group(inboundChannel.eventLoop())
         .channel(ctx.channel().getClass())
         .handler(new HexDumpProxyBackendHandler(inboundChannel))
         .option(ChannelOption.AUTO_READ, false);
        ChannelFuture f = b.connect(remoteHost, remotePort);
        outboundChannel = f.channel();
        f.addListener((ChannelFutureListener) future -> {
            if (future.isSuccess()) {
                // connection complete start to read first data
                inboundChannel.read();
            } else {
                // Close the connection if the connection attempt has failed.
                inboundChannel.close();
            }
        });
    }

    @Override
    public void channelRead(final ChannelHandlerContext ctx, Object msg) {
        if (outboundChannel.isActive()) {
            outboundChannel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {
                if (future.isSuccess()) {
                    // was able to flush out data, start to read the next chunk
                    ctx.channel().read();
                } else {
                    future.channel().close();
                }
            });
        }
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) {
        if (outboundChannel != null) {
            closeOnFlush(outboundChannel);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        closeOnFlush(ctx.channel());
    }

    /**
     * Closes the specified channel after all queued write requests are flushed.
     */
    static void closeOnFlush(Channel ch) {
        if (ch.isActive()) {
            ch.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
        }
    }
}
