/*
    * 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:
    *
    *   https://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.socksproxy;
  
  import io.netty.channel.ChannelHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.socksx.SocksMessage;
  import io.netty.handler.codec.socksx.v4.Socks4CommandRequest;
  import io.netty.handler.codec.socksx.v4.Socks4CommandType;
  import io.netty.handler.codec.socksx.v5.DefaultSocks5InitialResponse;
  import io.netty.handler.codec.socksx.v5.DefaultSocks5PasswordAuthResponse;
  import io.netty.handler.codec.socksx.v5.DefaultSocks5PrivateAuthResponse;
  import io.netty.handler.codec.socksx.v5.Socks5AuthMethod;
  import io.netty.handler.codec.socksx.v5.Socks5InitialRequest;
  import io.netty.handler.codec.socksx.v5.Socks5CommandRequest;
  import io.netty.handler.codec.socksx.v5.Socks5CommandRequestDecoder;
  import io.netty.handler.codec.socksx.v5.Socks5CommandType;
  import io.netty.handler.codec.socksx.v5.Socks5PasswordAuthRequest;
  import io.netty.handler.codec.socksx.v5.Socks5PasswordAuthStatus;
  import io.netty.handler.codec.socksx.v5.Socks5PrivateAuthRequest;
  import io.netty.handler.codec.socksx.v5.Socks5PrivateAuthStatus;
  
  @ChannelHandler.Sharable
  public final class SocksServerHandler extends SimpleChannelInboundHandler<SocksMessage> {
  
      public static final SocksServerHandler INSTANCE = new SocksServerHandler();
  
      private SocksServerHandler() { }
  
      @Override
      public void channelRead0(ChannelHandlerContext ctx, SocksMessage socksRequest) throws Exception {
          switch (socksRequest.version()) {
              case SOCKS4a:
                  Socks4CommandRequest socksV4CmdRequest = (Socks4CommandRequest) socksRequest;
                  if (socksV4CmdRequest.type() == Socks4CommandType.CONNECT) {
                      ctx.pipeline().addLast(new SocksServerConnectHandler());
                      ctx.pipeline().remove(this);
                      ctx.fireChannelRead(socksRequest);
                  } else {
                      ctx.close();
                  }
                  break;
              case SOCKS5:
                  if (socksRequest instanceof Socks5InitialRequest) {
                      // auth support example
                      //ctx.pipeline().addFirst(new Socks5PasswordAuthRequestDecoder());
                      //ctx.write(new DefaultSocks5AuthMethodResponse(Socks5AuthMethod.PASSWORD));
                      ctx.pipeline().addFirst(new Socks5CommandRequestDecoder());
                      ctx.write(new DefaultSocks5InitialResponse(Socks5AuthMethod.NO_AUTH));
                  } else if (socksRequest instanceof Socks5PasswordAuthRequest) {
                      ctx.pipeline().addFirst(new Socks5CommandRequestDecoder());
                      ctx.write(new DefaultSocks5PasswordAuthResponse(Socks5PasswordAuthStatus.SUCCESS));
                  } else if (socksRequest instanceof Socks5PrivateAuthRequest) {
                      ctx.pipeline().addFirst(new Socks5CommandRequestDecoder());
                      ctx.write(new DefaultSocks5PrivateAuthResponse(Socks5PrivateAuthStatus.SUCCESS));
                  } else if (socksRequest instanceof Socks5CommandRequest) {
                      Socks5CommandRequest socks5CmdRequest = (Socks5CommandRequest) socksRequest;
                      if (socks5CmdRequest.type() == Socks5CommandType.CONNECT) {
                          ctx.pipeline().addLast(new SocksServerConnectHandler());
                          ctx.pipeline().remove(this);
                          ctx.fireChannelRead(socksRequest);
                      } else {
                          ctx.close();
                      }
                  } else {
                      ctx.close();
                  }
                  break;
              case UNKNOWN:
                  ctx.close();
                  break;
          }
      }
  
      @Override
      public void channelReadComplete(ChannelHandlerContext ctx) {
          ctx.flush();
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable throwable) {
          throwable.printStackTrace();
          SocksServerUtils.closeOnFlush(ctx.channel());
      }
  }