/*
    * 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.handler.codec.socks;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.ReplayingDecoder;
  import io.netty.handler.codec.socks.SocksCmdResponseDecoder.State;
  import io.netty.util.CharsetUtil;
  import io.netty.util.NetUtil;
  import io.netty.util.internal.UnstableApi;
  
  import java.util.List;
  
  /**
   * Decodes {@link ByteBuf}s into {@link SocksCmdResponse}.
   * Before returning SocksResponse decoder removes itself from pipeline.
   */
  public class SocksCmdResponseDecoder extends ReplayingDecoder<State> {
  
      private SocksCmdStatus cmdStatus;
      private SocksAddressType addressType;
  
      public SocksCmdResponseDecoder() {
          super(State.CHECK_PROTOCOL_VERSION);
      }
  
      @Override
      protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> out) throws Exception {
          switch (state()) {
              case CHECK_PROTOCOL_VERSION: {
                  if (byteBuf.readByte() != SocksProtocolVersion.SOCKS5.byteValue()) {
                      out.add(SocksCommonUtils.UNKNOWN_SOCKS_RESPONSE);
                      break;
                  }
                  checkpoint(State.READ_CMD_HEADER);
              }
              case READ_CMD_HEADER: {
                  cmdStatus = SocksCmdStatus.valueOf(byteBuf.readByte());
                  byteBuf.skipBytes(1); // reserved
                  addressType = SocksAddressType.valueOf(byteBuf.readByte());
                  checkpoint(State.READ_CMD_ADDRESS);
              }
              case READ_CMD_ADDRESS: {
                  switch (addressType) {
                      case IPv4: {
                          String host = NetUtil.intToIpAddress(ByteBufUtil.readIntBE(byteBuf));
                          int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                          out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                          break;
                      }
                      case DOMAIN: {
                          int fieldLength = byteBuf.readByte();
                          String host = byteBuf.readString(fieldLength, CharsetUtil.US_ASCII);
                          int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                          out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                          break;
                      }
                      case IPv6: {
                          byte[] bytes = new byte[16];
                          byteBuf.readBytes(bytes);
                          String host = SocksCommonUtils.ipv6toStr(bytes);
                          int port = ByteBufUtil.readUnsignedShortBE(byteBuf);
                          out.add(new SocksCmdResponse(cmdStatus, addressType, host, port));
                          break;
                      }
                      case UNKNOWN: {
                          out.add(SocksCommonUtils.UNKNOWN_SOCKS_RESPONSE);
                          break;
                      }
                      default: {
                          throw new Error();
                      }
                  }
                  break;
              }
              default: {
                  throw new Error();
              }
          }
          ctx.pipeline().remove(this);
      }
  
      @UnstableApi
      public enum State {
         CHECK_PROTOCOL_VERSION,
         READ_CMD_HEADER,
         READ_CMD_ADDRESS
     }
 }