/*
    * Copyright 2014 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.socksx.v4;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.EncoderException;
  import io.netty.handler.codec.MessageToByteEncoder;
  import io.netty.util.AsciiString;
  import io.netty.util.NetUtil;
  
  /**
   * Encodes a {@link Socks4CommandRequest} into a {@link ByteBuf}.
   */
  @Sharable
  public final class Socks4ClientEncoder extends MessageToByteEncoder<Socks4CommandRequest> {
  
      /**
       * The singleton instance of {@link Socks4ClientEncoder}
       */
      public static final Socks4ClientEncoder INSTANCE = new Socks4ClientEncoder();
  
      private static final byte[] IPv4_DOMAIN_MARKER = {0x00, 0x00, 0x00, 0x01};
  
      private Socks4ClientEncoder() {
          super(Socks4CommandRequest.class);
      }
  
      @Override
      protected void encode(ChannelHandlerContext ctx, Socks4CommandRequest msg, ByteBuf out) throws Exception {
          out.writeByte(msg.version().byteValue());
          out.writeByte(msg.type().byteValue());
          ByteBufUtil.writeShortBE(out, msg.dstPort());
          if (NetUtil.isValidIpV4Address(msg.dstAddr())) {
              out.writeBytes(NetUtil.createByteArrayFromIpAddressString(msg.dstAddr()));
              ByteBufUtil.writeAscii(out, sanitize("userId", msg.userId()));
              out.writeByte(0);
          } else {
              out.writeBytes(IPv4_DOMAIN_MARKER);
              ByteBufUtil.writeAscii(out, sanitize("userId", msg.userId()));
              out.writeByte(0);
              ByteBufUtil.writeAscii(out, sanitize("dstAddr", msg.dstAddr()));
              out.writeByte(0);
          }
      }
  
      private CharSequence sanitize(String fieldName, String strValue) {
          for (int i = 0, len = strValue.length(); i < len; i++) {
              char c = strValue.charAt(i);
              // SOCKS4 uses NUL-bytes as field delimiters.
              if (AsciiString.c2b(c) == 0) {
                  throw new EncoderException("Illegal character in " + fieldName + " field.");
              }
          }
          return strValue;
      }
  }