/*
    * 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.v5;
  
  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.internal.ObjectUtil;
  import io.netty.util.internal.StringUtil;
  
  import java.util.List;
  import java.util.RandomAccess;
  
  /**
   * Encodes a client-side {@link Socks5Message} into a {@link ByteBuf}.
   */
  @Sharable
  public class Socks5ClientEncoder extends MessageToByteEncoder<Socks5Message> {
  
      public static final Socks5ClientEncoder DEFAULT = new Socks5ClientEncoder();
  
      private final Socks5AddressEncoder addressEncoder;
  
      /**
       * Creates a new instance with the default {@link Socks5AddressEncoder}.
       */
      protected Socks5ClientEncoder() {
          this(Socks5AddressEncoder.DEFAULT);
      }
  
      /**
       * Creates a new instance with the specified {@link Socks5AddressEncoder}.
       */
      public Socks5ClientEncoder(Socks5AddressEncoder addressEncoder) {
          this.addressEncoder = ObjectUtil.checkNotNull(addressEncoder, "addressEncoder");
      }
  
      /**
       * Returns the {@link Socks5AddressEncoder} of this encoder.
       */
      protected final Socks5AddressEncoder addressEncoder() {
          return addressEncoder;
      }
  
      @Override
      protected void encode(ChannelHandlerContext ctx, Socks5Message msg, ByteBuf out) throws Exception {
          if (msg instanceof Socks5InitialRequest) {
              encodeAuthMethodRequest((Socks5InitialRequest) msg, out);
          } else if (msg instanceof Socks5PasswordAuthRequest) {
              encodePasswordAuthRequest((Socks5PasswordAuthRequest) msg, out);
          } else if (msg instanceof Socks5CommandRequest) {
              encodeCommandRequest((Socks5CommandRequest) msg, out);
          } else {
              throw new EncoderException("unsupported message type: " + StringUtil.simpleClassName(msg));
          }
      }
  
      private static void encodeAuthMethodRequest(Socks5InitialRequest msg, ByteBuf out) {
          out.writeByte(msg.version().byteValue());
  
          final List<Socks5AuthMethod> authMethods = msg.authMethods();
          final int numAuthMethods = authMethods.size();
          writeFieldLength(out, numAuthMethods);
  
          if (authMethods instanceof RandomAccess) {
              for (int i = 0; i < numAuthMethods; i ++) {
                  out.writeByte(authMethods.get(i).byteValue());
              }
          } else {
              for (Socks5AuthMethod a: authMethods) {
                  out.writeByte(a.byteValue());
              }
          }
      }
  
      private static void encodePasswordAuthRequest(Socks5PasswordAuthRequest msg, ByteBuf out) {
          out.writeByte(0x01);
  
          final String username = msg.username();
          writeFieldLength(out, username.length());
          ByteBufUtil.writeAscii(out, username);
  
         final String password = msg.password();
         writeFieldLength(out, password.length());
         ByteBufUtil.writeAscii(out, password);
     }
 
     private void encodeCommandRequest(Socks5CommandRequest msg, ByteBuf out) throws Exception {
         out.writeByte(msg.version().byteValue());
         out.writeByte(msg.type().byteValue());
         out.writeByte(0x00);
 
         final Socks5AddressType dstAddrType = msg.dstAddrType();
         out.writeByte(dstAddrType.byteValue());
         String addrValue = msg.dstAddr();
         if (addrValue != null && dstAddrType == Socks5AddressType.DOMAIN) {
             checkFieldLength(addrValue.length());
         }
         addressEncoder.encodeAddress(dstAddrType, addrValue, out);
         ByteBufUtil.writeShortBE(out, msg.dstPort());
     }
 
     private static void writeFieldLength(ByteBuf out, int length) {
         checkFieldLength(length);
         out.writeByte(length);
     }
 
     private static void checkFieldLength(int length) {
         if (length > 255 || length < 0) {
             throw new EncoderException("Invalid field length value: " + length);
         }
     }
 }