/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF 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 org.apache.mina.proxy.handlers.socks;
  
  import java.util.Arrays;
  
  import org.apache.mina.core.buffer.IoBuffer;
  import org.apache.mina.core.filterchain.IoFilter.NextFilter;
  import org.apache.mina.proxy.session.ProxyIoSession;
  import org.apache.mina.proxy.utils.ByteUtilities;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Socks4LogicHandler.java - SOCKS4/SOCKS4a authentication mechanisms logic handler.
   * 
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   * @since MINA 2.0.0-M3
   */
  public class Socks4LogicHandler extends AbstractSocksLogicHandler {
  
      private static final Logger LOGGER = LoggerFactory.getLogger(Socks4LogicHandler.class);
  
      /**
       * @see AbstractSocksLogicHandler#AbstractSocksLogicHandler(ProxyIoSession)
       * 
       * @param proxyIoSession The original session
       */
      public Socks4LogicHandler(final ProxyIoSession proxyIoSession) {
          super(proxyIoSession);
      }
  
      /**
       * Perform the handshake.
       * 
       * @param nextFilter the next filter
       */
      @Override
      public void doHandshake(final NextFilter nextFilter) {
          if (LOGGER.isDebugEnabled()) {
              LOGGER.debug(" doHandshake()");
          }
  
          // Send request
          writeRequest(nextFilter, request);
      }
  
      /**
       * Encode a SOCKS4/SOCKS4a request and writes it to the next filter
       * so it can be sent to the proxy server.
       * 
       * @param nextFilter the next filter
       * @param request the request to send.
       */
      protected void writeRequest(final NextFilter nextFilter, final SocksProxyRequest request) {
          try {
              boolean isV4ARequest = Arrays.equals(request.getIpAddress(), SocksProxyConstants.FAKE_IP);
              byte[] userID = request.getUserName().getBytes("ASCII");
              byte[] host = isV4ARequest ? request.getHost().getBytes("ASCII") : null;
  
              int len = 9 + userID.length;
  
              if (isV4ARequest) {
                  len += host.length + 1;
              }
  
              IoBuffer buf = IoBuffer.allocate(len);
  
              buf.put(request.getProtocolVersion());
              buf.put(request.getCommandCode());
              buf.put(request.getPort());
              buf.put(request.getIpAddress());
              buf.put(userID);
              buf.put(SocksProxyConstants.TERMINATOR);
  
              if (isV4ARequest) {
                  buf.put(host);
                  buf.put(SocksProxyConstants.TERMINATOR);
              }
  
              if (LOGGER.isDebugEnabled()) {
                  if (isV4ARequest) {
                     LOGGER.debug("  sending SOCKS4a request");
                 } else {
                     LOGGER.debug("  sending SOCKS4 request");
                 }
             }
 
             buf.flip();
             writeData(nextFilter, buf);
         } catch (Exception ex) {
             closeSession("Unable to send Socks request: ", ex);
         }
     }
 
     /**
      * Handle incoming data during the handshake process. Should consume only the
      * handshake data from the buffer, leaving any extra data in place.
      * 
      * @param nextFilter the next filter
      * @param buf the server response data buffer
      */
     @Override
     public void messageReceived(final NextFilter nextFilter, final IoBuffer buf) {
         try {
             if (buf.remaining() >= SocksProxyConstants.SOCKS_4_RESPONSE_SIZE) {
                 handleResponse(buf);
             }
         } catch (Exception ex) {
             closeSession("Proxy handshake failed: ", ex);
         }
     }
 
     /**
      * Handle a SOCKS4/SOCKS4a response from the proxy server. Test
      * the response buffer reply code and call {@link #setHandshakeComplete()}
      * if access is granted.
      * 
      * @param buf the buffer holding the server response data.
      * @throws Exception if server response is malformed or if request is rejected
      * by the proxy server.
      */
     protected void handleResponse(final IoBuffer buf) throws Exception {
         byte first = buf.get(0);
 
         if (first != 0) {
             throw new Exception("Socks response seems to be malformed");
         }
 
         byte status = buf.get(1);
 
         // Consumes all the response data from the buffer
         buf.position(buf.position() + SocksProxyConstants.SOCKS_4_RESPONSE_SIZE);
 
         if (status == SocksProxyConstants.V4_REPLY_REQUEST_GRANTED) {
             setHandshakeComplete();
         } else {
             throw new Exception("Proxy handshake failed - Code: 0x" + ByteUtilities.asHex(new byte[] { status }) + " ("
                     + SocksProxyConstants.getReplyCodeAsString(status) + ")");
         }
     }
 }