/*
    *  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.directory.server.dhcp.io;
  
  
  import java.io.UnsupportedEncodingException;
  import java.net.InetAddress;
  import java.nio.ByteBuffer;
  import java.util.Iterator;
  
  import org.apache.directory.server.dhcp.messages.DhcpMessage;
  import org.apache.directory.server.dhcp.messages.HardwareAddress;
  import org.apache.directory.server.dhcp.options.DhcpOption;
  import org.apache.directory.server.dhcp.options.OptionsField;
  import org.apache.directory.server.dhcp.options.dhcp.DhcpMessageType;
  import org.apache.directory.server.i18n.I18n;
  
  
  /**
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class DhcpMessageEncoder
  {
      /**
       * Converts a DhcpMessage object into a byte buffer.
       * 
       * @param byteBuffer ByteBuffer to put DhcpMessage into
       * @param message DhcpMessage to encode into ByteBuffer
       */
      public void encode( ByteBuffer byteBuffer, DhcpMessage message )
      {
          byteBuffer.put( message.getOp() );
  
          HardwareAddress hardwareAddress = message.getHardwareAddress();
  
          byteBuffer.put( ( byte ) ( null != hardwareAddress ? hardwareAddress.getType() : 0 ) );
          byteBuffer.put( ( byte ) ( null != hardwareAddress ? hardwareAddress.getLength() : 0 ) );
          byteBuffer.put( ( byte ) message.getHopCount() );
          byteBuffer.putInt( message.getTransactionId() );
          byteBuffer.putShort( ( short ) message.getSeconds() );
          byteBuffer.putShort( message.getFlags() );
  
          writeAddress( byteBuffer, message.getCurrentClientAddress() );
          writeAddress( byteBuffer, message.getAssignedClientAddress() );
          writeAddress( byteBuffer, message.getNextServerAddress() );
          writeAddress( byteBuffer, message.getRelayAgentAddress() );
  
          writeBytes( byteBuffer, ( null != hardwareAddress ? hardwareAddress.getAddress() : new byte[]
              {} ), 16 );
  
          writeString( byteBuffer, message.getServerHostname(), 64 );
          writeString( byteBuffer, message.getBootFileName(), 128 );
  
          OptionsField options = message.getOptions();
  
          // update message type option (if set)
          if ( null != message.getMessageType() )
          {
              options.add( new DhcpMessageType( message.getMessageType() ) );
          }
  
          encodeOptions( options, byteBuffer );
      }
  
  
      /**
       * Write a zero-terminated string to a field of len bytes.
       * 
       * @param byteBuffer
       * @param serverHostname
       * @param i
       */
      private void writeString( ByteBuffer byteBuffer, String string, int len )
      {
          if ( null == string )
          {
              string = "";
          }
  
          try
          {
             byte[] sbytes = string.getBytes( "ASCII" );
 
             // writeBytes will automatically zero-pad and thus terminate the
             // string.
             writeBytes( byteBuffer, sbytes, len );
         }
         catch ( UnsupportedEncodingException e )
         {
             // should not happen
             throw new RuntimeException( I18n.err( I18n.ERR_635 ), e );
         }
     }
 
 
     /**
      * Write an InetAddress to the byte buffer.
      * 
      * @param byteBuffer
      * @param currentClientAddress
      */
     private void writeAddress( ByteBuffer byteBuffer, InetAddress currentClientAddress )
     {
         if ( null == currentClientAddress )
         {
             byte[] emptyAddress =
                 { 0, 0, 0, 0 };
             byteBuffer.put( emptyAddress );
         }
         else
         {
             byte[] addressBytes = currentClientAddress.getAddress();
             byteBuffer.put( addressBytes );
         }
     }
 
 
     /**
      * Write an array of bytes to the buffer. Write exactly len bytes,
      * truncating if more than len, padding if less than len bytes are
      * available.
      * 
      * @param byteBuffer
      * @param currentClientAddress
      */
     private void writeBytes( ByteBuffer byteBuffer, byte[] bytes, int len )
     {
         if ( null == bytes )
         {
             bytes = new byte[]
                 {};
         }
 
         byteBuffer.put( bytes, 0, Math.min( len, bytes.length ) );
 
         // pad as necessary
         int remain = len - bytes.length;
 
         while ( remain-- > 0 )
         {
             byteBuffer.put( ( byte ) 0 );
         }
     }
 
     private static final byte[] VENDOR_MAGIC_COOKIE =
         { ( byte ) 99, ( byte ) 130, ( byte ) 83, ( byte ) 99 };
 
 
     public void encodeOptions( OptionsField options, ByteBuffer message )
     {
         message.put( VENDOR_MAGIC_COOKIE );
 
         for ( Iterator i = options.iterator(); i.hasNext(); )
         {
             DhcpOption/../../../../org/apache/directory/server/dhcp/options/DhcpOption.html#DhcpOption">DhcpOption option = ( DhcpOption ) i.next();
             option.writeTo( message );
         }
 
         // add end option
         message.put( ( byte ) 0xff );
     }
 }