/*
    *  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.protocol;
  
  
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  
  import org.apache.directory.server.dhcp.messages.DhcpMessage;
  import org.apache.directory.server.dhcp.messages.MessageType;
  import org.apache.directory.server.dhcp.service.DhcpService;
  import org.apache.mina.core.service.IoHandlerAdapter;
  import org.apache.mina.core.session.IdleStatus;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.filter.codec.ProtocolCodecFilter;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Implementation of a DHCP protocol handler which delegates the work of
   * generating replys to a DhcpService implementation.
   * 
   * @see org.apache.directory.server.dhcp.service.DhcpService
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class DhcpProtocolHandler extends IoHandlerAdapter
  {
      private static final Logger LOG = LoggerFactory.getLogger( DhcpProtocolHandler.class );
  
      /**
       * Default DHCP client port
       */
      public static final int CLIENT_PORT = 68;
  
      /**
       * Default DHCP server port
       */
      public static final int SERVER_PORT = 67;
  
      /**
       * The DHCP service implementation. The implementation is supposed to be
       * thread-safe.
       */
      private final DhcpService dhcpService;
  
  
      /**
       * 
       */
      public DhcpProtocolHandler( DhcpService service )
      {
          this.dhcpService = service;
      }
  
  
      @Override
      public void sessionCreated( IoSession session ) throws Exception
      {
          LOG.debug( "{} CREATED", session.getLocalAddress() );
          session.getFilterChain().addFirst( "codec",
              new ProtocolCodecFilter( new DhcpProtocolCodecFactory() ) );
      }
  
  
      @Override
      public void sessionOpened( IoSession session )
      {
          LOG.debug( "{} -> {} OPENED", session.getRemoteAddress(), session
              .getLocalAddress() );
      }
  
  
      @Override
      public void sessionClosed( IoSession session )
      {
          LOG.debug( "{} -> {} CLOSED", session.getRemoteAddress(), session
              .getLocalAddress() );
      }
  
  
     @Override
     public void sessionIdle( IoSession session, IdleStatus status )
     {
         // ignore
     }
 
 
     @Override
     public void exceptionCaught( IoSession session, Throwable cause )
     {
         LOG.error( "EXCEPTION CAUGHT ", cause );
         cause.printStackTrace( System.out );
 
         session.closeNow();
     }
 
 
     @Override
     public void messageReceived( IoSession session, Object message )
         throws Exception
     {
         if ( LOG.isDebugEnabled() )
         {
             LOG.debug( "{} -> {} RCVD: {} ", message, session.getRemoteAddress(),
                 session.getLocalAddress() );
         }
 
         final DhcpMessage./../../../org/apache/directory/server/dhcp/messages/DhcpMessage.html#DhcpMessage">DhcpMessage request = ( DhcpMessage ) message;
 
         final DhcpMessage reply = dhcpService.getReplyFor(
             ( InetSocketAddress ) session.getServiceAddress(),
             ( InetSocketAddress ) session.getRemoteAddress(), request );
 
         if ( null != reply )
         {
             final InetSocketAddress isa = determineMessageDestination( request, reply );
             session.write( reply, isa );
         }
     }
 
 
     /**
      * Determine where to send the message: <br>
      * If the 'giaddr' field in a DHCP message from a client is non-zero, the
      * server sends any return messages to the 'DHCP server' port on the BOOTP
      * relay agent whose address appears in 'giaddr'. If the 'giaddr' field is
      * zero and the 'ciaddr' field is nonzero, then the server unicasts DHCPOFFER
      * and DHCPACK messages to the address in 'ciaddr'. If 'giaddr' is zero and
      * 'ciaddr' is zero, and the broadcast bit is set, then the server broadcasts
      * DHCPOFFER and DHCPACK messages to 0xffffffff. If the broadcast bit is not
      * set and 'giaddr' is zero and 'ciaddr' is zero, then the server unicasts
      * DHCPOFFER and DHCPACK messages to the client's hardware address and
      * 'yiaddr' address. In all cases, when 'giaddr' is zero, the server
      * broadcasts any DHCPNAK messages to 0xffffffff.
      * 
      * @param request
      * @param reply
      * @return
      */
     //This will suppress PMD.AvoidUsingHardCodedIP warnings in this class
     @SuppressWarnings("PMD.AvoidUsingHardCodedIP")
     private InetSocketAddress determineMessageDestination( DhcpMessage request,
         DhcpMessage reply )
     {
 
         final MessageType mt = reply.getMessageType();
 
         if ( !isNullAddress( request.getRelayAgentAddress() ) )
         {
             // send to agent, if received via agent.
             return new InetSocketAddress( request.getRelayAgentAddress(), SERVER_PORT );
         }
         else if ( null != mt && mt == MessageType.DHCPNAK )
         {
             // force broadcast for DHCPNAKs
             return new InetSocketAddress( "255.255.255.255", 68 );
         }
         else
         {
             // not a NAK...
             if ( !isNullAddress( request.getCurrentClientAddress() ) )
             {
                 // have a current address? unicast to it.
                 return new InetSocketAddress( request.getCurrentClientAddress(),
                     CLIENT_PORT );
             }
             else
             {
                 return new InetSocketAddress( "255.255.255.255", 68 );
             }
         }
     }
 
 
     /**
      * Determine, whether the given address ist actually the null address
      * "0.0.0.0".
      * 
      * @param relayAgentAddress
      * @return
      */
     private boolean isNullAddress( InetAddress addr )
     {
         final byte[] a = addr.getAddress();
 
         for ( int i = 0; i < a.length; i++ )
         {
             if ( a[i] != 0 )
             {
                 return false;
             }
         }
 
         return true;
     }
 
 
     @Override
     public void messageSent( IoSession session, Object message )
     {
         if ( LOG.isDebugEnabled() )
         {
             LOG.debug( "{} -> {} SENT: ", message, session.getRemoteAddress(),
                 session.getLocalAddress() );
         }
     }
 
     
     @Override
     public void inputClosed( IoSession session )
     {
     }
 }