/*******************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate

Copyright 2002-2007, Rice University. Copyright 2006-2007, Max Planck Institute 
for Software Systems.  All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

- Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

- Neither the name of Rice  University (RICE), Max Planck Institute for Software 
Systems (MPI-SWS) nor the names of its contributors may be used to endorse or 
promote products derived from this software without specific prior written 
permission.

This software is provided by RICE, MPI-SWS and the contributors on an "as is" 
basis, without any representations or warranties of any kind, express or implied 
including, but not limited to, representations or warranties of 
non-infringement, merchantability or fitness for a particular purpose. In no 
event shall RICE, MPI-SWS or contributors be liable for any direct, indirect, 
incidental, special, exemplary, or consequential damages (including, but not 
limited to, procurement of substitute goods or services; loss of use, data, or 
profits; or business interruption) however caused and on any theory of 
liability, whether in contract, strict liability, or tort (including negligence
or otherwise) arising in any way out of the use of this software, even if 
advised of the possibility of such damage.

*******************************************************************************/ 

package rice.p2p.past.messaging;

import java.io.*;

import rice.*;
import rice.environment.Environment;
import rice.p2p.commonapi.*;
import rice.p2p.commonapi.rawserialization.*;
import rice.p2p.past.*;
import rice.p2p.util.rawserialization.*;

/**
 * @(#) ContinuationMessage.java
 *
 * This class the abstraction of a message used internally by Past which serves
 * as a continuation (for receiving the results of an operation).
 *
 * @version $Id: ContinuationMessage.java 3613 2007-02-15 14:45:14Z jstewart $
 *
 * @author Alan Mislove
 * @author Ansley Post
 * @author Peter Druschel
 */
public abstract class ContinuationMessage extends PastMessage implements Continuation {

  static final long serialVersionUID = 1321112527034107161L; 
  
  // the response data
  protected Object response;

  // the response exception, if one is thrown
  protected Exception exception;
  
  /**
    * Constructor which takes a unique integer Id, as well as the
   * data to be stored
   *
   * @param uid The unique id
   * @param source The source handle
   * @param dest The destination address
   */
  protected ContinuationMessage(int uid, NodeHandle source, Id dest) {
    super(uid, source, dest); 
  }

  /**
    * Method which builds a response for this message, using the provided
   * object as a result.
   *
   * @param o The object argument
   */
  public void receiveResult(Object o) {
    setResponse();
    response = o;
  }

  /**
    * Method which builds a response for this message, using the provided
   * exception, which was thrown
   *
   * @param e The exception argument
   */
  public void receiveException(Exception e) {
    setResponse();
//    System.out.println("ContinuationMessage.receiveException("+e+")");
//    e.printStackTrace();
    exception = e;
  }

  /**
    * Method by which this message is supposed to return it's response.
   *
   * @param c The continuation to return the reponse to.
   */
  public void returnResponse(Continuation c, Environment env, String instance) {
    if (exception == null)
      c.receiveResult(response);
    else
      c.receiveException(exception);
  }

  /**
   * Returns the response
   *
   * @return The response
   */
  public Object getResponse() {
    return response;
  }
  
  /**
   * No response or exception.
   */
  public static byte S_EMPTY = 0;
  /**
   * Subclass handled serialization.
   */
  public static byte S_SUB = 1; 
  /**
   * Java Serialized Response
   */
  public static byte S_JAVA_RESPONSE = 3;
  /**
   * Java Serialized Exception
   */
  public static byte S_JAVA_EXCEPTION = 2;
  
  
  /**
   * The serialization stategy is that usually the subtype will have an optimal
   * serialization strategy, but sometimes we will have to revert to java serialization
   * 
   * @param buf
   * @param endpoint
   * @throws IOException
   */
  public ContinuationMessage(InputBuffer buf, Endpoint endpoint) throws IOException {
    super(buf, endpoint); 
    serType = buf.readByte();
    if (serType > S_SUB) deserialize(buf, endpoint); // not empty, and not handled by the sub
  }
  
  /**
   * 
   * @param buf
   * @throws IOException
   */
  public void deserialize(InputBuffer buf, Endpoint endpoint) throws IOException {
    byte[] array = new byte[buf.readInt()];
    buf.read(array);
    ObjectInputStream ois = new JavaDeserializer(new ByteArrayInputStream(array), endpoint);
    Object content;     
    try {
      content = ois.readObject();
      if (serType == S_JAVA_RESPONSE) {
        response = content;
      } else {
        exception = (Exception)content; 
      }
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("Unknown class type in message - closing channel.", e);
    }          
  }

  /**
   * Deprecated to cause warnings.
   * 
   * use serialize(OutputBuffer buf, boolean javaSerialize)
   */
//  public void serialize(OutputBuffer buf) throws IOException {
//    throw new RuntimeException("Illegal call.  Must call serialize(OutputBuffer, boolean");
//  }
  
  public abstract void serialize(OutputBuffer buf) throws IOException;
  
  protected byte serType;
  
  /**
   * If you want this class to serialize itself, set javaSerialize to true,
   * otherwise, the subclass is expected to do an optimal serializatoin
   * 
   * @param buf
   * @param javaSerialize
   * @throws IOException
   */
  public void serialize(OutputBuffer buf, boolean javaSerialize) throws IOException {
//    System.out.println("ContinuationMessage<"+getClass().getName()+">.serialize("+javaSerialize+") resp:"+response+" exc:"+exception+" id:"+id+" src:"+source+" dst:"+dest);
    super.serialize(buf);
    
    serType = S_EMPTY;
    
    if (javaSerialize) {
      Object content = response;
      if (response != null) {
        serType = S_JAVA_RESPONSE;
      } else {
        serType = S_JAVA_EXCEPTION;
        content = exception;
      }
      
      if (content == null) {
        serType = S_EMPTY;
        buf.writeByte(serType);
      } else {      
//      if (true) throw new IOException("Test");
//        System.out.println("ContinuationMessage<"+getClass().getName()+">.serialize():"+serType+" "+response+" "+exception);
        try {
          buf.writeByte(serType);        
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          ObjectOutputStream oos = new ObjectOutputStream(baos);
          
          // write out object and find its length
          oos.writeObject(content);
          oos.close();
          
          byte[] temp = baos.toByteArray();
          buf.writeInt(temp.length);
          buf.write(temp, 0, temp.length);
        } catch (IOException ioe) {
          throw new JavaSerializationException(content, ioe);
        }
      }
    } else {
      buf.writeByte(S_SUB); 
    }
  }
}

