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

"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.pastry.socket;

import java.io.*;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;

import rice.environment.Environment;
import rice.environment.logging.Logger;
import rice.pastry.*;

/**
 * Class which serves as an "reader" for messages sent across the wire via the
 * Pastry socket protocol. This class builds up an object as it is being sent
 * across the wire, and when it has recieved all of an object, it informs the
 * WirePastryNode by using the recieveMessage(msg) method. The
 * SocketChannelReader is designed to be reused, to read objects continiously
 * off of one stream.
 *
 * @version $Id: SocketChannelReader.java,v 1.5 2004/03/08 19:53:57 amislove Exp
 *      $
 * @author Alan Mislove
 */
public class SocketChannelReader {
  
  // the pastry node
  private SocketPastryNode spn;

  // the cached size of the message
  private int objectSize = -1;

  // for reading from the socket
  private ByteBuffer buffer;

  // for reading the size of the object (header)
  private ByteBuffer sizeBuffer;
  
  // the address this reader is reading from
  protected SourceRoute path;
  
  // the environment to use
  protected Environment environment;

  protected Logger logger;
  
  /**
   * Constructor which creates this SocketChannelReader and the WirePastryNode.
   * Once the reader has completely read a message, it deserializes the message
   * and hands it off to the pastry node.
   *
   * @param spn The PastryNode the SocketChannelReader serves.
   */
  public SocketChannelReader(SocketPastryNode spn, SourceRoute path) {
    this(spn.getEnvironment(), path);
    this.spn = spn;
  }
  
  public SocketChannelReader(Environment env, SourceRoute path) {
    this.environment = env;
    this.path = path;
    this.logger = env.getLogManager().getLogger(SocketChannelReader.class, null);
    sizeBuffer = ByteBuffer.allocateDirect(4);
  }
  
  /**
   * Sets this reader's path
   *
   * @param path The path this reader is using
   */
  protected void setPath(SourceRoute path) {
    this.path = path;
  }
  
  /**
   * Method which is to be called when there is data available on the specified
   * SocketChannel. The data is read in, and if the object is done being read,
   * it is parsed.
   *
   * @param sc The channel to read from.
   * @return The object read off the stream, or null if no object has been
   *      completely read yet
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public SocketBuffer read(final SocketChannel sc) throws IOException {
    if (objectSize == -1) {
      int read = sc.read(sizeBuffer);

      // implies that the channel is closed
      if (read == -1) 
        throw new IOException("Error on read - the channel has been closed.");

      if (sizeBuffer.remaining() == 0)
        initializeObjectBuffer(sc);
      else
        return null;
    }

    if (objectSize != -1) {
      int read = sc.read(buffer);

      if (logger.level <= Logger.FINEST) logger.log(
          "(R) Read " + read + " bytes of object... " + buffer.remaining()+" remaining.");

      // implies that the channel is closed
      if (read == -1) 
        throw new ClosedChannelException();

      if (buffer.remaining() == 0) {
        buffer.flip();

        final byte[] objectArray = new byte[objectSize];
        buffer.get(objectArray);
        final int size = objectSize + 8;
        reset();
        
        // TODO pool
        SocketBuffer obj = new SocketBuffer(objectArray,spn);
        
        if (logger.level <= Logger.FINER) logger.log(
            "(R) Deserialized bytes into object " + obj);
        
        if (spn != null)
          spn.broadcastReceivedListeners(obj.getInnermostAddress(),obj.getInnermostType(), (path == null ? (InetSocketAddress) sc.socket().getRemoteSocketAddress() : path.getLastHop().getAddress(((SocketNodeHandle)spn.getLocalHandle()).eaddress)), size, NetworkListener.TYPE_TCP);

        if (logger.level <= Logger.FINER) logger.log("COUNT: Read message(5) " + obj + " of size " + size + " from " + path);
        
        return obj;        
      }
    }

    return null;
  }
  
  /**
   * Resets this input stream so that it is ready to read another object off of
   * the queue.
   */
  public void reset() {
    objectSize = -1;

    buffer = null;
    sizeBuffer.clear();
  }

  
  byte[] sizeArray = new byte[4];
  ByteArrayInputStream bais = new ByteArrayInputStream(sizeArray);
  DataInputStream dis = new DataInputStream(bais);
  
  /**
   * Private method which is designed to read the header of the incoming
   * message, and prepare the buffer for the object appropriately.
   *
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  private void initializeObjectBuffer(SocketChannel sc) throws IOException {
    // flip the buffer
    sizeBuffer.flip();

    // allocate space for the header
    sizeBuffer.get(sizeArray, 0, sizeArray.length);
    
    // read the object size
    dis.reset();
    bais.reset();

    
//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//    +               Payload Length                                  +
//    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    
    objectSize = dis.readInt();
    
    if (objectSize <= 0) 
      throw new IOException("Found message of improper number of bytes - " + objectSize + " bytes");
    
    if (logger.level <= Logger.FINER) logger.log(
        "(R) Found object of " + objectSize + " bytes from "+sc.socket().getRemoteSocketAddress());
    
    // allocate the appropriate space
    try {
      buffer = ByteBuffer.allocateDirect(objectSize);
    } catch (OutOfMemoryError oome) {
      if (logger.level <= Logger.SEVERE) logger.logException(
          "SCR ran out of memory allocating an object of size "+objectSize+" from "+path, oome);
      throw oome; 
    }
  }
}
