/*
 * IMPLEMENTATION DETAILS
 * 
 * All methods with buffers that can be direct or non direct have
 * a companion argument 'db' which is true if the buffer is direct.
 * 
 * Checking if a buffer is direct is faster in Java than C.
 */
package mpi;

import java.nio.*;
import static mpi.MPI.assertDirectBuffer;

/**
 * This class represents {@code MPI_Message}.
 */
public final class Message
{
// Auxiliary status. It's used to avoid creating status objects in the C side.
// In Java side it will be copied: new Status(status)
// It is necessary because calling java methods from C is very slow.
private final Status status = new Status();

protected long handle;
private static long NULL, NO_PROC;

static
{
    init();
}

private static native void init();

/**
 * Creates a {@code MPI_MESSAGE_NULL}.
 */
public Message()
{
    handle = NULL;
}

/**
 * Tests if the message is {@code MPI_MESSAGE_NULL}.
 * @return true if the message is {@code MPI_MESSAGE_NULL}.
 */
public boolean isNull()
{
    return handle == NULL;
}

/**
 * Tests if the message is {@code MPI_MESSAGE_NO_PROC}.
 * @return true if the message is {@code MPI_MESSAGE_NO_PROC}.
 */
public boolean isNoProc()
{
    return handle == NO_PROC;
}

/**
 * Java binding of {@code MPI_MPROBE}.
 * @param source rank of the source
 * @param tag    message tag
 * @param comm   communicator
 * @return status object
 * @throws MPIException 
 */
public Status mProbe(int source, int tag, Comm comm) throws MPIException
{
    MPI.check();
    Status stat = new Status();
    handle = mProbe(source, tag, comm.handle, stat);
    return stat;
}

private native long mProbe(int source, int tag, long comm, Status status)
        throws MPIException;

/**
 * Java binding of {@code MPI_IMPROBE}.
 * @param source rank of the source
 * @param tag    message tag
 * @param comm   communicator
 * @return status object if there is a message, {@code null} otherwise
 * @throws MPIException 
 */
public Status imProbe(int source, int tag, Comm comm) throws MPIException
{
    MPI.check();

    return imProbe(source, tag, comm.handle, status)
           ? new Status(status) : null;
}

private native boolean imProbe(int source, int tag, long comm, Status status)
        throws MPIException;

/**
 * Java binding of {@code MPI_MRECV}.
 * @param buf   receive buffer
 * @param count number of elements in receve buffer
 * @param type  datatype of each receive buffer element
 * @return status object
 */
public Status mRecv(Object buf, int count, Datatype type) throws MPIException
{
    MPI.check();
    int off = 0;
    boolean db = false;

    if(buf instanceof Buffer && !(db = ((Buffer)buf).isDirect()))
    {
        off = ((Buffer)buf).arrayOffset();
        buf = ((Buffer)buf).array();
    }

    Status stat = new Status();
    handle = mRecv(handle, buf,db,off,count, type.handle, type.baseType, stat);
    return stat;
}

private native long mRecv(
        long message, Object buf, boolean db, int offset, int count,
        long type, int baseType, Status status) throws MPIException;

/**
 * Java binding of {@code MPI_IMRECV}.
 * @param buf   receive buffer
 * @param count number of elements in receve buffer
 * @param type  datatype of each receive buffer element
 * @return request object
 * @throws MPIException 
 */
public Request imRecv(Buffer buf, int count, Datatype type)
    throws MPIException
{
    MPI.check();
    assertDirectBuffer(buf);
    return new Request(imRecv(handle, buf, count, type.handle));
}

private native long imRecv(long message, Object buf, int count, long type)
        throws MPIException;

} // Message