//======================================================================================================================
//
//  This file is part of waLBerla. waLBerla is free software: you can 
//  redistribute it and/or modify it under the terms of the GNU General Public
//  License as published by the Free Software Foundation, either version 3 of 
//  the License, or (at your option) any later version.
//  
//  waLBerla is distributed in the hope that it will be useful, but WITHOUT 
//  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
//  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License 
//  for more details.
//  
//  You should have received a copy of the GNU General Public License along
//  with waLBerla (see COPYING.txt). If not, see <http://www.gnu.org/licenses/>.
//
//! \file MPITextFile.cpp
//! \ingroup core
//! \author Christian Godenschwager <christian.godenschwager@fau.de>
//
//======================================================================================================================

#include "MPITextFile.h"

#include "core/mpi/Reduce.h"

#include <fstream>

namespace walberla {
namespace mpi {


//======================================================================================================================
/*!
 *  \brief Writes file using MPI IO with each process providing a part of it
 *
 *  This method has the be called collectively by all the processes in comm. The file will be assembled in the order of
 *  the ranks of the calling processes.
 *
 *  \param filename          The name of the file to be written
 *  \param processLocalPart  The part of the file belonging to the calling process (size may differ among processes)
 */
//======================================================================================================================
void writeMPITextFile( const std::string & filename, const std::string & processLocalPart, 
                       const MPI_Comm comm /*= MPI_COMM_WORLD*/ )
{
   WALBERLA_NON_MPI_SECTION()
   {
      std::ofstream ofs( filename.c_str() );
      ofs << processLocalPart;
      ofs.close();
   }

   WALBERLA_MPI_SECTION()
   {
      int rank, numProcesses;
      MPI_Comm_rank( comm, &rank         );
      MPI_Comm_size( comm, &numProcesses );

      if( processLocalPart.size() > numeric_cast<std::string::size_type>( std::numeric_limits<int>::max() ) )
         WALBERLA_ABORT( "writeMPITextFile does not support more than " << std::numeric_limits<int>::max() << " characters per process!" );

      MPI_File mpiFile;
      int result = MPI_SUCCESS;
      result = MPI_File_open( comm, const_cast<char*>( filename.c_str() ), MPI_MODE_WRONLY | MPI_MODE_CREATE, MPI_INFO_NULL, 
                              &mpiFile );
      if( result != MPI_SUCCESS )
         WALBERLA_ABORT( "Error while opening file \"" << filename << "\" for writing. MPI Error is \"" << MPIManager::instance()->getMPIErrorString( result ) << "\"" );

      const MPI_Offset filesize = numeric_cast<MPI_Offset>( allReduce( processLocalPart.size(), mpi::SUM, comm ) );
      
      size_t exscanResult;
      size_t input = processLocalPart.size();
      MPI_Exscan( &input, &exscanResult, 1, MPITrait<size_t>::type(), MPI_SUM, comm );
      if( rank == 0 )
         exscanResult = size_t( 0 );

      const MPI_Offset offset = numeric_cast<MPI_Offset>( exscanResult );
      
      MPI_File_set_size( mpiFile, filesize );

      MPI_Datatype arraytype;
      MPI_Type_contiguous( int_c( processLocalPart.size() ), MPITrait<char>::type(), &arraytype);
      MPI_Type_commit( &arraytype );
      
      result = MPI_File_set_view( mpiFile, offset, MPITrait<char>::type(), arraytype, const_cast<char*>( "native" ),
                                  MPI_INFO_NULL );

      if( result != MPI_SUCCESS )
         WALBERLA_ABORT( "Internal MPI-IO error! MPI Error is \"" << MPIManager::instance()->getMPIErrorString( result ) << "\"" );

      result = MPI_File_write_all( mpiFile, const_cast<char*>( processLocalPart.c_str() ), int_c( processLocalPart.size() ),
                                   MPITrait<char>::type(), MPI_STATUS_IGNORE );

      if( result != MPI_SUCCESS )
         WALBERLA_ABORT( "Error while writing to file \"" << filename << "\". MPI Error is \"" << MPIManager::instance()->getMPIErrorString( result ) << "\"" );

      result = MPI_File_close( &mpiFile );

      if( result != MPI_SUCCESS )
         WALBERLA_ABORT( "Error while closing file \"" << filename << "\". MPI Error is \"" << MPIManager::instance()->getMPIErrorString( result ) << "\"" );

      MPI_Type_free( &arraytype );
   }
}

} // namespace mpi
} // namespace walberla