/*
  Copyright 2020 Equinor AS.

  This file is part of the Open Porous Media project (OPM).

  OPM 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.

  OPM 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 OPM.  If not, see <http://www.gnu.org/licenses/>.
*/
/*!
 * \file FieldPropsDatahandle.hpp
 * \brief File containing a data handle for communicating the FieldProperties
 *
 * \author Markus Blatt, OPM-OP AS
 */

#ifndef PROPS_CENTROIDS_DATAHANDLE_HPP
#define PROPS_CENTROIDS_DATAHANDLE_HPP

#if HAVE_MPI
#include <opm/simulators/utils/ParallelEclipseState.hpp>
#include <opm/simulators/utils/ParallelRestart.hpp>
#include <dune/grid/common/datahandleif.hh>
#include <dune/grid/common/mcmgmapper.hh>
#include <dune/grid/common/partitionset.hh>
#include <dune/common/parallel/mpihelper.hh>
#include <unordered_map>
#include <iostream>

namespace Opm
{

/*!
 * \brief A Data handle to communicate the field properties and cell centroids during load balance.
 * \tparam Grid The type of grid where the load balancing is happening.
 * \todo Maybe specialize this for CpGrid to save some space, later.
 */
template<class Grid>
class PropsCentroidsDataHandle
    : public Dune::CommDataHandleIF< PropsCentroidsDataHandle<Grid>, double>
{
public:
    //! \brief the data type we send (ints are converted to double)
    using DataType = double;

    //! \brief Constructor
    //! \param grid The grid where the loadbalancing is happening.
    //! \param globalProps The field properties of the global grid
    //! \param distributedProps The distributed field properties
    //! \param eclGridOnRoot A pointer to eclipse grid on rank zero,
    //!                      nullptr otherwise.
    //! \param centroids Array to store the centroids in upon destruction
    //!                  of the object.
    //! \param cartMapper The cartesian index mapper of the grid.
    PropsCentroidsDataHandle(const Grid& grid, ParallelEclipseState& eclState,
                             const EclipseGrid* eclGridOnRoot,
                             std::vector<double>& centroids,
                             const typename Dune::CartesianIndexMapper<Grid>& cartMapper)
        : m_grid(grid), m_distributed_fieldProps(eclState.m_fieldProps),
          m_centroids(centroids)
    {
        // Scatter the keys
        const auto& comm = Dune::MPIHelper::getCollectiveCommunication();
        if (comm.rank() == 0)
        {
            const auto& globalProps = eclState.globalFieldProps();
            m_intKeys = globalProps.keys<int>();
            m_doubleKeys = globalProps.keys<double>();
            std::size_t packSize = Mpi::packSize(m_intKeys, comm) +
                Mpi::packSize(m_doubleKeys,comm);
            std::vector<char> buffer(packSize);
            int position = 0;
            Mpi::pack(m_intKeys, buffer, position, comm);
            Mpi::pack(m_doubleKeys, buffer, position, comm);
            comm.broadcast(&position, 1, 0);
            comm.broadcast(buffer.data(), position, 0);

            // copy data to persistent map based on local id
            m_no_data = m_intKeys.size() + m_doubleKeys.size() +
                Grid::dimensionworld;
            const auto& idSet = m_grid.localIdSet();
            const auto& gridView = m_grid.levelGridView(0);
            using ElementMapper =
                Dune::MultipleCodimMultipleGeomTypeMapper<typename Grid::LevelGridView>;
            ElementMapper elemMapper(gridView, Dune::mcmgElementLayout());

            for( const auto &element : elements( gridView, Dune::Partitions::interiorBorder ) )
            {
                const auto& id = idSet.id(element);
                auto index = elemMapper.index(element);
                auto& data = elementData_[id];
                data.reserve(m_no_data);

                for (const auto& intKey : m_intKeys)
                    data.push_back(globalProps.get_int(intKey)[index]);

                for (const auto& doubleKey : m_doubleKeys)
                    data.push_back(globalProps.get_double(doubleKey)[index]);

                auto cartIndex = cartMapper.cartesianIndex(index);
                const auto& center = eclGridOnRoot->getCellCenter(cartIndex);
                for (int dim = 0; dim < Grid::dimensionworld; ++dim)
                    data.push_back(center[dim]);
            }
        }
        else
        {
            int bufferSize;
            comm.broadcast(&bufferSize, 1, 0);
            std::vector<char> buffer(bufferSize);
            comm.broadcast(buffer.data(), bufferSize, 0);
            int position{};
            Mpi::unpack(m_intKeys, buffer, position, comm);
            Mpi::unpack(m_doubleKeys, buffer, position, comm);
            m_no_data = m_intKeys.size() + m_doubleKeys.size() +
                Grid::dimensionworld;
        }
    }

    ~PropsCentroidsDataHandle()
    {
        // distributed grid is now correctly set up.
        for(const auto& intKey : m_intKeys)
            m_distributed_fieldProps.m_intProps[intKey].resize(m_grid.size(0));

        for(const auto& doubleKey : m_doubleKeys)
            m_distributed_fieldProps.m_doubleProps[doubleKey].resize(m_grid.size(0));

        m_centroids.resize(m_grid.size(0) * Grid::dimensionworld);

        // copy data for the persistent mao to the field properties
        const auto& idSet = m_grid.localIdSet();
        const auto& gridView = m_grid.levelGridView(0);
        using ElementMapper =
            Dune::MultipleCodimMultipleGeomTypeMapper<typename Grid::LevelGridView>;
        ElementMapper elemMapper(gridView, Dune::mcmgElementLayout());

        for( const auto &element : elements( gridView, Dune::Partitions::all ) )
        {
            std::size_t counter{};
            const auto& id = idSet.id(element);
            auto index = elemMapper.index(element);
            auto data = rcvdElementData_.find(id);
            assert(data != elementData_.end());

            for(const auto& intKey : m_intKeys)
                m_distributed_fieldProps.m_intProps[intKey][index] = static_cast<int>(data->second[counter++]);

            for(const auto& doubleKey : m_doubleKeys)
                m_distributed_fieldProps.m_doubleProps[doubleKey][index] = data->second[counter++];

            auto centroidIter = m_centroids.begin() + Grid::dimensionworld * index;
            auto centroidIterEnd = centroidIter + Grid::dimensionworld;
            for ( ; centroidIter != centroidIterEnd; ++centroidIter )
                *centroidIter = data->second[counter++];
        }
    }

    bool contains(int /* dim */, int codim)
    {
        return codim == 0;
    }

    bool fixedsize(int /* dim */, int /* codim */)
    {
        return true;
    }
    bool fixedSize(int /* dim */, int /* codim */)
    {
        return true;
    }

    template<class EntityType>
    std::size_t size(const EntityType /* entity */)
    {
        return m_no_data;
    }

    template<class BufferType, class EntityType>
    void gather(BufferType& buffer, const EntityType& e) const
    {
        auto iter = elementData_.find(m_grid.localIdSet().id(e));
        assert(iter != elementData_.end());
        for(const auto& data : iter->second)
            buffer.write(data);
    }

    template<class BufferType, class EntityType>
    void scatter(BufferType& buffer, const EntityType& e, std::size_t n)
    {
        assert(n == m_no_data);
        auto& array = rcvdElementData_[m_grid.localIdSet().id(e)];
        array.resize(n);
        for(auto& data: array)
        {
            buffer.read(data);
        }
    }

private:
    using LocalIdSet = typename Grid::LocalIdSet;
    const Grid& m_grid;
    //! \brief The distributed field properties for receiving
    ParallelFieldPropsManager& m_distributed_fieldProps;
    //! \brief The names of the keys of the integer fields.
    std::vector<std::string> m_intKeys;
    //! \brief The names of the keys of the double fields.
    std::vector<std::string> m_doubleKeys;
    /// \brief The data per element as a vector mapped from the local id.
    std::unordered_map<typename LocalIdSet::IdType, std::vector<double> > elementData_;
    /*! \brief The data received per element as a vector mapped from the local id.
     *
     * Needed because CpGrid is in violation of the requirement that local ids
     * need to be persistent across grid modifications
     */
    std::unordered_map<typename LocalIdSet::IdType, std::vector<double> > rcvdElementData_;
    /// \brief The cell centroids of the distributed grid.
    std::vector<double>& m_centroids;
    /// \brief The amount of data to send for each element
    std::size_t m_no_data;
};

} // end namespace Opm
#endif // HAVE_MPI
#endif // PROPS_CENTROIDS_DATAHANDLE_HPP