#ifndef EIGEN3_HDF5_SPARSE_HPP_
#define EIGEN3_HDF5_SPARSE_HPP_

#include <vector>

#include <eigen3-hdf5.hpp>
#include <Eigen/Sparse>

#include <H5public.h>

#if H5_VERSION_LE( 1, 10, 0 )
// typedef  H5::H5Location Eigen3Hdf5_H5Location;
// typedef  H5::CommonFG Eigen3Hdf5_H5CommonFG;
#define Eigen3Hdf5_H5Location H5::H5Location
#define Eigen3Hdf5_H5CommonFG H5::CommonFG
#else
// typedef H5::H5Object Eigen3Hdf5_H5Location;
// typedef H5::H5Object Eigen3Hdf5_H5CommonFG;
#define Eigen3Hdf5_H5Location H5::H5Object
#define Eigen3Hdf5_H5CommonFG H5::H5Object
#endif

namespace Eigen3HDF5
{

template <typename Scalar>
class MyTriplet : public Eigen::Triplet<Scalar>
{
public:
	MyTriplet ( void )
		: Eigen::Triplet<Scalar>()
	{
	}

	MyTriplet ( const unsigned int& i, const unsigned int& j, const Scalar& v = Scalar(0) )
		: Eigen::Triplet<Scalar>( i, j, v )
	{
	}


	static std::size_t offsetof_row( void ) { return( offsetof( MyTriplet<Scalar>, m_row ) ); }


	static std::size_t offsetof_col( void ) { return( offsetof( MyTriplet<Scalar>, m_col ) ); }


	static std::size_t offsetof_value( void ) { return( offsetof( MyTriplet<Scalar>, m_value ) ); }
};

template <typename T>
class SparseH5Type : public H5::CompType
{
public:
	SparseH5Type ( void )
		: CompType( sizeof( MyTriplet<T> ) )
	{
		const H5::DataType* const datatypei = DatatypeSpecialization<unsigned int>::get();
		const H5::DataType* const datatype = DatatypeSpecialization<T>::get();

		assert( datatype->getSize() == sizeof( T ) );
		this->insertMember( std::string( "r" ), MyTriplet<T>::offsetof_row(), *datatypei );
		this->insertMember( std::string( "c" ), MyTriplet<T>::offsetof_col(), *datatypei );
		this->insertMember( std::string( "v" ), MyTriplet<T>::offsetof_value(), *datatype );
		this->pack();
	}


	static const SparseH5Type<T>* get_singleton( void )
	{
		// NOTE: constructing this could be a race condition
		static SparseH5Type<T> singleton;

		return( &singleton );
	}
};


template <typename SparseMatrixType>
void save_sparse( Eigen3Hdf5_H5CommonFG& h5group, const std::string& name, const SparseMatrixType& mat, const H5::DSetCreatPropList& plist = H5::DSetCreatPropList::DEFAULT )
{
	typedef typename SparseMatrixType::Scalar Scalar;
	// save the actual sparse matrix
	std::vector<MyTriplet<Scalar> > data;
	data.reserve( mat.nonZeros() );
	for ( int k = 0; k < mat.outerSize(); ++k )
	{
		for ( typename SparseMatrixType::InnerIterator it( mat, k ); it; ++it )
		{
			if ( it.value() != Scalar( 0 ) )
			{
				data.push_back( MyTriplet<Scalar>( it.row(), it.col(), it.value() ) );
			}
		}
	}
	const hsize_t nnz = data.size();
	const H5::DataSpace dataspace( 1, &nnz );
	const H5::DataType* const datatype = SparseH5Type<Scalar>::get_singleton();
	H5::DataSet dataset = h5group.createDataSet( name, *datatype, dataspace, plist );
	dataset.write( data.data(), *datatype );
	// save the matrix's shape as an attribute
	Eigen::Matrix<typename SparseMatrixType::Index, 2, 1> shape;
	shape( 0 ) = mat.rows();
	shape( 1 ) = mat.cols();
	save_attribute( dataset, "shape", shape );
}


template <typename SparseMatrixType>
void load_sparse( const Eigen3Hdf5_H5CommonFG& h5group, const std::string& name, SparseMatrixType& mat )
{
	typedef typename SparseMatrixType::Scalar Scalar;
	const H5::DataSet dataset = h5group.openDataSet( name );
	const H5::DataSpace dataspace = dataset.getSpace();
	const std::size_t ndims = dataspace.getSimpleExtentNdims();
	if ( ndims != 1 )
	{
		throw std::runtime_error( "HDF5 array has incorrect number of dimensions to represent a sparse matrix." );
	}
	Eigen::Matrix<typename SparseMatrixType::Index, 2, 1> shape;
	load_attribute( dataset, "shape", shape );
	hsize_t nnz;
	dataspace.getSimpleExtentDims( &nnz ); // assumes ndims == 1 in the data representation
	const H5::DataType* const datatype = SparseH5Type<Scalar>::get_singleton();
	std::vector<MyTriplet<Scalar> > data( nnz );
	dataset.read( data.data(), *datatype, dataspace );
	mat.resize( shape( 0 ), shape( 1 ) ); // NOTE: this also clears all existing values
	mat.setFromTriplets( data.begin(), data.end() );
}

} // namespace Eigen3HDF5

#endif