/***********************************************************************
 * Software License Agreement (BSD License)
 *
 * Copyright 2008-2010  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2010  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR 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.
 *************************************************************************/


#ifndef FLANN_MPI_HPP_
#define FLANN_MPI_HPP_

#include <boost/mpi.hpp>
#include <boost/serialization/array.hpp>
#include <flann/flann.hpp>
#include <flann/io/hdf5.h>

namespace flann
{
namespace mpi {

template<typename DistanceType>
struct SearchResults {
    flann::Matrix<int> indices;
    flann::Matrix<DistanceType> dists;

    template<typename Archive>
    void serialize(Archive& ar, const unsigned int version) {
        ar & indices.rows;
        ar & indices.cols;
        if (Archive::is_loading::value) {
            indices.data = new int[indices.rows*indices.cols];
        }
        ar & boost::serialization::make_array(indices.data, indices.rows*indices.cols);
        if (Archive::is_saving::value) {
            indices.free();
        }
        ar & dists.rows;
        ar & dists.cols;
        if (Archive::is_loading::value) {
            dists.data = new DistanceType[dists.rows*dists.cols];
        }
        ar & boost::serialization::make_array(dists.data, dists.rows*dists.cols);
        if (Archive::is_saving::value) {
            dists.free();
        }
    }
};

template<typename DistanceType>
struct ResultsMerger {
    SearchResults<DistanceType> operator()(SearchResults<DistanceType> a, SearchResults<DistanceType> b) {
        SearchResults<DistanceType> results;
        results.indices.rows = a.indices.rows;
        results.indices.cols = a.indices.cols;
        results.indices.data = new int[results.indices.rows*results.indices.cols];
        results.dists.rows = a.dists.rows;
        results.dists.cols = a.dists.cols;
        results.dists.data = new DistanceType[results.dists.rows*results.dists.cols];


        for (size_t i = 0;i < results.dists.rows;++i) {
            size_t idx = 0;
            size_t a_idx = 0;
            size_t b_idx = 0;
            while (idx < results.dists.cols) {
                if (a.dists[i][a_idx] <= b.dists[i][b_idx]) {
                    results.dists[i][idx] = a.dists[i][a_idx];
                    results.indices[i][idx] = a.indices[i][a_idx];
                    idx++;
                    a_idx++;
                }
                else {
                    results.dists[i][idx] = b.dists[i][b_idx];
                    results.indices[i][idx] = b.indices[i][b_idx];
                    idx++;
                    b_idx++;
                }
            }
        }

        a.indices.free();
        a.dists.free();
        b.indices.free();
        b.dists.free();
        return results;
    }
};



template<typename Distance>
class Index
{
    typedef typename Distance::ElementType ElementType;
    typedef typename Distance::ResultType DistanceType;

    flann::Index<Distance>* flann_index;
    flann::Matrix<ElementType> dataset;
    int size_;
    int offset_;

public:
    Index(const std::string& file_name,
          const std::string& dataset_name,
          const IndexParams& params);

    ~Index();

    void buildIndex() {
        flann_index->buildIndex();
    }

    void knnSearch(const flann::Matrix<ElementType>& queries,
                   flann::Matrix<int>& indices,
                   flann::Matrix<DistanceType>& dists,
                   int knn, const
                   SearchParams& params);

    int radiusSearch(const flann::Matrix<ElementType>& query,
                     flann::Matrix<int>& indices,
                     flann::Matrix<DistanceType>& dists,
                     float radius,
                     const SearchParams& params);

// void save(std::string filename);

    int veclen() const {
        return flann_index->veclen();
    }

    int size() const {
        return size_;
    }

    const IndexParams* getIndexParameters() {
        return flann_index->getParameters();
    }
};


template<typename Distance>
Index<Distance>::Index(const std::string& file_name, const std::string& dataset_name, const IndexParams& params)
{
    boost::mpi::communicator world;
    flann_algorithm_t index_type = params.getIndexType();
    if (index_type == SAVED) {
        throw FLANNException("Saving/loading of MPI indexes is not currently supported.");
    }
    flann::mpi::load_from_file(dataset, file_name, dataset_name);
    flann_index = new flann::Index<Distance>(dataset, params);

    std::vector<int> sizes;
    // get the sizes of all MPI indices
    all_gather(world, flann_index->size(), sizes);
    size_ = 0;
    offset_ = 0;
    for (size_t i = 0;i < sizes.size();++i) {
        if (i < world.rank()) offset_ += sizes[i];
        size_ += sizes[i];
    }
}

template<typename Distance>
Index<Distance>::~Index()
{
    delete flann_index;
    dataset.free();
}

template<typename Distance>
void Index<Distance>::knnSearch(const flann::Matrix<ElementType>& queries, flann::Matrix<int>& indices, flann::Matrix<DistanceType>& dists, int knn, const SearchParams& params)
{
    boost::mpi::communicator world;
    flann::Matrix<int> local_indices(new int[queries.rows*knn], queries.rows, knn);
    flann::Matrix<ElementType> local_dists(new ElementType[queries.rows*knn], queries.rows, knn);

    flann_index->knnSearch(queries, local_indices, local_dists, knn, params);
    for (size_t i = 0;i < local_indices.rows;++i) {
        for (size_t j = 0;j < local_indices.cols;++j) {
            local_indices[i][j] += offset_;
        }
    }
    SearchResults<DistanceType> local_results;
    local_results.indices = local_indices;
    local_results.dists = local_dists;
    SearchResults<DistanceType> results;

    // perform MPI reduce
    reduce(world, local_results, results, ResultsMerger<DistanceType>(), 0);

    if (world.rank() == 0) {
        for (int i = 0;i < results.indices.rows;++i) {
            for (int j = 0;j < results.indices.cols;++j) {
                indices[i][j] = results.indices[i][j];
                dists[i][j] = results.dists[i][j];
            }
        }
        results.indices.free();
        results.dists.free();
    }
}

template<typename Distance>
int Index<Distance>::radiusSearch(const flann::Matrix<ElementType>& query, flann::Matrix<int>& indices, flann::Matrix<DistanceType>& dists, float radius, const SearchParams& params)
{
    boost::mpi::communicator world;
    flann::Matrix<int> local_indices(new int[indices.rows*indices.cols], indices.rows, indices.cols);
    flann::Matrix<DistanceType> local_dists(new DistanceType[dists.rows*dists.cols], dists.rows, dists.cols);

    flann_index->radiusSearch(query, local_indices, local_dists, radius, params);
    for (size_t i = 0;i < local_indices.rows;++i) {
        for (size_t j = 0;j < local_indices.cols;++j) {
            local_indices[i][j] += offset_;
        }
    }
    SearchResults<DistanceType> local_results;
    local_results.indices = local_indices;
    local_results.dists = local_dists;
    SearchResults<DistanceType> results;

    // perform MPI reduce
    reduce(world, local_results, results, ResultsMerger<DistanceType>(), 0);

    if (world.rank() == 0) {
        for (int i = 0;i < std::min(results.indices.rows, indices.rows);++i) {
            for (int j = 0;j < std::min(results.indices.cols, indices.cols);++j) {
                indices[i][j] = results.indices[i][j];
                dists[i][j] = results.dists[i][j];
            }
        }
        results.indices.free();
        results.dists.free();
    }
    return 0;
}

}
} //namespace flann::mpi

//namespace boost { namespace mpi {
//  template<>
//  struct is_commutative<flann::mpi::ResultsMerger, flann::mpi::SearchResults> : mpl::true_ { };
//} } // end namespace boost::mpi


#endif /* FLANN_MPI_HPP_ */