/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2024 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_UTIL_SPATIAL_INDEX_HPP
#define MAPNIK_UTIL_SPATIAL_INDEX_HPP

// mapnik
#include <mapnik/coord.hpp>
#include <mapnik/geometry/box2d.hpp>
#include <mapnik/query.hpp>
#include <mapnik/geom_util.hpp>
// stl
#include <type_traits>
#include <cstring>

using mapnik::box2d;
using mapnik::query;

namespace mapnik {
namespace util {

struct index_record
{
    std::uint64_t off;
    std::uint64_t size;
    box2d<float> box;
};

template<typename InputStream>
bool check_spatial_index(InputStream& in)
{
    char header[17]; // mapnik-index
    std::memset(header, 0, 17);
    in.read(header, 16);
    return (std::strncmp(header, "mapnik-index", 12) == 0);
}

template<typename Value, typename Filter, typename InputStream, typename BBox = box2d<double>>
class spatial_index
{
    using bbox_type = BBox;

  public:
    static void query(Filter const& filter, InputStream& in, std::vector<Value>& pos);
    static bbox_type bounding_box(InputStream& in);
    static void query_first_n(Filter const& filter, InputStream& in, std::vector<Value>& pos, std::size_t count);

  private:
    spatial_index();
    ~spatial_index();
    spatial_index(spatial_index const&);
    spatial_index& operator=(spatial_index const&);
    static int read_ndr_integer(InputStream& in);
    static void read_envelope(InputStream& in, bbox_type& envelope);
    static void query_node(Filter const& filter, InputStream& in, std::vector<Value>& results);
    static void
      query_first_n_impl(Filter const& filter, InputStream& in, std::vector<Value>& results, std::size_t count);
};

template<typename Value, typename Filter, typename InputStream, typename BBox>
BBox spatial_index<Value, Filter, InputStream, BBox>::bounding_box(InputStream& in)
{
    static_assert(std::is_standard_layout<Value>::value, "Values stored in quad-tree must be standard layout type");
    if (!check_spatial_index(in))
        throw std::runtime_error("Invalid index file (regenerate with shapeindex)");
    in.seekg(16 + 4, std::ios::beg);
    typename spatial_index<Value, Filter, InputStream, BBox>::bbox_type box;
    read_envelope(in, box);
    in.seekg(0, std::ios::beg);
    return box;
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
void spatial_index<Value, Filter, InputStream, BBox>::query(Filter const& filter,
                                                            InputStream& in,
                                                            std::vector<Value>& results)
{
    static_assert(std::is_standard_layout<Value>::value, "Values stored in quad-tree must be standard layout type");
    if (!check_spatial_index(in))
        throw std::runtime_error("Invalid index file (regenerate with shapeindex)");
    in.seekg(16, std::ios::beg);
    query_node(filter, in, results);
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
void spatial_index<Value, Filter, InputStream, BBox>::query_node(Filter const& filter,
                                                                 InputStream& in,
                                                                 std::vector<Value>& results)
{
    int offset = read_ndr_integer(in);
    typename spatial_index<Value, Filter, InputStream, BBox>::bbox_type node_ext;
    read_envelope(in, node_ext);
    int num_shapes = read_ndr_integer(in);
    if (!filter.pass(node_ext))
    {
        in.seekg(offset + num_shapes * sizeof(Value) + 4, std::ios::cur);
        return;
    }

    for (int i = 0; i < num_shapes; ++i)
    {
        Value item;
        in.read(reinterpret_cast<char*>(&item), sizeof(Value));
        results.push_back(std::move(item));
    }

    int children = read_ndr_integer(in);
    for (int j = 0; j < children; ++j)
    {
        query_node(filter, in, results);
    }
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
void spatial_index<Value, Filter, InputStream, BBox>::query_first_n(Filter const& filter,
                                                                    InputStream& in,
                                                                    std::vector<Value>& results,
                                                                    std::size_t count)
{
    static_assert(std::is_standard_layout<Value>::value, "Values stored in quad-tree must be standard layout type");
    if (!check_spatial_index(in))
        throw std::runtime_error("Invalid index file (regenerate with shapeindex)");
    in.seekg(16, std::ios::beg);
    query_first_n_impl(filter, in, results, count);
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
void spatial_index<Value, Filter, InputStream, BBox>::query_first_n_impl(Filter const& filter,
                                                                         InputStream& in,
                                                                         std::vector<Value>& results,
                                                                         std::size_t count)
{
    if (results.size() == count)
        return;
    int offset = read_ndr_integer(in);
    typename spatial_index<Value, Filter, InputStream, BBox>::bbox_type node_ext;
    read_envelope(in, node_ext);
    int num_shapes = read_ndr_integer(in);
    if (!filter.pass(node_ext))
    {
        in.seekg(offset + num_shapes * sizeof(Value) + 4, std::ios::cur);
        return;
    }

    for (int i = 0; i < num_shapes; ++i)
    {
        Value item;
        in.read(reinterpret_cast<char*>(&item), sizeof(Value));
        if (results.size() < count)
            results.push_back(std::move(item));
    }
    int children = read_ndr_integer(in);
    for (int j = 0; j < children; ++j)
    {
        query_first_n_impl(filter, in, results, count);
    }
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
int spatial_index<Value, Filter, InputStream, BBox>::read_ndr_integer(InputStream& in)
{
    char b[4];
    in.read(b, 4);
    return (b[0] & 0xff) | (b[1] & 0xff) << 8 | (b[2] & 0xff) << 16 | (b[3] & 0xff) << 24;
}

template<typename Value, typename Filter, typename InputStream, typename BBox>
void spatial_index<Value, Filter, InputStream, BBox>::read_envelope(InputStream& in, BBox& envelope)
{
    in.read(reinterpret_cast<char*>(&envelope), sizeof(envelope));
}

} // namespace util
} // namespace mapnik

#endif // MAPNIK_UTIL_SPATIAL_INDEX_HPP
