// Copyright (c) 2014 Stefan Walk
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Classification/include/CGAL/Classification/ETHZ/internal/random-forest/common-libraries.hpp $
// $Id: include/CGAL/Classification/ETHZ/internal/random-forest/common-libraries.hpp b26b07a1242 $
// SPDX-License-Identifier: LicenseRef-RFL
// License notice in Installation/LICENSE.RFL
//
// Author(s)     : Stefan Walk

// Modifications from original library:
//  * changed inclusion protection tag
//  * moved to namespace CGAL::internal::
//  * init_feature_class_data() does not resize anymore (it's done
//    later directly in the splitter). WARNING: all splitters other
//    than the default won't be working correctly (but experimentally
//    they are less good and we don't use them - we keep them just in
//    case)
//  * sample reduction is now 36.8% (to account for the correction of
//    the randomization of the input which used to implicitly ignore
//    this proportion of items)
//  * map_points() in axis aligned splitter now only uses a subset of
//    the points for evaluation (for timing optimization=

#ifndef CGAL_INTERNAL_LIBLEARNING_RANDOMFOREST_COMMON_LIBRARIES_H
#define CGAL_INTERNAL_LIBLEARNING_RANDOMFOREST_COMMON_LIBRARIES_H
#include <algorithm>
#include <numeric>
#include <limits>
#include <list>
#include <CGAL/IO/binary_file_io.h>
#include <boost/version.hpp>
#include <boost/bind/bind.hpp>
#include <boost/ptr_container/ptr_vector.hpp>
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int_distribution.hpp>
#include <boost/random/uniform_01.hpp>
#include <boost/random/normal_distribution.hpp>
#if defined(CGAL_LINKED_WITH_BOOST_IOSTREAMS) && defined(CGAL_LINKED_WITH_BOOST_SERIALIZATION)
#include <boost/serialization/vector.hpp>
#endif
#include <boost/scoped_ptr.hpp>
#include <memory>
#include <boost/make_shared.hpp>
#include <unordered_set>
#include <iostream>
#include <cstdio>

#include "../dataview.h"

namespace CGAL { namespace internal {

namespace liblearning {
namespace RandomForest {

typedef std::vector< std::pair<float, int> > FeatureClassDataFloat;
inline void init_feature_class_data(FeatureClassDataFloat& /*data*/, int /*n_classes*/, int /* n_samples */)
{
//    data.resize(n_samples);
}
typedef std::unordered_set<int> FeatureSet;

typedef boost::random::uniform_int_distribution<> UniformIntDist;
typedef boost::random::normal_distribution<> NormalDist;
typedef boost::random::mt19937 RandomGen;
typedef boost::random::uniform_01<> UnitDist;

struct ForestParams {
    size_t n_classes;
    size_t n_features;
    size_t n_samples;
    size_t n_in_bag_samples;
    size_t max_depth;
    size_t n_trees;
    size_t min_samples_per_node;
    float  sample_reduction;
    ForestParams() :
        n_classes(0),
        n_features(0),
        n_samples(0),
        n_in_bag_samples(0),
        max_depth(42),
        n_trees(100),
        min_samples_per_node(5),
        sample_reduction(0.368f)
    {}
#if defined(CGAL_LINKED_WITH_BOOST_IOSTREAMS) && defined(CGAL_LINKED_WITH_BOOST_SERIALIZATION)
    template <typename Archive>
    void serialize(Archive& ar, unsigned /*version*/)
    {
        ar & BOOST_SERIALIZATION_NVP(n_classes);
        ar & BOOST_SERIALIZATION_NVP(n_features);
        ar & BOOST_SERIALIZATION_NVP(n_samples);
        ar & BOOST_SERIALIZATION_NVP(n_in_bag_samples);
        ar & BOOST_SERIALIZATION_NVP(max_depth);
        ar & BOOST_SERIALIZATION_NVP(n_trees);
        ar & BOOST_SERIALIZATION_NVP(min_samples_per_node);
        ar & BOOST_SERIALIZATION_NVP(sample_reduction);
    }
#endif

    void write (std::ostream& os)
    {
      I_Binary_write_size_t_into_uinteger32 (os, n_classes);
      I_Binary_write_size_t_into_uinteger32 (os, n_features);
      I_Binary_write_size_t_into_uinteger32 (os, n_samples);
      I_Binary_write_size_t_into_uinteger32 (os, n_in_bag_samples);
      I_Binary_write_size_t_into_uinteger32 (os, max_depth);
      I_Binary_write_size_t_into_uinteger32 (os, n_trees);
      I_Binary_write_size_t_into_uinteger32 (os, min_samples_per_node);
      I_Binary_write_float32 (os, sample_reduction);
    }

    void read (std::istream& is)
    {
      I_Binary_read_size_t_from_uinteger32 (is, n_classes);
      I_Binary_read_size_t_from_uinteger32 (is, n_features);
      I_Binary_read_size_t_from_uinteger32 (is, n_samples);
      I_Binary_read_size_t_from_uinteger32 (is, n_in_bag_samples);
      I_Binary_read_size_t_from_uinteger32 (is, max_depth);
      I_Binary_read_size_t_from_uinteger32 (is, n_trees);
      I_Binary_read_size_t_from_uinteger32 (is, min_samples_per_node);
      I_Binary_read_float32 (is, sample_reduction);
    }
};

struct QuadraticSplitter {
    typedef float FeatureType;
    typedef FeatureClassDataFloat FeatureClassData;
    int n_features;
    std::vector<FeatureType> w;
    FeatureType threshold;
    QuadraticSplitter() : n_features(0) {}
    QuadraticSplitter(int n_features, std::vector<FeatureType> const& w) :
        n_features(n_features), w(w)
    {}
    void set_threshold(FeatureType new_threshold) {
        threshold = new_threshold;
    }
    FeatureType map_sample(FeatureType const* v) const {
        double result = 0.0;
        int i_feature = 0;
        for (; i_feature < n_features; ++i_feature) {
            result += w[i_feature] * v[i_feature];
        }
        for (int i_1 = 0; i_1 < n_features; ++i_1) {
            for (int i_2 = 0; i_2 < n_features; ++i_2) {
                result += w[i_feature++] * v[i_1] * v[i_2];
            }
        }
        return result;
    }
    bool classify_sample(FeatureType const* v) const {
        return map_sample(v) > threshold;
    }
    void map_points(DataView2D<FeatureType> samples,
                    DataView2D<int>   labels,
                    int const*      sample_idxes,
                    int             n_samples,
                    FeatureClassData&        data_points) const
    {
        for (int i_sample = 0; i_sample < n_samples; ++i_sample) {
            int sample_idx    = sample_idxes[i_sample];
            int sample_class  = labels(sample_idx, 0);
            FeatureType sample_fval = map_sample(samples.row_pointer(sample_idx));
            data_points[i_sample] = std::make_pair(sample_fval, sample_class);
        }
    }
#if defined(CGAL_LINKED_WITH_BOOST_IOSTREAMS) && defined(CGAL_LINKED_WITH_BOOST_SERIALIZATION)
    template <typename Archive>
    void serialize(Archive& ar, unsigned /*version*/)
    {
        ar & BOOST_SERIALIZATION_NVP(n_features);
        ar & BOOST_SERIALIZATION_NVP(w);
        ar & BOOST_SERIALIZATION_NVP(threshold);
    }
#endif
};

struct LinearSplitter {
    typedef float FeatureType;
    typedef FeatureClassDataFloat FeatureClassData;
    std::vector<FeatureType> w;
    FeatureType threshold;
    LinearSplitter() {}
    LinearSplitter(std::vector<FeatureType> const& w) :
        w(w)
    {}
    void set_threshold(FeatureType new_threshold) {
        threshold = new_threshold;
    }
    bool classify_sample(FeatureType const* v) const {
        return std::inner_product(w.begin(), w.end(), v, 0.0f) > threshold;
    }
    void map_points(DataView2D<FeatureType> samples,
                    DataView2D<int>   labels,
                    int const*      sample_idxes,
                    int             n_samples,
                    FeatureClassData&        data_points) const
    {
        for (int i_sample = 0; i_sample < n_samples; ++i_sample) {
            int sample_idx    = sample_idxes[i_sample];
            int sample_class  = labels(sample_idx, 0);
            FeatureType sample_fval = std::inner_product(w.begin(), w.end(),
                                                   samples.row_pointer(sample_idx), 0.0f);
            data_points[i_sample] = std::make_pair(sample_fval, sample_class);
        }
    }
#if defined(CGAL_LINKED_WITH_BOOST_IOSTREAMS) && defined(CGAL_LINKED_WITH_BOOST_SERIALIZATION)
    template <typename Archive>
    void serialize(Archive& ar, unsigned /*version*/)
    {
        ar & BOOST_SERIALIZATION_NVP(w);
        ar & BOOST_SERIALIZATION_NVP(threshold);
    }
#endif
};

struct AxisAlignedSplitter {
    typedef float FeatureType;
    typedef FeatureClassDataFloat FeatureClassData;
    int feature;
    FeatureType threshold;
    AxisAlignedSplitter() : feature(-1) {}
    AxisAlignedSplitter(int feature) :
        feature(feature)
    {}
    void set_threshold(FeatureType new_threshold) {
        threshold = new_threshold;
    }
    bool classify_sample(FeatureType const* v) const {
        return v[feature] > threshold;
    }
    void map_points(DataView2D<FeatureType> samples,
                    DataView2D<int>   labels,
                    int const*      sample_idxes,
                    int             n_samples,
                    FeatureClassData&        data_points) const
    {
      std::size_t size = (std::min)(std::size_t(5000), std::size_t(n_samples));
      data_points.clear();
      data_points.reserve(size);

      std::size_t step = n_samples / size;

      for (int i_sample = 0; i_sample < n_samples; i_sample += step) {
        // determine index of this sample ...
        int sample_idx    = sample_idxes[i_sample];
        // determine class ...
        int sample_class  = labels(sample_idx, 0);
        // determine value of the selected feature for this sample
        FeatureType sample_fval = samples(sample_idx, feature);
        data_points.push_back(std::make_pair(sample_fval, sample_class));
      }
    }
#if defined(CGAL_LINKED_WITH_BOOST_IOSTREAMS) && defined(CGAL_LINKED_WITH_BOOST_SERIALIZATION)
    template <typename Archive>
    void serialize(Archive& ar, unsigned /*version*/)
    {
        ar & BOOST_SERIALIZATION_NVP(feature);
        ar & BOOST_SERIALIZATION_NVP(threshold);
    }
#endif

    void write (std::ostream& os)
    {
      os.write((char*)(&feature), sizeof(int));
      os.write((char*)(&threshold), sizeof(FeatureType));
    }

    void read (std::istream& is)
    {
      is.read((char*)(&feature), sizeof(int));
      is.read((char*)(&threshold), sizeof(FeatureType));
    }
};

struct AxisAlignedRandomSplitGenerator {
    typedef float FeatureType;
    FeatureSet features;
    FeatureSet::const_iterator it;

    void init(DataView2D<FeatureType> samples,
              DataView2D<int>   /*labels*/,
              int*            /*sample_idxes*/,
              int             /*n_samples*/,
              size_t          /*n_classes*/,
              RandomGen&      gen)
    {
        features.clear();
        int n_features = samples.cols;
        size_t n_used_features = std::sqrt(n_features);
        UniformIntDist dist(0, n_features - 1);
        // insert into set until required number of unique features is found
        while (features.size() < n_used_features) {
            features.insert(dist(gen));
        }
        it = features.begin();
    }
    AxisAlignedSplitter gen_proposal(RandomGen& /*gen*/)
    {
        if (it == features.end()) {
            it = features.begin();
        }
        return AxisAlignedSplitter(*it++);
    }
    size_t num_proposals() const {
        return features.size();
    }
};

struct LinearSplitGenerator {
    typedef float FeatureType;
    size_t n_features;
    size_t n_proposals;
    LinearSplitGenerator(size_t n_proposals = 5) :
        n_proposals(n_proposals)
    {}
    void init(DataView2D<FeatureType> samples,
              DataView2D<int>   /*labels*/,
              int*            /*sample_idxes*/,
              int             /*n_samples*/,
              size_t          /*n_classes*/,
              RandomGen&      /*gen*/)
    {
        n_features = samples.cols;
    }
    size_t num_proposals() const {
        return n_proposals;
    }
    LinearSplitter gen_proposal(RandomGen& gen) {
        NormalDist dist;
        std::vector<FeatureType> weights(n_features);
        for (size_t i_feature = 0; i_feature < n_features; ++i_feature) {
            weights[i_feature] = dist(gen);
        }
        return LinearSplitter(weights);
    }
};

struct QuadraticSplitGenerator {
    typedef float FeatureType;
    size_t n_features;
    size_t n_proposals;
    QuadraticSplitGenerator(size_t n_proposals = 5) :
        n_proposals(n_proposals)
    {}
    void init(DataView2D<FeatureType> samples,
              DataView2D<int>   /*labels*/,
              int*            /*sample_idxes*/,
              int             /*n_samples*/,
              size_t          /*n_classes*/,
              RandomGen&      /*gen*/)
    {
        n_features = samples.cols;
    }
    size_t num_proposals() const {
        return n_proposals;
    }
    QuadraticSplitter gen_proposal(RandomGen& gen) {
        NormalDist dist;
        std::vector<FeatureType> weights(n_features + n_features*n_features);
        for (size_t i_feature = 0; i_feature < weights.size(); ++i_feature) {
            weights[i_feature] = dist(gen);
        }
        return QuadraticSplitter(n_features, weights);
    }
};

}
}

}} // namespace CGAL::internal::

#endif

