/*    This file is part of the Gudhi Library. The Gudhi library
 *    (Geometric Understanding in Higher Dimensions) is a generic C++
 *    library for computational topology.
 *
 *    Author(s):       Pawel Dlotko
 *
 *    Copyright (C) 2016 Inria
 *
 *    This program 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.
 *
 *    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef PSSK_H_
#define PSSK_H_

// gudhi include
#include <gudhi/Persistence_heat_maps.h>

#include <limits>
#include <utility>
#include <vector>

namespace Gudhi {
namespace Persistence_representations {

/**
* This is a version of a representation presented in https://arxiv.org/abs/1412.6821
* In that paper the authors are using the representation just to compute kernel. Over here, we extend the usability by
*far.
* Note that the version presented here is not exact, since we are discretizing the kernel.
* The only difference with respect to the original class is the method of creation. We have full (square) image, and for
*every point (p,q), we add a kernel at (p,q) and the negative kernel
* at (q,p)
**/

class PSSK : public Persistence_heat_maps<constant_scaling_function> {
 public:
  PSSK() : Persistence_heat_maps() {}

  PSSK(const std::vector<std::pair<double, double> >& interval,
       std::vector<std::vector<double> > filter = create_Gaussian_filter(5, 1), size_t number_of_pixels = 1000,
       double min_ = -1, double max_ = -1)
      : Persistence_heat_maps() {
    this->construct(interval, filter, number_of_pixels, min_, max_);
  }

  PSSK(const char* filename, std::vector<std::vector<double> > filter = create_Gaussian_filter(5, 1),
       size_t number_of_pixels = 1000, double min_ = -1, double max_ = -1,
       unsigned dimension = std::numeric_limits<unsigned>::max())
      : Persistence_heat_maps() {
    std::vector<std::pair<double, double> > intervals_;
    if (dimension == std::numeric_limits<unsigned>::max()) {
      intervals_ = read_persistence_intervals_in_one_dimension_from_file(filename);
    } else {
      intervals_ = read_persistence_intervals_in_one_dimension_from_file(filename, dimension);
    }
    this->construct(intervals_, filter, number_of_pixels, min_, max_);
  }

 protected:
  void construct(const std::vector<std::pair<double, double> >& intervals_,
                 std::vector<std::vector<double> > filter = create_Gaussian_filter(5, 1),
                 size_t number_of_pixels = 1000, double min_ = -1, double max_ = -1);
};

// if min_ == max_, then the program is requested to set up the values itself based on persistence intervals
void PSSK::construct(const std::vector<std::pair<double, double> >& intervals_,
                     std::vector<std::vector<double> > filter, size_t number_of_pixels, double min_, double max_) {
  bool dbg = false;
  if (dbg) {
    std::cerr << "Entering construct procedure \n";
    getchar();
  }

  if (min_ == max_) {
    // in this case, we want the program to set up the min_ and max_ values by itself.
    min_ = std::numeric_limits<int>::max();
    max_ = -std::numeric_limits<int>::max();

    for (size_t i = 0; i != intervals_.size(); ++i) {
      if (intervals_[i].first < min_) min_ = intervals_[i].first;
      if (intervals_[i].second > max_) max_ = intervals_[i].second;
    }
    // now we have the structure filled in, and moreover we know min_ and max_ values of the interval, so we know the
    // range.

    // add some more space:
    min_ -= fabs(max_ - min_) / 100;
    max_ += fabs(max_ - min_) / 100;
  }

  if (dbg) {
    std::cerr << "min_ : " << min_ << std::endl;
    std::cerr << "max_ : " << max_ << std::endl;
    std::cerr << "number_of_pixels : " << number_of_pixels << std::endl;
    getchar();
  }

  this->min_ = min_;
  this->max_ = max_;

  // initialization of the structure heat_map
  std::vector<std::vector<double> > heat_map_;
  for (size_t i = 0; i != number_of_pixels; ++i) {
    std::vector<double> v(number_of_pixels, 0);
    heat_map_.push_back(v);
  }
  this->heat_map = heat_map_;

  if (dbg) std::cerr << "Done creating of the heat map, now we will fill in the structure \n";

  for (size_t pt_nr = 0; pt_nr != intervals_.size(); ++pt_nr) {
    // compute the value of intervals_[pt_nr] in the grid:
    int x_grid =
        static_cast<int>((intervals_[pt_nr].first - this->min_) / (this->max_ - this->min_) * number_of_pixels);
    int y_grid =
        static_cast<int>((intervals_[pt_nr].second - this->min_) / (this->max_ - this->min_) * number_of_pixels);

    if (dbg) {
      std::cerr << "point : " << intervals_[pt_nr].first << " , " << intervals_[pt_nr].second << std::endl;
      std::cerr << "x_grid : " << x_grid << std::endl;
      std::cerr << "y_grid : " << y_grid << std::endl;
    }

    // x_grid and y_grid gives a center of the kernel. We want to have its lower left corner. To get this, we need to
    // shift x_grid and y_grid by a grid diameter.
    x_grid -= filter.size() / 2;
    y_grid -= filter.size() / 2;
    // note that the numbers x_grid and y_grid may be negative.

    if (dbg) {
      std::cerr << "After shift : \n";
      std::cerr << "x_grid : " << x_grid << std::endl;
      std::cerr << "y_grid : " << y_grid << std::endl;
      std::cerr << "filter.size() : " << filter.size() << std::endl;
      getchar();
    }

    for (size_t i = 0; i != filter.size(); ++i) {
      for (size_t j = 0; j != filter.size(); ++j) {
        // if the point (x_grid+i,y_grid+j) is the correct point in the grid.
        if (((x_grid + i) >= 0) && (x_grid + i < this->heat_map.size()) && ((y_grid + j) >= 0) &&
            (y_grid + j < this->heat_map.size())) {
          if (dbg) {
            std::cerr << y_grid + j << " " << x_grid + i << std::endl;
          }
          this->heat_map[y_grid + j][x_grid + i] += filter[i][j];
          this->heat_map[x_grid + i][y_grid + j] += -filter[i][j];
        }
      }
    }
  }
}  // construct

}  // namespace Persistence_representations
}  // namespace Gudhi

#endif  // PSSK_H_