/* 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):       David Salinas
 *
 *    Copyright (C) 2014  INRIA Sophia Antipolis-Mediterranee (France)
 *
 *    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 UTILS_EDGE_CONTRACTOR_H_
#define UTILS_EDGE_CONTRACTOR_H_


#include <gudhi/Skeleton_blocker_contractor.h>
#include <gudhi/Contraction/Edge_profile.h>
#include <gudhi/Contraction/policies/Cost_policy.h>

#include <vector>

/**
 * Iteratively puts every vertex at the center of its neighbors
 */
template<typename SkBlComplex> class Edge_contractor {
 private:
  SkBlComplex& complex_;
  unsigned num_contractions_;

  /**
   * @brief return a cost corresponding to the squared length of the edge
   */
  template< typename EdgeProfile> class Length_cost : public contraction::Cost_policy<EdgeProfile> {
   public:
    typedef typename contraction::Cost_policy<EdgeProfile>::Cost_type Cost_type;
    typedef typename EdgeProfile::Point Point;

    Cost_type operator()(const EdgeProfile& profile, const boost::optional<Point>& placement) const override {
      Cost_type res;
      if (!placement)
        return res;
      return Geometry_trait::Squared_distance_d()(profile.p0(), profile.p1());  // not working??
    }
  };

  /**
   * @brief return a cost corresponding to the squared length of the edge
   */
  template< typename EdgeProfile> class Middle_placement : public contraction::Placement_policy<EdgeProfile> {
   public:
    typedef typename contraction::Placement_policy<EdgeProfile>::Placement_type Placement_type;
    typedef typename EdgeProfile::Point Point;

    Placement_type operator()(const EdgeProfile& profile) const override {
      std::vector<double> mid_coords(profile.p0().dimension(), 0);
      for (int i = 0; i < profile.p0().dimension(); ++i) {
        mid_coords[i] = (profile.p0()[i] + profile.p1()[i]) / 2.;
      }
      return Point(profile.p0().dimension(), mid_coords.begin(), mid_coords.end());
    }
  };

 public:
  typedef typename SkBlComplex::Vertex_handle Vertex_handle;
  typedef typename SkBlComplex::Edge_handle Edge_handle;

  /**
   * @brief Modify complex to be the expansion of the k-nearest neighbor
   * symetric graph.
   */
  Edge_contractor(SkBlComplex& complex, unsigned num_contractions) :
      complex_(complex), num_contractions_(num_contractions) {
    typedef typename contraction::Edge_profile<Complex> Profile;
    num_contractions = (std::min)(static_cast<int>(num_contractions), static_cast<int>(complex_.num_vertices() - 1));
    typedef typename contraction::Skeleton_blocker_contractor<Complex> Contractor;
    Contractor contractor(complex_,
                          new Length_cost<contraction::Edge_profile < Complex >> (),
                          new Middle_placement<contraction::Edge_profile < Complex >> (),
                          contraction::make_link_valid_contraction<Profile>(),
                          contraction::make_remove_popable_blockers_visitor<Profile>());
    contractor.contract_edges(num_contractions);
  }
};

#endif  // UTILS_EDGE_CONTRACTOR_H_