// Copyright (c) 2009 INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.1/Mesh_3/include/CGAL/Mesh_3/Odt_move.h $
// $Id: include/CGAL/Mesh_3/Odt_move.h 08b27d3db14 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Stephane Tayeb
//
//******************************************************************************
// File Description :
//******************************************************************************

#ifndef CGAL_MESH_3_ODT_MOVE_H
#define CGAL_MESH_3_ODT_MOVE_H

#include <CGAL/license/Mesh_3.h>

#include <CGAL/Mesh_3/config.h>

#include <CGAL/Mesh_3/Uniform_sizing_field.h>

#include <string>

namespace CGAL {

namespace Mesh_3 {

template <typename C3T3,
  typename SizingField = Uniform_sizing_field<typename C3T3::Triangulation> >
class Odt_move
{
  typedef typename C3T3::Triangulation                        Tr;
  typedef typename Tr::Geom_traits                            GT;

  typedef typename Tr::Vertex_handle                          Vertex_handle;
  typedef typename Tr::Facet                                  Facet;
  typedef typename Tr::Cell_handle                            Cell_handle;

  typedef typename Tr::Bare_point                             Bare_point;
  typedef typename Tr::Weighted_point                         Weighted_point;

  typedef typename std::vector<Facet>                         Facet_vector;
  typedef typename std::vector<Cell_handle>                   Cell_vector;

  typedef typename GT::FT                                     FT;
  typedef typename GT::Vector_3                               Vector_3;

public:
  typedef SizingField                                         Sizing_field;

  Vector_3 operator()(const Vertex_handle& v,
                      const Cell_vector& incident_cells,
                      const C3T3& c3t3,
                      const Sizing_field& sizing_field = Sizing_field()) const
  {
    // Don't move edge or corner vertices
    if ( c3t3.in_dimension(v) < 2 )
    {
      return CGAL::NULL_VECTOR;
    }

    // Compute move
    const Tr& tr = c3t3.triangulation();

    typename GT::Construct_point_3 cp = tr.geom_traits().construct_point_3_object();
    typename GT::Construct_vector_3 vector = tr.geom_traits().construct_vector_3_object();

    Vector_3 move = CGAL::NULL_VECTOR;
    FT sum_volume(0);

    for ( typename Cell_vector::const_iterator cit = incident_cells.begin() ;
         cit != incident_cells.end() ;
         ++cit )
    {
      const Cell_handle& cell = *cit;

      // Consider only cells of complex
      if ( ! c3t3.is_in_complex(cell) )
        continue;

      // Get points
      Bare_point circumcenter = tr.dual(cell);

      // Compute move
      const Weighted_point& p = tr.point(cell, cell->index(v));
      Vector_3 p_circum = vector(cp(p), circumcenter);
      FT volume = volume_quadrature(cell, tr, sizing_field);

      move = move + p_circum * volume;
      sum_volume += volume;
    }

    // Add boundary terms if needed
    if ( c3t3.in_dimension(v) == 2 )
    {
//      move = move + (1.0 / 12.0) * move_odt_2D(v, c3t3, sizing_field);
    }

    if ( FT(0) != sum_volume )
      return move/sum_volume;
    else
      return CGAL::NULL_VECTOR;
  }

#if defined(CGAL_MESH_3_OPTIMIZER_VERBOSE) \
 || defined (CGAL_MESH_3_EXPORT_PERFORMANCE_DATA)
  static std::string name() { return std::string("Odt"); }
#endif

private:
  // 1-point at cell centroid
  FT volume_quadrature(const Cell_handle& cell,
                       const Tr& tr,
                       const Sizing_field& sizing_field) const
  {
    typename GT::Construct_centroid_3 centroid = tr.geom_traits().construct_centroid_3_object();
    typename GT::Compute_volume_3 volume = tr.geom_traits().compute_volume_3_object();

    Bare_point c = centroid(tr.tetrahedron(cell));
    FT s = sizing_field(c, std::make_pair(cell, true));
    CGAL_assertion(!is_zero(s));

    // Points of cell are positively oriented
    FT abs_volume = volume(tr.tetrahedron(cell));
    CGAL_assertion(abs_volume >= 0);

    return abs_volume / (s*s*s);
  }

//  /**
//   * @class Is_on_c3t3_boundary
//   *
//   * A functor which returns false if a facet is on the boundary of c3t3
//   */
//  class Is_not_on_c3t3_boundary
//  {
//  public:
//    Is_not_on_c3t3_boundary(const C3T3& c3t3) : c3t3_(c3t3) { }
//
//    bool operator()(const Facet& f) const
//    {
//      return ( ! c3t3_.is_in_complex(f) ) ||
//             ( c3t3_.is_in_complex(f.first) &&
//               c3t3_.is_in_complex(f.first->neighbor(f.second)) );
//    }
//
//  private:
//    const C3T3& c3t3_;
//  };
//
//  // boundary terms
//  Vector_3 move_odt_2D(const Vertex_handle& v,
//                       const C3T3& c3t3,
//                       const Sizing_field& sizing_field) const
//  {
//    // Triangulation
//    const Tr& tr = c3t3.triangulation();
//
//    // Get boundary facets
//    Facet_vector incident_facets;
//    tr.finite_incident_facets(v, std::back_inserter(incident_facets));
//
//    typename Facet_vector::iterator in_c3t3_incident_end =
//      std::remove_if(incident_facets.begin(), incident_facets.end(),
//                     Is_not_on_c3t3_boundary(c3t3));
//
//    // Compute boundary terms
//    Vector_3 move = CGAL::NULL_VECTOR;
//    for(typename Facet_vector::iterator fit = incident_facets.begin();
//        fit != in_c3t3_incident_end;
//        ++fit)
//    {
//      CGAL_assertion(c3t3.is_in_complex(*fit));
//
//      // Normal
//      FT area = area_quadrature(*fit, tr, sizing_field);
//      Vector_3 facet_normal = area * normal_outside(*fit, c3t3);
//
//      // Sq length
//      FT sq_length_sum = sq_length_facet_quadrature(v, *fit, tr, sizing_field);
//
//      // Move
//      move = move + sq_length_sum * facet_normal;
//    }
//
//    return move;
//  }
//
//  // 1-point at facet centroid
//  FT area_quadrature(const Facet& facet,
//                     const Tr& tr,
//                     const Sizing_field& sizing_field) const
//  {
//    typename GT::Compute_area_3 area = tr.geom_traits().compute_area_3_object();
//    typename GT::Construct_centroid_3 centroid = tr.geom_traits().construct_centroid_3_object();
//
//    Bare_point c = centroid(tr.triangle(facet));
//    FT s = sizing_field(c, facet.first->vertex(0));
//
//    return ( area(tr.triangle(facet)) / (s*s) );
//  }
//
//  // 1-point at segment midpoint
//  FT sq_length_quadrature(const int& vertex_index_1,
//                          const int& vertex_index_2,
//                          const Cell_handle cell,
//                          const Tr& tr,
//                          const Sizing_field& sizing_field) const
//  {
//    typename GT::Construct_point_3 cp = tr.geom_traits().construct_point_3_object();
//    typename GT::Construct_midpoint_3 midpoint = tr.geom_traits().construct_midpoint_3_object();
//    typename GT::Compute_squared_distance_3 sq_distance = tr.geom_traits().compute_squared_distance_3_object();
//
//    const Weighted_point& wp1 = tr.point(cell, vertex_index_1);
//    const Weighted_point& wp2 = tr.point(cell, vertex_index_2);
//    const Bare_point& p1 = cp(wp1);
//    const Bare_point& p2 = cp(wp2);
//
//    Bare_point c = midpoint(p1, p2);
//    FT s = sizing_field(c, cell->vertex(vertex_index_1));
//
//    return ( sq_distance(p1, p2) / s );
//  }
//
//  FT sq_length_facet_quadrature(const Vertex_handle& v,
//                                const Facet& f,
//                                const Tr& tr,
//                                const Sizing_field& sizing_field) const
//  {
//    // get indices
//    const int& vertex_index = f.first->index(v);
//    int k1 = (vertex_index+1)&3;
//    int k2 = (vertex_index+2)&3;
//    int k3 = (vertex_index+3)&3;
//
//    if ( k2 == f.second ) { std::swap(k1,k2); }
//    else if ( k3 == f.second ) { std::swap(k1,k3); }
//
//    // Here k1 is opposite vertex index in f.first, facet vertices indices
//    // are (vertex_index,k2,k3)
//
//    FT sqd_v2 = sq_length_quadrature(vertex_index, k2, f.first, tr, sizing_field);
//    FT sqd_v3 = sq_length_quadrature(vertex_index, k3, f.first, tr, sizing_field);
//
//    return (sqd_v2 + sqd_v3);
//  }
//
//  Vector_3 normal_outside(const Facet& f, const C3T3& c3t3) const
//  {
//    typename GT::Construct_point_3 cp = c3t3.triangulation().geom_traits().construct_point_3_object();
//    typename GT::Construct_normal_3 normal = c3t3.triangulation().geom_traits().construct_normal_3_object();
//
//    const Cell_handle& cell = f.first;
//    const int& i = f.second;
//
//    int k1 = (i+1)&3;
//    int k2 = (i+2)&3;
//    int k3 = (i+3)&3;
//
//    // Orient normals to the outside of cell
//    if ( (i&1) == 1 )
//      std::swap(k1,k2);
//
//    // Make sure normals are oriented outside
//    if ( ! c3t3.is_in_complex(cell) )
//      std::swap(k1,k2);
//
//    const Weighted_point& wp1 = c3t3.triangulation().point(cell, k1);
//    const Weighted_point& wp2 = c3t3.triangulation().point(cell, k2);
//    const Weighted_point& wp3 = c3t3.triangulation().point(cell, k3);
//
//    return normal(cp(p1), cp(p2), cp(p3));
//  }
};

} // end namespace Mesh_3

} //namespace CGAL

#endif // CGAL_MESH_3_ODT_MOVE_H
