// Copyright (c) 2009 INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
// 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.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: https://github.com/CGAL/cgal/blob/releases/CGAL-4.14.1/Mesh_3/include/CGAL/Mesh_3/tet_soup_to_c3t3.h $
// $Id: tet_soup_to_c3t3.h c5fc0b6 %aI Mael Rouxel-Labbé
// SPDX-License-Identifier: GPL-3.0+
//
//
// Author(s)     : Mael Rouxel-Labbé, Maxime Gimeno
//
//******************************************************************************
//
//******************************************************************************

#ifndef CGAL_MESH_3_TET_SOUP_TO_C3T3_H
#define CGAL_MESH_3_TET_SOUP_TO_C3T3_H

#include <CGAL/license/Mesh_3.h>

#include <CGAL/disable_warnings.h>
#include <CGAL/assertions.h>
#include <CGAL/IO/File_medit.h>

#include <boost/array.hpp>
#include <boost/unordered_map.hpp>
#include <boost/foreach.hpp>


namespace CGAL
{
template<class Tr>
void build_vertices(Tr& tr,
                    const std::vector<typename Tr::Point>& points,
                    std::vector<typename Tr::Vertex_handle>& vertex_handle_vector)
{
  typedef typename Tr::Vertex_handle            Vertex_handle;

  vertex_handle_vector[0] = tr.tds().create_vertex(); // creates the infinite vertex
  tr.set_infinite_vertex(vertex_handle_vector[0]);

  // build vertices
  for(std::size_t i=0; i<points.size(); ++i)
  {
    Vertex_handle vh = tr.tds().create_vertex();
    vertex_handle_vector[i+1] = vh;
    vh->set_point(points[i]);
  }
}

template<class Tr>
void add_facet_to_incident_cells_map(const typename Tr::Cell_handle c, int i,
                                     boost::unordered_map<std::set<typename Tr::Vertex_handle>,
                                     std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map)
{
  typedef typename Tr::Vertex_handle                                Vertex_handle;
  typedef typename Tr::Cell_handle                                  Cell_handle;
  typedef std::set<Vertex_handle>                                   Facet;
  typedef std::pair<Cell_handle, int>                               Incident_cell;
  typedef boost::unordered_map<Facet, std::vector<Incident_cell> >  Incident_cells_map;

  // the opposite vertex of f in c is i
  Facet f;
  f.insert(c->vertex((i + 1) % 4));
  f.insert(c->vertex((i + 2) % 4));
  f.insert(c->vertex((i + 3) % 4));
  CGAL_precondition(f.size() == 3);

  Incident_cell e = std::make_pair(c, i);
  std::vector<Incident_cell> vec;
  vec.push_back(e);
  std::pair<typename Incident_cells_map::iterator, bool> is_insert_successful =
      incident_cells_map.insert(std::make_pair(f, vec));
  if(!is_insert_successful.second) // the entry already exists in the map
  {
    // a facet must have exactly two incident cells
    CGAL_assertion(is_insert_successful.first->second.size() == 1);
    is_insert_successful.first->second.push_back(e);
  }
}

template<class Tr>
void build_finite_cells(Tr& tr,
                        const std::vector<boost::array<int,5> >& finite_cells,
                        const std::vector<typename Tr::Vertex_handle>& vertex_handle_vector,
                        boost::unordered_map<std::set<typename Tr::Vertex_handle>,
                        std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                        const std::map<boost::array<int,3>, int>& border_facets)
{
  typedef boost::array<int, 5>              Tet_with_ref; // 4 ids + 1 reference

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

  CGAL_assertion_code(
    typename Tr::Geom_traits::Construct_point_3 cp =
      tr.geom_traits().construct_point_3_object();
  )

  // build the finite cells
  for(std::size_t i=0; i<finite_cells.size(); ++i)
  {
    const Tet_with_ref& tet = finite_cells[i];
    boost::array<Vertex_handle, 4> vs;

    for(int j=0; j<4; ++j)
    {
      CGAL_precondition(static_cast<std::size_t>(tet[j]) < tr.number_of_vertices() && tet[j] >= 0);
      vs[j] = vertex_handle_vector.at(tet[j] + 1);
      CGAL_postcondition(vs[j] != Vertex_handle());
      CGAL_postcondition(!tr.is_infinite(vs[j]));
      vs[j]->set_dimension(3);
    }

    // this assertion also tests for degeneracy
    CGAL_assertion(CGAL::orientation(cp(tr.point(vs[0])), cp(tr.point(vs[1])),
                                     cp(tr.point(vs[2])), cp(tr.point(vs[3])))
                     == POSITIVE);

    Cell_handle c = tr.tds().create_cell(vs[0], vs[1], vs[2], vs[3]);
    c->info() = tet[4]; // the cell's info keeps the reference of the tetrahedron

    CGAL_precondition(tet[4] > 0);
    // assign cells to vertices
    for(int j=0; j<4; ++j)
    {
      if(vs[j]->cell() == Cell_handle())
        vs[j]->set_cell(c);
    }

    // build the map used for adjacency later
    for(int j=0; j<4; ++j)
    {
      add_facet_to_incident_cells_map<Tr>(c, j, incident_cells_map);
      if(border_facets.size() != 0)
      {
        boost::array<int,3> facet;
        facet[0]=tet[(j+1) % 4];
        facet[1]=tet[(j+2) % 4];
        facet[2]=tet[(j+3) % 4];
        //find the circular permutation that puts the smallest index in the first place.
        int n0 = (std::min)((std::min)(facet[0], facet[1]), facet[2]);
        int k=0;
        boost::array<int,3> f;
        do
        {
          f[0]=facet[(0+k)%3];
          f[1]=facet[(1+k)%3];
          f[2]=facet[(2+k)%3];
          ++k;
        } while(f[0] != n0);

        typename std::map<boost::array<int,3>, int>::const_iterator it = border_facets.find(f);
        if(it != border_facets.end())
        {
          c->set_surface_patch_index(j, it->second);
        }
        else
        {
          int temp = f[2];
          f[2] = f[1];
          f[1] = temp;

          it = border_facets.find(f);
          if(it != border_facets.end())
            c->set_surface_patch_index(j, it->second);
          else
            c->set_surface_patch_index(j, 0);
        }
      }
    }
  }
}

template<class Tr>
void add_infinite_facets_to_incident_cells_map(typename Tr::Cell_handle c,
                                               int inf_vert_pos,
                                               std::map<std::set<typename Tr::Vertex_handle>,
                                               std::vector<std::pair<typename Tr::Cell_handle,
                                               int> > >& incident_cells_map)
{
  int l = (inf_vert_pos + 1) % 4;
  add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map);
  l = (inf_vert_pos + 2) % 4;
  add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map);
  l = (inf_vert_pos + 3) % 4;
  add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map);
}

template<class Tr>
void build_infinite_cells(Tr& tr,
                          boost::unordered_map<std::set<typename Tr::Vertex_handle>,
                          std::vector<std::pair<typename Tr::Cell_handle,
                          int> > >& incident_cells_map)
{
  typedef typename Tr::Vertex_handle                               Vertex_handle;
  typedef typename Tr::Cell_handle                                 Cell_handle;
  typedef std::set<Vertex_handle>                                  Facet;
  typedef std::pair<Cell_handle, int>                              Incident_cell;
  typedef boost::unordered_map<Facet, std::vector<Incident_cell> > Incident_cells_map;

  // check the incident cells map for facets who only have one incident cell
  // and build the infinite cell on the opposite side
  typename Incident_cells_map::iterator it = incident_cells_map.begin();
  typename Incident_cells_map::iterator end = incident_cells_map.end();
  for(; it != end; ++it)
  {
    if(it->second.size() == 2) // facet already has both its incident cells
      continue;
    CGAL_assertion(it->second.size() == 1);

    Cell_handle c = it->second[0].first;
    int i = it->second[0].second;

    Cell_handle opp_c;
    // the infinite cell that we are creating needs to be well oriented...
    int inf_vert_position_in_opp_c = 0;
    if(i == 0 || i == 2)
      opp_c = tr.tds().create_cell(tr.infinite_vertex(),
                                   c->vertex((i+1)%4),
                                   c->vertex((i+2)%4),
                                   c->vertex((i+3)%4));
    else
      opp_c = tr.tds().create_cell(tr.infinite_vertex(),
                                   c->vertex((i+1)%4),
                                   c->vertex((i+3)%4),
                                   c->vertex((i+2)%4));

    // set the infinite_vertex's incident cell
    if(tr.infinite_vertex()->cell() == Cell_handle())
      tr.infinite_vertex()->set_cell(opp_c);

    // add the facets to the incident cells map

    // the only finite facet
    it->second.push_back(std::make_pair(opp_c, inf_vert_position_in_opp_c));
    CGAL_assertion(it->second.size() == 2);
  }
}

template<class Tr>
bool assign_neighbors(Tr& tr,
                      const boost::unordered_map<std::set<typename Tr::Vertex_handle>,
                      std::vector<std::pair<typename Tr::Cell_handle,
                      int> > >& incident_cells_map)
{
  typedef typename Tr::Vertex_handle                                 Vertex_handle;
  typedef typename Tr::Cell_handle                                   Cell_handle;
  typedef std::set<Vertex_handle>                                    Facet;
  typedef std::pair<Cell_handle, int>                                Incident_cell;
  typedef boost::unordered_map<Facet, std::vector<Incident_cell> >   Incident_cells_map;

  typename Incident_cells_map::const_iterator icit = incident_cells_map.begin();
  for(; icit!=incident_cells_map.end(); ++icit)
  {
    const std::vector<Incident_cell>& adjacent_cells = icit->second;
    if(adjacent_cells.size() != 2)
      return false;

    Cell_handle c0 = adjacent_cells[0].first;
    int i0 = adjacent_cells[0].second;
    Cell_handle c1 = adjacent_cells[1].first;
    int i1 = adjacent_cells[1].second;

    tr.tds().set_adjacency(c0, i0, c1, i1);
  }
  return true;
}

template<class Tr, bool c3t3_loader_failed>
bool build_triangulation(Tr& tr,
                         const std::vector<typename Tr::Point>& points,
                         const std::vector<boost::array<int,5> >& finite_cells,
                         const std::map<boost::array<int,3>, int>& border_facets)
{
  typedef typename Tr::Vertex_handle            Vertex_handle;
  typedef typename Tr::Cell_handle              Cell_handle;
  typedef std::set<Vertex_handle>               Facet;

  // associate to a face the two (at most) incident tets and the id of the face in the cell
  typedef std::pair<Cell_handle, int>                   Incident_cell;
  typedef boost::unordered_map<Facet, std::vector<Incident_cell> >  Incident_cells_map;

  Incident_cells_map incident_cells_map;
  std::vector<Vertex_handle> vertex_handle_vector(points.size() + 1); // id to vertex_handle

  CGAL_precondition(!points.empty());

  if(finite_cells.empty())
  {
    std::cout << "WARNING: No finite cells were provided. Only the points will be loaded."<<std::endl;
  }

  tr.tds().clear(); // not tr.clear() since it calls tr.init() which we don't want

  build_vertices<Tr>(tr, points, vertex_handle_vector);
  BOOST_FOREACH(Vertex_handle vh, vertex_handle_vector)
  {
    vh->set_dimension(-1);
  }
  if(!finite_cells.empty())
  {
    build_finite_cells<Tr>(tr, finite_cells, vertex_handle_vector, incident_cells_map, border_facets);
    build_infinite_cells<Tr>(tr, incident_cells_map);
    tr.tds().set_dimension(3);
    if(!assign_neighbors<Tr>(tr, incident_cells_map))
      return false;
    std::cout << "built triangulation : " << std::endl;
    std::cout << tr.number_of_cells() << " cells" << std::endl;
  }
  std::cout << tr.number_of_vertices() << " vertices" << std::endl;

  if(c3t3_loader_failed)
    return true;
  else
    return tr.is_valid(true);
}

template<class Tr, bool c3t3_loader_failed>
bool build_triangulation_from_file(std::istream& is,
                                   Tr& tr)
{
  typedef typename Tr::Point                                  Point_3;

  typedef boost::array<int, 3> Facet; // 3 = id
  typedef boost::array<int, 5> Tet_with_ref; // first 4 = id, fifth = reference

  std::vector<Tet_with_ref> finite_cells;
  std::vector<Point_3> points;
  std::map<Facet, int> border_facets;

  // grab the vertices
  int dim;
  int nv, nf, ntet, ref;
  std::string word;

  is >> word >> dim; // MeshVersionFormatted 1
  is >> word >> dim; // Dimension 3

  CGAL_assertion(dim == 3);

  std::cout << "Reading .mesh file..." << std::endl;
  while(is >> word && word != "End")
  {
    if(word == "Vertices")
    {
      is >> nv;
      for(int i=0; i<nv; ++i)
      {
        double x,y,z;
        is >> x >> y >> z >> ref;
        points.push_back(Point_3(x,y,z));
      }
    }

    if(word == "Triangles")
    {
      is >> nf;
      for(int i=0; i<nf; ++i)
      {
        int n1, n2, n3, surface_patch_id;
        is >> n1 >> n2 >> n3 >> surface_patch_id;
        Facet facet;
        facet[0] = n1 - 1;
        facet[1] = n2 - 1;
        facet[2] = n3 - 1;
        //find the circular permutation that puts the smallest index in the first place.
        int n0 = (std::min)((std::min)(facet[0],facet[1]), facet[2]);
        int k=0;
        Facet f;
        do
        {
          f[0] = facet[(0+k)%3];
          f[1] = facet[(1+k)%3];
          f[2] = facet[(2+k)%3];
          ++k;
        } while(f[0] != n0);
        border_facets.insert(std::make_pair(f, surface_patch_id));
      }
    }

    if(word == "Tetrahedra")
    {
      is >> ntet;
      for(int i=0; i<ntet; ++i)
      {
        int n0, n1, n2, n3, reference;
        is >> n0 >> n1 >> n2 >> n3 >> reference;
        Tet_with_ref t;
        t[0] = n0 - 1;
        t[1] = n1 - 1;
        t[2] = n2 - 1;
        t[3] = n3 - 1;
        t[4] = reference;
        finite_cells.push_back(t);
      }
    }
  }

  std::cout << points.size() << " points" << std::endl;
  std::cout << border_facets.size() << " border facets" << std::endl;
  std::cout << finite_cells.size() << " cells" << std::endl;

  if(finite_cells.empty())
    return false;

  bool is_well_built = build_triangulation<Tr, c3t3_loader_failed>(tr, points, finite_cells, border_facets);
  return is_well_built;
}

}  // namespace CGAL

#include <CGAL/enable_warnings.h>

#endif // CGAL_MESH_3_TET_SOUP_TO_C3T3_H
