// 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/v6.2-beta1/SMDS_3/include/CGAL/SMDS_3/tet_soup_to_c3t3.h $
// $Id: include/CGAL/SMDS_3/tet_soup_to_c3t3.h 431cfb5357d $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Mael Rouxel-Labbé, Maxime Gimeno
//
//******************************************************************************
//
//******************************************************************************

#ifndef CGAL_SMDS_3_TET_SOUP_TO_C3T3_H
#define CGAL_SMDS_3_TET_SOUP_TO_C3T3_H

#include <CGAL/license/SMDS_3.h>

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

#include <boost/unordered_map.hpp>

#include <array>
#include <map>
#include <utility>
#include <vector>

namespace CGAL {
namespace SMDS_3 {

template<typename Vh>
std::array<Vh, 3> make_ordered_vertex_array(const Vh vh0, const Vh vh1, const Vh vh2)
{
  std::array<Vh, 3> ft = { {vh0, vh1, vh2} };
  if (ft[1] < ft[0]) std::swap(ft[0], ft[1]);
  if (ft[2] < ft[1]) std::swap(ft[1], ft[2]);
  if (ft[1] < ft[0]) std::swap(ft[0], ft[1]);
  return ft;
}

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

  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(Point(points[i]));
  }
}

template <class Tr>
bool add_facet_to_incident_cells_map(const typename Tr::Cell_handle c, int i,
                                     boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                                                          std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                                     const bool verbose,
                                     const bool allow_non_manifold)
{
  typedef typename Tr::Vertex_handle                                Vertex_handle;
  typedef typename Tr::Cell_handle                                  Cell_handle;
  typedef std::array<Vertex_handle, 3>                              Facet_vvv;
  typedef std::pair<Cell_handle, int>                               Incident_cell;
  typedef boost::unordered_map<Facet_vvv, std::vector<Incident_cell> > Incident_cells_map;

  bool success = true;

  // the opposite vertex of f in c is i
  Facet_vvv f = CGAL::SMDS_3::make_ordered_vertex_array(c->vertex((i + 1) % 4),
                                                        c->vertex((i + 2) % 4),
                                                        c->vertex((i + 3) % 4));
  CGAL_precondition(f[0] != f[1] && f[1] != f[2]);

  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.emplace(f, vec);
  if(!is_insert_successful.second) // the entry already exists in the map
  {
    // A finite facet must have exactly two incident cells
    //
    // If there is a non-manifold edge on the boundary, the infinite facet being
    // that edge + the infinite vertex has (strictly) more than 2 incident cells
    if(is_insert_successful.first->second.size() != 1)
    {
      if(!allow_non_manifold)
      {
        success = false;
        if(verbose)
          std::cerr << "Error: " << is_insert_successful.first->second.size() << " previous incidences" << std::endl;
      }
      else if(verbose)
      {
        std::cerr << "Warning: " << is_insert_successful.first->second.size() << " previous incidences" << std::endl;
      }
    }
    is_insert_successful.first->second.push_back(e);
  }
  return success;
}

template <class Tr, typename CellRange, typename SubdomainsRange, typename FacetPatchMap>
bool build_finite_cells(Tr& tr,
                        const CellRange& finite_cells,
                        const SubdomainsRange& subdomains,
                        const std::vector<typename Tr::Vertex_handle>& vertex_handle_vector,
                        boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                                             std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                        const FacetPatchMap& border_facets,
                        const bool verbose,
                        const bool replace_domain_0)
{
  typedef typename Tr::Vertex_handle                            Vertex_handle;
  typedef typename Tr::Cell_handle                              Cell_handle;
  typedef typename Tr::Cell::Surface_patch_index                Surface_patch_index;

  bool success = true;

  CGAL_assertion_code(
    typename Tr::Geom_traits::Construct_point_3 cp = tr.geom_traits().construct_point_3_object();
    typename Tr::Geom_traits::Orientation_3 orientation = tr.geom_traits().orientation_3_object();
  )

  typename SubdomainsRange::value_type max_domain = 0;
  if(replace_domain_0)
  {
    for(std::size_t i=0; i<finite_cells.size(); ++i)
    {
      if(subdomains[i] > max_domain)
        max_domain = subdomains[i];
    }
  }

  // build the finite cells
  for(std::size_t i=0; i<finite_cells.size(); ++i)
  {
    const auto& tet = finite_cells[i];
    std::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(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->set_subdomain_index(subdomains[i]); // the cell's info keeps the reference of the tetrahedron
    if(replace_domain_0 && subdomains[i] == 0)
      c->set_subdomain_index(max_domain+1); // the cell's info keeps the reference of the tetrahedron

    // 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)
    {
      // do not allow non-manifoldness in the finite cells case
      if(!CGAL::SMDS_3::add_facet_to_incident_cells_map<Tr>(c, j, incident_cells_map, verbose, false))
        success = false;

      if(border_facets.size() != 0)
      {
        std::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)({facet[0], facet[1], facet[2]});
        do
        {
          std::rotate(std::begin(facet), std::next(std::begin(facet)), std::end(facet));
        }
        while(facet[0] != n0);

        typename FacetPatchMap::const_iterator it = border_facets.find(facet);
        if(it != border_facets.end())
        {
          c->set_surface_patch_index(j, it->second);
        }
        else
        {
          std::swap(facet[1], facet[2]); // facet[0] is still the smallest, no need to rotate again

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

  return success;
}

template<class Tr>
bool add_infinite_facets_to_incident_cells_map(typename Tr::Cell_handle c,
                                               int inf_vert_pos,
                                               boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                                                                    std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                                               const bool verbose,
                                               const bool allow_non_manifold)
{
  int l = (inf_vert_pos + 1) % 4;
  bool b1 = CGAL::SMDS_3::add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map, verbose, allow_non_manifold);
  l = (inf_vert_pos + 2) % 4;
  bool b2 = CGAL::SMDS_3::add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map, verbose, allow_non_manifold);
  l = (inf_vert_pos + 3) % 4;
  bool b3 = CGAL::SMDS_3::add_facet_to_incident_cells_map<Tr>(c, l, incident_cells_map, verbose, allow_non_manifold);

  return b1 && b2 && b3;
}

template<class Tr>
bool build_infinite_cells(Tr& tr,
                          boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                                               std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                          const bool verbose,
                          const bool allow_non_manifold)
{
  typedef typename Tr::Vertex_handle                               Vertex_handle;
  typedef typename Tr::Cell_handle                                 Cell_handle;
  typedef std::array<Vertex_handle, 3>                             Facet_vvv;
  typedef std::pair<Cell_handle, int>                              Incident_cell;
  typedef boost::unordered_map<Facet_vvv, std::vector<Incident_cell> > Incident_cells_map;

  bool success = true;

  std::vector<Cell_handle> infinite_cells;

  // 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;

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

    infinite_cells.push_back(opp_c);

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

    // the only finite facet
    it->second.emplace_back(opp_c, 0);
    CGAL_assertion(it->second.size() == 2);

    opp_c->set_surface_patch_index(0, c->surface_patch_index(i));
  }

#ifdef CGAL_TET_SOUP_TO_C3T3_DEBUG
  for (auto icit : incident_cells_map)
    CGAL_assertion(icit.second.size() == 2);

  std::map<Facet_vvv, int> facets;
  for (const Cell_handle c : infinite_cells)
  {
    for (int i = 1; i < 4; ++i)
    {
      std::array<Vertex_handle, 3> vs = CGAL::SMDS_3::make_ordered_vertex_array(c->vertex((i + 1) % 4),
                                                                                c->vertex((i + 2) % 4),
                                                                                c->vertex((i + 3) % 4));
      if (facets.find(vs) == facets.end())
        facets.emplace(vs, 1);
      else
        facets[vs]++;
    }
  }

  for (auto fp : facets)
  {
    if (fp.second != 2)
    {
      std::cout << "Warning: non manifold edge" << std::endl;
      std::cout << "fp.second = " << fp.second << std::endl;
      std::cout << tr.point(fp.first[0]) << " "
                << tr.point(fp.first[1]) << " "
                << tr.point(fp.first[2]) << std::endl;
      success = false;
    }
//    CGAL_assertion(fp.second == 2);
  }
#endif

  // add the facets to the incident cells map
  for (const Cell_handle& c : infinite_cells)
  {
    if(!CGAL::SMDS_3::add_infinite_facets_to_incident_cells_map<Tr>(c,
                                                                    c->index(tr.infinite_vertex()),
                                                                    incident_cells_map,
                                                                    verbose,
                                                                    allow_non_manifold))
      success = false;
  }

  return success;
}

template<typename Tr>
bool is_infinite(const std::array<typename Tr::Vertex_handle, 3>& f,
                 const Tr& tr)
{
  for (auto vh : f)
  {
    if (tr.infinite_vertex() == vh)
      return true;
  }
  return false;
}

template<class Tr>
bool assign_neighbors(Tr& tr,
                      const boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                                                 std::vector<std::pair<typename Tr::Cell_handle, int> > >& incident_cells_map,
                      const bool allow_non_manifold)
{
  typedef typename Tr::Cell_handle                                   Cell_handle;
  typedef std::pair<Cell_handle, int>                                Incident_cell;
  typedef boost::unordered_map<std::array<typename Tr::Vertex_handle, 3>,
                               std::vector<Incident_cell> >          Incident_cells_map;

  bool success = true;

  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)
    {
      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);
    }
    else if(!allow_non_manifold)
    {
      CGAL_assertion_code(const auto& f = icit->first);
      CGAL_assertion(is_infinite(f, tr));

      CGAL_assertion(adjacent_cells.size() % 2 == 0);
      success = false;
    }
  }
  return success;
}

template<class Tr,
         typename PointRange,
         typename CellRange,
         typename FacetPatchMap>
bool build_triangulation_impl(Tr& tr,
                              const PointRange& points,
                              const CellRange& finite_cells,
                              const std::vector<typename Tr::Cell::Subdomain_index>& subdomains,
                              const FacetPatchMap& border_facets,
                              std::vector<typename Tr::Vertex_handle>& vertex_handle_vector,
                              const bool verbose,// = false,
                              const bool replace_domain_0,// = false,
                              const bool allow_non_manifold) // = false
{
  if (verbose)
    std::cout << "build_triangulation_impl()..." << std::endl;

  typedef typename Tr::Vertex_handle            Vertex_handle;
  typedef typename Tr::Cell_handle              Cell_handle;
  typedef std::array<Vertex_handle, 3>          Facet_vvv;

  // 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_vvv, std::vector<Incident_cell> >  Incident_cells_map;

  CGAL_precondition(!points.empty());

  bool success = true;
  Incident_cells_map incident_cells_map;

  // id to vertex_handle
  // index 0 is for infinite vertex; 1 to n for points in `points`
  vertex_handle_vector.resize(points.size() + 1);

  if(finite_cells.empty())
  {
    if (verbose)
      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);
  for(Vertex_handle vh : vertex_handle_vector)
    vh->set_dimension(-1);

  if(verbose)
    std::cout << "build vertices done (" << tr.tds().number_of_vertices() << " vertices)" << std::endl;

  if (!finite_cells.empty())
  {
    if (!CGAL::SMDS_3::build_finite_cells<Tr>(tr, finite_cells, subdomains, vertex_handle_vector,
                                              incident_cells_map, border_facets, verbose, replace_domain_0))
    {
      if (verbose)
        std::cerr << "Error: build_finite_cells went wrong!" << std::endl;
      success = false;
    }
    else if(verbose)
    {
      std::cout << "build finite cells done (" << tr.tds().cells().size() << " cells)" << std::endl;
    }

    if (!CGAL::SMDS_3::build_infinite_cells<Tr>(tr, incident_cells_map, verbose, allow_non_manifold))
    {
      if(verbose)
        std::cerr << "Error: build_infinite_cells went wrong!" << std::endl;
      success = false;
    }
    else if(verbose)
    {
      std::cout << "build infinite cells done (" << tr.tds().cells().size() << " cells)" << std::endl;
    }

    tr.tds().set_dimension(3);

    if (!CGAL::SMDS_3::assign_neighbors<Tr>(tr, incident_cells_map, allow_non_manifold))
    {
      if(verbose)
        std::cerr << "Error: assign_neighbors went wrong!" << std::endl;
      success = false;
    }
    else if(verbose)
    {
      std::cout << "assign neighbors done" << std::endl;
    }

    if (verbose)
    {
      std::cout << "built triangulation!" << std::endl;
    }
  }

  // disabled because the TDS is not valid when cells do not cover the convex hull of vertices
  // return tr.tds().is_valid();

  return success;

}

template<class Tr,
         typename PointRange,
         typename CellRange,
         typename FacetPatchMap>
bool build_triangulation_one_subdomain(Tr& tr,
                                       const PointRange& points,
                                       const CellRange& finite_cells,
                                       const typename Tr::Cell::Subdomain_index& subdomain,
                                       const FacetPatchMap& border_facets,
                                       std::vector<typename Tr::Vertex_handle>& vertex_handle_vector,
                                       const bool verbose,// = false,
                                       const bool replace_domain_0,// = false
                                       const bool allow_non_manifold)// = false
{
  std::vector<typename Tr::Cell::Subdomain_index> subdomains(finite_cells.size(), subdomain);
  return build_triangulation_impl(tr, points, finite_cells, subdomains,
                                  border_facets, vertex_handle_vector,
                                  verbose, replace_domain_0,
                                  allow_non_manifold);
}

template<class Tr,
         typename PointRange,
         typename CellRange,
         typename FacetPatchMap>
bool build_triangulation_one_subdomain(Tr& tr,
                                       const PointRange& points,
                                       const CellRange& finite_cells,
                                       const typename Tr::Cell::Subdomain_index& subdomain,
                                       const FacetPatchMap& border_facets,
                                       const bool verbose,// = false,
                                       const bool replace_domain_0,// = false
                                       const bool allow_non_manifold)//= false
{
  std::vector<typename Tr::Cell::Subdomain_index> subdomains(finite_cells.size(), subdomain);
  std::vector<typename Tr::Vertex_handle> vertex_handle_vector;
  return build_triangulation_impl(tr, points, finite_cells, subdomains,
                                  border_facets, vertex_handle_vector,
                                  verbose, replace_domain_0,
                                  allow_non_manifold);
}

template<class Tr,
         typename PointRange,
         typename CellRange,
         typename SubdomainsRange,
         typename FacetPatchMap>
bool build_triangulation_with_subdomains_range(Tr& tr,
                                               const PointRange& points,
                                               const CellRange& finite_cells,
                                               const SubdomainsRange& subdomains,
                                               const FacetPatchMap& border_facets,
                                               const bool verbose,// = false
                                               const bool replace_domain_0,// = false,
                                               const bool allow_non_manifold)
{
  std::vector<typename Tr::Vertex_handle> vertex_handle_vector;
  std::vector<typename Tr::Cell::Subdomain_index> subdomains_vector(
      subdomains.begin(), subdomains.end());
  return build_triangulation_impl(tr, points, finite_cells, subdomains_vector, border_facets,
                                  vertex_handle_vector,
                                  verbose, replace_domain_0,
                                  allow_non_manifold);
}

template<class Tr>
bool build_triangulation_from_file(std::istream& is,
                                   Tr& tr,
                                   const bool verbose,
                                   const bool replace_domain_0,
                                   const bool allow_non_manifold)
{
  using Point_3 = typename Tr::Point;
  using Subdomain_index = typename Tr::Cell::Subdomain_index;
  using Surface_patch_index = typename Tr::Cell::Surface_patch_index;

  using Facet        = std::array<int, 3>; // 3 = id
  using Tet_with_ref = std::array<int, 4>; // 4 = id

  if(!is)
    return false;

  std::vector<Tet_with_ref> finite_cells;
  std::vector<Subdomain_index> subdomains;
  std::vector<Point_3> points;
  boost::unordered_map<Facet, Surface_patch_index> border_facets;

  int dim;
  int nv, nf, ntet, ref;
  std::string word;

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

  CGAL_assertion(dim == 3);

  if(verbose)
  {
    std::cout << "Reading .mesh file..." << std::endl;
    std::cout << "Replace domain #0 = " << replace_domain_0 << std::endl;
    std::cout << "Allow non-manifoldness = " << allow_non_manifold << std::endl;
  }

  bool is_CGAL_mesh = false;

  std::string line;
  while(std::getline(is, line) && line != "End")
  {
    // remove trailing whitespace, in particular a possible '\r' from Windows
    // end-of-line encoding
    if(!line.empty() && std::isspace(line.back())) {
      line.pop_back();
    }
    if (line.size() > 0 && line.at(0) == '#' &&
        line.find("CGAL::Mesh_complex_3_in_triangulation_3") != std::string::npos)
    {
      is_CGAL_mesh = true; // with CGAL meshes, domain 0 should be kept
      continue;
    }

    if(line.find("Vertices") != std::string::npos)
    {
      is >> nv;
      if(verbose)
        std::cerr << "Reading "<< nv << " vertices" << std::endl;
      for(int i=0; i<nv; ++i)
      {
        typename Tr::Geom_traits::FT x,y,z;
        if(!(is >> x >> y >> z >> ref))
        {
          if(verbose)
            std::cerr << "Issue while reading vertices" << std::endl;
          return false;
        }
        points.emplace_back(x,y,z);
      }
    }

    if(line.find("Triangles") != std::string::npos)
    {
      bool has_negative_surface_patch_ids = false;
      Surface_patch_index max_surface_patch_id{0};
      is >> nf;

      if(verbose)
        std::cerr << "Reading "<< nf << " triangles" << std::endl;

      for(int i=0; i<nf; ++i)
      {
        int n[3];
        Surface_patch_index surface_patch_id;
        if(!(is >> n[0] >> n[1] >> n[2] >> surface_patch_id))
        {
          if(verbose)
            std::cerr << "Issue while reading triangles" << std::endl;
          return false;
        }
        has_negative_surface_patch_ids |= (surface_patch_id < 0);
        max_surface_patch_id = (std::max)(max_surface_patch_id, surface_patch_id);
        Facet facet;
        facet[0] = n[0] - 1;
        facet[1] = n[1] - 1;
        facet[2] = n[2] - 1;

        if(verbose)
          std::cout << "Looking at face #" << i << ": " << n[0] << " " << n[1] << " " << n[2] << std::endl;

        CGAL_warning_code(
        for(int j=0; j<3; ++j)
          for(int k=0; k<3; ++k)
            if(j != k)
              CGAL_warning(n[j] != n[k]);
        )

        // find the circular permutation that puts the smallest index in the first place.
        int n0 = (std::min)({facet[0],facet[1], facet[2]});
        do
        {
          std::rotate(std::begin(facet), std::next(std::begin(facet)), std::end(facet));
        }
        while(facet[0] != n0);

        border_facets.emplace(facet, surface_patch_id);
      }
      if(has_negative_surface_patch_ids)
      {
        if(verbose)
          std::cerr << "Warning: negative surface patch ids" << std::endl;
        for(auto& facet_and_patch_id  : border_facets) {
          if(facet_and_patch_id.second < 0)
            facet_and_patch_id.second = max_surface_patch_id - facet_and_patch_id.second;
        }
      }
    }

    if(line.find("Tetrahedra") != std::string::npos)
    {
      is >> ntet;

      if(verbose)
        std::cerr << "Reading "<< ntet << " tetrahedra" << std::endl;

      for(int i=0; i<ntet; ++i)
      {
        int n[4];
        int reference;

        if(!(is >> n[0] >> n[1] >> n[2] >> n[3] >> reference))
        {
          if(verbose)
            std::cerr << "Issue while reading tetrahedra" << std::endl;
          return false;
        }

        if(verbose)
          std::cout << "Looking at tet #" << i << ": " << n[0] << " " << n[1] << " " << n[2] << " " << n[3] << std::endl;

        CGAL_warning_code(
        for(int j=0; j<4; ++j)
          for(int k=0; k<4; ++k)
            if(j != k)
              CGAL_warning(n[j] != n[k]);
        )

        Tet_with_ref t;
        t[0] = n[0] - 1;
        t[1] = n[1] - 1;
        t[2] = n[2] - 1;
        t[3] = n[3] - 1;

        finite_cells.push_back(t);
        subdomains.push_back(reference);
      }
    }
  }

  if (verbose)
  {
    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;

  CGAL_assertion(finite_cells.size() == subdomains.size());

  return build_triangulation_with_subdomains_range(tr,
                                                   points, finite_cells, subdomains, border_facets,
                                                   verbose,
                                                   replace_domain_0 && !is_CGAL_mesh,
                                                   allow_non_manifold);
}

} // namespace SMDS_3
} // namespace CGAL

#endif // CGAL_SMDS_3_TET_SOUP_TO_C3T3_H
