// Copyright (c) 2022 GeometryFactory (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.2-beta1/Shape_detection/include/CGAL/Polygon_mesh_processing/region_growing.h $
// $Id: include/CGAL/Polygon_mesh_processing/region_growing.h 431cfb5357d $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Sébastien Loriot


#ifndef CGAL_POLYGON_MESH_PROCESSING_REGION_GROWING_H
#define CGAL_POLYGON_MESH_PROCESSING_REGION_GROWING_H

#include <CGAL/license/Polygon_mesh_processing/miscellaneous.h>

#include <CGAL/boost/graph/named_params_helper.h>
#include <CGAL/Named_function_parameters.h>
#include <CGAL/Shape_detection/Region_growing/Region_growing.h>
#include <CGAL/Shape_detection/Region_growing/Polygon_mesh.h>
#include <CGAL/Shape_detection/Region_growing/Segment_set.h>
#include <CGAL/property_map.h>

namespace CGAL {
namespace Polygon_mesh_processing {

namespace internal
{
  template <class GT, class Pair>
  void fill_region_primitive_map(const std::vector<Pair>&, internal_np::Param_not_found) {}

  template <class GT, class Pair, class RegionMap>
  void fill_plane_or_vector_map(const std::vector<Pair>& normals, RegionMap region_map, typename GT::Vector_3)
  {
    typedef typename boost::property_traits<RegionMap>::key_type KT;
    for (KT i = 0 ; i<static_cast<KT>(normals.size()); ++i)
      put(region_map, i, normals[i].first.orthogonal_vector());
  }

  template <class GT, class Pair, class RegionMap>
  void fill_plane_or_vector_map(const std::vector<Pair>& normals, RegionMap region_map, typename GT::Plane_3)
  {
    typedef typename boost::property_traits<RegionMap>::key_type KT;
    for (KT i = 0; i < static_cast<KT>(normals.size()); ++i)
      put(region_map, i, normals[i].first);
  }

  template <class GT, class Pair, class RegionMap>
  void fill_region_primitive_map(const std::vector<Pair>& normals, RegionMap region_map)
  {
    fill_plane_or_vector_map<GT>(normals, region_map, typename boost::property_traits<RegionMap>::value_type());
  }

template<typename PolygonMesh, typename ECM>
class One_ring_neighbor_query_with_constraints
{
  using face_descriptor = typename boost::graph_traits<PolygonMesh>::face_descriptor;
  using halfedge_descriptor = typename boost::graph_traits<PolygonMesh>::halfedge_descriptor;
  using Face_graph = PolygonMesh;
public:

  using Item = typename boost::graph_traits<PolygonMesh>::face_descriptor;
  using Region = std::vector<Item>;

  One_ring_neighbor_query_with_constraints(const PolygonMesh& pmesh, ECM ecm)
    : m_face_graph(pmesh)
    , m_ecm(ecm)
  {}

  void operator()(
    const Item query,
    std::vector<Item>& neighbors) const {

    neighbors.clear();
    const auto query_hedge = halfedge(query, m_face_graph);

    for (halfedge_descriptor h : halfedges_around_face(query_hedge, m_face_graph))
    {
      if (get(m_ecm, edge(h, m_face_graph))) continue;
      face_descriptor f=face(opposite(h,m_face_graph), m_face_graph);
      if (f != boost::graph_traits<PolygonMesh>::null_face())
      {
        neighbors.push_back(f);
      }
    }
  }

private:
  const Face_graph& m_face_graph;
  ECM m_ecm;
};

template<typename GeomTraits, typename PolygonMesh, typename VertexToPointMap, typename ECM, typename Least_squares_fitting_tag>
struct Region_and_Sorting_helper {};

template<typename GeomTraits, typename PolygonMesh, typename VertexToPointMap, typename ECM>
struct Region_and_Sorting_helper<GeomTraits, PolygonMesh, VertexToPointMap, ECM, Tag_true>
{
  using Neighbor_query = One_ring_neighbor_query_with_constraints<PolygonMesh, ECM>;
  using Plane_Region_type = CGAL::Shape_detection::Polygon_mesh::Least_squares_plane_fit_region<GeomTraits, PolygonMesh, VertexToPointMap>;
  using Plane_Sorting_type = CGAL::Shape_detection::Polygon_mesh::Least_squares_plane_fit_sorting<GeomTraits, PolygonMesh, Neighbor_query>;

  using Polyline_graph = CGAL::Shape_detection::Polygon_mesh::Polyline_graph<PolygonMesh, VertexToPointMap>;
  using Segment_map = typename Polyline_graph::Segment_map;
  using Item = typename Polyline_graph::Item;

  using Line_region = CGAL::Shape_detection::Segment_set::Least_squares_line_fit_region<GeomTraits, Item, Segment_map>;
  using Line_sorting = CGAL::Shape_detection::Segment_set::Least_squares_line_fit_sorting<GeomTraits, Item, Polyline_graph, Segment_map>;
};

template<typename GeomTraits, typename PolygonMesh, typename VertexToPointMap, typename ECM>
struct Region_and_Sorting_helper<GeomTraits, PolygonMesh, VertexToPointMap, ECM, Tag_false>
{
  using Neighbor_query = One_ring_neighbor_query_with_constraints<PolygonMesh, ECM>;
  using Plane_Region_type = CGAL::Shape_detection::Polygon_mesh::Plane_face_region<GeomTraits, PolygonMesh, VertexToPointMap>;
  using Plane_Sorting_type = CGAL::Shape_detection::Polygon_mesh::Face_area_sorting<GeomTraits, PolygonMesh>;

  using Polyline_graph = CGAL::Shape_detection::Polygon_mesh::Polyline_graph<PolygonMesh, VertexToPointMap>;
  using Segment_map = typename Polyline_graph::Segment_map;
  using Item = typename Polyline_graph::Item;

  using Line_region = CGAL::Shape_detection::Segment_set::Line_segment_region<GeomTraits, Item, Segment_map>;
  using Line_sorting = CGAL::Shape_detection::Segment_set::Segment_length_sorting<GeomTraits, Item, Segment_map>;
};

} // namespace internal

/*!
  \ingroup PMP_detect_features_grp

  \brief applies a region growing algorithm to fit planes on faces of a mesh.

  See Section \ref Shape_detection_RegionGrowing for more details on the method.

  @tparam PolygonMesh a model of `FaceListGraph`
  @tparam RegionMap a model of `WritablePropertyMap` with `boost::graph_traits<PolygonMesh>::%face_descriptor` as key type and `std::size_t` as value type.
  @tparam NamedParameters a sequence of \ref bgl_namedparameters "Named Parameters"

  @param mesh the polygon mesh whose faces are used for region growing
  @param region_map a property map storing the region index of each face. Values start at `0` up to the value returned minus `1`.
         `std::size_t(-1)` is put for faces with no region assigned (it can happen if `minimum_region_size > 1` or for a non-triangular
          face having a fitting plane not satisfying the maximum distance criterium).
  @param np an optional sequence of \ref bgl_namedparameters "Named Parameters" among the ones listed below

  @return the number of regions detected

  \cgalNamedParamsBegin
    \cgalParamNBegin{maximum_distance}
      \cgalParamDescription{the maximum distance from a face to a plane such that it is considered part of the region of the plane}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{1}
    \cgalParamNEnd
    \cgalParamNBegin{maximum_angle}
      \cgalParamDescription{the maximum angle (in degrees) between the normals of the supporting planes of two adjacent faces
                            such that they are considered part of the same region}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{25 degrees}
      \cgalParamExtra{this parameter and `cosine_of_maximum_angle` are exclusive}
    \cgalParamNEnd
    \cgalParamNBegin{least_squares_fitting}
      \cgalParamDescription{Refit the plane primitive regularly to the region during the region growing algorithm.
                            If false, the plane is equal to the support plane of the seed face.}
      \cgalParamType{`CGAL::Boolean_tag`}
      \cgalParamDefault{`CGAL::Tag_false()`}
      \cgalParamExtra{Valid values are CGAL::Tag_true() or CGAL::Tag_false().}
    \cgalParamNEnd
    \cgalParamNBegin{postprocess_regions}
      \cgalParamDescription{Apply a postprocessing step to the output of the region growing algorithm.}
      \cgalParamType{`bool`}
      \cgalParamDefault{false}
    \cgalParamNEnd
    \cgalParamNBegin{cosine_of_maximum_angle}
      \cgalParamDescription{The maximum angle, given as a cosine, between the normals of the supporting planes of adjacent faces
                            such that they are considered part of the same region}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{`cos(25 * PI / 180)`}
      \cgalParamExtra{this parameter and `maximum_angle` are exclusive}
    \cgalParamNEnd
    \cgalParamNBegin{minimum_region_size}
      \cgalParamDescription{the minimum number of faces such that a new region can be created from a set of faces}
      \cgalParamType{`std::size_t`}
      \cgalParamDefault{1}
    \cgalParamNEnd
    \cgalParamNBegin{vertex_point_map}
      \cgalParamDescription{a property map associating points to the vertices of `mesh`}
      \cgalParamType{a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::%vertex_descriptor`
                     as key type and `%Point_3` as value type}
      \cgalParamDefault{`boost::get(CGAL::vertex_point, mesh)`}
      \cgalParamExtra{If this parameter is omitted, an internal property map for `CGAL::vertex_point_t`
                      must be available in `PolygonMesh`.}
    \cgalParamNEnd
    \cgalParamNBegin{geom_traits}
      \cgalParamDescription{an instance of a geometric traits class}
      \cgalParamType{a class model of `Kernel`}
      \cgalParamDefault{a \cgal Kernel deduced from the point type, using `CGAL::Kernel_traits`}
      \cgalParamExtra{The geometric traits class must be compatible with the vertex point type.}
    \cgalParamNEnd
      \cgalParamNBegin{face_normal_map}
        \cgalParamDescription{a property map associating normal vectors to the faces of `mesh`.}
        \cgalParamType{a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::%face_descriptor`
                       as key type and `GT::Vector_3` as value type, `GT` being the type of the parameter `geom_traits`.}
        \cgalParamDefault{If this parameter is omitted, face normals will be estimated using cross products of vectors created
                          from consecutive vertices of the face.}
      \cgalParamNEnd
    \cgalParamNBegin{region_primitive_map}
      \cgalParamDescription{a property map filled by this function and that will contain for each region
                            the plane (or only its orthognonal vector) estimated that approximates it.}
      \cgalParamType{a class model of `WritablePropertyMap` with the value type of `RegionMap` as key and
                     `GeomTraits::Plane_3` or `GeomTraits::Vector_3` as value type,
                     `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{None}
    \cgalParamNEnd
  \cgalNamedParamsEnd
 */
template<typename PolygonMesh,
                  typename RegionMap,
                  typename NamedParameters = parameters::Default_named_parameters>
std::size_t
region_growing_of_planes_on_faces(const PolygonMesh& mesh,
                                  RegionMap region_map,
                                  const NamedParameters& np = parameters::default_values())
{
  namespace RG_PM = CGAL::Shape_detection::Polygon_mesh;

  using VPM = typename GetVertexPointMap < PolygonMesh, NamedParameters>::const_type;
  using Traits = typename GetGeomTraits<PolygonMesh, NamedParameters>::type;

  using parameters::choose_parameter;
  using parameters::get_parameter;

  typedef typename boost::graph_traits<PolygonMesh>::edge_descriptor edge_descriptor;
  typedef typename internal_np::Lookup_named_param_def <
      internal_np::edge_is_constrained_t,
      NamedParameters,
      Static_boolean_property_map<edge_descriptor, false> // default (no constraint pmap)
    > ::type ECM;
  ECM ecm = choose_parameter(get_parameter(np, internal_np::edge_is_constrained),
                             Static_boolean_property_map<edge_descriptor, false>());

  typedef typename internal_np::Lookup_named_param_def <
    internal_np::least_squares_fitting_t,
    NamedParameters,
    Tag_false // default (using Plane_face_region)
  > ::type Least_squares_fitting;

  using Helper = internal::Region_and_Sorting_helper<Traits, PolygonMesh, VPM, ECM, Least_squares_fitting>;
  using Neighbor_query = typename Helper::Neighbor_query;
  using Region_type = typename Helper::Plane_Region_type;
  using Sorting = typename Helper::Plane_Sorting_type;
  using Region_growing = CGAL::Shape_detection::Region_growing<Neighbor_query, Region_type, RegionMap>;

  Neighbor_query neighbor_query(mesh, ecm);
  Region_type region_type(mesh, np);
  Sorting sorting(mesh, neighbor_query, np);
  sorting.sort();

  std::vector<typename Region_growing::Primitive_and_region> regions;
  Region_growing region_growing(
    faces(mesh), sorting.ordered(), neighbor_query, region_type, region_map);

  typedef typename boost::graph_traits<PolygonMesh>::face_descriptor face_descriptor;
  typedef typename boost::graph_traits<PolygonMesh>::halfedge_descriptor halfedge_descriptor;
  std::vector<std::pair<typename Traits::Plane_3, std::vector<face_descriptor> > > tmp;
  region_growing.detect(std::back_inserter(tmp));

  if (choose_parameter(get_parameter(np, internal_np::postprocess_regions), false))
  {
    // first try for a postprocessing: look at regions made of one face and check if a
    // larger region contains its 3 vertices and if so assigned it to it.
    typedef typename boost::property_traits<RegionMap>::value_type Id;
    for (std::size_t i=0; i<tmp.size(); ++i)
    {
      if (tmp[i].second.size() == 1)
      {
        face_descriptor f0=tmp[i].second[0];
        std::map<Id, int> vertex_incidence;
        halfedge_descriptor h0 = halfedge(f0, mesh);
        for (int k=0; k<3; ++k)
        {
          std::set<Id> ids_for_v;
          for (halfedge_descriptor h : halfedges_around_target(h0, mesh))
          {
            if (!is_border(h, mesh))
            {
              Id id = get(region_map, face(h, mesh));
              if (std::size_t(id)!=i)
                ids_for_v.insert(id);
            }
          }
          h0=next(h0, mesh);
          for (Id id : ids_for_v)
            vertex_incidence.insert(std::make_pair(id, 0)).first->second+=1;
        }
        std::set<Id> candidates;
        for (const std::pair<const Id, int>& p : vertex_incidence)
        {
          if (p.second == 3)
            candidates.insert(p.first);
        }
        if (candidates.size() == 1)
        {
          Id new_id = *candidates.begin();
          put(region_map, f0, static_cast<Id>(new_id));
          tmp[new_id].second.push_back(f0);
          tmp[i].second.clear();
        }
      }
    }
    auto last = std::remove_if(tmp.begin(), tmp.end(),
                               [](const std::pair<typename Traits::Plane_3, std::vector<face_descriptor>>& p)
                               {return p.second.empty();});
    tmp.erase(last, tmp.end());

    //update region map
    for (Id i=0; i<static_cast<Id>(tmp.size()); ++i)
    {
      for (face_descriptor f : tmp[i].second)
        put(region_map, f, i);
    }

  }

  internal::fill_region_primitive_map<Traits>(tmp, parameters::get_parameter(np, internal_np::region_primitive_map));

  return tmp.size();
}

/*!
  \ingroup PMP_detect_features_grp

  \brief detects the corners on the boundary of almost planar regions by applying the region growing algorithm fitting lines on segment edges of a partition of a mesh.

    More precisely, a corner on the boundary of a region is a vertex that is either shared by at least three regions (two if it is also a vertex on the boundary of the mesh), or that is incident to two segments edges assigned to different lines.
  See Section \ref Shape_detection_RegionGrowing for more details on the method.

  @tparam PolygonMesh a model of `FaceListGraph` and `EdgeListGraph`
  @tparam RegionMap a model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::%face_descriptor` as key type and `std::size_t` as value type.
  @tparam CornerIdMap a model of `WritablePropertyMap` with `boost::graph_traits<PolygonMesh>::%vertex_descriptor` as key type and `std::size_t` as value type.
  @tparam NamedParameters a sequence of \ref bgl_namedparameters "Named Parameters"

  @param mesh polygon mesh for region growing.
  @param region_map property map providing the region index of each face, values must be in `[0, nb_regions-1]`.
  @param corner_id_map property map storing the corner index of each vertex. Values start at `0` up to the value returned minus 1.
         `std::size_t(-1)` is put for vertices that are not corners.
  @param nb_regions the number of patches in the partition of `mesh` defined by `region_map`
  @param np an optional sequence of \ref bgl_namedparameters "Named Parameters" among the ones listed below

  @return the number of corners detected

  \cgalNamedParamsBegin
    \cgalParamNBegin{edge_is_constrained_map}
      \cgalParamDescription{a property map filled by this function such that an edge is marked as constrained
                            if it is at the interface of two different regions or on the boundary of the mesh}
      \cgalParamType{a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::%edge_descriptor`
                     as key type and `bool` as value type}
      \cgalParamDefault{Unused if not provided}
      \cgalParamExtra{The value for each edge must be initialized to `false`.}
    \cgalParamNEnd
    \cgalParamNBegin{maximum_distance}
      \cgalParamDescription{the maximum distance from a segment to a line such that it is considered part of the region of the line}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{1}
    \cgalParamNEnd
    \cgalParamNBegin{maximum_angle}
      \cgalParamDescription{the maximum angle in degrees between two adjacent segments
                            such that they are considered part of the same region}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{25 degrees}
      \cgalParamExtra{this parameter and `cosine_of_maximum_angle` are exclusive}
    \cgalParamNEnd
    \cgalParamNBegin{cosine_of_maximum_angle}
      \cgalParamDescription{The maximum angle, given as a cosine, for the smallest angle
                            between the supporting line of a segment and an adjacent segment
                            such that they are considered part of the same region}
      \cgalParamType{`GeomTraits::FT` with `GeomTraits` being the type of the parameter `geom_traits`}
      \cgalParamDefault{`cos(25 * PI / 180)`}
      \cgalParamExtra{this parameter and `maximum_angle` are exclusive}
    \cgalParamNEnd
    \cgalParamNBegin{least_squares_fitting}
      \cgalParamDescription{Refit the line primitive regularly to the region during the region growing algorithm.
                            If false, the line primitive is equal to the support line of the seed edge.}
      \cgalParamType{`CGAL::Boolean_tag`}
      \cgalParamDefault{`CGAL::Tag_false()`}
      \cgalParamExtra{Valid values are CGAL::Tag_true() or CGAL::Tag_false().}
    \cgalParamNEnd
    \cgalParamNBegin{vertex_point_map}
      \cgalParamDescription{a property map associating points to the vertices of `mesh`}
      \cgalParamType{a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::%vertex_descriptor`
                     as key type and `%Point_3` as value type}
      \cgalParamDefault{`boost::get(CGAL::vertex_point, mesh)`}
      \cgalParamExtra{If this parameter is omitted, an internal property map for `CGAL::vertex_point_t`
                      must be available in `PolygonMesh`.}
    \cgalParamNEnd
    \cgalParamNBegin{geom_traits}
      \cgalParamDescription{an instance of a geometric traits class}
      \cgalParamType{a class model of `Kernel`}
      \cgalParamDefault{a \cgal Kernel deduced from the point type, using `CGAL::Kernel_traits`}
      \cgalParamExtra{The geometric traits class must be compatible with the vertex point type.}
    \cgalParamNEnd
  \cgalNamedParamsEnd
 */
template <typename PolygonMesh,
          typename RegionMap,
          typename CornerIdMap,
          typename NamedParameters = parameters::Default_named_parameters>
std::size_t
detect_corners_of_regions(
  const PolygonMesh& mesh,
  RegionMap region_map,
  std::size_t nb_regions,
  CornerIdMap corner_id_map,
  const NamedParameters& np = parameters::default_values())
{
  using parameters::choose_parameter;
  using parameters::get_parameter;
  using parameters::is_default_parameter;

  using VPM = typename GetVertexPointMap < PolygonMesh, NamedParameters>::const_type;
  using Traits = typename GetGeomTraits<PolygonMesh, NamedParameters>::type;
  using Graph_traits = boost::graph_traits<PolygonMesh>;
  using halfedge_descriptor = typename Graph_traits::halfedge_descriptor;
  using edge_descriptor = typename Graph_traits::edge_descriptor;
  using face_descriptor = typename Graph_traits::face_descriptor;
  using vertex_descriptor = typename Graph_traits::vertex_descriptor;

  using Default_ecm = typename boost::template property_map<PolygonMesh, CGAL::dynamic_edge_property_t<bool> >::const_type;
  using Ecm = typename internal_np::Lookup_named_param_def <
                internal_np::edge_is_constrained_t,
                NamedParameters,
                Default_ecm
              > ::type;

  Default_ecm dynamic_ecm;
  if(is_default_parameter<NamedParameters, internal_np::edge_is_constrained_t>::value)
  {
    dynamic_ecm = get(CGAL::dynamic_edge_property_t<bool>(), mesh);
    for (edge_descriptor e : edges(mesh))
      put(dynamic_ecm, e, false);
  }
  Ecm ecm = choose_parameter(get_parameter(np, internal_np::edge_is_constrained), dynamic_ecm);

  typedef typename internal_np::Lookup_named_param_def <
    internal_np::least_squares_fitting_t,
    NamedParameters,
    Tag_false // default (using Line_segment_region)
  > ::type Least_squares_fitting;

  using Helper = internal::Region_and_Sorting_helper<Traits, PolygonMesh, VPM, Ecm, Least_squares_fitting>;

  using Polyline_graph     = typename Helper::Polyline_graph;

  using Line_region  = typename Helper::Line_region;
  using Line_sorting = typename Helper::Line_sorting;
  using RG_lines     = CGAL::Shape_detection::Region_growing<Polyline_graph, Line_region>;

  // mark as constrained edges at the interface of two regions
  for (edge_descriptor e : edges(mesh))
  {
    halfedge_descriptor h = halfedge(e, mesh);
    face_descriptor f1 = face(h, mesh);
    face_descriptor f2 = face(opposite(h, mesh), mesh);
    // an edge is constrained if it is a border edge or if the regions assigned to the two faces are different
    if (f1 == Graph_traits::null_face() || f2 == Graph_traits::null_face() || get(region_map,f1)!=get(region_map,f2))
      put(ecm, e, true);
  }

  //init to -1 by default
  for(vertex_descriptor v : vertices(mesh))
  {
    put(corner_id_map, v, std::size_t(-1));
  }

  // filter trivial edges: incident to a plane with only one face
  // such an edge cannot be removed and its vertices are corners
  std::vector<int> nb_faces_per_patch(nb_regions,0);
  for(face_descriptor f : faces(mesh))
  {
    std::size_t pid = get(region_map, f);
    nb_faces_per_patch[pid]+=1;
  }

  std::vector<edge_descriptor> filtered_edges, trivial_edges;
  for (edge_descriptor e : edges(mesh))
  {
    halfedge_descriptor h=halfedge(e,mesh);
    std::size_t r1 = is_border(h, mesh)?std::size_t(-1):get(region_map, face(h, mesh));
    h=opposite(h, mesh);
    std::size_t r2 = is_border(h, mesh)?std::size_t(-1):get(region_map, face(h, mesh));
    if ( (r1!=std::size_t(-1) && nb_faces_per_patch[r1]==1) || (r2!=std::size_t(-1) && nb_faces_per_patch[r2]==1) )
      trivial_edges.push_back(e);
    else
      filtered_edges.push_back(e);
  }

  Polyline_graph pgraph(mesh, filtered_edges, region_map, np);
  const auto& segment_range = pgraph.segment_range();

  Line_region line_region(np.segment_map(pgraph.segment_map()));

  std::vector< std::pair<typename Line_region::Primitive, std::vector<edge_descriptor> > > subregions; // TODO dump into pmap lines
  if (!segment_range.empty())
  {
    Line_sorting line_sorting(
      segment_range, pgraph, CGAL::parameters::segment_map(pgraph.segment_map()));
    line_sorting.sort();

    RG_lines rg_lines(
      segment_range, pgraph, line_region);

    rg_lines.detect(std::back_inserter(subregions));
  }

#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
  std::ofstream debug_corners("corners.xyz");
  debug_corners.precision(17);
  std::ofstream debug_edges("contraints.polylines.txt");
  debug_edges.precision(17);
#endif

  // detect vertex corner id
  std::size_t cid=0;
  for (const std::pair<typename Line_region::Primitive, std::vector<edge_descriptor>>& r : subregions)
  {
    std::vector<std::size_t> vertex_count(num_vertices(mesh), 0);
    std::vector<vertex_descriptor> line_vertices;
    auto register_vertex = [&vertex_count, &line_vertices]
                           (vertex_descriptor v)
    {
      if (vertex_count[v]==0)
        line_vertices.push_back(v);
      vertex_count[v]+=1;
    };
    for (edge_descriptor e : r.second)
    {
      put(ecm, e, true);
      register_vertex(source(e, mesh));
      register_vertex(target(e, mesh));
#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
      debug_edges << "2 " << mesh.point(source(e, mesh)) << " " << mesh.point(target(e, mesh)) << "\n";
#endif
    }

    for (vertex_descriptor v : line_vertices)
      if (vertex_count[v]==1)
      {
        if (get(corner_id_map, v) == std::size_t(-1))
        {
#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
          debug_corners << mesh.point(v) << "\n";
#endif
          put(corner_id_map, v, cid++);
        }
      }
  }

  // process trivial edges (could be done before if needed)
  for(edge_descriptor e : trivial_edges)
  {
#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
    debug_edges << "2 " << mesh.point(source(e, mesh)) << " " << mesh.point(target(e, mesh)) << "\n";
#endif
    put(ecm, e, true);
    if (get(corner_id_map, source(e, mesh))==std::size_t(-1))
    {
#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
      debug_corners << mesh.point(source(e, mesh)) << "\n";
#endif
      put(corner_id_map, source(e, mesh), cid++);
    }
    if (get(corner_id_map, target(e, mesh))==std::size_t(-1))
    {
#ifdef CGAL_DEBUG_DETECT_CORNERS_OF_REGIONS
      debug_corners << mesh.point(target(e, mesh)) << "\n";
#endif
      put(corner_id_map, target(e, mesh), cid++);
    }
  }

  return cid;
}

} } // end of CGAL::Polygon_mesh_processing namespace

#endif //CGAL_POLYGON_MESH_PROCESSING_REGION_GROWING_H
