// Copyright (c) 2003-2007  INRIA Sophia-Antipolis (France).
// Copyright (c) 2008       GeometryFactory (France)
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v5.6/Surface_mesher/include/CGAL/IO/Complex_2_in_triangulation_3_polyhedron_builder.h $
// $Id: Complex_2_in_triangulation_3_polyhedron_builder.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Laurent Rineau

#ifndef CGAL_IO_COMPLEX_2_IN_TRIANGULATION_3_POLYHEDRON_BUILDER_H
#define CGAL_IO_COMPLEX_2_IN_TRIANGULATION_3_POLYHEDRON_BUILDER_H

#include <CGAL/license/Surface_mesher.h>

#include <CGAL/disable_warnings.h>

#include <CGAL/Modifier_base.h>
#include <CGAL/Polyhedron_incremental_builder_3.h>

#include <stack>
#include <set>

namespace CGAL {

template <class C2T3, class Polyhedron_>
class Complex_2_in_triangulation_3_polyhedron_builder
  : public CGAL::Modifier_base<typename Polyhedron_::HalfedgeDS>
{
public:
  typedef C2T3 C2t3;
  typedef Polyhedron_ Polyhedron;
  typedef typename Polyhedron::HalfedgeDS HDS;

private:
  typedef typename C2T3::Triangulation Tr;

  const C2t3& c2t3;
  typedef CGAL::Modifier_base<typename Polyhedron::HalfedgeDS> Base;

  template <class IBuilder, class Vertex_handle>
  int get_vertex_index(IBuilder& builder, Vertex_handle vh, std::map<Vertex_handle, int>& V, int& inum)
  {
    typedef typename std::map<Vertex_handle, int>::iterator map_iterator;
    std::pair<map_iterator,bool> insert_res = V.insert( std::make_pair(vh,inum) );
    if ( insert_res.second ){
      typename Tr::Point p = static_cast<typename Tr::Point>(vh->point());
      builder.add_vertex(p);
      ++inum;
    }
    return insert_res.first->second;
  }

public:
  Complex_2_in_triangulation_3_polyhedron_builder(const C2t3& c2t3)
    : Base(), c2t3(c2t3)
  {
  }

  void operator()(HDS& hds) {
    typedef typename Tr::Vertex_handle Vertex_handle;
    typedef typename Tr::Geom_traits::Vector_3 Vector;
    typedef typename Tr::Edge Edge;
    typedef typename Tr::Facet Facet;
    typedef typename Tr::Finite_facets_iterator Finite_facets_iterator;

    const Tr& tr = c2t3.triangulation();
    CGAL::Polyhedron_incremental_builder_3<HDS> builder(hds, true);
    const typename Tr::size_type number_of_facets = c2t3.number_of_facets();
    builder.begin_surface(tr.number_of_vertices(),
                          number_of_facets);
    {
      // Finite vertices coordinates.
      Finite_facets_iterator fit = tr.finite_facets_begin();
      std::set<Facet> oriented_set;
      std::stack<Facet> stack;

      CGAL_assertion_code(typename Tr::size_type nb_facets = 0; )

      while (oriented_set.size() != number_of_facets) {
        while ( fit->first->is_facet_on_surface(fit->second) == false ||
                oriented_set.find(*fit) != oriented_set.end() ||

                oriented_set.find(c2t3.opposite_facet(*fit)) !=
                oriented_set.end() ) {
          ++fit;
        }
        oriented_set.insert(*fit);
        stack.push(*fit);
        while(! stack.empty() ) {
          Facet f = stack.top();
          stack.pop();
          for(int ih = 0 ; ih < 3 ; ++ih) {
            const int i1  = tr.vertex_triple_index(f.second, tr. cw(ih));
            const int i2  = tr.vertex_triple_index(f.second, tr.ccw(ih));
            if( c2t3.face_status(Edge(f.first, i1, i2)) == C2t3::REGULAR ) {
              Facet fn = c2t3.neighbor(f, ih);
              if (oriented_set.find(fn) == oriented_set.end() &&
                  oriented_set.find(c2t3.opposite_facet(fn)) == oriented_set.end())
              {
                oriented_set.insert(fn);
                stack.push(fn);
              }
            } // end "if the edge is regular"
          } // end "for each neighbor of f"
        } // end "stack non empty"
      } // end "oriented_set not full"

      // Orients the whole mesh towards outside:
      // - find the facet with max z
      typename std::set<Facet>::const_iterator top_facet = oriented_set.begin();
      for(typename std::set<Facet>::const_iterator fit = oriented_set.begin();
          fit != oriented_set.end();
          ++fit)
      {
        double top_z =
          (top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 0))->point().z()
         + top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 1))->point().z()
         + top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 2))->point().z())/3.;
        double z =
          (fit->first->vertex(tr.vertex_triple_index(fit->second, 0))->point().z()
         + fit->first->vertex(tr.vertex_triple_index(fit->second, 1))->point().z()
         + fit->first->vertex(tr.vertex_triple_index(fit->second, 2))->point().z())/3.;
        if (top_z < z)
          top_facet = fit;
      }
      // - orient the facet with max z towards +Z axis
      Vertex_handle v0 = top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 0));
      Vertex_handle v1 = top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 1));
      Vertex_handle v2 = top_facet->first->vertex(tr.vertex_triple_index(top_facet->second, 2));
      Vector normal = cross_product(v1->point()-v0->point(), v2->point()-v1->point());
      const Vector Z(0, 0, 1);
      bool regular_orientation = (Z * normal >= 0);

      //used to set indices of vertices
      std::map<Vertex_handle, int> V;
      int inum = 0;

      for(typename std::set<Facet>::const_iterator fit =
            oriented_set.begin();
          fit != oriented_set.end();
          ++fit)
      {
        int indices[3];
        int index = 0;
        for (int i=0; i<3; i++)
          indices[index++] = get_vertex_index(
            builder, fit->first->vertex(tr.vertex_triple_index(fit->second, i)), V, inum
          );
        builder.begin_facet();
          builder.add_vertex_to_facet(indices[0]);
          builder.add_vertex_to_facet(regular_orientation ? indices[1] : indices[2]);
          builder.add_vertex_to_facet(regular_orientation ? indices[2] : indices[1]);
        builder.end_facet();
        CGAL_assertion_code(++nb_facets);
      }
      CGAL_assertion(nb_facets == number_of_facets);
      //         for( Finite_facets_iterator fit = tr.finite_facets_begin();
      //              fit != tr.finite_facets_end(); ++fit)
      //           if ((*fit).first->is_facet_on_surface((*fit).second)==true)
      //           {
      //             int indices[3];
      //             int index = 0;
      //             for (int i=0; i<3; i++)
      //               std::cerr << ( indices[index++] = V[(*fit).first->vertex(tr.vertex_triple_index(fit->second, i))] ) << ", ";
      //             std::cerr << "\n";
      //             if( builder.test_facet(indices+0, indices+3) )
      //               builder.add_facet(indices+0, indices+3);
      //             else
      //             {
      //               builder.begin_facet();
      //               builder.add_vertex_to_facet(indices[2]);
      //               builder.add_vertex_to_facet(indices[1]);
      //               builder.add_vertex_to_facet(indices[0]);
      //               builder.end_facet();
      //             }
      //             CGAL_assertion_code(++nb_facets);
      //           }
    }
    builder.end_surface();
  } // end operator()
}; // end Complex_2_in_triangulation_3_polyhedron_builder

} // end namespace CGAL

#include <CGAL/enable_warnings.h>

#endif  // CGAL_IO_COMPLEX_2_IN_TRIANGULATION_3_POLYHEDRON_BUILDER_H
