// Copyright (c) 2023-2024  GeometryFactory Sarl (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Constrained_triangulation_3/include/CGAL/Constrained_triangulation_3/internal/cdt_debug_io.h $
// $Id: include/CGAL/Constrained_triangulation_3/internal/cdt_debug_io.h b26b07a1242 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Laurent Rineau

#ifndef CGAL_CDT_3_DEBUG_IO_H
#define CGAL_CDT_3_DEBUG_IO_H

#include <CGAL/license/Constrained_triangulation_3.h>

#include <CGAL/IO/polygon_soup_io.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/orient_polygon_soup.h>
#include <CGAL/Polygon_mesh_processing/repair_polygon_soup.h>
#include <CGAL/Polygon_mesh_processing/polygon_soup_to_polygon_mesh.h>

#include <ostream>

namespace CGAL {

  template <typename Tr, typename Facets>
  auto export_facets_to_surface_mesh(const Tr& tr, Facets&& facets_range) {
    using Point_3 = typename Tr::Geom_traits::Point_3;
    const auto size = std::distance(facets_range.begin(), facets_range.end());
    std::vector<Point_3> points;
    points.reserve(size * 3);
    std::vector<std::array<std::size_t, 3>> facets;
    facets.reserve(size);

    std::size_t i = 0;
    for(const auto& [cell, facet_index] : facets_range) {
      const auto v0 = cell->vertex(Tr::vertex_triple_index(facet_index, 0));
      const auto v1 = cell->vertex(Tr::vertex_triple_index(facet_index, 1));
      const auto v2 = cell->vertex(Tr::vertex_triple_index(facet_index, 2));
      points.push_back(tr.point(v0));
      points.push_back(tr.point(v1));
      points.push_back(tr.point(v2));
      facets.push_back({i, i+1, i+2});
      i += 3;
    }
    CGAL::Polygon_mesh_processing::merge_duplicate_points_in_polygon_soup(points, facets);
    CGAL::Polygon_mesh_processing::orient_polygon_soup(points, facets);
    Surface_mesh<Point_3> mesh;
    CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh(points, facets, mesh);
    return mesh;
  }

  template <typename Tr, typename Facets>
  void write_facets(std::ostream& out, const Tr& tr, Facets&& facets_range) {
    const auto mesh = export_facets_to_surface_mesh(tr, std::forward<Facets>(facets_range));
    CGAL::IO::write_OFF(out, mesh);
  }

}

#endif // CGAL_CDT_3_DEBUG_IO_H

