#include <CGAL/boost/graph/graph_traits_Linear_cell_complex_for_combinatorial_map.h>

// Simplification function
#include <CGAL/Surface_mesh_simplification/edge_collapse.h>

// Stop-condition policy
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Edge_count_stop_predicate.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Edge_length_cost.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Midpoint_placement.h>

#include <CGAL/IO/polygon_mesh_io.h>

#include <iostream>
#include <fstream>

typedef CGAL::Simple_cartesian<double>                                                   Kernel;
typedef CGAL::Linear_cell_complex_traits<3, Kernel>                                      MyTraits;
typedef CGAL::Linear_cell_complex_for_bgl_combinatorial_map_helper<2, 3, MyTraits>::type LCC;

namespace SMS = CGAL::Surface_mesh_simplification;

int main(int argc, char** argv)
{
  LCC lcc;
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cube-subdivided.off");

  if(!CGAL::IO::read_polygon_mesh(filename, lcc))
  {
    std::cerr << "Failed to read input mesh: " << filename << std::endl;
    return EXIT_FAILURE;
  }

  if(!CGAL::is_triangle_mesh(lcc))
  {
    std::cerr << "Input geometry is not triangulated." << std::endl;
    return EXIT_FAILURE;
  }

  lcc.display_characteristics(std::cout) << ", is_valid=" << CGAL::is_valid(lcc) << std::endl;

  // This is a stop predicate (defines when the algorithm terminates).
  // In this example, the simplification stops when the number of undirected edges
  // left in the surface mesh drops below the specified number (1000 by default)
  const std::size_t edge_count_threshold = (argc > 2) ? std::stoi(argv[2]) : 1000;
  SMS::Edge_count_stop_predicate<LCC> stop(edge_count_threshold);

  // This the actual call to the simplification algorithm.
  // The surface mesh and stop conditions are mandatory arguments.
  // The index maps are needed because the vertices and edges
  // of this surface mesh lack an "id()" field.
  std::cout << "Collapsing edges of LCC: " << filename << ", aiming for " << edge_count_threshold << " final edges..." << std::endl;
  int r = SMS::edge_collapse(lcc, stop,
                             CGAL::parameters::halfedge_index_map(get(CGAL::halfedge_index, lcc))
                                              .vertex_index_map(get(boost::vertex_index, lcc))
                                              .get_cost(SMS::Edge_length_cost<LCC>())
                                              .get_placement(SMS::Midpoint_placement<LCC>()));

  std::cout << "\nFinished!\n" << r << " edges removed.\n"
            << (lcc.number_of_darts()/2) << " final edges.\n";

  lcc.display_characteristics(std::cout) << ", is_valid=" << CGAL::is_valid(lcc) << std::endl;

  CGAL::IO::write_polygon_mesh((argc > 3 ? argv[3] : "out.off"), lcc);

  return EXIT_SUCCESS;
}
