/* ---------------------------------------------------------------------
 *
 * Copyright (C) 1999 - 2019 by the deal.II authors
 *
 * This file is part of the deal.II library.
 *
 * The deal.II library is free software; you can use it, redistribute
 * it, and/or modify it under the terms of the GNU Lesser General
 * Public License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * The full text of the license can be found in the file LICENSE.md at
 * the top level directory of deal.II.
 *
 * ---------------------------------------------------------------------
 */
#include <deal.II/grid/tria.h>
#include <deal.II/grid/tria_accessor.h>
#include <deal.II/grid/tria_iterator.h>
#include <deal.II/grid/grid_generator.h>
#include <deal.II/grid/grid_out.h>
#include <iostream>
#include <fstream>
#include <cmath>
using namespace dealii;
void first_grid()
{
  Triangulation<2> triangulation;
  GridGenerator::hyper_cube(triangulation);
  triangulation.refine_global(4);
  std::ofstream out("grid-1.eps");
  GridOut       grid_out;
  grid_out.write_eps(triangulation, out);
  std::cout << "Grid written to grid-1.eps" << std::endl;
}
void second_grid()
{
  Triangulation<2> triangulation;
  const Point<2> center(1, 0);
  const double   inner_radius = 0.5, outer_radius = 1.0;
  GridGenerator::hyper_shell(
    triangulation, center, inner_radius, outer_radius, 10);
  for (unsigned int step = 0; step < 5; ++step)
    {
      for (auto &cell : triangulation.active_cell_iterators())
        {
          for (unsigned int v = 0; v < GeometryInfo<2>::vertices_per_cell; ++v)
            {
              const double distance_from_center =
                center.distance(cell->vertex(v));
              if (std::fabs(distance_from_center - inner_radius) < 1e-10)
                {
                  cell->set_refine_flag();
                  break;
                }
            }
        }
      triangulation.execute_coarsening_and_refinement();
    }
  std::ofstream out("grid-2.eps");
  GridOut       grid_out;
  grid_out.write_eps(triangulation, out);
  std::cout << "Grid written to grid-2.eps" << std::endl;
}
int main()
{
  first_grid();
  second_grid();
}