/* ------------------------------------------------------------------------
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 * Copyright (C) 1999 - 2023 by the deal.II authors
 *
 * This file is part of the deal.II library.
 *
 * Part of the source code is dual licensed under Apache-2.0 WITH
 * LLVM-exception OR LGPL-2.1-or-later. Detailed license information
 * governing the source code and code contributions can be found in
 * LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
 *
 * ------------------------------------------------------------------------
 */
 
 
#include <deal.II/grid/tria.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.svg");
  GridOut       grid_out;
  grid_out.write_svg(triangulation, out);
  std::cout << "  Grid written to grid-1.svg" << 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 (const auto &cell : triangulation.active_cell_iterators())
        {
          for (const auto v : cell->vertex_indices())
            {
              const double distance_from_center =
                center.distance(cell->vertex(v));
 
              if (std::fabs(distance_from_center - inner_radius) <=
                  1e-6 * inner_radius)
                {
                  cell->set_refine_flag();
                  break;
                }
            }
        }
 
      triangulation.execute_coarsening_and_refinement();
    }
 
 
  std::ofstream out("grid-2.svg");
  GridOut       grid_out;
  grid_out.write_svg(triangulation, out);
 
  std::cout << "  Grid written to grid-2.svg" << std::endl;
}
 
int main()
{
  cout << "\n";
  cout << "step-1():\n";
  cout << "  dealii example code.\n";
  cout << "\n";

  first_grid();
  second_grid();

  cout << "\n";
  cout << "step-1():\n";
  cout << "  Normal end of execution.\n";

  return 0;
}