// Copyright (c) 2015,2016 GeometryFactory
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.2-beta1/Mesh_3/include/CGAL/Mesh_3/Construct_initial_points_gray_image.h $
// $Id: include/CGAL/Mesh_3/Construct_initial_points_gray_image.h 431cfb5357d $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Laurent Rineau, Jane Tournois and Ange Clement

#ifndef CGAL_MESH_3_CONSTRUCT_INITIAL_POINTS_GRAY_IMAGE_H
#define CGAL_MESH_3_CONSTRUCT_INITIAL_POINTS_GRAY_IMAGE_H

#include <CGAL/license/Mesh_3.h>

#include <CGAL/Labeled_mesh_domain_3.h>
#include <CGAL/Mesh_3/Construct_initial_points_labeled_image.h>

#include <CGAL/Image_3.h>

namespace CGAL
{

/*!
 * \ingroup PkgMesh3Initializers
 *
 * Functor for generating initial points in gray images.
 * This functor is a model of the `InitialPointsGenerator_3` concept,
 * and can be passed as a parameter to `CGAL::make_mesh_3()` using the
 * `CGAL::parameters::initial_points_generator()` parameter function.
 *
 * On images that contain multiple connected components,
 * this functor will scan the full image and
 * output enough points on the surface of each component
 * to initialize them all. Each connected component is guaranteed to be
 * represented by at least one cell of the triangulation.
 *
 * \cgalModels{InitialPointsGenerator_3}
 *
 * @tparam C3t3 model of `MeshComplex_3InTriangulation_3`
 * @tparam MeshDomain model of `MeshDomain_3`
 * @tparam Functor a function object that takes the number type in which the image is encoded,
 *         and returns the `MeshDomain::Index` of the corresponding subcomplex index.
 *         The default type is `CGAL::Null_functor`.
 *
 * \sa `CGAL::parameters::initial_points_generator()`
 * \sa `CGAL::make_mesh_3()`
 * \sa `CGAL::Construct_initial_points_labeled_image`
 */
template <typename C3t3, typename MeshDomain, typename Functor = CGAL::Null_functor>
struct Construct_initial_points_gray_image
{
  const CGAL::Image_3 & image_;
  const MeshDomain& domain_;
  const typename MeshDomain::R::FT iso_value_;
  Functor image_values_to_subdomain_indices_;

  /*!
  * Constructs a functor for generating initial points in gray images.
  * @param image the gray image that defines the mesh domain
  * @param domain the mesh domain
  * @param iso_value the iso value corresponding to the surface of the domain
  * @param image_values_to_subdomain_indices a function object that takes
  *          the number type in which `image` is encoded,
  *          and returns the corresponding `MeshDomain::Index`.
  *          The default functor is `CGAL::Null_functor`
  *          and corresponds to meshing the areas where the image values are
  *          greater than `iso_value`.
  */
  Construct_initial_points_gray_image(const CGAL::Image_3 & image,
         const MeshDomain& domain,
         const double iso_value,
         const Functor image_values_to_subdomain_indices = CGAL::Null_functor())
      : image_(image)
      , domain_(domain)
      , iso_value_(static_cast<typename MeshDomain::R::FT>(iso_value))
      , image_values_to_subdomain_indices_(image_values_to_subdomain_indices)
  { }

  /*!
  * \brief constructs at least `n` points by collecting them on the surface of all
  * subdomains in the image,
  * even if they are not connected components.
  * Using this functor guarantees to initialize each connected component.
  *
  * @tparam OutputIterator model of `OutputIterator` for
  * tuple-like objects containing
  * - a `Weighted_point_3` for the point
  * - an `int` for the minimal dimension of the subcomplexes on which the point lies
  * - a `MeshDomain::Index` for the corresponding subcomplex index
  * @tparam MeshDomain model of `MeshDomain_3`
  * @tparam C3t3 model of `MeshComplex_3InTriangulation_3`
  *
  */
  template <typename OutputIterator>
  OutputIterator operator()(OutputIterator pts, const int n = 20) const
  {
    using CGAL::Mesh_3::internal::Create_gray_image_values_to_subdomain_indices;
    using C_i_v_t_s_i = Create_gray_image_values_to_subdomain_indices<Functor>;
    using Image_values_to_subdomain_indices = typename C_i_v_t_s_i::type;

    Image_values_to_subdomain_indices transform_fct =
      C_i_v_t_s_i()(image_values_to_subdomain_indices_, iso_value_);
    Construct_initial_points_labeled_image<C3t3, MeshDomain> init_pts{ image_, domain_ };
    init_pts(pts, transform_fct, n);
    return pts;
  }
};

} // end namespace CGAL

#endif // CGAL_MESH_3_CONSTRUCT_INITIAL_POINTS_GRAY_IMAGE_H
