// Copyright (c) 2012 Geometry Factory. All rights reserved.
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Polyline_simplification_2/include/CGAL/Polyline_simplification_2/Scaled_squared_distance_cost.h $
// $Id: include/CGAL/Polyline_simplification_2/Scaled_squared_distance_cost.h b26b07a1242 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Andreas Fabri, Fernando Cacciola
//
#ifndef CGAL_POLYLINE_SIMPLIFICATION_2_SCALED_SQUARED_DISTANCE_COST_H
#define CGAL_POLYLINE_SIMPLIFICATION_2_SCALED_SQUARED_DISTANCE_COST_H

#include <CGAL/license/Polyline_simplification_2.h>


#include <CGAL/algorithm.h>
#include <CGAL/Constrained_triangulation_plus_2.h>

namespace CGAL {

namespace Polyline_simplification_2
{
/// \ingroup PkgPolylineSimplification2Classes


/// This class is a cost function which calculates the cost as a scaled variant of the square of the distance between the original and simplified polylines.
///
/// \cgalModels{ PolylineSimplificationCostFunction}
class Scaled_squared_distance_cost
{

public:

  /// Initializes the cost function.
  Scaled_squared_distance_cost() {}

  /// Given a vertex in constraint iterator `vicq` computes `vicp=std::prev(vicq)` and `vicr=std::next(vicq)`,
  /// returns the maximum of the square distances between each point along the original subpolyline
  /// between `vicp` and `vicr`,
  /// and the straight line segment  from `*vicp->point() to *vicr->point()` divided by the shortest squared distance between
  /// that segment and each of the vertices adjacent to `vicq`.
  /// \tparam CDT  must be `CGAL::Constrained_Delaunay_triangulation_2` with a vertex type that
  /// is model of  `PolylineSimplificationVertexBase_2`.
    template<class CDT>
    std::optional<typename CDT::Geom_traits::FT>
    operator()(const Constrained_triangulation_plus_2<CDT>& pct
               , typename Constrained_triangulation_plus_2<CDT>::Vertices_in_constraint_iterator vicq) const
  {
    typedef typename Constrained_triangulation_plus_2<CDT>::Points_in_constraint_iterator Points_in_constraint_iterator;
    typedef typename Constrained_triangulation_plus_2<CDT>::Vertex_circulator Vertex_circulator;
    typedef typename Constrained_triangulation_plus_2<CDT>::Geom_traits Geom_traits ;
    typedef typename Geom_traits::FT                                  FT;
    typedef typename Geom_traits::Compute_squared_distance_2 Compute_squared_distance;
    typedef typename Geom_traits::Construct_segment_2        Construct_segment;
    typedef typename Geom_traits::Segment_2                  Segment;
    typedef typename Geom_traits::Point_2                    Point;

    Compute_squared_distance compute_squared_distance = pct.geom_traits().compute_squared_distance_2_object() ;
    Construct_segment        construct_segment        = pct.geom_traits().construct_segment_2_object() ;
    typedef typename Constrained_triangulation_plus_2<CDT>::Vertices_in_constraint_iterator Vertices_in_constraint_iterator;

    Vertices_in_constraint_iterator vicp = std::prev(vicq);
    Vertices_in_constraint_iterator vicr = std::next(vicq);

    Point const& lP = (*vicp)->point();
    Point const& lR = (*vicr)->point();

    Segment lP_R = construct_segment(lP, lR) ;

    FT d1(0);
    Points_in_constraint_iterator pp(vicp), rr(vicr);
    ++pp;

    for ( ;pp != rr; ++pp )
      d1 = (std::max)(d1, compute_squared_distance( lP_R, *pp ) ) ;


    FT d2=0;
    bool d2_uninitialized = true;

    Vertex_circulator vc = pct.incident_vertices(*vicq), done(vc);
    do {
      if((vc != pct.infinite_vertex()) && (vc != *vicp) && (vc != *vicr)){
        if(d2_uninitialized){
          d2 = compute_squared_distance(vc->point(), (*vicq)->point());
          d2_uninitialized = false;
        } else {
          d2 = (std::min)(d2, compute_squared_distance(vc->point(), (*vicq)->point()));
        }
      }
      ++vc;
    }while(vc != done);

    return d2_uninitialized ?
      std::optional<FT>(std::nullopt) :
      std::optional<FT>(d1 / d2);
  }

};



} // namespace Polyline_simplification_2


} //namespace CGAL

#endif // CGAL_POLYLINE_SIMPLIFICATION_2_SCALED_SQUARED_DISTANCE_COST_H




