// Copyright (c) 2006,2007,2009,2010,2011 Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Arrangement_on_surface_2/include/CGAL/Arr_topology_traits/Arr_unb_planar_batched_pl_helper.h $
// $Id: include/CGAL/Arr_topology_traits/Arr_unb_planar_batched_pl_helper.h b26b07a1242 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Baruch Zukerman <baruchzu@post.tau.ac.il>
//                 Ron Wein <wein@post.tau.ac.il>
//                 Efi Fogel <efif@post.tau.ac.il>

#ifndef CGAL_ARR_UNB_PLANAR_BATCHED_PL_HELPER_H
#define CGAL_ARR_UNB_PLANAR_BATCHED_PL_HELPER_H

#include <CGAL/license/Arrangement_on_surface_2.h>

/*! \file
 *
 * Definition of the Arr_unb_planar_batched_pl_helper class-template.
 */

namespace CGAL {

/*! \class Arr_unb_planar_batched_pl_helper
 *
 * A helper class for the batched point-location sweep-line visitor, suitable
 * for an Arrangement_on_surface_2 instantiated with a topology-traits class
 * for unbounded curves in the plane.
 */
template <typename GeometryTraits_2, typename Arrangement_, typename Event_,
          typename Subcurve_>
class Arr_unb_planar_batched_pl_helper {
public:
  typedef GeometryTraits_2                              Geometry_traits_2;
  typedef Arrangement_                                  Arrangement_2;
  typedef Event_                                        Event;
  typedef Subcurve_                                     Subcurve;
  typedef typename Subcurve::Allocator                  Allocator;

private:
  typedef Geometry_traits_2                             Gt2;

public:
  typedef typename Arrangement_2::Face_const_handle     Face_const_handle;

protected:
  typedef typename Arrangement_2::Topology_traits       Topology_traits;
  typedef typename Arrangement_2::Halfedge_const_handle Halfedge_const_handle;
  typedef typename Arrangement_2::Vertex_const_handle   Vertex_const_handle;

  // Data members:
  const Topology_traits* m_top_traits;  // The topology-traits class.
  Halfedge_const_handle m_top_fict;     // The current top fictitious halfedge.

public:
  /*! constructs.
   * \param arr The arrangement.
   */
  Arr_unb_planar_batched_pl_helper(const Arrangement_2* arr) :
    m_top_traits(arr->topology_traits())
  {}

  /// \name Notification functions.
  //@{

  /* A notification issued before the sweep process starts. */
  void before_sweep();

  /*! A notification invoked after the sweep-line finishes handling the given
   * event.
   */
  void after_handle_event(Event* event);
  //@}

  /*! obtains the current top face. */
  Face_const_handle top_face() const { return (m_top_fict->face()); }
};

//-----------------------------------------------------------------------------
// Member-function definitions:
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// A notification issued before the sweep process starts.
//
template <typename Tr, typename Arr, typename Event_, typename Subcurve_>
void Arr_unb_planar_batched_pl_helper<Tr, Arr, Event_, Subcurve_>::
before_sweep()
{
  // Initialize the fictitious halfedge lying on the top edge of the
  // fictitious face. We start from the leftmost halfedge, which is
  // incident to the top-left vertex and directed from right to left.
  Vertex_const_handle v_tl =
    Vertex_const_handle(m_top_traits->top_left_vertex());

  m_top_fict = v_tl->incident_halfedges();
  if (m_top_fict->direction() == ARR_LEFT_TO_RIGHT)
    m_top_fict = m_top_fict->next()->twin();

  CGAL_assertion_code(
    Vertex_const_handle v_tr =
      Vertex_const_handle(m_top_traits->top_right_vertex());
  );
  CGAL_assertion
    ((m_top_fict->source() == v_tr) ||
     (m_top_fict->source()->parameter_space_in_x() == ARR_INTERIOR &&
      m_top_fict->source()->parameter_space_in_y() == ARR_TOP_BOUNDARY));
}

//-----------------------------------------------------------------------------
// A notification invoked after the sweep-line finishes handling the given
// event.
//
template <typename Tr, typename Arr, typename Event_, typename Subcurve_>
void Arr_unb_planar_batched_pl_helper<Tr, Arr, Event_, Subcurve_>::
after_handle_event(Event* event)
{
  // If the event is at infinity and occurs on the top edge of the fictitious
  // face (namely x is finite and y = +oo), we have to update the fictitious
  // edge we keep.
  if (event->is_closed()) return;

  if (event->parameter_space_in_x() != ARR_INTERIOR) return;

  if (event->parameter_space_in_y() == ARR_TOP_BOUNDARY)
    m_top_fict = m_top_fict->twin()->next()->twin();
}

} // namespace CGAL

#endif

