// Copyright (c) 2006  Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.5-branch/Arrangement_on_surface_2/include/CGAL/Arr_topology_traits/Arr_spherical_overlay_helper.h $
// $Id: Arr_spherical_overlay_helper.h 41118 2007-12-07 14:25:32Z efif $
// 
//
// 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_SPHERICAL_OVERLAY_HELPER_H
#define CGAL_ARR_SPHERICAL_OVERLAY_HELPER_H

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

#include <CGAL/Arr_topology_traits/Arr_spherical_construction_helper.h>

CGAL_BEGIN_NAMESPACE

/*! \class Arr_spherical_overlay_helper
 * A helper class for the overlay sweep-line visitor, suitable for the overlay
 * of Arrangement_on_surface_2 objects instantiated with a topology-traits
 * class for bounded curves in the plane.
 */
template <class Traits_,
          class ArrangementRed_,
          class ArrangementBlue_,
          class Arrangement_,
          class Event_,
          class Subcurve_>
class Arr_spherical_overlay_helper
{
public:

  typedef Traits_                                         Traits_2; 
  typedef Arrangement_                                    Arrangement_2;
  typedef Event_                                          Event;
  typedef Subcurve_                                       Subcurve;

  typedef typename Traits_2::X_monotone_curve_2           X_monotone_curve_2;
  typedef typename Traits_2::Point_2                      Point_2;

  // The input arrangements (the "red" and the "blue" one):
  typedef ArrangementRed_                                 Arrangement_red_2;
  typedef typename Arrangement_red_2::Face_const_handle   Face_handle_red;

  typedef ArrangementBlue_                                Arrangement_blue_2;
  typedef typename Arrangement_blue_2::Face_const_handle  Face_handle_blue;

  // Define the helper class for the construction visitor.
  typedef Arr_spherical_construction_helper<Traits_2, Arrangement_2, Event,
                                            Subcurve>     Construction_helper;

protected:
  // Data members:
  const typename Arrangement_red_2::Topology_traits * m_red_top_traits;
  const typename Arrangement_blue_2::Topology_traits * m_blue_top_traits;

  //! Red spherical face
  Face_handle_red m_red_nf;

  //! Blue spherical face
  Face_handle_blue m_blue_nf;

public:
  /*! Constructor, given the input red and blue arrangements. */
  Arr_spherical_overlay_helper(const Arrangement_red_2 * red_arr,
                               const Arrangement_blue_2 * blue_arr) :
    m_red_top_traits(red_arr->topology_traits()),
    m_blue_top_traits(blue_arr->topology_traits())
  {}

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

  /* A notification issued before the sweep process starts. */
  void before_sweep()
  {
    // Get the spherical faces in both arrangements.
      /* RWRW:
    m_red_nf = Face_handle_red(m_red_top_traits->spherical_face());
    m_blue_nf = Face_handle_blue(m_blue_top_traits->spherical_face());
      */
    m_red_nf = Face_handle_red(m_red_top_traits->south_face());
    m_blue_nf = Face_handle_blue(m_blue_top_traits->south_face());
    return;
  }

  /*! A notification invoked before the sweep-line starts handling the given
   * event.
   */  
  void before_handle_event(Event * event)
  {
    if (event->parameter_space_in_y() != ARR_TOP_BOUNDARY &&
        event->parameter_space_in_x() != ARR_LEFT_BOUNDARY)
      return;

    Arr_curve_end ind = (event->number_of_left_curves() == 0 &&
                     event->number_of_right_curves() != 0) ?
      ARR_MIN_END : ARR_MAX_END;

    const Subcurve  *sc = (ind == ARR_MIN_END) ?
      (*(event->right_curves_begin())) :
      (*(event->left_curves_begin()));

    if (event->parameter_space_in_y() == ARR_TOP_BOUNDARY)
    {
      // The curve is incident to the north pole.
      switch (sc->color()) {
       case Traits_2::RED :
        if (ind == ARR_MIN_END)
          m_red_nf = sc->red_halfedge_handle()->twin()->face();
        else
          m_red_nf = sc->red_halfedge_handle()->face();
        break;
          
       case Traits_2::BLUE :
        if (ind == ARR_MIN_END)
          m_blue_nf = sc->blue_halfedge_handle()->twin()->face();
        else
          m_blue_nf = sc->blue_halfedge_handle()->face();
        break;

       case Traits_2::RB_OVERLAP :
        if (ind == ARR_MIN_END)
        {
          m_red_nf = sc->red_halfedge_handle()->twin()->face();
          m_blue_nf = sc->blue_halfedge_handle()->twin()->face();
        }
        else
        {
          m_red_nf = sc->red_halfedge_handle()->face();
          m_blue_nf = sc->blue_halfedge_handle()->face();
        }
        break;
      }
    }
    else
    {
      // The curve extends to the right from the curve of discontinuity.
      CGAL_assertion (ind == ARR_MIN_END);
      switch (sc->color()) {
       case Traits_2::RED :
        m_red_nf = sc->red_halfedge_handle()->twin()->face();
        break;
          
       case Traits_2::BLUE :
        m_blue_nf = sc->blue_halfedge_handle()->twin()->face();
        break;

       case Traits_2::RB_OVERLAP :
        m_red_nf = sc->red_halfedge_handle()->twin()->face();
        m_blue_nf = sc->blue_halfedge_handle()->twin()->face();
        break;
      }
    }

    return;
  }
  //@}

  /*! Get the current red top face. */
  Face_handle_red red_top_face() const
  {
    return m_red_nf;
  }

  /*! Get the current blue top face. */
  Face_handle_blue blue_top_face() const
  {
    return m_blue_nf;
  }
};

CGAL_END_NAMESPACE

#endif
