// Copyright (c) 2006-2007  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-3.4-branch/Arrangement_on_surface_2/include/CGAL/Arr_topology_traits/Arr_spherical_insertion_helper.h $
// $Id: Arr_spherical_insertion_helper.h 41118 2007-12-07 14:25:32Z efif $
// 
//
// Author(s)     : Ron Wein <wein@post.tau.ac.il>
//                 Efi Fogel <efif@post.tau.ac.il>

#ifndef CGAL_ARR_SPHERICAL_INSERTION_HELPER_H
#define CGAL_ARR_SPHERICAL_INSERTION_HELPER_H

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

#include <CGAL/Sweep_line_2/Arr_construction_sl_visitor.h>
#include <CGAL/Arr_topology_traits/Arr_spherical_construction_helper.h>

CGAL_BEGIN_NAMESPACE

/*! \class Arr_spherical_insertion_helper
 * A helper class for the insertion sweep-line visitors, suitable
 * for an Arrangement_on_surface_2 instantiated with a topology-traits class
 * for bounded curves in the plane.
 */
template <class Traits_, class Arrangement_, class Event_, class Subcurve_> 
class Arr_spherical_insertion_helper :
  public Arr_spherical_construction_helper<Traits_, Arrangement_,
                                           Event_, Subcurve_>
{
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;

  typedef Arr_spherical_construction_helper<Traits_2, Arrangement_2, Event,
                                            Subcurve>   Base;

  typedef Sweep_line_empty_visitor<Traits_2, Subcurve, Event>
                                                        Base_visitor;

  typedef Arr_spherical_insertion_helper<Traits_2, Arrangement_2, Event,
                                         Subcurve>      Self;

  typedef Arr_construction_sl_visitor<Self>             Parent_visitor;

  typedef typename Arrangement_2::Face_handle           Face_handle;
  typedef typename Arrangement_2::Halfedge_handle       Halfedge_handle;

  typedef typename Base::Indices_list                   Indices_list;
  typedef typename Base::Halfedge_indices_map           Halfedge_indices_map;

public:
  /*! Constructor */
  Arr_spherical_insertion_helper (Arrangement_2 *arr) :
    Base (arr)
  {}

  /*! Destructor. */
  virtual ~Arr_spherical_insertion_helper ()
  {}

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

  /* A notification issued before the sweep process starts. */
  virtual void before_sweep()
  {
    // Get the unbounded face.
    this->m_spherical_face = Face_handle(this->m_top_traits->south_face());
  }

  /*!
   * A notification invoked before the sweep-line starts handling the given
   * event.
   */
  virtual void before_handle_event (Event* event);
  //@}

};

//-----------------------------------------------------------------------------
// Memeber-function definitions:
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// A notification invoked before the sweep-line starts handling the given
// event.
//
template <class Tr, class Arr, class Evnt, class Sbcv> 
void Arr_spherical_insertion_helper<Tr,Arr,Evnt,Sbcv>::before_handle_event
    (Event* event)
{
  // Ignore events that do not have boundary conditions.
  const Arr_parameter_space ps_x = event->parameter_space_in_x();
  const Arr_parameter_space ps_y = event->parameter_space_in_y();

  if (ps_x == ARR_INTERIOR && ps_y == ARR_INTERIOR)
    return;

  // The is exactly one curve incident to an event with boundary conditions.
  // Obtain this curve and check whether it already exists in the arrangement.
  CGAL_assertion(((event->number_of_left_curves() == 0) &&
                  (event->number_of_right_curves() == 1)) ||
                 ((event->number_of_left_curves() == 1) &&
                  (event->number_of_right_curves() == 0)));

  const Arr_curve_end   ind =
    (event->number_of_left_curves() == 0 &&
     event->number_of_right_curves() == 1) ? ARR_MIN_END : ARR_MAX_END;
  const X_monotone_curve_2& xc = (ind == ARR_MIN_END) ?
    (*(event->right_curves_begin()))->last_curve() :
    (*(event->left_curves_begin()))->last_curve();

  if (xc.halfedge_handle() == Halfedge_handle())
  {
    // The curve is not in the arrangement, use the base construction helper
    // to handle the event:
    Base::before_handle_event (event);
    return;
  }

  // In case we encounter an existing curve incident to the curve of
  // discontinuity (and exteding to its right) or to the north pole,
  // we have to update the current top face (the spherical face).
  if (ps_y == ARR_TOP_BOUNDARY)
  {
    this->m_spherical_face = (ind == ARR_MIN_END) ?
      xc.halfedge_handle()->twin()->face() : xc.halfedge_handle()->face();
  }
  else if (ps_x == ARR_LEFT_BOUNDARY)
  {
    CGAL_assertion (ind == ARR_MIN_END);
    this->m_spherical_face = xc.halfedge_handle()->twin()->face();
  }

  return;
}

CGAL_END_NAMESPACE

#endif
