// Copyright (c) 1997  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_unb_planar_overlay_helper.h $
// $Id: Arr_unb_planar_overlay_helper.h 41108 2007-12-06 15:26:30Z 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_UNB_PLANAR_OVERLAY_HELPER_H
#define CGAL_ARR_UNB_PLANAR_OVERLAY_HELPER_H

/*!
 * Definition of the Arr_unb_planar_overlay_helper class-template.
 */

#include <CGAL/Arr_topology_traits/Arr_unb_planar_construction_helper.h>

CGAL_BEGIN_NAMESPACE

/*! \class Arr_unb_planar_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 unbounded curves in the plane.
 */
template <class Traits_,
          class ArrangementRed_,
          class ArrangementBlue_,
          class Arrangement_,
          class Event_,
          class Subcurve_>
class Arr_unb_planar_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::Halfedge_const_handle
                                                          Halfedge_handle_red;
  typedef typename Arrangement_red_2::Face_const_handle   Face_handle_red;
  typedef typename Arrangement_red_2::Vertex_const_handle Vertex_handle_red;

  typedef ArrangementBlue_                                Arrangement_blue_2;
  typedef typename Arrangement_blue_2::Halfedge_const_handle
                                                          Halfedge_handle_blue;
  typedef typename Arrangement_blue_2::Face_const_handle  Face_handle_blue;
  typedef typename Arrangement_blue_2::Vertex_const_handle
                                                          Vertex_handle_blue;

  // Define the helper class for the construction visitor.
  typedef Arr_unb_planar_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;

  Halfedge_handle_red        m_red_th;    // Red top fictitious halfedge.
  Halfedge_handle_blue       m_blue_th;   // Blue top fictitious halfedge.

  Vertex_handle_red          v_red_tl;    // Red top-left fictitious vertex. 
  Vertex_handle_blue         v_blue_tl;   // Blue top-left fictitious vertex.

public:

  /*! Constructor, given the input red and blue arrangements. */
  Arr_unb_planar_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 ();

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

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

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

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

//-----------------------------------------------------------------------------
// A notification issued before the sweep process starts.
//
template <class Tr, class ArrR, class ArrB, class Arr, class Evnt, class Sbcv>
void Arr_unb_planar_overlay_helper<Tr,ArrR,ArrB,Arr,Evnt,Sbcv>::before_sweep ()
{
  // Get the top-left fictitious vertices in both arrangements.
  v_red_tl = Vertex_handle_red (m_red_top_traits->top_left_vertex());
  v_blue_tl = Vertex_handle_blue (m_blue_top_traits->top_left_vertex());

  // Get the fictitious halfedges incident to the bottom-left fictitious
  // vertices in both red and blue arrangements. If there are no vertices
  // at x = -oo, we take the halfedge incident to the top-left vertex that
  // lies on the top edge of the fictitious face.
  Vertex_handle_red   v_red_bl = 
    Vertex_handle_red (m_red_top_traits->bottom_left_vertex());

  m_red_th = v_red_bl->incident_halfedges();

  if (m_red_th->source()->parameter_space_in_x() != ARR_LEFT_BOUNDARY)
    m_red_th = m_red_th->next()->twin();
  
  if (m_red_th->source() == v_red_tl)
    m_red_th = m_red_th->prev();

  Vertex_handle_blue  v_blue_bl = 
    Vertex_handle_blue (m_blue_top_traits->bottom_left_vertex());
  
  m_blue_th = v_blue_bl->incident_halfedges();
  if (m_blue_th->source()->parameter_space_in_x() != ARR_LEFT_BOUNDARY)
    m_blue_th = m_blue_th->next()->twin();
  
  if (m_blue_th->source() == v_blue_tl)
    m_blue_th = m_blue_th->prev();

  return;
}

//-----------------------------------------------------------------------------
// A notification invoked before the sweep-line starts handling the given
// event.
//
template <class Tr, class ArrR, class ArrB, class Arr, class Evnt, class Sbcv>
void Arr_unb_planar_overlay_helper<Tr,ArrR,ArrB,Arr,Evnt,Sbcv>::
before_handle_event (Event* e)
{
  // Nothing to do in case the event represents a finite point.
  if (e->is_finite())
    return;
  
  // In case the event occurs on the left edge of the fictitious face (x = -oo)
  // or on its top edge (finite x and y = +oo), update the fictitious top
  // halfedges.
  if (e->parameter_space_in_x() == ARR_LEFT_BOUNDARY ||
      (e->parameter_space_in_x() == ARR_INTERIOR && 
       e->parameter_space_in_y() == ARR_TOP_BOUNDARY))
  {
    switch (e->curve().color())
    {
    case (Traits_2::RED) :
      // Update the red top fictitious halfedge.
      m_red_th = m_red_th->twin()->next()->twin();
      if (m_red_th->source() == v_red_tl)
        m_red_th = m_red_th->prev();
      break;
      
    case (Traits_2::BLUE) :
      // Update the blue top fictitious halfedge.
      m_blue_th = m_blue_th->twin()->next()->twin();
      if (m_blue_th->source() == v_blue_tl)
        m_blue_th = m_blue_th->prev();
      break;
        
    case Traits_2::RB_OVERLAP :
      // Update both red and blue top fictitious halfedges.
      m_red_th = m_red_th->twin()->next()->twin();
      if (m_red_th->source() == v_red_tl) 
        m_red_th = m_red_th->prev();

      m_blue_th = m_blue_th->twin()->next()->twin();
      if (m_blue_th->source() == v_blue_tl)
        m_blue_th = m_blue_th->prev();

      break;
    }
  }

  return;
}

CGAL_END_NAMESPACE

#endif
