// Copyright (c) 2005  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_walk_along_line_point_location.h $
// $Id: Arr_walk_along_line_point_location.h 35622 2006-12-25 08:56:47Z wein $
// 
//
// Author(s)     : Ron Wein   <wein@post.tau.ac.il>
//                 (based on old version by Oren Nechushtan
//                                      and Iddo Hanniel)
#ifndef CGAL_ARR_WALK_ALONG_LINE_POINT_LOCATION_H
#define CGAL_ARR_WALK_ALONG_LINE_POINT_LOCATION_H

/*! \file
 * Definition of the Arr_walk_along_line_point_location<Arrangement> template.
 */

#include <CGAL/Arrangement_2/Arr_traits_adaptor_2.h>

CGAL_BEGIN_NAMESPACE

/*! \class
 * A class that answers point-location and vertical ray-shooting queries
 * on a planar arrangement by walking on a vertical ray emanating from the
 * query point, going from "infinity" (the unbounded face) until reaching
 * the point.
 * The Arrangement parameter corresponds to an arrangement instantiation
 * of type Arrangement_on_surface_2<GeomTraits, TopTraits>. The topology
 * traits class has to support the additional method initial_face().
 */
template <class Arrangement_>
class Arr_walk_along_line_point_location
{
public:

  typedef Arrangement_                                   Arrangement_2;
  typedef typename Arrangement_2::Geometry_traits_2      Geometry_traits_2;
  typedef typename Arrangement_2::Topology_traits        Topology_traits;

  typedef typename Arrangement_2::Vertex_const_handle    Vertex_const_handle;
  typedef typename Arrangement_2::Halfedge_const_handle  Halfedge_const_handle;
  typedef typename Arrangement_2::Face_const_handle      Face_const_handle;

  typedef typename Geometry_traits_2::Point_2            Point_2;
  typedef typename Geometry_traits_2::X_monotone_curve_2 X_monotone_curve_2;

protected:

  typedef Arr_traits_basic_adaptor_2<Geometry_traits_2>  Traits_adaptor_2;
  typedef typename Arrangement_2::Ccb_halfedge_const_circulator
                                             Ccb_halfedge_const_circulator;
  typedef typename Arrangement_2::Inner_ccb_const_iterator
                                             Inner_ccb_const_iterator;
  typedef typename Arrangement_2::Isolated_vertex_const_iterator
                                             Isolated_vertex_const_iterator;

  // Data members:
  const Arrangement_2     *p_arr;        // The associated arrangement.  
  const Traits_adaptor_2  *geom_traits;  // Its associated geometry traits.
  const Topology_traits   *top_traits;   // Its associated topology traits.

public:

  /*! Default constructor. */
  Arr_walk_along_line_point_location () : 
    p_arr (NULL),
    geom_traits (NULL),
    top_traits (NULL)
  {}
        
  /*! Constructor given an arrangement. */
  Arr_walk_along_line_point_location (const Arrangement_2& arr) :
    p_arr (&arr)
  {
    geom_traits =
      static_cast<const Traits_adaptor_2*> (p_arr->geometry_traits());
    top_traits = p_arr->topology_traits();
  }

  /*! Attach an arrangement object. */
  void attach (const Arrangement_2& arr) 
  {
    p_arr = &arr;
    geom_traits =
      static_cast<const Traits_adaptor_2*> (p_arr->geometry_traits());
    top_traits = p_arr->topology_traits();
  }

  /*! Detach from the current arrangement object. */
  void detach ()
  {
    p_arr = NULL;
    geom_traits = NULL;
    top_traits = NULL;
  }
 
  /*!
   * Locate the arrangement feature containing the given point.
   * \param p The query point.
   * \return An object representing the arrangement feature containing the
   *         query point. This object is either a Face_const_handle or a
   *         Halfedge_const_handle or a Vertex_const_handle.
   */
  Object locate (const Point_2& p) const;

  /*!
   * Locate the arrangement feature which a upward vertical ray emanating from
   * the given point hits.
   * \param p The query point.
   * \return An object representing the arrangement feature the ray hits.
   *         This object is either an empty object or a
   *         Halfedge_const_handle or a Vertex_const_handle.
   */
  Object ray_shoot_up (const Point_2& p) const
  {
    return (_vertical_ray_shoot (p, true));
  }

  /*!
   * Locate the arrangement feature which a downward vertical ray emanating
   * from the given point hits.
   * \param p The query point.
   * \return An object representing the arrangement feature the ray hits.
   *         This object is either an empty object or a
   *         Halfedge_const_handle or a Vertex_const_handle.
   */
  Object ray_shoot_down (const Point_2& p) const
  {
    return (_vertical_ray_shoot (p, false));
  }

protected:

  /*!
   * Locate the arrangement feature which a vertical ray emanating from the
   * given point hits.
   * \param p The query point.
   * \param shoot_up Indicates whether the ray is directed upward or downward.
   * \return An object representing the arrangement feature the ray hits.
   *         This object is either a Face_const_handle or a
   *         Halfedge_const_handle or a Vertex_const_handle.
   */
  Object _vertical_ray_shoot (const Point_2& p, bool shoot_up) const;

  /*!
   * Check whether the query point lies inside the given onncected component.
   * \param p The query point.
   * \param circ A circulator for the halfedges along the connected component
   *             boundary.
   * \param shoot_up Whether we shoot the vertical ray up or down.
   * \param inclusive Indicates whether the vertical ray includes the point p:
   *                  If not (in case of vertical ray shooting) we should find
   *                  the edge or vertex right above (or below) the query point
   *                  p. If it does (in case of point location) and p lies on
   *                  a vertex of on an edge, we return this feature.
   * \param closest_he Input: The closest halfedge to p so far.
   *                   Output: The updated closest halfedge.
   * \param is_on_edge Output: Is the query point located on closest_he.
   * \param closest_to_target Output: Whether the closest point to p in
   *                                  closest_he to p is its target (in case
   *                                  p is not located on closest_he). 
   * \return (true) if p is contained in the connected component;
   *         (false) otherwise.
   */
  bool _is_in_connected_component (const Point_2& p,
				   Ccb_halfedge_const_circulator circ,
				   bool shoot_up,
				   bool inclusive,
				   Halfedge_const_handle& closest_he,
				   bool& is_on_edge,
				   bool& closest_to_target) const;

  /*!
   * Find the first halfedge around a given target vertex, when going clockwise
   * from "6 o'clock" around this vertex (when shooting up) or starting from
   * "12 o'clock (when shooting down).
   * \param v The given vertex.
   * \param shoot_up If (true) we should start from "6 o'clock",
   *                 if (false) we should start from "12 o'clock".
   * \return The first halfedge we encounter.
   */
  Halfedge_const_handle _first_around_vertex (Vertex_const_handle v,
					      bool shoot_up) const;
};

CGAL_END_NAMESPACE

// The member-function definitions can be found under:
#include <CGAL/Arr_point_location/Arr_walk_along_line_pl_impl.h>

#endif
