// 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-3.6-branch/Arrangement_on_surface_2/include/CGAL/Sweep_line_2/Sweep_line_functors.h $
// $Id: Sweep_line_functors.h 51984 2009-09-20 16:18:10Z efif $
// 
//
// Author(s)     : Tali Zvi <talizvi@post.tau.ac.il>
//                 Baruch Zukerman <baruchzu@post.tau.ac.il>
//                 Ron Wein <wein@post.tau.ac.il>
//                 Efi Fogel <efif@post.tau.ac.il>

#ifndef CGAL_SWEEP_LINE_FUNCTORS_H
#define CGAL_SWEEP_LINE_FUNCTORS_H

/*! \file
 * Comparison functors used by the sweep-line algorithm.
 */

#include <CGAL/assertions.h>
#include <CGAL/enum.h>
#include <CGAL/Arr_enums.h>
#include <CGAL/Arrangement_2/Arr_traits_adaptor_2.h>

CGAL_BEGIN_NAMESPACE

/*! \class
 * A functor used to compare events and event points in an xy-lexicographic
 * order. Used to maintain the order of the event queue (the X-structure)
 * in the sweep-line algorithm.
 */
template <class Traits_, class Event_>
class Compare_events
{
public:

  typedef Traits_                                   Traits_2;
  typedef Event_                                    Event;

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

  // should be ok, as Traits_2 is supposed to be the adaptor
  typedef typename Traits_2::Arr_left_side_category          Arr_left_side_category;
  typedef typename Traits_2::Arr_bottom_side_category        Arr_bottom_side_category;
  typedef typename Traits_2::Arr_top_side_category           Arr_top_side_category;
  typedef typename Traits_2::Arr_right_side_category         Arr_right_side_category;

private:

  // Data members:
  const Traits_2 * m_traits;                // The geometric-traits object.
  
  Arr_parameter_space  m_ps_in_x;           // Storing curve information when
  Arr_parameter_space  m_ps_in_y;           // comparing a curve end with
  Arr_curve_end        m_index;             // boundary conditions.

public:
  
  /*! Cosntructor. */
  Compare_events (const Traits_2 * traits) :
    m_traits (traits)
  {}
  
  /*!
   * Compare two existing events.
   * This operator is called by the multiset assertions only in
   * debug mode (to verify that event was inserted at the right place).
   */
  Comparison_result operator()(const Event* e1, const Event* e2) const
  {
    const bool  on_boundary1 = e1->is_on_boundary();
    const bool  on_boundary2 = e2->is_on_boundary();

    if (! on_boundary1 && ! on_boundary2)
    {
      // Both events do not have boundary conditions - just compare the points.
      return (m_traits->compare_xy_2_object()(e1->point(), e2->point()));
    }

    if (! on_boundary1)
    {
      // Compare the point associated with the first event with the second
      // boundary event.
      return ( this->operator()(e1->point(), e2) );
    }

    if (! on_boundary2)
    {
      // Compare the point associated with the second event with the first
      // boundary event.
      return (CGAL::opposite(this->operator()(e2->point(), e1)));
    }

    return (_compare_curve_end_with_event (e1->curve(), _curve_end(e1),
                                           e1->parameter_space_in_x(),
                                           e1->parameter_space_in_y(),
                                           e2));
  }

  /*!
   * Compare a point, which should be inserted into the event queue,
   * with an existing event point.
   */
  Comparison_result operator() (const Point_2& pt, const Event* e2) const
  {
    const bool  on_boundary2 = e2->is_on_boundary();
    
    if (! on_boundary2)
    {
      // If e2 is a normal event, just compare pt and the event point.
      return (m_traits->compare_xy_2_object() (pt, e2->point()));
    }

    // Get the sign of the event's boundary condition in x. Note that a valid
    // point is always larger than any negative boundary event and smaller
    // than any positive boundary event.
    Arr_parameter_space ps_x2 = e2->parameter_space_in_x();

    if (ps_x2 == ARR_LEFT_BOUNDARY)
      return (LARGER);
    else if (ps_x2 == ARR_RIGHT_BOUNDARY)
      return (SMALLER);
    
    // Get the curve end that e2 represents, and compare the x-position of the
    // given point and this curve end.
    Arr_curve_end         ind = _curve_end(e2);
    Comparison_result res =
      m_traits->compare_x_near_boundary_2_object()(pt, e2->curve(), ind);

    if (res != EQUAL)
      return (res);

    // The event and the point has the same x-position. Get the sign of the
    // event's boundary condition in y. Note that a valid point is always
    // larger than any negative boundary event and smaller than any positive
    // boundary event.
    Arr_parameter_space ps_y2 = e2->parameter_space_in_y();

    CGAL_assertion (ps_y2 != ARR_INTERIOR);
    return (ps_y2 == ARR_BOTTOM_BOUNDARY) ? LARGER : SMALLER;
  }

  /*!
   * Compare a curve end, which should be inserted into the event queue,
   * with an existing event point.
   * Note that the index of the curve end as well as its boundary conditions
   * must be set beforehand using set_index() and set_parameter_space_in_x/y(). 
   */
  Comparison_result operator() (const X_monotone_curve_2& cv,
                                const Event* e2) const
  {
    return _compare_curve_end_with_event(cv, m_index, m_ps_in_x, m_ps_in_y, e2);
  }

  /// \name Set the boundary conditions of a curve end we are about to compare.
  //@{
  void set_parameter_space_in_x (Arr_parameter_space bx)
  {
    m_ps_in_x = bx;
  }

  void set_parameter_space_in_y (Arr_parameter_space by)
  {
    m_ps_in_y = by;
  }

  void set_index (Arr_curve_end ind)
  {
    m_index = ind;
  }
  //@}

private:

  /*!
   * Compare a given curve end with an event.
   * \param cv The curve.
   * \param ind The curve end.
   * \param ps_x The boundary condition of the curve end in x.
   * \param ps_y The boundary condition of the curve end in y.
   * \param e2 The event, which may have boundary conditions.
   * \return The comparison result of the curve end with the event.
   */
  Comparison_result 
  _compare_curve_end_with_event (const X_monotone_curve_2& cv,
                                 Arr_curve_end ind,
                                 Arr_parameter_space ps_x,
                                 Arr_parameter_space ps_y,
                                 const Event* e2) const
  {
    // Check if the curve end has a boundary condition in x.
    if (ps_x == ARR_LEFT_BOUNDARY)
    {
      if (e2->parameter_space_in_x() == ARR_LEFT_BOUNDARY)
      {
        // Both defined on the left boundary - compare them there.
        CGAL_assertion (ind == ARR_MIN_END);

        return (m_traits->compare_y_near_boundary_2_object() (cv, e2->curve(),
                                                              ind));
      }

      // The curve end is obviously smaller.
      return (SMALLER);
    }

    if (ps_x == ARR_RIGHT_BOUNDARY)
    {
      if (e2->parameter_space_in_x() == ARR_RIGHT_BOUNDARY)
      {
        // Both defined on the right boundary - compare them there.
        CGAL_assertion (ind == ARR_MAX_END);

        return (m_traits->compare_y_near_boundary_2_object() (cv, e2->curve(),
                                                              ind));
      }

      // The curve end is obviously larger.
      return (LARGER);
    }
      
    // Check if the event has a boundary condition in x. Note that if it
    // has a negative boundary condition, the curve end is larger than it,
    // and if it has a positive boundary condition, the curve end is smaller.
    if (e2->parameter_space_in_x() == ARR_LEFT_BOUNDARY)
      return (LARGER);
    
    if (e2->parameter_space_in_x() == ARR_RIGHT_BOUNDARY)
      return (SMALLER);

    CGAL_assertion (ps_y != ARR_INTERIOR);
    Comparison_result res;

    // Act according to the boundary sign of the event.
    if (e2->parameter_space_in_y() == ARR_BOTTOM_BOUNDARY)
    {
      // Compare the x-positions of the two entities.
      res = m_traits->compare_x_near_boundary_2_object() (cv, ind, e2->curve(),
                                                          _curve_end(e2));

      if (res != EQUAL)
        return (res);
      
      // In case of equal x-positions, the curve end is larger than the event,
      // which lies on the bottom boundary (unless it also lies on the bottom
      // boundary).
      if (ps_y == ARR_BOTTOM_BOUNDARY)
        return (EQUAL);

      return (LARGER);
    }

    if (e2->parameter_space_in_y() == ARR_TOP_BOUNDARY)
    {
      // Compare the x-positions of the two entities.
      res = m_traits->compare_x_near_boundary_2_object() (cv, ind, e2->curve(),
                                                          _curve_end(e2));

      if (res != EQUAL)
        return (res);
       
      // In case of equal x-positions, the curve end is smaller than the event,
      // which lies on the top boundary (unless it also lies on the top
      // boundary).
      if (ps_y == ARR_TOP_BOUNDARY)
        return (EQUAL);

      return (SMALLER);
    }

    // If we reached here, e2 is not a boundary event and is associated with
    // a valid point. We compare the x-position of this point with the curve
    // end.
    res = m_traits->compare_x_near_boundary_2_object() (e2->point(), cv, ind);

    if (res != EQUAL)
      return (CGAL::opposite(res));

    // In case of equal x-positions, is the curve end has a negative boundary
    // sign, then it lies on the bottom boundary below the event. Otherwise,
    // it lies on the top aboundary above the event e2.
    return (ps_y == ARR_BOTTOM_BOUNDARY) ? SMALLER : LARGER;
  }

  /*! Detemine if the given event represents a left or a right curve end. */
  inline Arr_curve_end _curve_end (const Event* e) const
  {
    return (e->has_left_curves()) ?
      ((e->is_right_end()) ? ARR_MAX_END : ARR_MIN_END) :
      ((e->is_left_end()) ? ARR_MIN_END : ARR_MAX_END);
  }
};

// Forward decleration:
template <class Traits, class Subcurve>
class Sweep_line_event;

/*! \class
 * A functor used to compare curves and curve endpoints by their vertical
 * y-order. Used to maintain the order of the status line (the Y-structure)
 * in the sweep-line algorithm.
 */
template <class Traits_, class Subcurve_> 
class Curve_comparer 
{
public:

  typedef Traits_                                        Traits_2;
  typedef Subcurve_                                      Subcurve;
  typedef Arr_traits_basic_adaptor_2<Traits_2>           Traits_adaptor_2;

  typedef typename Traits_adaptor_2::Point_2 Point_2;
  typedef typename Traits_adaptor_2::X_monotone_curve_2  X_monotone_curve_2;
  typedef Sweep_line_event<Traits_2, Subcurve>           Event;

private:

  const Traits_adaptor_2 * m_traits;    // A geometric-traits object.
  Event            **m_curr_event;      // Points to the current event point.

public:
  
  /*! Constructor. */
  template <class Sweep_event>
  Curve_comparer (const Traits_adaptor_2 * t, Sweep_event** e_ptr) :
    m_traits(t),
    m_curr_event(reinterpret_cast<Event**>(e_ptr))
  {}

  /*!
   * Compare the vertical position of two subcurves in the status line.
   * This operator is called only in debug mode.
   */
  Comparison_result operator()(const Subcurve *c1, const Subcurve *c2) const
  {
    // In case to two curves are right curves at the same event, compare
    // to the right of the event point.
    if (std::find((*m_curr_event)->right_curves_begin(), 
                  (*m_curr_event)->right_curves_end(),
                  c1) != (*m_curr_event)->right_curves_end() &&
        std::find((*m_curr_event)->right_curves_begin(), 
                  (*m_curr_event)->right_curves_end(),
                  c2) != (*m_curr_event)->right_curves_end())
    {
      return (m_traits->compare_y_at_x_right_2_object()
              (c1->last_curve(), c2->last_curve(), (*m_curr_event)->point()));
    }

    Arr_parameter_space ps_x1 = 
      m_traits->parameter_space_in_x_2_object()(c1->last_curve(), ARR_MIN_END);
    Arr_parameter_space ps_y1 = 
      m_traits->parameter_space_in_y_2_object()(c1->last_curve(), ARR_MIN_END);

    if ((ps_x1 == ARR_INTERIOR) && (ps_y1 == ARR_INTERIOR))
    {
      // The first curve has a valid left endpoint. Compare the y-position
      // of this endpoint to the second subcurve. 
      return m_traits->compare_y_at_x_2_object()
        (m_traits->construct_min_vertex_2_object()(c1->last_curve()),
         c2->last_curve());
    }

    // We use the fact that the two curves are interior disjoint. As c2 is
    // already in the status line, then if c1 left end has a negative boundary
    // condition it obviously above it.
    CGAL_assertion (ps_x1 != ARR_RIGHT_BOUNDARY);

    if (ps_x1 == ARR_LEFT_BOUNDARY)
      return (LARGER);

    // For similar reasons, if c1 begins on the bottom boundary it is below
    // c2, if it is on the top boundary it is above it.
    CGAL_assertion (ps_y1 != ARR_INTERIOR);
    return (ps_y1 == ARR_BOTTOM_BOUNDARY) ? SMALLER : LARGER;
  }

  /*!
   * Compare the relative y-order of the given point and the given subcurve.
   */
  Comparison_result operator() (const Point_2& pt, const Subcurve *sc) const
  {
    return (m_traits->compare_y_at_x_2_object()(pt, sc->last_curve()));
  }

};

CGAL_END_NAMESPACE

#endif
