// Copyright (c) 2005,2006,2007,2009,2010,2011 Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
// You can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation,
// either version 3 of the License, or (at your option) any later version.
//
// 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.
//
// $URL$
// $Id$
// 
//
// Author(s)     : Efi Fogel <efif@post.tau.ac.il>
//                 Ron Wein  <wein@post.tau.ac.il>
//                 (based on old version by: Iddo Hanniel,
//                                           Eyal Flato,
//                                           Oren Nechushtan,
//                                           Ester Ezra,
//                                           Shai Hirsch,
//                                           and Eugene Lipovetsky)

#ifndef CGAL_ARR_NON_CACHING_SEGMENT_BASIC_TRAITS_2_H
#define CGAL_ARR_NON_CACHING_SEGMENT_BASIC_TRAITS_2_H

/*! \file The basic non-caching segment traits-class for the arrangement
 * package. This traits class handles x-monotone non-intersecting segments.
 * It is a model of the ArrangementBasicTraits_2 concept. The class is
 * templated by a kernel and inherits from it all the types and many of the
 * functors required by the concept it models.
 */

#include <CGAL/Algebraic_structure_traits.h>
#include <CGAL/number_utils.h>
#include <CGAL/tags.h>
#include <CGAL/Arr_tags.h>
#include <CGAL/assertions.h>
#include <CGAL/Arr_geometry_traits/Segment_assertions.h>

namespace CGAL {

/*! \class
 * A model of the ArrangementBasicTraits_2 concept that handles x-monotone
 * non-intersecting line segments.
 */
template <class T_Kernel>
class Arr_non_caching_segment_basic_traits_2 : public T_Kernel
{
public:

  typedef T_Kernel                              Kernel;

  typedef typename Kernel::FT                   FT;

private:
  typedef Algebraic_structure_traits<FT> AST; 
  typedef typename AST::Is_exact FT_is_exact; 
public:

  typedef Boolean_tag<FT_is_exact::value> Has_exact_division;

  typedef
  CGAL::Segment_assertions<Arr_non_caching_segment_basic_traits_2<Kernel> >
                                                Segment_assertions;

  // Categories:
  typedef Tag_true                              Has_left_category;
  typedef Tag_false                             Has_do_intersect_category;
 
  typedef Arr_oblivious_side_tag                Left_side_category;
  typedef Arr_oblivious_side_tag                Bottom_side_category;
  typedef Arr_oblivious_side_tag                Top_side_category;
  typedef Arr_oblivious_side_tag                Right_side_category;
    
  /*! Default Constructor */
  Arr_non_caching_segment_basic_traits_2()
  {}
  
  /// \name Types and functor inherited from the kernel
  //@{

  // Traits types:
  typedef typename Kernel::Point_2                 Point_2;
  typedef typename Kernel::Segment_2               X_monotone_curve_2;
  typedef unsigned int                             Multiplicity;

  /*! Compare the x-coordinates of two points */
  typedef typename Kernel::Compare_x_2             Compare_x_2;

  /*! Compare two points lexigoraphically; by x, then by y */
  typedef typename Kernel::Compare_xy_2            Compare_xy_2;

  /*! Obtain the left endpoint of a given segment */
  typedef typename Kernel::Construct_min_vertex_2  Construct_min_vertex_2;

  /*! Obtain the right endpoint of a given segment */
  typedef typename Kernel::Construct_max_vertex_2  Construct_max_vertex_2;
  
  /*! Check whether a given segment is vertical */
  typedef typename Kernel::Is_vertical_2           Is_vertical_2;
  
  /*! Return the location of a given point with respect to an input segment */
  typedef typename Kernel::Compare_y_at_x_2        Compare_y_at_x_2;
  
  /*! Check if two segments or if two points are identical */
  typedef typename Kernel::Equal_2                 Equal_2;

  //@}

  /// \name Functor introduced here (based on the kernel)
  //@{

  /*! \class 
   * A functor for comparing two segments to the left of a point 
   */
  class Compare_y_at_x_left_2 {
  public:
    
    /* 
     * Compare the y value of two segments immediately to the left of their
     * intersection point.
     * \param cv1 The first segment.
     * \param cv2 The second segment.
     * \param p The intersection point.
     * \pre The point p lies on both segments, and both of them must be also be
     *      defined (lexicographically) to its left.
     * \return The relative position of cv1 with respect to cv2 immdiately to
     *         the left of p: SMALLER, LARGER or EQUAL.
     */
    Comparison_result operator()(const X_monotone_curve_2 & cv1,
                                 const X_monotone_curve_2 & cv2,
                                 const Point_2 & p) const
    {
      Kernel kernel;

      // The two segments must be defined at q and also to its left.
      CGAL_precondition
        (Segment_assertions::_assert_is_point_on(p, cv1, Has_exact_division())&&
         Segment_assertions::_assert_is_point_on(p, cv2, Has_exact_division()));

      CGAL_precondition_code(
        Compare_xy_2 compare_xy = kernel.compare_xy_2_object();
        typename Kernel::Construct_vertex_2 construct_vertex =
          kernel.construct_vertex_2_object();
        const Point_2 & source1 = construct_vertex(cv1, 0);
        const Point_2 & target1 = construct_vertex(cv1, 1);
        const Point_2 & left1 =
          (kernel.less_xy_2_object()(source1, target1)) ? source1 : target1;
        const Point_2 & source2 = construct_vertex(cv2, 0);
        const Point_2 & target2 = construct_vertex(cv2, 1);
        const Point_2 & left2 =
          (kernel.less_xy_2_object()(source2, target2)) ? source2 : target2;
        );
      
      CGAL_precondition(compare_xy(left1, p) == SMALLER &&
                        compare_xy(left2, p) == SMALLER);
    
      // Compare the slopes of the two segments to determine thir relative
      // position immediately to the left of q.
      // Notice that we swap the order of the curves in order to obtain the
      // correct result to the left of p.
      return kernel.compare_slope_2_object()(cv2, cv1);
    }
  };

  /*! Obtain a Compare_y_at_x_left_2 functor object. */
  Compare_y_at_x_left_2 compare_y_at_x_left_2_object() const
  {
    return Compare_y_at_x_left_2();
  }
  
  /*! \class
   * A functor for comparing two segments to the right of a point. 
   */
  class Compare_y_at_x_right_2 {
  public:
    
    /*! 
     * Compare the y value of two segments immediately to the right of their
     * intersection point.
     * \param cv1 The first segment.
     * \param cv2 The second segment.
     * \param p The intersection point.
     * \pre The point p lies on both segments, and both of them must be also be
     *      defined (lexicographically) to its right.
     * \return The relative position of cv1 with respect to cv2 immdiately to
     *         the right of p: SMALLER, LARGER or EQUAL.
     */

    Comparison_result operator()(const X_monotone_curve_2 & cv1,
                                 const X_monotone_curve_2 & cv2,
                                 const Point_2 & p) const
    {
      Kernel kernel;

      // The two segments must be defined at q and also to its right.
      CGAL_precondition
        (Segment_assertions::_assert_is_point_on(p, cv1, Has_exact_division())&&
         Segment_assertions::_assert_is_point_on(p, cv2, Has_exact_division()));

      CGAL_precondition_code(
        Compare_xy_2 compare_xy = kernel.compare_xy_2_object();
        typename Kernel::Construct_vertex_2 construct_vertex =
          kernel.construct_vertex_2_object();
        const Point_2 & source1 = construct_vertex(cv1, 0);
        const Point_2 & target1 = construct_vertex(cv1, 1);
        const Point_2 & right1 =
          (kernel.less_xy_2_object()(source1, target1)) ? target1 : source1;
        const Point_2 & source2 = construct_vertex(cv2, 0);
        const Point_2 & target2 = construct_vertex(cv2, 1);
        const Point_2 & right2 =
          (kernel.less_xy_2_object()(source2, target2)) ? target2 : source2;
        );

      CGAL_precondition(compare_xy(right1, p) == LARGER &&
                        compare_xy(right2, p) == LARGER);

      // Compare the slopes of the two segments to determine thir relative
      // position immediately to the left of q.
       return kernel.compare_slope_2_object()(cv1, cv2);
    }
  };

  /*! Obtain a Compare_y_at_x_right_2 functor object. */
  Compare_y_at_x_right_2 compare_y_at_x_right_2_object() const
  {
    return Compare_y_at_x_right_2();
  }
  //@}

  /// \name Functor definitions for the landmarks point-location strategy.
  //@{
  typedef double                          Approximate_number_type;

  class Approximate_2
  {
  public:

    /*!
     * Return an approximation of a point coordinate.
     * \param p The exact point.
     * \param i The coordinate index (either 0 or 1).
     * \pre i is either 0 or 1.
     * \return An approximation of p's x-coordinate (if i == 0), or an 
     *         approximation of p's y-coordinate (if i == 1).
     */
    Approximate_number_type operator() (const Point_2& p,
                                        int i) const
    {
      CGAL_precondition (i == 0 || i == 1);

      if (i == 0)
	return (CGAL::to_double(p.x()));
      else
	return (CGAL::to_double(p.y()));
    }
  };

  /*! Get an Approximate_2 functor object. */
  Approximate_2 approximate_2_object () const
  {
    return Approximate_2();
  }

  typedef typename Kernel::Construct_segment_2    Construct_x_monotone_curve_2;

  /*! Get a Construct_x_monotone_curve_2 functor object. */
  Construct_x_monotone_curve_2 construct_x_monotone_curve_2_object () const
  {
    return (this->construct_segment_2_object());
  }
  //@}
};

} //namespace CGAL

#endif
