// Copyright (c) 2005  Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v5.1/Envelope_3/include/CGAL/Env_plane_traits_3.h $
// $Id: Env_plane_traits_3.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Baruch Zukerman     <baruchzu@post.tau.ac.il>

#ifndef CGAL_ENV_PLANE_TRAITS_3_H
#define CGAL_ENV_PLANE_TRAITS_3_H

#include <CGAL/license/Envelope_3.h>


#include <CGAL/basic.h>
#include <CGAL/tags.h>
#include <CGAL/representation_tags.h>
#include <CGAL/enum.h>
#include <CGAL/Arr_tags.h>
#include <CGAL/Arr_linear_traits_2.h>
#include <CGAL/number_utils.h>
#include <CGAL/Envelope_3/Envelope_base.h>
#include <CGAL/Envelope_3/Env_plane_traits_3_functions.h>

namespace CGAL {

template <class Kernel_>
class Env_plane_traits_3 : public Arr_linear_traits_2<Kernel_>
{
public:
  typedef Kernel_                              Kernel;
  typedef typename Kernel::FT                  FT;
  typedef Arr_linear_traits_2<Kernel>          Base;
  typedef Env_plane_traits_3<Kernel>           Self;

  typedef typename Base::Multiplicity          Multiplicity;
  typedef typename Base::Point_2               Point_2;
  typedef typename Base::Curve_2               Curve_2;
  typedef typename Base::X_monotone_curve_2    X_monotone_curve_2;
  typedef typename Kernel::Plane_3             Plane_3;
  typedef typename Kernel::Vector_2            Vector_2;
  typedef typename Kernel::Vector_3            Vector_3;
  typedef typename Kernel::Segment_2           Segment_2;
  typedef typename Kernel::Ray_2               Ray_2;
  typedef typename Kernel::Line_2              Line_2;
  typedef typename Kernel::Line_3              Line_3;
  typedef typename Kernel::Object_3            Object_3;
  typedef std::pair<Curve_2, Multiplicity>     Intersection_curve;

  typedef typename Base::Left_side_category    Left_side_category;
  typedef typename Base::Bottom_side_category  Bottom_side_category;
  typedef typename Base::Top_side_category     Top_side_category;
  typedef typename Base::Right_side_category   Right_side_category;

  class Is_vertical_3
  {
  public:
    bool operator()(const Plane_3& h) const
    {
      return CGAL::is_zero(h.c());
    }
  };

  Is_vertical_3 is_vertical_3_object() const
  {
    return Is_vertical_3();
  }

  class _Env_plane
  {
  protected:
    Plane_3              m_plane;
    Line_2               m_line;
    bool                 m_is_all_plane; // true -> all plane, false -> halfplane
    bool                 m_is_vert;

  public:
    _Env_plane()
    {}

    _Env_plane(const Plane_3& h) : m_plane(h),
                                   m_is_all_plane(true)
    {
      Self s;
      m_is_vert = s.is_vertical_3_object()(h);
    }

    _Env_plane(const Plane_3& h, const Line_2& l) : m_plane(h),
                                                    m_line(l),
                                                    m_is_all_plane(false),
                                                    m_is_vert(false)
    {
      CGAL_precondition_code(Self s);
      CGAL_precondition(!s.is_vertical_3_object()(h));
    }

    bool is_vertical() const
    {
      return m_is_vert;
    }

    const Plane_3& plane() const
    {
      return m_plane;
    }


    operator Plane_3 () const
    {
      return (m_plane);
    }

    const Line_2& line() const
    {
      CGAL_assertion(!m_is_all_plane);
      return m_line;
    }

    bool is_all_plane() const
    {
      return m_is_all_plane;
    }
  };

  typedef _Env_plane               Xy_monotone_surface_3;
  typedef _Env_plane               Surface_3;

  class Make_xy_monotone_3
  {
  public:

    template <class OutputIterator>
    OutputIterator operator()(const Surface_3& s,
                              bool /* is_lower */,
                              OutputIterator o) const
    {
      *o++ = s;
      return o;
    }
  };

  Make_xy_monotone_3 make_xy_monotone_3_object() const
  {
    return Make_xy_monotone_3();
  }

  class Compare_z_at_xy_3
  {
  public:

    Comparison_result operator()(const Point_2& p,
                                 const Xy_monotone_surface_3& h1,
                                 const Xy_monotone_surface_3& h2) const
    {
      const Plane_3& plane1 = h1.plane();
      const Plane_3& plane2 = h2.plane();
      Sign sign_of_c1c2 = CGAL::sign(plane1.c() * plane2.c());
      Sign sign_of_expr =
        CGAL::sign ((p.x()*plane1.a() + p.y()*plane1.b() +
                     plane1.d())*plane2.c() -
                    (p.x()*plane2.a() + p.y()*plane2.b() +
                     plane2.d())*plane1.c());
      int i = -1 * static_cast<int>(sign_of_c1c2) *
        static_cast<int>(sign_of_expr);
      return static_cast<Comparison_result>(i);
    }

    Comparison_result operator()(const X_monotone_curve_2& cv,
                                 const Xy_monotone_surface_3& h1,
                                 const Xy_monotone_surface_3& h2) const
    {
      Kernel k;
      Point_2 p;
      if(cv.is_segment())
        p = k.construct_midpoint_2_object()(cv.left(), cv.right());
      else
        if(cv.is_ray())
          p = k.construct_point_on_2_object()(cv.ray(), 1);
        else
        {
          CGAL_assertion(cv.is_line());
          p = k.construct_point_on_2_object()(cv.line(), 1);
        }

      return this->operator()(p, h1, h2);
    }

    Comparison_result operator()(const Xy_monotone_surface_3& h1,
                                 const Xy_monotone_surface_3& h2) const
    {
      CGAL_assertion(h1.is_all_plane() && h2.is_all_plane());

      const Plane_3& p1 = h1.plane();
      const Plane_3& p2 = h2.plane();
      const FT& res = p2.d()*p1.c() - p1.d()*p2.c();
      int i = static_cast<int>(CGAL::sign(p1.c()*p2.c())) *
        static_cast<int>(CGAL::sign (res));
      return static_cast<Comparison_result>(i);
    }
  };

  Compare_z_at_xy_3 compare_z_at_xy_3_object() const
  {
    return Compare_z_at_xy_3();
  }

  class Compare_z_at_xy_above_3
  {
  public:
    Comparison_result operator()(const X_monotone_curve_2& cv,
                                 const Xy_monotone_surface_3& h1,
                                 const Xy_monotone_surface_3& h2) const
    {
      const Plane_3& plane1 = h1.plane();
      const Plane_3& plane2 = h2.plane();

      const FT& a1 = plane1.a(),
        b1 = plane1.b(),
        c1 = plane1.c();

      const FT& a2 = plane2.a(),
        b2 = plane2.b(),
        c2 = plane2.c();

      // our line is a3*x + b3*y + c3 = 0
      // it is assumed that the planes intersect over this line
      const Line_2& line = cv.supp_line();
      const FT& a3 = line.a(),
        b3 = line.b(),
        c3 = line.c();

      // if the line was parallel to the y-axis (i.e x = const),
      // then it was enough to compare dz/dx of both planes
      // for general line, we change coordinates to (v, w), preserving
      // orientation, so the line is the w-axis in the new coordinates
      // (i.e v = const).
      //
      // ( v )  =  A ( x )    where A = (  a3  b3 )
      //   w           y                  -b3  a3
      //
      // so v =  a3*x + b3*y
      //    w = -b3*x + a3*y
      // preserving orientation since detA = a3^2 +b3^2 > 0
      //
      // We compute the planes equations in the new coordinates
      // and compare dz/dv
      //
      // ( x )  =  A^(-1) ( v )    where A^(-1) = ( a3  -b3 ) * detA^(-1)
      //   y                w                       b3   a3
      // so x = (a3*v - b3*w)*(1/detA)
      //    y = (b3*v + a3*w)*(1/detA)
      // plane1 ==> (a1a3 + b1b3)v + (b1a3 - a1b3)w + (c1z + d1)*detA = 0
      // plane2 ==> (a2a3 + b2b3)v + (b2a3 - a2b3)w + (c2z + d2)*detA = 0
      //
      // dz/dv(1) = (-a1a3 - b1b3) / c1*detA
      // dz/dv(2) = (-a2a3 - b2b3) / c2*detA
      // since detA>0 we can omit it.
      //
      Sign s1 = CGAL_NTS sign((a2*a3+b2*b3)/c2-(a1*a3+b1*b3)/c1);

      // We only need to make sure that w is in the correct direction
      // (going from down to up)
      // the original segment endpoints p1=(x1,y1) and p2=(x2,y2)
      // are transformed to (v1,w1) and (v2,w2), so we need that w2 > w1
      // (otherwise the result should be multiplied by -1)

      Kernel k;
      Point_2 p1 (k.construct_point_on_2_object()(line, 0));
      Point_2 p2 (k.construct_point_on_2_object()(line, 1));

      if(k.compare_xy_2_object()(p1, p2) == LARGER)
        std::swap(p1, p2);

      CGAL_assertion(k.compare_xy_2_object()(p1, p2) == SMALLER);

      const FT& x1 = p1.x(),
        y1 = p1.y(),
        x2 = p2.x(),
        y2 = p2.y();

      Sign s2 = CGAL_NTS sign(-b3*x1+a3*y1-(-b3*x2+a3*y2));
      return s1 * s2;
    }

  };

  Compare_z_at_xy_above_3 compare_z_at_xy_above_3_object() const
  {
    return Compare_z_at_xy_above_3();
  }

  class Compare_z_at_xy_below_3
  {
  public:
    Comparison_result operator()(const X_monotone_curve_2& cv,
                                 const Xy_monotone_surface_3& h1,
                                 const Xy_monotone_surface_3& h2) const
    {
      Compare_z_at_xy_above_3 cmp_above;
      return CGAL::opposite(cmp_above(cv, h1, h2));
    }

  };

  Compare_z_at_xy_below_3 compare_z_at_xy_below_3_object() const
  {
    return Compare_z_at_xy_below_3();
  }


  class Construct_projected_boundary_2
  {
  public:

    template <class OutputIterator>
    OutputIterator operator()(const Xy_monotone_surface_3& s,
                              OutputIterator o) const
    {
      if(s.is_all_plane())
      {
        if(!s.is_vertical())
          return o;

        const Plane_3& h = s.plane();
        Line_2 proj_line(h.a(), h.b(), h.d());
        *o++ = make_object(std::make_pair(X_monotone_curve_2(proj_line),
                                          ON_ORIENTED_BOUNDARY));
        return o;
      }

      // s is half-plane
      Kernel k;
      const Point_2& p1 = k.construct_point_on_2_object()(s.line(), 0);
      const Point_2& p2 = k.construct_point_on_2_object()(s.line(), 1);
      Comparison_result res = k.compare_xy_2_object()(p1, p2);

      Oriented_side side =
        (res == SMALLER) ? ON_POSITIVE_SIDE : ON_NEGATIVE_SIDE;
      *o++ = make_object(std::make_pair(X_monotone_curve_2(s.line()), side));
      return o;
    }
  };

  Construct_projected_boundary_2
  construct_projected_boundary_2_object() const
  {
    return Construct_projected_boundary_2();
  }


  class Construct_projected_intersections_2
  {
  public:

    template <class OutputIterator>
    OutputIterator operator()(const Xy_monotone_surface_3& s1,
                              const Xy_monotone_surface_3& s2,
                              OutputIterator o) const
    {
      Kernel k;

      const Plane_3& h1 = s1.plane();
      const Plane_3& h2 = s2.plane();

      if(s1.is_vertical() && s2.is_vertical())
      {
        Line_2 l1(h1.a(), h1.b(), h1.d());
        Line_2 l2(h2.a(), h2.b(), h2.d());
        Object obj = k.intersect_2_object()(l1, l2);

        Point_2 p;
        if(assign(p, obj))
          *o++ = make_object(p);

        // otherwise, the vertical planes are parallel or overlap, so we return
        // nothing.
        return o;
      }

      if(s1.is_all_plane() && s2.is_all_plane())
      {
        Object obj = k.intersect_3_object()(h1, h2);
        Line_3 l;
        if(assign(l, obj))
          *o++ = make_object(Intersection_curve(project_xy(l, k), 1));

        return o;
      }

      if(s1.is_all_plane() && !s2.is_all_plane())
      {
        Object obj = plane_half_plane_proj_intersection(h1,
                                                        h2,
                                                        s2.line(),
                                                        k);
        if(obj.is_empty())
          return o;
        Line_2 temp_l;
        if(assign(temp_l, obj))
        {
          *o++ = make_object(Intersection_curve(temp_l, 1));
          return o;
        }
        Ray_2 ray;
        if(assign(ray, obj))
        {
          *o++ = make_object(Intersection_curve(ray, 1));
          return o;
        }
        return o;
      }
      if(!s2.is_all_plane() && s2.is_all_plane())
      {
        Object obj = plane_half_plane_proj_intersection(h2,
                                                        h1,
                                                        s1.line(),
                                                        k);
        if(obj.is_empty())
          return o;
        Line_2 line;
        if(assign(line, obj))
        {
          *o++ = make_object(Intersection_curve(line, 1));
          return o;
        }
        Ray_2 ray;
        if(assign(ray, obj))
        {
          *o++ = make_object(Intersection_curve(ray, 1));
          return o;
        }
        return o;

      }

      CGAL_assertion(!s2.is_all_plane() && !s2.is_all_plane());
      Object obj =
        half_plane_half_plane_proj_intersection(h1, s1.line(), h2, s2.line(), k);

      if(obj.is_empty())
        return o;
      Line_2 line;
      if(assign(line, obj))
      {
        *o++ = make_object(Intersection_curve(line, 1));
        return o;
      }
      Ray_2 ray;
      if(assign(ray, obj))
      {
        *o++ = make_object(Intersection_curve(ray, 1));
        return o;
      }

      Segment_2 seg;
      if(assign(seg, obj))
      {
        *o++ = make_object(Intersection_curve(seg, 1));
        return o;
      }

      Point_2 p;
      if(assign(p, obj))
      {
        *o++ = make_object(p);
        return o;
      }
      return o;
    }
  };

  Construct_projected_intersections_2
  construct_projected_intersections_2_object() const
  {
    return Construct_projected_intersections_2();
  }

};

} //namespace CGAL

#endif