// Copyright (c) 2003,2006  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Apollonius_graph_2/include/CGAL/Apollonius_graph_2/Predicate_constructions_C2.h $
// $Id: include/CGAL/Apollonius_graph_2/Predicate_constructions_C2.h b26b07a1242 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Menelaos Karavelas <mkaravel@iacm.forth.gr>



#ifndef CGAL_APOLLONIUS_GRAPH_2_PREDICATE_CONSTRUCTIONS_2_H
#define CGAL_APOLLONIUS_GRAPH_2_PREDICATE_CONSTRUCTIONS_2_H 1

#include <CGAL/license/Apollonius_graph_2.h>


#include <CGAL/Apollonius_graph_2/basic.h>

namespace CGAL {

namespace ApolloniusGraph_2 {

template< class K >
class Inverted_weighted_point_2
  : public K::Site_2
{
public:
  typedef typename K::Site_2             K_Site_2;
  typedef typename K::FT                 FT;
private:
  FT   _p;
public:
  Inverted_weighted_point_2(const K_Site_2& wp, const FT& p)
    : K_Site_2(wp), _p(p) {}

  inline FT p() const { return _p; }
};


template< class K >
class Weighted_point_inverter_2
{
public:
  typedef typename K::Point_2               Point_2;
  typedef typename K::Site_2                Site_2;
  typedef Inverted_weighted_point_2<K>      Inverted_weighted_point;
  typedef typename K::FT                    FT;
private:
  Site_2 _pole;
public:
  Weighted_point_inverter_2(const Site_2& pole)
    : _pole(pole) {}

  Inverted_weighted_point operator()(const Site_2& wp)
    {
      FT xs = wp.x() - _pole.x();
      FT ys = wp.y() - _pole.y();
      FT ws = wp.weight() - _pole.weight();
      FT ps = CGAL::square(xs) + CGAL::square(ys)
        - CGAL::square(ws);

      return
        Inverted_weighted_point(Site_2(Point_2(xs, ys), ws), ps);
    }

  Site_2 pole() const { return _pole; }
};


template< class K >
class Voronoi_radius_2
{
  // this class stores the coefficients for the tritangent circle
  // radius equation. In particular we have:
  //             a x^2 - 2 b x + c = 0;
  // x here represents the inverse of the radius
public:
  typedef typename K::FT                  FT;
  typedef Inverted_weighted_point_2<K>    Inverted_weighted_point;

private:
  FT _a, _b, _c;
  FT _c2, _delta;
  FT _dxp, _dyp, _dwp;

  Voronoi_radius_2(FT a, FT b, FT c, FT c2, FT delta,
                   FT dxp, FT dyp, FT dwp)
    : _a(a), _b(b), _c(c), _c2(c2), _delta(delta), _dxp(dxp),
      _dyp(dyp), _dwp(dwp) {}

public:
  Voronoi_radius_2(const Inverted_weighted_point& u1,
                   const Inverted_weighted_point& u2)
    {
      FT dxp = determinant(u1.x(), u1.p(), u2.x(), u2.p());
      FT dyp = determinant(u1.y(), u1.p(), u2.y(), u2.p());
      FT dwp = determinant(u1.weight(), u1.p(), u2.weight(), u2.p());
      FT dxy = determinant(u1.x(), u1.y(), u2.x(), u2.y());
      FT dxw = determinant(u1.x(), u1.weight(), u2.x(), u2.weight());
      FT dyw = determinant(u1.y(), u1.weight(), u2.y(), u2.weight());

      _a = CGAL::square(dxp) + CGAL::square(dyp);
      _b = dxp * dxw + dyp * dyw;
      _c = CGAL::square(dxw) + CGAL::square(dyw) - CGAL::square(dxy);
      _c2 = dxy;
      _delta = _a - CGAL::square(dwp);
      _dxp = dxp;
      _dyp = dyp;
      _dwp = dwp;
    }

  inline FT a() const { return _a; }
  inline FT b() const { return _b; }
  inline FT c() const { return _c; }

  inline FT c1() const { return _b; }
  inline FT c2() const { return _c2; }
  inline FT delta() const { return _delta; }
  inline FT d() const { return _a; }

  inline FT dxp() const { return _dxp; }
  inline FT dyp() const { return _dyp; }
  inline FT dwp() const { return _dwp; }

  inline bool is_first_root() const { return CGAL::is_negative(_c2); }

  Voronoi_radius_2 get_symmetric()
    {
      return Voronoi_radius_2(_a, _b, _c, -_c2, _delta, -_dxp, -_dyp, -_dwp);
    }
};


template< class K >
class Bitangent_line_2
{
  // this class computes and stores the data for the left bitangent
  // line of the weighted points p1, p2 oriented from p1 to p2
  // or the left bitangent line of the inverted weighted point u1 and
  // u2, oriented from u1 to u2
public:
  typedef typename K::Point_2               Point_2;
  typedef typename K::Site_2                Site_2;
  typedef Inverted_weighted_point_2<K>      Inverted_weighted_point;
  typedef typename K::FT                    FT;
protected:
  FT _a1, _a2;
  FT _b1, _b2;
  FT _c1, _c2;
  FT _delta;
  FT _d;
  FT _dw;
  FT _dxw, _dyw;

  Bitangent_line_2(FT a1, FT a2, FT b1, FT b2, FT c1, FT c2,
                   FT delta, FT d, FT dw, FT dxw, FT dyw)
    : _a1(a1), _a2(a2), _b1(b1), _b2(b2), _c1(c1), _c2(c2),
      _delta(delta), _d(d), _dw(dw),_dxw(dxw), _dyw(dyw) {}

  inline void
  store(FT dx, FT dy, FT dw)
    {
      _dw = dw;
      _a1 = dx * dw;
      _a2 = dy;
      _b1 = dy * dw;
      _b2 = -dx;
    }

  inline void
  store(FT dx, FT dy, FT dw, FT dxy, FT dxw, FT dyw)
    {
      store(dx, dy, dw);
      _c1 = dx * dxw + dy * dyw;
      _c2 = dxy;
      _d = CGAL::square(dx) + CGAL::square(dy);
      _delta = _d - CGAL::square(dw);
      _dxw = dxw;
      _dyw = dyw;
    }

public:
  Bitangent_line_2(const Site_2& p1, const Site_2& p2)
    {
      FT dx = p1.x() - p2.x();
      FT dy = p1.y() - p2.y();
      FT dw = p1.weight() - p2.weight();
      FT dxy = determinant(p1.x(), p1.y(), p2.x(), p2.y());
      FT dxw = determinant(p1.x(), p1.weight(), p2.x(), p2.weight());
      FT dyw = determinant(p1.y(), p1.weight(), p2.y(), p2.weight());

      store(dx, dy, dw, dxy, dxw, dyw);
    }


  Bitangent_line_2(const Inverted_weighted_point& u1,
                   const Inverted_weighted_point& u2)
    {
      FT dxp = determinant(u1.x(), u1.p(), u2.x(), u2.p());
      FT dyp = determinant(u1.y(), u1.p(), u2.y(), u2.p());
      FT dwp = determinant(u1.weight(), u1.p(), u2.weight(), u2.p());
      FT dxy = determinant(u1.x(), u1.y(), u2.x(), u2.y());
      FT dxw = determinant(u1.x(), u1.weight(), u2.x(), u2.weight());
      FT dyw = determinant(u1.y(), u1.weight(), u2.y(), u2.weight());

      store(dxp, dyp, dwp, dxy, dxw, dyw);
    }

  Bitangent_line_2 get_symmetric() const
    {
      return
        Bitangent_line_2(_a1, -_a2, _b1, -_b2, _c1, -_c2, _delta, _d,
                         -_dw, -_dxw, -_dyw);
    }

  Bitangent_line_2 get_rot90() const
    {
      return
        Bitangent_line_2(-_b1, -_b2, _a1, _a2, _c1, _c2, _delta, _d,
                         _dw, -_dyw, _dxw);
    }

  Bitangent_line_2 perpendicular(const Point_2& p) const
    {
      // THIS DOES NOT KEEP TRACK OF THE ADDITIONALLY STORED
      // QUANTITIES; THIS IS INEVITABLE IN ANY CASE SINCE GIVEN p WE
      // CANNOT ANY LONGER HOPE TO KEEP TRACK OF THOSE
      Bitangent_line_2 rotated = get_rot90();
      rotated._c1 = _b1 * p.x() - _a1 * p.y();
      rotated._c2 = _b2 * p.x() - _a2 * p.y();

      return rotated;
    }

  Bitangent_line_2 perpendicular(const Inverted_weighted_point& u) const
    {
      // THIS DOES NOT KEEP TRACK OF THE ADDITIONALLY STORED
      // QUANTITIES; THIS IS INEVITABLE IN ANY CASE SINCE GIVEN p WE
      // CANNOT ANY LONGER HOPE TO KEEP TRACK OF THOSE
      Bitangent_line_2 rotated = get_rot90();
      rotated._c1 = (_b1 * u.x() - _a1 * u.y()) * u.p();
      rotated._c2 = (_b2 * u.x() - _a2 * u.y()) * u.p();

      return rotated;
    }

  inline FT a1() const { return _a1; }
  inline FT a2() const { return _a2; }
  inline FT b1() const { return _b1; }
  inline FT b2() const { return _b2; }
  inline FT c1() const { return _c1; }
  inline FT c2() const { return _c2; }
  inline FT delta() const { return _delta; }
  inline FT d() const { return _d; }

  inline FT dx() const { return -_b2; }
  inline FT dy() const { return _a2; }
  inline FT dw() const { return _dw; }
  inline FT dxw() const { return _dxw; }
  inline FT dyw() const { return _dyw; }
};


template< class K >
class Voronoi_circle_2 : public Bitangent_line_2<K>
{
public:
  typedef Inverted_weighted_point_2<K>     Inverted_weighted_point;
  typedef Bitangent_line_2<K>              Bitangent_line;
  typedef Voronoi_radius_2<K>              Voronoi_radius;
  typedef typename Bitangent_line::FT      FT;

protected:
  FT _gamma;

  inline
  void compute_gamma()
    {
      _gamma = CGAL::square(this->_dxw) + CGAL::square(this->_dyw)
        - CGAL::square(this->_c2);
    }

public:
  Voronoi_circle_2(const Voronoi_radius& vr)
    : Bitangent_line(FT(0), FT(0), FT(0), FT(0), vr.b(), vr.c2(),
                     vr.delta(), vr.d(), FT(0), FT(0), FT(0)), _gamma(vr.c())
    {
      this->store(vr.dxp(), vr.dyp(), vr.dwp());
    }

  Voronoi_circle_2(const Bitangent_line& bl)
    : Bitangent_line(bl.a1(), bl.a2(), bl.b1(), bl.b2(), bl.c1(), bl.c2(),
                     bl.delta(), bl.d(), bl.dw(), bl.dxw(), bl.dyw())
    {
      compute_gamma();
    }

  inline FT alpha() const { return this->_d; }
  inline FT beta() const { return  this->_c1; }
  inline FT gamma() const { return _gamma; }

  inline bool is_first_root() const {
    return CGAL::is_negative(this->_c2);
  }

  FT compute_P4(const Inverted_weighted_point& u1,
                const Inverted_weighted_point& u2,
                const Inverted_weighted_point& u3) const
    {
      FT dx1 = determinant(u2.x(), u2.p(), u1.x(), u1.p());
      FT dy1 = determinant(u2.y(), u2.p(), u1.y(), u1.p());
      FT dw1 = determinant(u2.weight(), u2.p(), u1.weight(), u1.p());

      FT dx3 = determinant(u3.x(), u3.p(), u2.x(), u2.p());
      FT dy3 = determinant(u3.y(), u3.p(), u2.y(), u2.p());
      FT dw3 = determinant(u3.weight(), u3.p(), u2.weight(), u2.p());

      FT u2Pv2 = CGAL::square(u2.x()) + CGAL::square(u2.y());
      FT u2Mv2 = CGAL::square(u2.x()) - CGAL::square(u2.y());
      FT u2v2 = FT(2) * u2.x() * u2.y();


      FT vvMuu = dy1 * dy3 - dx1 * dx3;
      FT vuPuv = dy1 * dx3 + dx1 * dy3;

      FT dx2Pdy2_1 = CGAL::square(dx1) + CGAL::square(dy1);
      FT dx2Pdy2_3 = CGAL::square(dx3) + CGAL::square(dy3);

      FT fr1_sq = CGAL::square(dw1) * dx2Pdy2_3;
      FT fr3_sq = CGAL::square(dw3) * dx2Pdy2_1;

      FT f1 = (fr1_sq + fr3_sq) * CGAL::square(u2Pv2);

      FT f2 = FT(2) * dw1 * dw3 * u2Pv2 * (u2Mv2 * vvMuu - u2v2 * vuPuv );
      FT f3 = CGAL::square(u2Mv2 * vuPuv + u2v2 * vvMuu);

      FT F = f1 + f2 - f3;


      FT uuPvv = dy1 * dy3 + dx1 * dx3;
      FT vuMuv = dy1 * dx3 - dx1 * dy3;

      FT G = fr1_sq + fr3_sq - FT(2) * dw1 * dw3 * uuPvv
        - CGAL::square(vuMuv);

      return (F * G);
    }
};

} //namespace ApolloniusGraph_2

} //namespace CGAL

#endif  // CGAL_APOLLONIUS_GRAPH_2_PREDICATE_CONSTRUCTIONS_2_H

