// Copyright (c) 1999-2004,2006-2009   INRIA Sophia-Antipolis (France).
// 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)     : Monique Teillaud <Monique.Teillaud@sophia.inria.fr>
//                 Sylvain Pion <Sylvain.Pion@sophia.inria.fr>
//                 Andreas Fabri <Andreas.Fabri@sophia.inria.fr>
//                 Nico Kruithof <Nico.Kruithof@sophia.inria.fr>
//                 Manuel Caroli <Manuel.Caroli@sophia.inria.fr>


#ifndef CGAL_PERIODIC_3_DELAUNAY_TRIANGULATION_3_H
#define CGAL_PERIODIC_3_DELAUNAY_TRIANGULATION_3_H

#include <CGAL/Periodic_3_triangulation_3.h>
#include <CGAL/spatial_sort.h>

// Needed by remove to fill the hole.
#include <CGAL/internal/Periodic_3_triangulation_remove_traits_3.h>
#include <CGAL/Delaunay_triangulation_3.h>

namespace CGAL {

template < class Gt,
            class Tds = Triangulation_data_structure_3 <
              Triangulation_vertex_base_3<
		Gt, Periodic_3_triangulation_ds_vertex_base_3<>
	      >,
              Triangulation_cell_base_3<
                Gt, Periodic_3_triangulation_ds_cell_base_3<>
              >
            >
          >
class Periodic_3_Delaunay_triangulation_3 :
    public Periodic_3_triangulation_3<Gt,Tds>
{
  typedef Periodic_3_Delaunay_triangulation_3<Gt,Tds>          Self;
public:
  typedef Periodic_3_triangulation_3<Gt,Tds>                   Base;

public:
  /** @name Template parameter types */ //@{
  typedef Gt                                    Geometric_traits;
  typedef Tds                                   Triangulation_data_structure;
  //@}

  ///Compatibility typedef:
  typedef Geometric_traits                      Geom_traits;
  typedef typename Gt::FT                       FT;

  typedef typename Gt::Point_3                  Point;
  typedef typename Gt::Segment_3                Segment;
  typedef typename Gt::Triangle_3               Triangle;
  typedef typename Gt::Tetrahedron_3            Tetrahedron;

  typedef typename Base::Periodic_point         Periodic_point;
  typedef typename Base::Periodic_segment       Periodic_segment;
  typedef typename Base::Periodic_triangle      Periodic_triangle;
  typedef typename Base::Periodic_tetrahedron   Periodic_tetrahedron;

  typedef typename Base::Cell_handle            Cell_handle;
  typedef typename Base::Vertex_handle          Vertex_handle;

  typedef typename Base::Cell                   Cell;
  typedef typename Base::Vertex                 Vertex;
  typedef typename Base::Facet                  Facet;
  typedef typename Base::Edge                   Edge;

  typedef typename Base::Cell_circulator        Cell_circulator;
  typedef typename Base::Facet_circulator       Facet_circulator;
  typedef typename Base::Cell_iterator          Cell_iterator;
  typedef typename Base::Facet_iterator         Facet_iterator;
  typedef typename Base::Edge_iterator          Edge_iterator;
  typedef typename Base::Vertex_iterator        Vertex_iterator;

  typedef typename Base::All_cells_iterator     All_cells_iterator;
  typedef typename Base::All_facets_iterator    All_facets_iterator;
  typedef typename Base::All_edges_iterator     All_edges_iterator;
  typedef typename Base::All_vertices_iterator  All_vertices_iterator;

  typedef typename Base::size_type              size_type;
  typedef typename Base::difference_type        difference_type;

  typedef typename Base::Locate_type            Locate_type;
  typedef typename Base::Iterator_type          Iterator_type;

  typedef typename Base::Offset                 Offset;
  typedef typename Base::Iso_cuboid             Iso_cuboid;
  typedef typename Base::Covering_sheets        Covering_sheets;
  //@}

#ifndef CGAL_CFG_USING_BASE_MEMBER_BUG_2
  using Base::cw;
  using Base::ccw;
  using Base::domain;
  using Base::geom_traits;
  using Base::int_to_off;
  using Base::number_of_sheets;
  using Base::number_of_vertices;
  using Base::number_of_edges;
  using Base::number_of_facets;
  using Base::number_of_cells;
  using Base::cells_begin;
  using Base::cells_end;
  using Base::vertices_begin;
  using Base::vertices_end;
  using Base::facets_begin;
  using Base::facets_end;
  using Base::tds;
  using Base::next_around_edge;
  using Base::vertex_triple_index;
  using Base::mirror_vertex;
  using Base::orientation;
  using Base::insert_dummy_points;
  using Base::swap;
  using Base::is_1_cover;
  using Base::is_virtual;
  using Base::point;
#endif

  // For strict-ansi compliance
  using Base::adjacent_vertices;
  using Base::combine_offsets;
  using Base::get_offset;
  using Base::get_original_vertex;
  using Base::get_location_offset;
  using Base::get_neighbor_offset;
  using Base::incident_edges;
  using Base::incident_facets;
  using Base::incident_cells;
  using Base::is_valid_conflict;
  using Base::locate;
  using Base::periodic_point;
  using Base::segment;

public:
  /** @name Creation */ //@{
  Periodic_3_Delaunay_triangulation_3(
      const Iso_cuboid& domain = Iso_cuboid(0,0,0,1,1,1),
      const Geometric_traits& gt = Geometric_traits())
    : Base(domain, gt) {}

  // copy constructor duplicates vertices and cells
  Periodic_3_Delaunay_triangulation_3(
      const Periodic_3_Delaunay_triangulation_3& tr) : Base(tr) { 
    CGAL_triangulation_expensive_postcondition( is_valid() );  
  }

  template < typename InputIterator >
  Periodic_3_Delaunay_triangulation_3(InputIterator first, InputIterator last,
      const Iso_cuboid& domain = Iso_cuboid(0,0,0,1,1,1),
      const Geometric_traits& gt = Geometric_traits() )
    : Base(domain, gt) {
    insert(first, last);
  }
  //@}

  /** @name Insertion */ //@{
  Vertex_handle insert(const Point & p, Cell_handle start = Cell_handle()) {
    Conflict_tester tester(p, this);
    Point_hider hider;
    return Base::insert_in_conflict(p, start, tester, hider);
  }

  Vertex_handle insert(const Point & p, Locate_type lt, Cell_handle c,
      int li, int lj) {
    Conflict_tester tester(p, this);
    Point_hider hider;
    return Base::insert_in_conflict(p,lt,c,li,lj, tester,hider);
  }

  template < class InputIterator >
  std::ptrdiff_t insert(InputIterator first, InputIterator last,
      bool is_large_point_set = false) {
    if (first == last) return 0;
    size_type n = number_of_vertices();
    // The heuristic discards the existing triangulation so it can only be
    // applied to empty triangulations.
    if (n!=0) is_large_point_set = false;

    std::vector<Point> points(first, last);
    std::random_shuffle (points.begin(), points.end());
    Cell_handle hint;
    std::vector<Vertex_handle> dummy_points, double_vertices;
    typename std::vector<Point>::iterator pbegin = points.begin();
    if (is_large_point_set)
      dummy_points = insert_dummy_points();
    else while (!is_1_cover()) {
	insert(*pbegin);
	++pbegin;
	if (pbegin == points.end()) return number_of_vertices() - n;
      }

    // Use Geom_traits::K for efficiency: spatial_sort creates a lot
    // of copies of the traits but does not need the domain that is
    // stored in it.
    spatial_sort (pbegin, points.end(), typename Geom_traits::K());

    Conflict_tester tester(*pbegin,this);
    Point_hider hider;
    double_vertices = Base::insert_in_conflict(
	points.begin(),points.end(),hint,tester,hider); 
   
    if (is_large_point_set) {
      typedef CGAL::Periodic_3_triangulation_remove_traits_3< Gt > P3removeT;
      typedef CGAL::Delaunay_triangulation_3< P3removeT > DT;
      typedef Vertex_remover< DT > Remover;
      P3removeT remove_traits(domain());
      DT dt(remove_traits);
      Remover remover(this,dt);
      Conflict_tester t(this);
      for (unsigned int i=0; i<dummy_points.size(); i++) {
	if (std::find(double_vertices.begin(), double_vertices.end(),
		dummy_points[i]) == double_vertices.end())
	  Base::remove(dummy_points[i],remover,t);
      }
    }

    return number_of_vertices() - n;
  }
  //@}

  /** @name Point moving */ //@{
  Vertex_handle move_point(Vertex_handle v, const Point & p);
  //@}

public:
  /** @name Removal */ //@{
  void remove(Vertex_handle v);

  template < typename InputIterator >
  std::ptrdiff_t remove(InputIterator first, InputIterator beyond) {
    std::size_t n = number_of_vertices();
    while (first != beyond) {
      remove(*first);
      ++first;
    }
    return n - number_of_vertices();
  }
  //@}

public:
  /** @name Wrapping the traits */ //@{
  Oriented_side side_of_oriented_sphere(const Point &p, const Point &q,
      const Point &r, const Point &s, const Point &t) const {
    return geom_traits().side_of_oriented_sphere_3_object()(p,q,r,s,t);
  }
  Oriented_side side_of_oriented_sphere(const Point &p, const Point &q,
      const Point &r, const Point &s, const Point &t, const Offset &o_p,
      const Offset &o_q, const Offset &o_r, const Offset &o_s,
      const Offset &o_t) const {
    return geom_traits().side_of_oriented_sphere_3_object()(
	p,q,r,s,t,o_p,o_q,o_r,o_s,o_t);
  }
  Comparison_result compare_distance(const Point &p, const Point &q,
      const Point &r) const {
      return geom_traits().compare_distance_3_object()(p, q, r);
  }
  Comparison_result compare_distance(const Point &p, const Point &q,
      const Point &r, const Offset &o_p, const Offset &o_q,
      const Offset &o_r) const {
    return geom_traits().compare_distance_3_object()(p, q, r, o_p, o_q, o_r);
  }
  //@}

private:
  /** @name Query helpers */ //@{
  Bounded_side _side_of_sphere(const Cell_handle& c, const Point& p,
      const Offset & offset = Offset(), bool perturb = false) const;

  Offset get_min_dist_offset(const Point & p, const Offset & o,
      const Vertex_handle vh) const;
  //@}

public:
  /** @name Queries */ //@{
  Bounded_side side_of_sphere(const Cell_handle& c, const Point& p,
      const Offset & offset = Offset(), bool perturb = false) const{
    Bounded_side bs = ON_UNBOUNDED_SIDE;
    int i=0;
    // TODO: optimize which copies to check depending on the offsets in
    // the cell.
    while (bs == ON_UNBOUNDED_SIDE && i<8) {
      bs= _side_of_sphere(c,p,combine_offsets(offset,int_to_off(i)),perturb);
      i++;
    }
    return bs;
  }

  Vertex_handle nearest_vertex(const Point& p,
      Cell_handle c = Cell_handle()) const;
  Vertex_handle nearest_vertex_in_cell(const Cell_handle& c,
      const Point & p, const Offset & offset = Offset()) const;

  /// Undocumented wrapper for find_conflicts.
  template <class OutputIteratorBoundaryFacets, class OutputIteratorCells>
  std::pair<OutputIteratorBoundaryFacets, OutputIteratorCells>
  find_conflicts(const Point &p, Cell_handle c,
      OutputIteratorBoundaryFacets bfit, OutputIteratorCells cit) const {
    Triple<OutputIteratorBoundaryFacets,OutputIteratorCells,Emptyset_iterator>
    t = find_conflicts(p, c, bfit, cit, Emptyset_iterator());
    return std::make_pair(t.first, t.second);
  }

  template <class OutputIteratorBoundaryFacets, class OutputIteratorCells,
            class OutputIteratorInternalFacets>
  Triple<OutputIteratorBoundaryFacets, OutputIteratorCells,
         OutputIteratorInternalFacets>
  find_conflicts(const Point &p, Cell_handle c,
      OutputIteratorBoundaryFacets bfit, OutputIteratorCells cit,
      OutputIteratorInternalFacets ifit) const;
  
  /// Returns the vertices on the boundary of the conflict hole.
  template <class OutputIterator>
  OutputIterator vertices_in_conflict(const Point&p, Cell_handle c,
      OutputIterator res) const;

  bool is_Gabriel(const Cell_handle c, int i) const;
  bool is_Gabriel(const Cell_handle c, int i, int j) const;
  bool is_Gabriel(const Facet& f)const {
    return is_Gabriel(f.first, f.second);
  }
  bool is_Gabriel(const Edge& e) const {
    return is_Gabriel(e.first, e.second, e.third);
  }
  //@}
  
private:
  /** @name Voronoi diagram helpers */ //@{
  bool is_canonical(const Periodic_segment &ps) const {
    if (number_of_sheets() == make_array(1,1,1)) return true;
    Offset o0 = ps.at(0).second;
    Offset o1 = ps.at(1).second;
    Offset cumm_off((std::min)(o0.x(),o1.x()),(std::min)(o0.y(),o1.y()),
	(std::min)(o0.z(),o1.z()));
    return (cumm_off == Offset(0,0,0));
  }
  //@}
public:
  Periodic_point periodic_circumcenter(Cell_handle c) const {
    CGAL_triangulation_precondition(c != Cell_handle());
    Point v = geom_traits().construct_circumcenter_3_object()(
        c->vertex(0)->point(), c->vertex(1)->point(),
	c->vertex(2)->point(), c->vertex(3)->point(),
        get_offset(c,0), get_offset(c,1),
	get_offset(c,2), get_offset(c,3));

    // check that v lies within the domain. If not: translate
    Iso_cuboid dom = domain();
    if (   !(v.x() < dom.xmin()) && v.x()<dom.xmax()
	&& !(v.y() < dom.ymin()) && v.y()<dom.ymax()
	&& !(v.z() < dom.zmin()) && v.z()<dom.zmax() )
      return std::make_pair(v,Offset());

    int ox=-1, oy=-1, oz=-1;
    if (v.x() < dom.xmin()) ox = 1;
    else if (v.x() < dom.xmax()) ox = 0;
    if (v.y() < dom.ymin()) oy = 1;
    else if (v.y() < dom.ymax()) oy = 0;
    if (v.z() < dom.zmin()) oz = 1;
    else if (v.z() < dom.zmax()) oz = 0;
    Offset transl_offx(0,0,0);
    Offset transl_offy(0,0,0);
    Offset transl_offz(0,0,0);
    Point dv(v);

    // Find the right offset such that the translation will yield a
    // point inside the original domain.
    while ( dv.x() < dom.xmin() || !(dv.x() < dom.xmax()) ) {
      transl_offx.x() = transl_offx.x() + ox;
      dv = point(std::make_pair(v,transl_offx));
    }
    while ( dv.y() < dom.ymin() || !(dv.y() < dom.ymax()) ) {
      transl_offy.y() = transl_offy.y() + oy;
      dv = point(std::make_pair(v,transl_offy));
    }
    while ( dv.z() < dom.zmin() || !(dv.z() < dom.zmax()) ) {
      transl_offz.z() = transl_offz.z() + oz;
      dv = point(std::make_pair(v,transl_offz));
    }

    Offset transl_off(transl_offx.x(),transl_offy.y(),transl_offz.z());
    Periodic_point ppv(std::make_pair(v,transl_off));

    CGAL_triangulation_assertion_code(Point rv(point(ppv));)
    CGAL_triangulation_assertion( !(rv.x() < dom.xmin()) && rv.x() < dom.xmax() );
    CGAL_triangulation_assertion( !(rv.y() < dom.ymin()) && rv.y() < dom.ymax() );
    CGAL_triangulation_assertion( !(rv.z() < dom.zmin()) && rv.z() < dom.zmax() );
    return ppv;
  }

private:
bool is_canonical(const Facet &f) const {
  if (number_of_sheets() == make_array(1,1,1)) return true;
  Offset cell_off0 = int_to_off(f.first->offset((f.second+1)&3));
  Offset cell_off1 = int_to_off(f.first->offset((f.second+2)&3));
  Offset cell_off2 = int_to_off(f.first->offset((f.second+3)&3));
  Offset diff_off((cell_off0.x() == 1 
	  && cell_off1.x() == 1 
	  && cell_off2.x() == 1)?-1:0,
      (cell_off0.y() == 1 
	  && cell_off1.y() == 1
	  && cell_off2.y() == 1)?-1:0,
      (cell_off0.z() == 1 
	  && cell_off1.z() == 1
	  && cell_off2.z() == 1)?-1:0);
  Offset off0 = combine_offsets(get_offset(f.first, (f.second+1)&3),
      diff_off);
  Offset off1 = combine_offsets(get_offset(f.first, (f.second+2)&3),
      diff_off);
  Offset off2 = combine_offsets(get_offset(f.first, (f.second+3)&3),
      diff_off);
  
  // If there is one offset with entries larger than 1 then we are
  // talking about a vertex that is too far away from the original
  // domain to belong to a canonical triangle.
  if (off0.x() > 1) return false;
  if (off0.y() > 1) return false;
  if (off0.z() > 1) return false;
  if (off1.x() > 1) return false;
  if (off1.y() > 1) return false;
  if (off1.z() > 1) return false;
  if (off2.x() > 1) return false;
  if (off2.y() > 1) return false;
  if (off2.z() > 1) return false;
  
  // If there is one direction of space for which all offsets are
  // non-zero then the edge is not canonical because we can
  // take the copy closer towards the origin in that direction.
  int offx = off0.x() & off1.x() & off2.x();
  int offy = off0.y() & off1.y() & off2.y();
  int offz = off0.z() & off1.z() & off2.z();
  
  return (offx == 0 && offy == 0 && offz == 0);
}
  
  bool canonical_dual_segment(Cell_handle c, int i, Periodic_segment& ps) const {
    CGAL_triangulation_precondition(c != Cell_handle());
    Offset off = get_neighbor_offset(c,i,c->neighbor(i));
    Periodic_point p1 = periodic_circumcenter(c);
    Periodic_point p2 = periodic_circumcenter(c->neighbor(i));
    Offset o1 = -p1.second;
    Offset o2 = combine_offsets(-p2.second,-off);
    Offset cumm_off((std::min)(o1.x(),o2.x()),
	(std::min)(o1.y(),o2.y()),(std::min)(o1.z(),o2.z()));
    const std::pair<Point,Offset> pp1 = std::make_pair(point(p1), o1-cumm_off);
    const std::pair<Point,Offset> pp2 = std::make_pair(point(p2), o2-cumm_off);
    ps = make_array(pp1,pp2);
    return (cumm_off == Offset(0,0,0));
  }

public:
  /** @name Voronoi diagram */ //@{
  Point dual(Cell_handle c) const {
    return point(periodic_circumcenter(c));
  }
  Periodic_segment dual(const Facet & f) const {
    return dual( f.first, f.second );
  }
  Periodic_segment dual(Cell_handle c, int i) const{
    Periodic_segment ps;
    canonical_dual_segment(c,i,ps);
    return ps;
  }

  template <class OutputIterator>
  OutputIterator dual(const Edge & e, OutputIterator points) const {
    return dual(e.first, e.second, e.third, points);
  }

  template <class OutputIterator>
  OutputIterator dual(Cell_handle c, int i, int j,
      OutputIterator points) const {
    Cell_circulator cstart = incident_cells(c, i, j);

    Offset offv = periodic_point(c,i).second;
    Vertex_handle v = c->vertex(i);

    Cell_circulator ccit = cstart;
    do {
      Point dual_orig = periodic_circumcenter(ccit).first;
      int idx = ccit->index(v);
      Offset off = periodic_point(ccit,idx).second;
      Point dual = point(std::make_pair(dual_orig,-off+offv));
      *points++ = dual;
      ++ccit;
    } while (ccit != cstart);
    return points;
  }

  template <class OutputIterator>
  OutputIterator dual(Vertex_handle v, OutputIterator points) const {
    std::vector<Cell_handle> cells;
    incident_cells(v,std::back_inserter(cells));

    for (unsigned int i=0; i<cells.size() ; i++) {
      Point dual_orig = periodic_circumcenter(cells[i]).first;
      int idx = cells[i]->index(v);
      Offset off = periodic_point(cells[i],idx).second;
      Point dual = point(std::make_pair(dual_orig,-off));
      *points++ = dual;
    }
    return points;
  }

  template <class Stream>
  Stream& draw_dual(Stream& os) const {
    CGAL_triangulation_assertion_code( unsigned int i = 0; )
    for (Facet_iterator fit = facets_begin(), end = facets_end();
	 fit != end; ++fit) {
      if (!is_canonical(*fit)) continue;
      Periodic_segment pso = dual(*fit);
      Segment so = segment(pso);
      CGAL_triangulation_assertion_code ( ++i; )
	os << so.source()<<' '<<so.target()<<' ';
    }
    CGAL_triangulation_assertion( i == number_of_facets() );
    return os;
  }

  /// Volume computations

  // Note: Polygon area computation requires to evaluate square roots
  // and thus cannot be done without changing the Traits concept.

  FT dual_volume(Vertex_handle v) const {
    std::list<Edge> edges;
    incident_edges(v, std::back_inserter(edges));

    FT vol(0);
    for (typename std::list<Edge>::iterator eit = edges.begin() ; 
	 eit != edges.end() ; ++eit) {

      // compute the dual of the edge *eit but handle the translations
      // with respect to the dual of v. That is why we cannot use one
      // of the existing dual functions here.
      Facet_circulator fstart = incident_facets(*eit);
      Facet_circulator fcit = fstart;
      std::vector<Point> pts;
      do {
	// TODO: possible speed-up by caching the circumcenters
	Point dual_orig = periodic_circumcenter(fcit->first).first;
	int idx = fcit->first->index(v);
	Offset off = periodic_point(fcit->first,idx).second;
	pts.push_back(point(std::make_pair(dual_orig,-off)));
	++fcit;
      } while (fcit != fstart);

      Point orig(0,0,0);
      for (unsigned int i=1 ; i<pts.size()-1 ; i++) 
	vol += Tetrahedron(orig,pts[0],pts[i],pts[i+1]).volume();
    }
    return vol;
  }

  /// Centroid computations

  // Note: Centroid computation for polygons requires to evaluate
  // square roots and thus cannot be done without changing the
  // Traits concept.

  // TODO: reuse the centroid computation from the PCA package
  Point dual_centroid(Vertex_handle v) const {
    std::list<Edge> edges;
    incident_edges(v, std::back_inserter(edges));

    FT vol(0);
    FT x(0), y(0), z(0);
    for (typename std::list<Edge>::iterator eit = edges.begin() ; 
	 eit != edges.end() ; ++eit) {

      // compute the dual of the edge *eit but handle the translations
      // with respect to the dual of v. That is why we cannot use one
      // of the existing dual functions here.
      Facet_circulator fstart = incident_facets(*eit);
      Facet_circulator fcit = fstart;
      std::vector<Point> pts;
      do {
	// TODO: possible speed-up by caching the circumcenters
	Point dual_orig = periodic_circumcenter(fcit->first).first;
	int idx = fcit->first->index(v);
	Offset off = periodic_point(fcit->first,idx).second;
	pts.push_back(point(std::make_pair(dual_orig,-off)));
	++fcit;
      } while (fcit != fstart);

      Point orig(0,0,0);
      FT tetvol;
      for (unsigned int i=1 ; i<pts.size()-1 ; i++) {
	tetvol = Tetrahedron(orig,pts[0],pts[i],pts[i+1]).volume();
	x += (pts[0].x() + pts[i].x() + pts[i+1].x()) * tetvol;
	y += (pts[0].y() + pts[i].y() + pts[i+1].y()) * tetvol;
	z += (pts[0].z() + pts[i].z() + pts[i+1].z()) * tetvol;
	vol += tetvol;
      }
    }
    x /= ( 4 * vol );
    y /= ( 4 * vol );
    z /= ( 4 * vol );

    Iso_cuboid d = domain();
    x = (x < d.xmin() ? x+d.xmax()-d.xmin() 
	: (x >= d.xmax() ? x-d.xmax()+d.xmin() : x));
    y = (y < d.ymin() ? y+d.ymax()-d.ymin() 
	: (y >= d.ymax() ? y-d.ymax()+d.ymin() : y));
    z = (z < d.zmin() ? z+d.zmax()-d.zmin() 
	: (z >= d.zmax() ? z-d.zmax()+d.zmin() : z));

    CGAL_triangulation_postcondition((d.xmin()<=x)&&(x<d.xmax()));
    CGAL_triangulation_postcondition((d.ymin()<=y)&&(y<d.ymax()));
    CGAL_triangulation_postcondition((d.zmin()<=z)&&(z<d.zmax()));

    return Point(x,y,z);
  }
  //@}
  
  /** @name Checking */ //@{
  bool is_valid(bool verbose = false, int level = 0) const;
  bool is_valid(Cell_handle c, bool verbose = false, int level = 0) const;
  //@}

protected:
  // Protected, because inheritors(e.g. periodic triangulation for meshing) 
  // of the class Periodic_3_Delaunay_triangulation_3 use this class
  class Conflict_tester;
private:
  class Point_hider;

#ifndef CGAL_CFG_OUTOFLINE_TEMPLATE_MEMBER_DEFINITION_BUG
  template <class TriangulationR3> struct Vertex_remover;
#else
  template <class TriangulationR3>
  struct Vertex_remover
  {
    typedef TriangulationR3      Triangulation_R3;
    
    typedef typename std::vector<Point>::iterator Hidden_points_iterator;
    
    typedef Triple < Vertex_handle, Vertex_handle, Vertex_handle > Vertex_triple;
    
    typedef typename Triangulation_R3::Triangulation_data_structure TDSE;
    typedef typename Triangulation_R3::Cell_handle        CellE_handle;
    typedef typename Triangulation_R3::Vertex_handle      VertexE_handle;
    typedef typename Triangulation_R3::Facet              FacetE;
    typedef typename Triangulation_R3::Finite_cells_iterator Finite_cellsE_iterator;
    
    typedef Triple< VertexE_handle, VertexE_handle, VertexE_handle >
      VertexE_triple;
    
    typedef std::map<Vertex_triple,Facet> Vertex_triple_Facet_map;
    typedef std::map<Vertex_triple, FacetE> Vertex_triple_FacetE_map;
    typedef typename Vertex_triple_FacetE_map::iterator
    Vertex_triple_FacetE_map_it;
    
  Vertex_remover(const Self *t, Triangulation_R3 &tmp_) : _t(t),tmp(tmp_) {}
    
    const Self *_t;
    Triangulation_R3 &tmp;
    
    void add_hidden_points(Cell_handle) {
      std::copy (hidden_points_begin(), hidden_points_end(), 
		 std::back_inserter(hidden));
    }
    
    Hidden_points_iterator hidden_points_begin() {
      return hidden.begin();
    }
    Hidden_points_iterator hidden_points_end() {
      return hidden.end();
    }
    //private:
    // The removal of v may un-hide some points,
    // Space functions output them.
    std::vector<Point> hidden;
  };
#endif //CGAL_CFG_OUTOFLINE_TEMPLATE_MEMBER_DEFINITION_BUG

  // unused and undocumented types and functions required to be
  // compatible to Alpha_shape_3
public:
  typedef Cell_iterator   Finite_cells_iterator;
  typedef Facet_iterator  Finite_facets_iterator;
  typedef Edge_iterator   Finite_edges_iterator;
  typedef Vertex_iterator Finite_vertices_iterator;

  int dimension() const { return 3; }
  template < class T >
  bool is_infinite(const T&, int = 0, int = 0) const { return false; }
  size_type number_of_finite_cells() const { return number_of_cells(); }
  size_type number_of_finite_facets() const { return number_of_facets(); }
  size_type number_of_finite_edges() const { return number_of_edges(); }
  size_type number_of_finite_vertices() const { return number_of_vertices(); }
};

template < class GT, class Tds >
typename Periodic_3_Delaunay_triangulation_3<GT,Tds>::Vertex_handle
Periodic_3_Delaunay_triangulation_3<GT,Tds>::nearest_vertex(const Point& p,
    Cell_handle start) const {
  if (number_of_vertices() == 0)
    return Vertex_handle();

  Locate_type lt;
  int li, lj;
  Cell_handle c = locate(p, lt, li, lj, start);
  if (lt == Base::VERTEX) return c->vertex(li);
  const Conflict_tester tester(p, this);
  Offset o = combine_offsets(Offset(),get_location_offset(tester,c));

  // - start with the closest vertex from the located cell.
  // - repeatedly take the nearest of its incident vertices if any
  // - if not, we're done.
  Vertex_handle nearest = nearest_vertex_in_cell(c, p, o);
  std::vector<Vertex_handle> vs;
  vs.reserve(32);
  while (true) {
    Vertex_handle tmp = nearest;
    Offset tmp_off = get_min_dist_offset(p,o,tmp);
    adjacent_vertices(nearest, std::back_inserter(vs));
    for (typename std::vector<Vertex_handle>::const_iterator
	   vsit = vs.begin(); vsit != vs.end(); ++vsit)
      tmp = (compare_distance(p,tmp->point(),(*vsit)->point(),
	      o,tmp_off,get_min_dist_offset(p,o,*vsit))
	  == SMALLER) ? tmp : *vsit;
    if (tmp == nearest)
      break;
    vs.clear();
    nearest = tmp;
  }

  return get_original_vertex(nearest);
}

// just trying the eight possibilities
template < class GT, class Tds >
typename Periodic_3_Delaunay_triangulation_3<GT,Tds>::Offset
Periodic_3_Delaunay_triangulation_3<GT,Tds>::get_min_dist_offset(
    const Point & p, const Offset & o, const Vertex_handle vh) const {
  Offset mdo = get_offset(vh);
  Offset min_off = Offset(0,0,0);
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(0,0,1)))
      == SMALLER ? min_off : Offset(0,0,1) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(0,1,0)))
      == SMALLER ? min_off : Offset(0,1,0) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(0,1,1)))
      == SMALLER ? min_off : Offset(0,1,1) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(1,0,0)))
      == SMALLER ? min_off : Offset(1,0,0) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(1,0,1)))
      == SMALLER ? min_off : Offset(1,0,1) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(1,1,0)))
      == SMALLER ? min_off : Offset(1,1,0) );
  min_off = (compare_distance(p,vh->point(),vh->point(),
	  o,combine_offsets(mdo,min_off),combine_offsets(mdo,Offset(1,1,1)))
      == SMALLER ? min_off : Offset(1,1,1) );
  return combine_offsets(mdo,min_off);
}

/// Returns the finite vertex of the cell c which is the closest to p.
template < class GT, class Tds >
typename Periodic_3_Delaunay_triangulation_3<GT,Tds>::Vertex_handle
Periodic_3_Delaunay_triangulation_3<GT,Tds>::nearest_vertex_in_cell(
    const Cell_handle& c, const Point & p, const Offset & o) const {
  CGAL_triangulation_precondition(number_of_vertices() != 0);
  Vertex_handle nearest = c->vertex(0);
  for (int i=1 ; i<4 ; i++) {
    nearest = (compare_distance(p,nearest->point(),c->vertex(i)->point(),
	    o,get_offset(c,c->index(nearest)),get_offset(c,i)) == SMALLER) ?
      nearest : c->vertex(i);
  }
  return nearest;
}

// ############################################################################

// TODO: reintroduce the commented lines.
template < class Gt, class Tds >
typename Periodic_3_Delaunay_triangulation_3<Gt,Tds>::Vertex_handle
Periodic_3_Delaunay_triangulation_3<Gt,Tds>::
move_point(Vertex_handle v, const Point & p) {
  CGAL_triangulation_expensive_precondition(is_vertex(v));
  // Remember an incident vertex to restart
  // the point location after the removal.
  // Cell_handle c = v->cell();
  //Vertex_handle old_neighbor = c->vertex(c->index(v) == 0 ? 1 : 0);
  //  CGAL_triangulation_assertion(old_neighbor != v);

  remove(v);

  if (number_of_vertices() == 0)
    return insert(p);
  return insert(p);//, old_neighbor->cell());
}

template < class Gt, class Tds >
void Periodic_3_Delaunay_triangulation_3<Gt,Tds>::remove(Vertex_handle v)
{
  typedef CGAL::Periodic_3_triangulation_remove_traits_3< Gt > P3removeT;
  typedef CGAL::Delaunay_triangulation_3< P3removeT >
    Euclidean_triangulation;
  typedef Vertex_remover< Euclidean_triangulation > Remover;
  P3removeT remove_traits(domain());
  Euclidean_triangulation tmp(remove_traits);
  Remover remover(this, tmp);
  Conflict_tester ct(this);

  Base::remove(v, remover, ct);
  CGAL_triangulation_expensive_assertion(is_valid());
}

template < class Gt, class Tds >
template <class OutputIteratorBoundaryFacets, class OutputIteratorCells,
          class OutputIteratorInternalFacets>
Triple<OutputIteratorBoundaryFacets, OutputIteratorCells,
       OutputIteratorInternalFacets>
Periodic_3_Delaunay_triangulation_3<Gt,Tds>::find_conflicts( const Point
&p,
    Cell_handle c, OutputIteratorBoundaryFacets bfit,
    OutputIteratorCells cit, OutputIteratorInternalFacets ifit) const {
  CGAL_triangulation_precondition(number_of_vertices() != 0);

  std::vector<Facet> facets;
  facets.reserve(64);
  std::vector<Cell_handle> cells;
  cells.reserve(32);

  Conflict_tester tester(p, this);
  Triple<typename std::back_insert_iterator<std::vector<Facet> >,
         typename std::back_insert_iterator<std::vector<Cell_handle> >,
         OutputIteratorInternalFacets> tit = Base::find_conflicts(c, tester,
              make_triple(std::back_inserter(facets),
                      std::back_inserter(cells), ifit));
  ifit = tit.third;

  // Reset the conflict flag on the boundary.
  for(typename std::vector<Facet>::iterator fit=facets.begin();
  fit != facets.end(); ++fit) {
    fit->first->neighbor(fit->second)->tds_data().clear();
    *bfit++ = *fit;
  }

  // Reset the conflict flag in the conflict cells.
  for(typename std::vector<Cell_handle>::iterator ccit=cells.begin();
      ccit != cells.end(); ++ccit) {
    (*ccit)->tds_data().clear();
    *cit++ = *ccit;
  }

  for (typename std::vector<Vertex_handle>::iterator
	 voit = this->v_offsets.begin();
       voit != this->v_offsets.end() ; ++voit) {
    (*voit)->clear_offset();
  }
  this->v_offsets.clear();

  return make_triple(bfit, cit, ifit);
}

template < class Gt, class Tds >
template <class OutputIterator>
OutputIterator
Periodic_3_Delaunay_triangulation_3<Gt,Tds>::vertices_in_conflict(
    const Point&p, Cell_handle c, OutputIterator res) const {
  if (number_of_vertices() == 0) return res;

  // Get the facets on the boundary of the hole.
  std::vector<Facet> facets;
  find_conflicts(p, c, std::back_inserter(facets), Emptyset_iterator());
  
  // Then extract uniquely the vertices.
  std::set<Vertex_handle> vertices;
  for (typename std::vector<Facet>::const_iterator i = facets.begin();
       i != facets.end(); ++i) {
    vertices.insert(i->first->vertex((i->second+1)&3));
    vertices.insert(i->first->vertex((i->second+2)&3));
    vertices.insert(i->first->vertex((i->second+3)&3));
  }
  
  return std::copy(vertices.begin(), vertices.end(), res);
}

template < class Gt, class Tds >
Bounded_side Periodic_3_Delaunay_triangulation_3<Gt,Tds>::
_side_of_sphere(const Cell_handle &c, const Point &q,
    const Offset &offset, bool perturb ) const {

  Point p0 = c->vertex(0)->point(),
        p1 = c->vertex(1)->point(),
        p2 = c->vertex(2)->point(),
        p3 = c->vertex(3)->point();
  Offset o0 = this->get_offset(c,0),
        o1 = this->get_offset(c,1),
        o2 = this->get_offset(c,2),
        o3 = this->get_offset(c,3),
        oq = offset;

  Oriented_side os = ON_NEGATIVE_SIDE;
  os= side_of_oriented_sphere(p0, p1, p2, p3, q, o0, o1, o2, o3, oq);

  if (os != ON_ORIENTED_BOUNDARY || !perturb)
    return (Bounded_side) os;

  //We are now in a degenerate case => we do a symbolic perturbation. 
  // We sort the points lexicographically.
  Periodic_point pts[5] = {std::make_pair(p0,o0), std::make_pair(p1,o1),
			   std::make_pair(p2,o2), std::make_pair(p3,o3),
			   std::make_pair(q,oq)};
  const Periodic_point *points[5] ={&pts[0],&pts[1],&pts[2],&pts[3],&pts[4]};

  std::sort(points, points+5,
      typename Base::template Perturbation_order<
	  typename Gt::Compare_xyz_3 >(
	  geom_traits().compare_xyz_3_object() ) );
  // We successively look whether the leading monomial, then 2nd monomial
  // of the determinant has non null coefficient.
  // 2 iterations are enough (cf paper)
  for (int i=4; i>2; --i) {
    if (points[i] == &pts[4]) {
      CGAL_triangulation_assertion(orientation(p0, p1, p2, p3, o0, o1, o2, o3)
          == POSITIVE);
      // since p0 p1 p2 p3 are non coplanar and positively oriented
      return ON_UNBOUNDED_SIDE;
    }
    Orientation o;
    if (points[i] == &pts[3] && 
        (o = orientation(p0, p1, p2, q, o0, o1, o2, oq)) != COPLANAR ) {
      return (Bounded_side) o;
    }
    if (points[i] == &pts[2] && 
        (o = orientation(p0, p1, q, p3, o0, o1, oq, o3)) != COPLANAR ) {
      return (Bounded_side) o;
    }
    if (points[i] == &pts[1] && 
        (o = orientation(p0, q, p2, p3, o0, oq, o2, o3)) != COPLANAR ) {
      return (Bounded_side) o;
    }
    if (points[i] == &pts[0] && 
        (o = orientation(q, p1, p2 ,p3, oq, o1, o2, o3)) != COPLANAR ) {
      return (Bounded_side) o;
    }
  }

  CGAL_triangulation_assertion(false);
  return ON_UNBOUNDED_SIDE;
}

template < class Gt, class Tds >
bool Periodic_3_Delaunay_triangulation_3<Gt,Tds>::
is_Gabriel(const Cell_handle c, int i) const {
  CGAL_triangulation_precondition(number_of_vertices() != 0);
  typename Geom_traits::Side_of_bounded_sphere_3
    side_of_bounded_sphere =
    geom_traits().side_of_bounded_sphere_3_object();

  if (side_of_bounded_sphere (
          c->vertex(vertex_triple_index(i,0))->point(),
	  c->vertex(vertex_triple_index(i,1))->point(),
	  c->vertex(vertex_triple_index(i,2))->point(),
          c->vertex(i)->point(),
          get_offset(c,vertex_triple_index(i,0)),
          get_offset(c,vertex_triple_index(i,1)),
          get_offset(c,vertex_triple_index(i,2)),
          get_offset(c,i) ) == ON_BOUNDED_SIDE ) return false;
  Cell_handle neighbor = c->neighbor(i);
  int in = neighbor->index(c);

  if (side_of_bounded_sphere(
          neighbor->vertex(vertex_triple_index(in,0))->point(),
	  neighbor->vertex(vertex_triple_index(in,1))->point(),
	  neighbor->vertex(vertex_triple_index(in,2))->point(),
          neighbor->vertex(in)->point(),
          get_offset(neighbor,vertex_triple_index(in,0)),
          get_offset(neighbor,vertex_triple_index(in,1)),
          get_offset(neighbor,vertex_triple_index(in,2)),
          get_offset(neighbor, in) ) == ON_BOUNDED_SIDE )
    return false;
  
  return true;
}

template < class Gt, class Tds >
bool Periodic_3_Delaunay_triangulation_3<Gt,Tds>::
is_Gabriel(const Cell_handle c, int i, int j) const {
  typename Geom_traits::Side_of_bounded_sphere_3
    side_of_bounded_sphere =
    geom_traits().side_of_bounded_sphere_3_object();

  Facet_circulator fcirc = incident_facets(c,i,j),
    fdone(fcirc);
  Vertex_handle v1 = c->vertex(i);
  Vertex_handle v2 = c->vertex(j);
  do {
    // test whether the vertex of cc opposite to *fcirc
    // is inside the sphere defined by the edge e = (s, i,j)
    // It is necessary to fetch the offsets from the current cell.
    Cell_handle cc = fcirc->first;
    int i1 = cc->index(v1);
    int i2 = cc->index(v2);
    int i3 = fcirc->second;
    Offset off1 = int_to_off(cc->offset(i1));
    Offset off2 = int_to_off(cc->offset(i2));
    Offset off3 = int_to_off(cc->offset(i3));
    if (side_of_bounded_sphere(
	    v1->point(), v2->point(), cc->vertex(fcirc->second)->point(),
	    off1, off2, off3) == ON_BOUNDED_SIDE ) return false;
  } while(++fcirc != fdone);
  return true;
}

template < class Gt, class Tds >
bool
Periodic_3_Delaunay_triangulation_3<Gt,Tds>::
is_valid(bool verbose, int level) const
{ 
  if (!Base::is_valid(verbose, level)) {
    if (verbose)
      std::cerr << "Delaunay: invalid base" << std::endl;
    return false;
  }

  Conflict_tester tester(this);
  if (!is_valid_conflict(tester, verbose, level)) {
    if (verbose)
      std::cerr << "Delaunay: conflict problems" << std::endl;
    return false;
  }

  if (verbose)
    std::cerr << "Delaunay valid triangulation" << std::endl;
  return true;
}

template < class GT, class TDS >
bool
Periodic_3_Delaunay_triangulation_3<GT,TDS>::
is_valid(Cell_handle ch, bool verbose, int level) const {
  bool error = false;
  if (!Base::is_valid(ch, verbose, level)) {
    error = true;
    if (verbose) {
      std::cerr << "geometrically invalid cell" << std::endl;
      for (int i=0; i<4; i++ )
	std::cerr << ch->vertex(i)->point() << ", ";
      std::cerr << std::endl;
    }
  }
  for (Vertex_iterator vit = vertices_begin(); vit != vertices_end(); ++ vit) {
    for (int i=-1; i<=1; i++)
      for (int j=-1; j<=1; j++)
	for (int k=-1; k<=1; k++) {
	  if (periodic_point(ch,0) == std::make_pair(periodic_point(vit).first,
		  periodic_point(vit).second+Offset(i,j,k))
	  || periodic_point(ch,1) == std::make_pair(periodic_point(vit).first,
		  periodic_point(vit).second+Offset(i,j,k))
          || periodic_point(ch,2) == std::make_pair(periodic_point(vit).first,
		  periodic_point(vit).second+Offset(i,j,k))
	  || periodic_point(ch,3) == std::make_pair(periodic_point(vit).first,
                  periodic_point(vit).second+Offset(i,j,k)) )
	    continue;
	  if (_side_of_sphere(ch, periodic_point(vit).first,
		  periodic_point(vit).second+Offset(i,j,k),true)
	      != ON_UNBOUNDED_SIDE) {
	    error = true;
	    if (verbose) {
	      std::cerr << "Delaunay invalid cell" << std::endl;
	      for (int i=0; i<4; i++ ) {
		Periodic_point pp = periodic_point(ch,i);
		std::cerr <<"("<<pp.first <<","<<pp.second<< "), ";
	      }
	      std::cerr << std::endl;
	    }
	  }
	}
  }
  return !error;
}

template < class GT, class Tds >
class Periodic_3_Delaunay_triangulation_3<GT,Tds>::Conflict_tester
{
  // stores a pointer to the triangulation,
  // a point, and an offset
  const Self *t;
  Point p;
  // stores the offset of a point in 27-cover
  mutable Offset o;

public:
  /// Constructor
  Conflict_tester(const Self *_t) : t(_t), p(Point()) {}
  Conflict_tester(const Point &pt, const Self *_t) : t(_t), p(pt) { }
  
  /** The functor
    *
    * gives true if the circumcircle of c contains p
    */
  bool operator()(const Cell_handle c, const Offset &off) const {
    return (t->_side_of_sphere(c, p, t->combine_offsets(o, off), true)
        == ON_BOUNDED_SIDE);
  }

  bool operator()(const Cell_handle c, const Point& pt,
      const Offset &off) const {
    return (t->_side_of_sphere(c, pt, o + off, true) == ON_BOUNDED_SIDE);
  }
  
  int compare_weight(Point, Point) const
  {
    return 0;
  }
  
  bool test_initial_cell(Cell_handle c, const Offset &off) const
  {
    if (!(operator()(c, off)))
      CGAL_triangulation_assertion(false);
    return true;
  }
  
  void set_point(const Point &_p) {
    p = _p;
  }

  void set_offset(const Offset &off) const {
    o = off;
  }
  
  const Offset &get_offset() const {
    return o;
  }
  
  const Point &point() const {
    return p;
  }
  
};

template < class GT, class Tds>
class Periodic_3_Delaunay_triangulation_3<GT,Tds>::Point_hider
{
public:
  Point_hider() {}

  template <class InputIterator>
  inline void set_vertices(InputIterator, InputIterator) const {}
  inline void reinsert_vertices(Vertex_handle ) {}
  inline Vertex_handle replace_vertex(Cell_handle c, int index,
                                      const Point &) {
    return c->vertex(index);
  }
  inline void hide_point(Cell_handle, const Point &) {}

  inline void hide(Point &, Cell_handle ) const {
    CGAL_triangulation_assertion(false);
  }

  inline void do_hide(const Point &, Cell_handle ) const {
    CGAL_triangulation_assertion(false);
  }
  template < class Tester > 
  inline bool replace_vertex(const Point &, Vertex_handle ,
      const Tester &) const {
    return true;
  }
  template <class Conflict_tester>
  inline void hide_points(Vertex_handle,
      const Conflict_tester &) {
    // No points to hide in the Delaunay triangulation.
  }

};

#ifndef CGAL_CFG_OUTOFLINE_TEMPLATE_MEMBER_DEFINITION_BUG 
template <class GT, class Tds>
template <class TriangulationR3>
struct Periodic_3_Delaunay_triangulation_3<GT,Tds>::Vertex_remover
{
  typedef TriangulationR3      Triangulation_R3;
  
  typedef typename std::vector<Point>::iterator Hidden_points_iterator;
  
  typedef Triple < Vertex_handle, Vertex_handle, Vertex_handle > Vertex_triple;
  
  typedef typename Triangulation_R3::Triangulation_data_structure TDSE;
  typedef typename Triangulation_R3::Cell_handle        CellE_handle;
  typedef typename Triangulation_R3::Vertex_handle      VertexE_handle;
  typedef typename Triangulation_R3::Facet              FacetE;
  typedef typename Triangulation_R3::Finite_cells_iterator Finite_cellsE_iterator;
    
  typedef Triple< VertexE_handle, VertexE_handle, VertexE_handle >
  VertexE_triple;
  
  typedef std::map<Vertex_triple,Facet> Vertex_triple_Facet_map;
  typedef std::map<Vertex_triple, FacetE> Vertex_triple_FacetE_map;
  typedef typename Vertex_triple_FacetE_map::iterator
  Vertex_triple_FacetE_map_it;
  
  Vertex_remover(const Self *t, Triangulation_R3 &tmp_) : _t(t),tmp(tmp_) {}
    
  const Self *_t;
  Triangulation_R3 &tmp;
    
  void add_hidden_points(Cell_handle) {
    std::copy (hidden_points_begin(), hidden_points_end(), 
	std::back_inserter(hidden));
  }
  
  Hidden_points_iterator hidden_points_begin() {
    return hidden.begin();
  }
  Hidden_points_iterator hidden_points_end() {
    return hidden.end();
  }
  //private:
  // The removal of v may un-hide some points,
  // Space functions output them.
  std::vector<Point> hidden;
};
#endif //CGAL_CFG_OUTOFLINE_TEMPLATE_MEMBER_DEFINITION_BUG

} //namespace CGAL

#endif // CGAL_PERIODIC_3_DELAUNAY_TRIANGULATION_3_H
