// Copyright (c) 1997  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/TDS_2/include/CGAL/Triangulation_ds_iterators_2.h $
// $Id: include/CGAL/Triangulation_ds_iterators_2.h b26b07a1242 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Mariette Yvinec

#ifndef CGAL_TRIANGULATION_DS_ITERATORS_2_H
#define CGAL_TRIANGULATION_DS_ITERATORS_2_H

#include <CGAL/license/TDS_2.h>


#include <iterator>
#include <CGAL/assertions.h>
#include <CGAL/tags.h>

namespace CGAL {

template <class Tds>
class Triangulation_ds_edge_iterator_2
{
public:
  typedef typename Tds::Edge           Edge;
  typedef typename Tds::Face_iterator  Face_iterator;
  typedef typename Tds::Face_handle    Face_handle;

  typedef Edge            value_type;
  typedef Edge*           pointer;
  typedef Edge&           reference;
  typedef std::size_t                            size_type;
  typedef std::ptrdiff_t                         difference_type;
  typedef std::bidirectional_iterator_tag        iterator_category;

  typedef Triangulation_ds_edge_iterator_2<Tds>  Edge_iterator;

private:
const Tds* _tds;
Face_iterator pos;
mutable Edge edge;

public:
  Triangulation_ds_edge_iterator_2()  {}
  Triangulation_ds_edge_iterator_2(const Tds * tds);
  Triangulation_ds_edge_iterator_2(const Tds* tds, int );

  bool  operator==(const Edge_iterator& fi) const ;
  bool  operator!=(const Edge_iterator& fi) const {return !(*this== fi);}
  Edge_iterator&    operator++();
  Edge_iterator&    operator--();
  Edge_iterator    operator++(int);
  Edge_iterator    operator--(int);
  Edge*     operator->() const;
  Edge&     operator*() const ;

private:
  void increment();
  void decrement();
  bool associated_edge();
};


// Edge iterator implementation

template<class Tds>
Triangulation_ds_edge_iterator_2<Tds>::
Triangulation_ds_edge_iterator_2(const Tds * tds)
 :  _tds(tds)
{
  edge.second = 0;
  if (_tds->dimension()<= 0) {
    pos = _tds->faces().end();       // there is no edge
    return;
  }
  pos = _tds->faces().begin();
  if (_tds->dimension() == 1) edge.second = 2;
    while ( pos != _tds->faces().end() && !associated_edge())
      increment();
}

template<class Tds>
Triangulation_ds_edge_iterator_2<Tds>::
Triangulation_ds_edge_iterator_2(const Tds * tds, int )
  : _tds(tds)
{
  pos = tds->faces().end();
  edge.second = 0;
  if (_tds->dimension() == 1) {edge.second = 2;}
}


template<class Tds>
inline
bool
Triangulation_ds_edge_iterator_2<Tds>::
operator==(const Edge_iterator& fi) const
{
  return _tds == fi._tds  && pos == fi.pos  && edge.second == fi.edge.second;
}

template<class Tds>
inline
void
Triangulation_ds_edge_iterator_2<Tds>::
increment()
{
  CGAL_precondition(_tds->dimension() >= 1);
  if (_tds->dimension() == 1) ++pos;
  else  if (edge.second == 2) {edge.second =  0; ++pos;}
  else       edge.second += 1;
  return;
}

template<class Tds>
inline
void
Triangulation_ds_edge_iterator_2<Tds>::
decrement()
{
  CGAL_precondition(_tds->dimension() >= 1);
  if (_tds->dimension() == 1) --pos;
  else    if (edge.second == 0) { edge.second = 2; --pos;}
  else  edge.second -= 1;
  return;
}

template<class Tds>
inline
bool
Triangulation_ds_edge_iterator_2<Tds>::
associated_edge()
{
  if (_tds->dimension() == 1) {return true;}
  return Face_handle(pos) < pos->neighbor(edge.second);
}

template<class Tds>
inline
Triangulation_ds_edge_iterator_2<Tds>&
Triangulation_ds_edge_iterator_2<Tds>::
operator++()
{
  //CGAL_precondition(pos != Iterator_base() &&
  //                               pos != _tds->faces().end());
  do     increment();
  while( pos != _tds->faces().end() && !associated_edge());
  return *this;
}


template<class Tds>
inline
Triangulation_ds_edge_iterator_2<Tds>&
Triangulation_ds_edge_iterator_2<Tds>::
operator--()
{
  // CGAL_precondition(pos != Iterator_base()
  //                          && *this != Edge_iterator(_tds));
  do      decrement();
  while ( !associated_edge() && *this != Edge_iterator(_tds) );
  return *this;
}


template<class Tds>
inline
Triangulation_ds_edge_iterator_2<Tds>
Triangulation_ds_edge_iterator_2<Tds>::
operator++(int)
{
  Edge_iterator tmp(*this);
  ++(*this);
  return tmp;
}

template<class Tds>
inline
Triangulation_ds_edge_iterator_2<Tds>
Triangulation_ds_edge_iterator_2<Tds>::
operator--(int)
{
  Edge_iterator tmp(*this);
  --(*this);
  return tmp;
}

template<class Tds>
inline
typename Triangulation_ds_edge_iterator_2<Tds>::Edge*
Triangulation_ds_edge_iterator_2<Tds>::
operator->() const
{
  edge.first = pos;
  return &edge;
}

template<class Tds>
inline
typename Triangulation_ds_edge_iterator_2<Tds>::Edge&
Triangulation_ds_edge_iterator_2<Tds>::
operator*() const
{
  edge.first = pos;
  return edge;
}
} //namespace CGAL

#endif //CGAL_TRIANGULATION_DS_ITERATORS_2_H

