// Copyright (c) 1999  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.0.1/TDS_3/include/CGAL/TDS_3/internal/Triangulation_ds_iterators_3.h $
// $Id: include/CGAL/TDS_3/internal/Triangulation_ds_iterators_3.h 50cfbde3b84 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Monique Teillaud <Monique.Teillaud@sophia.inria.fr>

#ifndef CGAL_INTERNAL_TRIANGULATION_DS_ITERATORS_3_H
#define CGAL_INTERNAL_TRIANGULATION_DS_ITERATORS_3_H

#include <CGAL/license/TDS_3.h>


#include <utility>

#include <CGAL/TDS_3/internal/Triangulation_ds_circulators_3.h>

namespace CGAL { namespace internal {

template < class Tds >
class Triangulation_ds_facet_iterator_3
{
// traverses the list of cells and reports all facets.
public:

  typedef typename Tds::Facet                    value_type;
  typedef const typename Tds::Facet *            pointer;
  typedef const typename Tds::Facet &            reference;
  typedef std::size_t                            size_type;
  typedef std::ptrdiff_t                         difference_type;
  typedef std::bidirectional_iterator_tag        iterator_category;

  typedef typename Tds::Facet                    Facet;
  typedef Triangulation_ds_facet_iterator_3<Tds> Facet_iterator;
  typedef typename Tds::Cell_iterator            Cell_iterator;

  Triangulation_ds_facet_iterator_3()
    : _tds(nullptr)
    {}

  Triangulation_ds_facet_iterator_3(const Tds * tds)
    : _tds(tds)
    {
      facet.second = 0;
      switch ( _tds->dimension() ) {
      case 2:
        pos = _tds->cells().begin();
        facet.second = 3;
        return;
      case 3:
        pos = _tds->cells().begin();
        while (// there must be at least one facet
               pos->neighbor(facet.second) < pos ) {
          increment();
        }
        return;
      default:
        pos = _tds->cells().end();
        return;
      }
    }

  // used to initialize the past-the end iterator
  Triangulation_ds_facet_iterator_3(const Tds* tds, int)
    : _tds(tds)
    {
        facet.second = 0;
        pos = _tds->cells().end();
        if (_tds->dimension() == 2)
            facet.second = 3;
    }

  Facet_iterator& operator++()
  {
    if (_tds->dimension() < 2)
        return *this;

    if (_tds->dimension() == 3) {
      do {
        increment();
      } while ( pos != _tds->cells().end()
             && pos->neighbor(facet.second) < pos );
      // reports a facet when the current cell has a pointer inferior
      // to the pointer of the neighbor cell
      return *this;
    }

    ++pos; // dimension 2
    return *this;
  }

  Facet_iterator& operator--()
  {
    if (_tds->dimension() < 2)
        return *this;

    if ( _tds->dimension() == 2 ) {
      --pos; // index remains 3
      return *this;
    }

    // dimension 3
    do{
      if (facet.second == 0) {
        // all the facets of the current cell have been examined
        facet.second = 3;
        --pos;
      }
      else
          --facet.second;
    } while ( pos != _tds->cells().end()
           && pos->neighbor(facet.second) < pos );
    // reports a facet when the current cell has a pointer inferior
    // to the pointer of the neighbor cell
    return *this;
  }

  Facet_iterator operator++(int)
    {
      Facet_iterator tmp(*this);
      ++(*this);
      return tmp;
    }

  Facet_iterator operator--(int)
    {
      Facet_iterator tmp(*this);
      --(*this);
      return tmp;
    }

  bool operator==(const Facet_iterator& fi) const
    {
      return _tds == fi._tds && pos == fi.pos &&
             facet.second == fi.facet.second;
    }

  bool operator!=(const Facet_iterator& fi) const
    {
      return !(*this == fi);
    }

  reference operator*() const
    {
      facet.first = pos;
      return facet;
    }

  pointer operator->() const
    {
      facet.first = pos;
      return &facet;
    }

private:
  const Tds*  _tds;
  Cell_iterator pos; // current "cell".
  mutable Facet facet; // current facet.

  void increment()
  {
    if (facet.second == 3) {
      // all the faces of the current cell have been examined
      facet.second = 0;
      ++pos;
    }
    // be careful : facet.second should always be 0 when pos = cells_end
    else
        ++facet.second;
  }
};

template < class Tds >
class Triangulation_ds_edge_iterator_3
{
// traverses the list of cells and reports each edge.
public:

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

  typedef typename Tds::Edge                      Edge;
  typedef Triangulation_ds_edge_iterator_3<Tds>   Edge_iterator;
  typedef typename Tds::Cell_iterator             Cell_iterator;
  typedef typename Tds::Cell_handle               Cell_handle;
  typedef internal::Triangulation_ds_cell_circulator_3<Tds> Cell_circulator;

  Triangulation_ds_edge_iterator_3()
    : _tds(nullptr)
    {
      edge.second = 0;
      edge.third = 1;
    }

  Triangulation_ds_edge_iterator_3(const Tds * tds)
    : _tds(tds)
    {
      edge.second = 0;
      edge.third = 1;
      switch ( _tds->dimension() ) {
      case 1:
        {
          pos = _tds->cells().begin();
          return;
        }
      case 2:
        {
          pos = _tds->cells().begin();
          while ( // there must be at least one edge
                 pos->neighbor(3-edge.second-edge.third) < pos ) {
            increment2();
          }
          return;
        }
      case 3:
        {
          pos = _tds->cells().begin();
          bool notfound = true;
          while ( // there must be at least one edge
                 notfound ) {
            edge.first = pos;
            Cell_circulator ccir = _tds->incident_cells(edge);
            do {
              ++ccir;
            } while ( pos < ccir );
            // loop terminates since it stops at least when ccir = pos
            if ( Cell_handle(ccir) == Cell_handle(pos) )
                // pos is the cell with minimal pointer
              notfound = false;
            else
              increment3();
          }
          return;
        }
      default:
        {
          pos = _tds->cells().end();
          return;
        }
      }
    }

  // used to initialize the past-the end iterator
  Triangulation_ds_edge_iterator_3(const Tds* tds, int)
    : _tds(tds)
    {
        edge.second = 0;
        edge.third = 1;
        pos = _tds->cells().end();
    }

  Edge_iterator& operator++()
  {
    switch ( _tds->dimension() ) {
    case 1:
      {
        ++pos;
        break;
      }
    case 2:
      {
        do {
          increment2();
        } while ( pos != _tds->cells().end() &&
                  pos->neighbor(3-edge.second-edge.third) < pos );
        break;
      }
    case 3:
      {
        bool notfound = true;
        do {
          increment3();
          if (pos != _tds->cells().end()) {
            edge.first = pos;
            Cell_circulator ccir = _tds->incident_cells(edge);
            do {
              ++ccir;
            } while ( Cell_handle(pos) < Cell_handle(ccir) );
            if ( Cell_handle(ccir) == Cell_handle(pos) )
                // pos is the cell with minimal pointer
              notfound = false;
          }
          else {
            edge.second=0; edge.third=1;
          }
        } while ( pos != _tds->cells().end() && notfound );
        break;
      }
    default:
      {
        return *this;
      }
    }
    return *this;
  }

  Edge_iterator& operator--()
  {
    switch ( _tds->dimension() ) {
    case 1:
      {
        --pos; // edge.second, edge.third remain 0, 1
        break;
      }
    case 2:
      {
        do {
          if (edge.second == 0) {
            edge.second = 2; edge.third = 0;
            --pos;
          }
          else {
            --edge.second;
            edge.third = edge.second+1;
            // case edge.second==2, edge.third==0 forbids to write edge.third--
          }
        } while ( pos != _tds->cells().end() &&
                  pos->neighbor(3-edge.second-edge.third) < pos );
        break;
      }
    case 3:
      {
        bool notfound = true;
        do {
          if (edge.second == 0) {
            if (edge.third == 1) {
              // all the edges of the current cell have been examined
              edge.second = 2; edge.third = 3;
              --pos;
            }
            else
              --edge.third;
          }
          else {
            if (edge.third == edge.second+1) {
              --edge.second;
              edge.third = 3;
            }
            else
              --edge.third;
          }
          if (pos != _tds->cells().end()) {
            edge.first = pos;
            Cell_circulator ccir = _tds->incident_cells(edge);
            do {
              ++ccir;
            } while ( Cell_handle(pos) < Cell_handle(ccir) );
            if ( Cell_handle(pos) == Cell_handle(ccir) )
                // pos is the cell with minimum pointer
              notfound = false;
          }
          else {
            edge.second=0; edge.third=1;
          }
        } while ( pos != _tds->cells().end() && notfound );
        break;
      }
    default :
      return *this;
    }
    // reports an edge when the current cell has a pointer inferior
    // to the pointer of the neighbor cell
    return *this;
  }

  Edge_iterator operator++(int)
    {
      Edge_iterator tmp(*this);
      ++(*this);
      return tmp;
    }

  Edge_iterator operator--(int)
    {
      Edge_iterator tmp(*this);
      --(*this);
      return tmp;
    }

  bool operator==(const Edge_iterator& ei) const
    {
      return _tds == ei._tds && pos == ei.pos &&
             edge.second == ei.edge.second && edge.third == ei.edge.third;
    }

  bool operator!=(const Edge_iterator& ei) const
    {
      return !(*this == ei);
    }

  reference operator*() const
    {
      edge.first = pos;
      return edge;
    }

  pointer operator->() const
    {
      edge.first = pos;
      return &edge;
    }

private:
  const Tds*  _tds;
  Cell_iterator pos; // current "cell". Even if the dimension is <3 when
              // there is no true cell yet.
  mutable Edge edge;  // keeps the indices of the current edge.

  void increment2()
  {
    if (edge.second == 2) { // edge.third == 0
      // all the edges of the current cell have been examined
      edge.second = 0; edge.third = 1;
      ++pos;
    }
    // be careful : index should always be 0 when pos = cells_end
    else {
      ++edge.second;
      if ( edge.second == 2 )
        edge.third = 0;
      else // edge.second==1
        edge.third = 2;
    }
  }

  void increment3()
  {
    if (edge.second == 2) { // then edge.third == 3
      // all the edges of the current cell have been examined
      edge.second = 0; edge.third = 1;
      ++pos;
    }
    else {
      if (edge.third == 3) {
        edge.second++;
        edge.third = edge.second+1;
      }
      else
        ++edge.third;
    }
  }
};

}} // namespace CGAL::internal

#endif // CGAL_INTERNAL_TRIANGULATION_DS_ITERATORS_3_H

