//=======================================================================

// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.

// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek

//

// Distributed under the Boost Software License, Version 1.0. (See

// accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

//=======================================================================

//

#ifndef BOOST_GRAPH_EDGE_LIST_HPP

#define BOOST_GRAPH_EDGE_LIST_HPP

#include <iterator>

#include <boost/config.hpp>

#include <boost/pending/ct_if.hpp>

#include <boost/pending/integer_range.hpp>

#include <boost/graph/graph_traits.hpp>

#include <boost/graph/properties.hpp>

namespace boost {

  //

  // The edge_list class is an EdgeListGraph module that is constructed

  // from a pair of iterators whose value type is a pair of vertex

  // descriptors.

  //

  // For example:

  //

  //  typedef std::pair<int,int> E;

  //  list<E> elist;

  //  ...

  //  typedef edge_list<list<E>::iterator> Graph;

  //  Graph g(elist.begin(), elist.end());

  //

  // If the iterators are random access, then Graph::edge_descriptor

  // is of Integral type, otherwise it is a struct, though it is

  // convertible to an Integral type.

  // 

  struct edge_list_tag { };

  // The implementation class for edge_list.

  template <class G, class EdgeIter, class T, class D>

  class edge_list_impl

  {

  public:

    typedef D edge_id;

    typedef T Vpair;

    typedef typename Vpair::first_type V;

    typedef V vertex_descriptor;

    typedef edge_list_tag graph_tag;

    typedef void edge_property_type;

    struct edge_descriptor

    {

      edge_descriptor() { }

      edge_descriptor(EdgeIter p, edge_id id) : _ptr(p), _id(id) { }

      operator edge_id() { return _id; }

      EdgeIter _ptr;

      edge_id _id;

    };

    typedef edge_descriptor E;

    struct edge_iterator

    {

      typedef edge_iterator self;

      typedef E value_type;

      typedef E& reference;

      typedef E* pointer;

      typedef std::ptrdiff_t difference_type;

      typedef std::input_iterator_tag iterator_category;

      edge_iterator() { }

      edge_iterator(EdgeIter iter) : _iter(iter), _i(0) { }

      E operator*() { return E(_iter, _i); }

      self& operator++() { ++_iter; ++_i; return *this; }

      self operator++(int) { self t = *this; ++(*this); return t; }

      bool operator==(const self& x) { return _iter == x._iter; }

      bool operator!=(const self& x) { return _iter != x._iter; }

      EdgeIter _iter;

      edge_id _i;

    };

    typedef void out_edge_iterator;

    typedef void in_edge_iterator;

    typedef void adjacency_iterator;

    typedef void vertex_iterator;

  };

  template <class G, class EI, class T, class D>

  std::pair<typename edge_list_impl<G,EI,T,D>::edge_iterator,

            typename edge_list_impl<G,EI,T,D>::edge_iterator>

  edges(const edge_list_impl<G,EI,T,D>& g_) {

    const G& g = static_cast<const G&>(g_);

    typedef typename edge_list_impl<G,EI,T,D>::edge_iterator edge_iterator;

    return std::make_pair(edge_iterator(g._first), edge_iterator(g._last));

  }

  template <class G, class EI, class T, class D>

  typename edge_list_impl<G,EI,T,D>::vertex_descriptor

  source(typename edge_list_impl<G,EI,T,D>::edge_descriptor e,

         const edge_list_impl<G,EI,T,D>&) {

    return (*e._ptr).first;

  }

  template <class G, class EI, class T, class D>

  typename edge_list_impl<G,EI,T,D>::vertex_descriptor

  target(typename edge_list_impl<G,EI,T,D>::edge_descriptor e,

           const edge_list_impl<G,EI,T,D>&) {

    return (*e._ptr).second;

  }

  template <class D, class E>

  class el_edge_property_map

    : public put_get_helper<D, el_edge_property_map<D,E> >{

  public:

    typedef E key_type;

    typedef D value_type;

    typedef D reference;

    typedef readable_property_map_tag category;

    value_type operator[](key_type e) const {

      return e._i;

    }

  };

  struct edge_list_edge_property_selector {

    template <class Graph, class Property, class Tag>

    struct bind_ {

      typedef el_edge_property_map<typename Graph::edge_id,

          typename Graph::edge_descriptor> type;

      typedef type const_type;

    };

  };

  template <>  

  struct edge_property_selector<edge_list_tag> {

    typedef edge_list_edge_property_selector type;

  };

  template <class G, class EI, class T, class D>

  typename property_map< edge_list_impl<G,EI,T,D>, edge_index_t>::type

  get(edge_index_t, const edge_list_impl<G,EI,T,D>&) {

    typedef typename property_map< edge_list_impl<G,EI,T,D>, 

      edge_index_t>::type EdgeIndexMap;

    return EdgeIndexMap();

  }

  template <class G, class EI, class T, class D>

  inline D

  get(edge_index_t, const edge_list_impl<G,EI,T,D>&,

      typename edge_list_impl<G,EI,T,D>::edge_descriptor e) {

    return e._i;

  }

  // A specialized implementation for when the iterators are random access.

  struct edge_list_ra_tag { };

  template <class G, class EdgeIter, class T, class D>

  class edge_list_impl_ra

  {

  public:

    typedef D edge_id;

    typedef T Vpair;

    typedef typename Vpair::first_type V;

    typedef edge_list_ra_tag graph_tag;

    typedef void edge_property_type;

    typedef edge_id edge_descriptor;

    typedef V vertex_descriptor;

    typedef typename boost::integer_range<edge_id>::iterator edge_iterator;

    typedef void out_edge_iterator;

    typedef void in_edge_iterator;

    typedef void adjacency_iterator;

    typedef void vertex_iterator;

  };

  template <class G, class EI, class T, class D>

  std::pair<typename edge_list_impl_ra<G,EI,T,D>::edge_iterator,

            typename edge_list_impl_ra<G,EI,T,D>::edge_iterator>

  edges(const edge_list_impl_ra<G,EI,T,D>& g_)

  {

    const G& g = static_cast<const G&>(g_);

    typedef typename edge_list_impl_ra<G,EI,T,D>::edge_iterator edge_iterator;

    return std::make_pair(edge_iterator(0), edge_iterator(g._last - g._first));

  }    

  template <class G, class EI, class T, class D>

  typename edge_list_impl_ra<G,EI,T,D>::vertex_descriptor

  source(typename edge_list_impl_ra<G,EI,T,D>::edge_descriptor e,

         const edge_list_impl_ra<G,EI,T,D>& g_)

  {

    const G& g = static_cast<const G&>(g_);

    return g._first[e].first;

  }

  template <class G, class EI, class T, class D>

  typename edge_list_impl_ra<G,EI,T,D>::vertex_descriptor

  target(typename edge_list_impl_ra<G,EI,T,D>::edge_descriptor  e,

         const edge_list_impl_ra<G,EI,T,D>& g_)

  {

    const G& g = static_cast<const G&>(g_);

    return g._first[e].second;

  }

  template <class E>

  class el_ra_edge_property_map

    : public put_get_helper<E, el_ra_edge_property_map<E> >{

  public:

    typedef E key_type;

    typedef E value_type;

    typedef E reference;

    typedef readable_property_map_tag category;

    value_type operator[](key_type e) const {

      return e;

    }

  };

  struct edge_list_ra_edge_property_selector {

    template <class Graph, class Property, class Tag>

    struct bind_ {

      typedef el_ra_edge_property_map<typename Graph::edge_descriptor> type;

      typedef type const_type;

    };

  };

  template <>  

  struct edge_property_selector<edge_list_ra_tag> {

    typedef edge_list_ra_edge_property_selector type;

  };

  template <class G, class EI, class T, class D>

  inline 

  typename property_map< edge_list_impl_ra<G,EI,T,D>, edge_index_t>::type

  get(edge_index_t, const edge_list_impl_ra<G,EI,T,D>&) {

    typedef typename property_map< edge_list_impl_ra<G,EI,T,D>, 

      edge_index_t>::type EdgeIndexMap;

    return EdgeIndexMap();

  }

  template <class G, class EI, class T, class D>

  inline D

  get(edge_index_t, const edge_list_impl_ra<G,EI,T,D>&, 

      typename edge_list_impl_ra<G,EI,T,D>::edge_descriptor e) {

    return e;

  }

  // Some helper classes for determining if the iterators are random access

  template <class Cat>

  struct is_random {

    enum { RET = false }; 

    typedef false_type type; 

  };

  template <>

  struct is_random<std::random_access_iterator_tag> { 

    enum { RET = true }; typedef true_type type; 

  };

  // The edge_list class conditionally inherits from one of the

  // above two classes.

  template <class EdgeIter, 

#if !defined BOOST_NO_STD_ITERATOR_TRAITS

            class T = typename std::iterator_traits<EdgeIter>::value_type,

            class D = typename std::iterator_traits<EdgeIter>::difference_type,

            class Cat = typename std::iterator_traits<EdgeIter>::iterator_category>

#else

            class T,

            class D, 

            class Cat>

#endif

  class edge_list

    : public ct_if_t< typename is_random<Cat>::type,

                    edge_list_impl_ra< edge_list<EdgeIter,T,D,Cat>, EdgeIter,T,D>,

                    edge_list_impl< edge_list<EdgeIter,T,D,Cat>, EdgeIter,T,D> 

             >::type

  {

  public:

    typedef directed_tag directed_category;

    typedef allow_parallel_edge_tag edge_parallel_category;

    typedef edge_list_graph_tag traversal_category;

    typedef std::size_t edges_size_type;

    typedef std::size_t vertices_size_type;

    typedef std::size_t degree_size_type;

    edge_list(EdgeIter first, EdgeIter last) : _first(first), _last(last) { 

      m_num_edges = std::distance(first, last);

    }

    edge_list(EdgeIter first, EdgeIter last, edges_size_type E)

      : _first(first), _last(last), m_num_edges(E) { }  

    EdgeIter _first, _last;

    edges_size_type m_num_edges;

  };

  template <class EdgeIter, class T, class D, class Cat>

  std::size_t num_edges(const edge_list<EdgeIter, T, D, Cat>& el) {

    return el.m_num_edges;

  }

#ifndef BOOST_NO_STD_ITERATOR_TRAITS

  template <class EdgeIter>

  inline edge_list<EdgeIter>

  make_edge_list(EdgeIter first, EdgeIter last)

  {

    return edge_list<EdgeIter>(first, last);

  }

#endif

} /* namespace boost */

#endif /* BOOST_GRAPH_EDGE_LIST_HPP */