#include <map>

   /// \addtogroup graph_maps

   /// @{

   /// Provides an immutable and unique id for each item in the graph.

   /// The IdMap class provides an unique and immutable mapping for each item

   /// in the graph.

   ///

   template <typename _Graph, typename _Item>

   class IdMap {

   public:

     typedef _Graph Graph;

     typedef int Value;

     typedef _Item Item;

     typedef _Item Key;

     /// \brief The class represents the inverse of the map.

     ///

     /// The class represents the inverse of the map.

     /// \see inverse()

     class InverseMap {

     public:

       /// \brief Constructor.

       ///

       /// Constructor for creating an id-to-item map.

       InverseMap(const Graph& _graph) : graph(&_graph) {}

       /// \brief Gives back the given item from its id.

       ///

       /// Gives back the given item from its id.

       /// 

       Item operator[](int id) const { return graph->fromId(id, Item());}

     private:

       const Graph* graph;

     };

     /// \brief Constructor.

     ///

     /// Constructor for creating id map.

     IdMap(const Graph& _graph) : graph(&_graph) {}

     /// \brief Gives back the \e id of the item.

     ///

     /// Gives back the immutable and unique \e id of the map.

     int operator[](const Item& item) const { return graph->id(item);}

     /// \brief Gives back the inverse of the map.

     ///

     /// Gives back the inverse of the map.

     InverseMap inverse() const { return InverseMap(*graph);} 

   private:

     const Graph* graph;

   };

   template <typename Map, typename Enable = void>

   struct ReferenceMapTraits {

     typedef typename Map::Value Value;

     typedef typename Map::Value& Reference;

     typedef const typename Map::Value& ConstReference;

     typedef typename Map::Value* Pointer;

     typedef const typename Map::Value* ConstPointer;

   };

   template <typename Map>

   struct ReferenceMapTraits<

     Map, 

     typename enable_if<typename Map::FullTypeTag, void>::type

   > {

     typedef typename Map::Value Value;

     typedef typename Map::Reference Reference;

     typedef typename Map::ConstReference ConstReference;

     typedef typename Map::Pointer Pointer;

     typedef typename Map::ConstPointer ConstPointer;

   };

   /// \brief General inversable graph-map type.

   /// This type provides simple inversable map functions. 

   /// The InversableMap wraps an arbitrary ReadWriteMap 

   /// and if a key is setted to a new value then store it

   /// in the inverse map.

   /// \param _Graph The graph type.

   /// \param _Map The map to extend with inversable functionality. 

   template <

     typename _Graph,

     typename _Item, 

     typename _Value,

     typename _Map 

     = typename ItemSetTraits<_Graph, _Item>::template Map<_Value> 

   >

   class InversableMap : protected _Map {

   public:

     typedef _Map Map;

     typedef _Graph Graph;

    /// The key type of InversableMap (Node, Edge, UndirEdge).

     typedef typename _Map::Key Key;

     /// The value type of the InversableMap.

     typedef typename _Map::Value Value;

     typedef std::map<Value, Key> InverseMap;

     typedef typename _Map::ConstReference ConstReference;

     /// \brief Constructor.

     ///

     /// Construct a new InversableMap for the graph.

     ///

     InversableMap(const Graph& graph) : Map(graph) {} 

     /// \brief The setter function of the map.

     ///

     void set(const Key& key, const Value& val) {

       Value oldval = Map::operator[](key);

       typename InverseMap::iterator it = invMap.find(oldval);

       if (it != invMap.end() && it->second == key) {

 	invMap.erase(it);

       }      

       invMap.insert(make_pair(val, key));

       Map::set(key, val);

     }

     /// \brief The getter function of the map.

     ///

     /// It gives back the value associated with the key.

     ConstReference operator[](const Key& key) const {

       return Map::operator[](key);

     }

     /// \brief Add a new key to the map.

     ///

     /// Add a new key to the map. It is called by the

     /// \c AlterationNotifier.

     virtual void add(const Key& key) {

       Map::add(key);

     }

     /// \brief Erase the key from the map.

     ///

     /// Erase the key to the map. It is called by the

     /// \c AlterationNotifier.

     virtual void erase(const Key& key) {

       Value val = Map::operator[](key);

       typename InverseMap::iterator it = invMap.find(val);

       if (it != invMap.end() && it->second == key) {

 	invMap.erase(it);

       }

       Map::erase(key);

     }

     /// \brief Clear the keys from the map and inverse map.

     ///

     /// Clear the keys from the map and inverse map. It is called by the

     /// \c AlterationNotifier.

     virtual void clear() {

       invMap.clear();

       Map::clear();

     }

     /// \brief It gives back the just readeable inverse map.

     ///

     /// It gives back the just readeable inverse map.

     const InverseMap& inverse() const {

       return invMap;

     } 

   private:

     InverseMap invMap;    

   };

   /// \brief Provides a mutable, continuous and unique descriptor for each 

   /// item in the graph.

   ///

   /// The DescriptorMap class provides a mutable, continuous and immutable

   /// mapping for each item in the graph.

   ///

   /// \param _Graph The graph class the \c DescriptorMap belongs to.

   /// \param _Item The Item is the Key of the Map. It may be Node, Edge or 

   /// UndirEdge.

   /// \param _Map A ReadWriteMap mapping from the item type to integer.

   template <

     typename _Graph,   

     typename _Item,

     typename _Map = typename ItemSetTraits<_Graph, _Item>::template Map<int>

   >

   class DescriptorMap : protected _Map {

     typedef _Item Item;

     typedef _Map Map;

   public:

     /// The graph class of DescriptorMap.

     typedef _Graph Graph;

     /// The key type of DescriptorMap (Node, Edge, UndirEdge).

     typedef typename _Map::Key Key;

     /// The value type of DescriptorMap.

     typedef typename _Map::Value Value;

     typedef std::vector<Item> InverseMap;

     /// \brief Constructor.

     ///

     /// Constructor for creating descriptor map.

     DescriptorMap(const Graph& _graph) : Map(_graph) {

       build();

     }

     /// \brief Add a new key to the map.

     ///

     /// Add a new key to the map. It is called by the

     /// \c AlterationNotifier.

     virtual void add(const Item& item) {

       Map::add(item);

       Map::set(item, invMap.size());

       invMap.push_back(item);

     }

     /// \brief Erase the key from the map.

     ///

     /// Erase the key to the map. It is called by the

     /// \c AlterationNotifier.

     virtual void erase(const Item& item) {

       Map::set(invMap.back(), Map::operator[](item));

       invMap[Map::operator[](item)] = invMap.back();

       Map::erase(item);

     }

     /// \brief Build the unique map.

     ///

     /// Build the unique map. It is called by the

     /// \c AlterationNotifier.

     virtual void build() {

       Map::build();

       Item it;

       const typename Map::Graph* graph = Map::getGraph(); 

       for (graph->first(it); it != INVALID; graph->next(it)) {

 	Map::set(it, invMap.size());

 	invMap.push_back(it);	

       }      

     }

     /// \brief Clear the keys from the map.

     ///

     /// Clear the keys from the map. It is called by the

     /// \c AlterationNotifier.

     virtual void clear() {

       invMap.clear();

       Map::clear();

     }

     /// \brief Gives back the \e descriptor of the item.

     ///

     /// Gives back the mutable and unique \e descriptor of the map.

     int operator[](const Item& item) const {

       return Map::operator[](item);

     }

     /// \brief Gives back the inverse of the map.

     ///

     /// Gives back the inverse of the map.

     const InverseMap inverse() const {

       return invMap;

     }

   private:

     std::vector<Item> invMap;

   };

   /// \brief Returns the source of the given edge.

   ///

   /// The SourceMap gives back the source Node of the given edge. 

   /// \author Balazs Dezso

   template <typename Graph>

   class SourceMap {

   public:

     typedef typename Graph::Node Value;

     typedef typename Graph::Edge Key;

     /// \brief Constructor

     ///

     /// Constructor

     /// \param _graph The graph that the map belongs to.

     SourceMap(const Graph& _graph) : graph(_graph) {}

     /// \brief The subscript operator.

     ///

     /// The subscript operator.

     /// \param edge The edge 

     /// \return The source of the edge 

     Value operator[](const Key& edge) {

       return graph.source(edge);

     }

   private:

     const Graph& graph;

   };

   /// \brief Returns a \ref SourceMap class

   ///

   /// This function just returns an \ref SourceMap class.

   /// \relates SourceMap

   template <typename Graph>

   inline SourceMap<Graph> sourceMap(const Graph& graph) {

     return SourceMap<Graph>(graph);

   } 

   /// \brief Returns the target of the given edge.

   ///

   /// The TargetMap gives back the target Node of the given edge. 

   /// \author Balazs Dezso

   template <typename Graph>

   class TargetMap {

   public:

     typedef typename Graph::Node Value;

     typedef typename Graph::Edge Key;

     /// \brief Constructor

     ///

     /// Constructor

     /// \param _graph The graph that the map belongs to.

     TargetMap(const Graph& _graph) : graph(_graph) {}

     /// \brief The subscript operator.

     ///

     /// The subscript operator.

     /// \param edge The edge 

     /// \return The target of the edge 

     Value operator[](const Key& key) {

       return graph.target(key);

     }

   private:

     const Graph& graph;

   };

   /// \brief Returns a \ref TargetMap class

   /// This function just returns an \ref TargetMap class.

   /// \relates TargetMap

   template <typename Graph>

   inline TargetMap<Graph> targetMap(const Graph& graph) {

     return TargetMap<Graph>(graph);

   }

   /// @}