/// \brief The undirected graph writer class.

   ///

   /// The \c UndirGraphWriter class provides the undir graph output. To write 

   /// a graph you should first give writing commands for the writer. You can 

   /// declare write command as \c NodeMap, \c EdgeMap or \c UndirEdgeMap 

   /// writing and labeled Node, Edge or UndirEdge writing.

   ///

   /// \code

   /// UndirGraphWriter<UndirListGraph> writer(std::cout, graph);

   /// \endcode

   ///

   /// The \c writeNodeMap() function declares a \c NodeMap writing 

   /// command in the \c UndirGraphWriter. You should give as parameter 

   /// the name of the map and the map object. The NodeMap writing 

   /// command with name "id" should write a unique map because it 

   /// is regarded as ID map.

   ///

   /// \code

   /// IdMap<UndirListGraph, Node> nodeIdMap;

   /// writer.writeNodeMap("id", nodeIdMap);

   ///

   /// writer.writeNodeMap("coords", coords);

   /// writer.writeNodeMap("color", colorMap);

   /// \endcode

   ///

   /// With the \c writeUndirEdgeMap() member function you can give an 

   /// undirected edge map writing command similar to the NodeMaps.

   ///

   /// \code

   /// DescriptorMap<ListGraph, Edge, ListGraph::EdgeMap<int> > 

   ///   edgeDescMap(graph);

   /// writer.writeUndirEdgeMap("descriptor", edgeDescMap);

   ///

   /// writer.writeUndirEdgeMap("weight", weightMap);

   /// writer.writeUndirEdgeMap("label", labelMap);

   /// \endcode

   /// 

   /// The EdgeMap handling is just a syntactical sugar. It writes

   /// two undirected edge map with '+' and '-' prefix in the name.

   ///

   /// \code

   /// writer.writeEdgeMap("capacity", capacityMap);

   /// \endcode

   ///

   ///

   /// With \c writeNode() and \c writeUndirEdge() functions you can 

   /// point out nodes and undirected edges in the graph. By example, you can 

   /// write out the source and target of the graph.

   ///

   /// \code

   /// writer.writeNode("source", sourceNode);

   /// writer.writeNode("target", targetNode);

   ///

   /// writer.writeUndirEdge("observed", undirEdge);

   /// \endcode

   ///

   /// After you give all write commands you must call the \c run() member

   /// function, which execute all the writer commands.

   ///

   /// \code

   /// writer.run();

   /// \endcode

   ///

   /// \see DefaultWriterTraits

   /// \see QuotedStringWriter

   /// \see IdMap

   /// \see DescriptorMap

   /// \see \ref GraphWriter

   /// \see \ref graph-io-page

   /// \author Balazs Dezso

   template <typename _Graph, typename _WriterTraits = DefaultWriterTraits> 

   class UndirGraphWriter {

   public:

     typedef _Graph Graph;

     typedef typename Graph::Node Node;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::UndirEdge UndirEdge;

     typedef _WriterTraits WriterTraits;

     /// \brief Construct a new UndirGraphWriter.

     ///

     /// Construct a new UndirGraphWriter. It writes the given graph

     /// to the given stream.

     UndirGraphWriter(std::ostream& _os, const Graph& _graph) 

       : writer(new LemonWriter(_os)), own_writer(true), 

 	nodeset_writer(*writer, _graph, std::string()),

 	undir_edgeset_writer(*writer, _graph, nodeset_writer, std::string()),

 	node_writer(*writer, nodeset_writer, std::string()),

 	undir_edge_writer(*writer, undir_edgeset_writer, std::string()),

 	attribute_writer(*writer, std::string()) {}

     /// \brief Construct a new UndirGraphWriter.

     ///

     /// Construct a new UndirGraphWriter. It writes into the given graph

     /// to the given file.

     UndirGraphWriter(const std::string& _filename, const Graph& _graph) 

       : writer(new LemonWriter(_filename)), own_writer(true), 

 	nodeset_writer(*writer, _graph, std::string()),

 	undir_edgeset_writer(*writer, _graph, nodeset_writer, std::string()),

 	node_writer(*writer, nodeset_writer, std::string()),

 	undir_edge_writer(*writer, undir_edgeset_writer, std::string()),

 	attribute_writer(*writer, std::string()) {}

     /// \brief Construct a new UndirGraphWriter.

     ///

     /// Construct a new UndirGraphWriter. It writes into the given graph

     /// to given LemonReader.

     UndirGraphWriter(LemonWriter& _writer, const Graph& _graph)

       : writer(_writer), own_writer(false), 

 	nodeset_writer(*writer, _graph, std::string()),

 	undir_edgeset_writer(*writer, _graph, nodeset_writer, std::string()),

 	node_writer(*writer, nodeset_writer, std::string()),

 	undir_edge_writer(*writer, undir_edgeset_writer, std::string()),

 	attribute_writer(*writer, std::string()) {}

     /// \brief Destruct the graph writer.

     ///

     /// Destruct the graph writer.

     ~UndirGraphWriter() {

       if (own_writer) 

 	delete writer;

     }

     /// \brief Add a new node map writer command for the writer.

     ///

     /// Add a new node map writer command for the writer.

     template <typename Map>

     UndirGraphWriter& writeNodeMap(std::string name, const Map& map) {

       nodeset_writer.writeNodeMap(name, map);

       return *this;

     }

     /// \brief Add a new node map writer command for the writer.

     ///

     /// Add a new node map writer command for the writer.

     template <typename Writer, typename Map>

     UndirGraphWriter& writeNodeMap(std::string name, const Map& map, 

 			      const Writer& writer = Writer()) {

       nodeset_writer.writeNodeMap(name, map, writer);

       return *this;

     }

     /// \brief Add a new edge map writer command for the writer.

     ///

     /// Add a new edge map writer command for the writer.

     template <typename Map>

     UndirGraphWriter& writeEdgeMap(std::string name, const Map& map) { 

       undir_edgeset_writer.writeEdgeMap(name, map);

       return *this;

     }

     /// \brief Add a new edge map writer command for the writer.

     ///

     /// Add a new edge map writer command for the writer.

     template <typename Writer, typename Map>

     UndirGraphWriter& writeEdgeMap(std::string name, const Map& map,

 				   const Writer& writer = Writer()) {

       undir_edgeset_writer.writeEdgeMap(name, map, writer);

       return *this;

     }

     /// \brief Add a new undirected edge map writer command for the writer.

     ///

     /// Add a new undirected edge map writer command for the writer.

     template <typename Map>

     UndirGraphWriter& writeUndirEdgeMap(std::string name, const Map& map) { 

       undir_edgeset_writer.writeUndirEdgeMap(name, map);

       return *this;

     }

     /// \brief Add a new undirected edge map writer command for the writer.

     ///

     /// Add a new edge undirected map writer command for the writer.

     template <typename Writer, typename Map>

     UndirGraphWriter& writeUndirEdgeMap(std::string name, const Map& map,

 					const Writer& writer = Writer()) {

       undir_edgeset_writer.writeUndirEdgeMap(name, map, writer);

       return *this;

     }

     /// \brief Add a new labeled node writer for the writer.

     ///

     /// Add a new labeled node writer for the writer.

     UndirGraphWriter& writeNode(std::string name, const Node& node) {

       node_writer.writeNode(name, node);

       return *this;

     }

     /// \brief Add a new labeled edge writer for the writer.

     ///

     /// Add a new labeled edge writer for the writer.

     UndirGraphWriter& writeUndirEdge(std::string name, const UndirEdge& edge) {

       undir_edge_writer.writeUndirEdge(name, edge);

     }

     /// \brief Add a new attribute writer command.

     ///

     ///  Add a new attribute writer command.

     template <typename Value>

     UndirGraphWriter& writeAttribute(std::string name, const Value& value) {

       attribute_writer.writeAttribute(name, value);

       return *this;

     }

     /// \brief Add a new attribute writer command.

     ///

     ///  Add a new attribute writer command.

     template <typename Writer, typename Value>

     UndirGraphWriter& writeAttribute(std::string name, const Value& value, 

 			       const Writer& writer) {

       attribute_writer.writeAttribute<Writer>(name, value, writer);

       return *this;

     }

     /// \brief Conversion operator to LemonWriter.

     ///

     /// Conversion operator to LemonWriter. It make possible

     /// to access the encapsulated \e LemonWriter, this way

     /// you can attach to this writer new instances of 

     /// \e LemonWriter::SectionWriter.

     operator LemonWriter&() {

       return *writer;

     }

     /// \brief Executes the writer commands.

     ///

     /// Executes the writer commands.

     void run() {

       writer->run();

     }

   private:

     LemonWriter* writer;

     bool own_writer;

     NodeSetWriter<Graph, WriterTraits> nodeset_writer;

     UndirEdgeSetWriter<Graph, WriterTraits> undir_edgeset_writer;

     NodeWriter<Graph> node_writer;

     UndirEdgeWriter<Graph> undir_edge_writer;

     AttributeWriter<WriterTraits> attribute_writer;

   };

   /// \brief Write an undirected graph to the output.

   ///

   /// Write an undirected graph to the output.

   /// \param os The output stream.

   /// \param g The graph.

   /// \param capacity The capacity undirected map.

   template<typename Graph, typename CapacityMap>

   void writeUndirGraph(std::ostream& os, const Graph &g, 

 		       const CapacityMap& capacity) {

     UndirGraphWriter<Graph> writer(os, g);

     writer.writeUndirEdgeMap("capacity", capacity);

     writer.run();

   }

   /// \brief Write an undirected graph to the output.

   ///

   /// Write an undirected graph to the output.

   /// \param os The output stream.

   /// \param g The graph.

   template<typename Graph>

   void writeUndirGraph(std::ostream& os, const Graph &g) {

     UndirGraphWriter<Graph> writer(os, g);

     writer.run();

   }