/* -*- C++ -*-
 * lemon/graph_reader.h - Part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
 * (Egervary Research Group on Combinatorial Optimization, EGRES).
 *
 * Permission to use, modify and distribute this software is granted
 * provided that this copyright notice appears in all copies. For
 * precise terms see the accompanying LICENSE file.
 *
 * This software is provided "AS IS" with no warranty of any kind,
 * express or implied, and with no claim as to its suitability for any
 * purpose.
 *
 */

///\ingroup io_group
///\file
///\brief Lemon Graph Format reader.

#ifndef LEMON_GRAPH_READER_H
#define LEMON_GRAPH_READER_H

#include <iostream>

#include <lemon/error.h>
#include <lemon/lemon_reader.h>

namespace lemon {

  /// \addtogroup io_group
  /// @{

  /// \brief The graph reader class.
  ///
  /// The \c GraphReader class provides the graph input. 
  /// Before you read this documentation it might be useful to read the general
  /// description of  \ref graph-io-page "Graph Input-Output".
  ///
  /// If you don't need very sophisticated
  /// behaviour then you can use the versions of the public function
  /// \ref readGraph() to read a graph (or a max flow instance etc).
  ///
  /// The file to be read may contain several maps and labeled nodes or 
  /// edges.
  ///
  /// If you read a graph you need not read all the maps and items just those
  /// that you need. The interface of the \c GraphReader is very similar to
  /// the GraphWriter but the reading method does not depend on the order the
  /// given commands (i.e. you don't have to insist on the order in which the
  /// maps are given in the file).
  ///
  /// The reader object assumes that not readed values do not contain 
  /// whitespaces, therefore it has some extra possibilities to control how
  /// it should skip the values when the string representation contains spaces.
  ///
  /// \code
  /// GraphReader<ListGraph> reader(std::cin, graph);
  /// \endcode
  ///
  /// The \c readNodeMap() function reads a map from the \c \@nodeset section.
  /// If there is a map that you do not want to read from the file and there is
  /// whitespace in the string represenation of the values then you should
  /// call the \c skipNodeMap() template member function with proper 
  /// parameters.
  ///
  /// \code
  /// reader.readNodeMap("coords", coords);
  ///
  /// reader.readNodeMap<QuotedStringReader>("label", labelMap);
  /// reader.skipNodeMap<QuotedStringReader>("description");
  ///
  /// reader.readNodeMap("color", colorMap);
  /// \endcode
  ///
  /// With the \c readEdgeMap() member function you can give an edge map
  /// reading command similar to the NodeMaps. 
  ///
  /// \code
  /// reader.readEdgeMap("weight", weightMap);
  /// reader.readEdgeMap("label", labelMap);
  /// \endcode
  ///
  /// With \c readNode() and \c readEdge() functions you can read 
  /// labeled Nodes and Edges.
  ///
  /// \code
  /// reader.readNode("source", sourceNode);
  /// reader.readNode("target", targetNode);
  ///
  /// reader.readEdge("observed", edge);
  /// \endcode
  ///
  /// With the \c readAttribute() functions you can read an attribute
  /// into a variable. You can specify the reader for the attribute as
  /// the nodemaps.
  ///
  /// After you give all read commands you must call the \c run() member
  /// function, which executes all the commands.
  ///
  /// \code
  /// reader.run();
  /// \endcode
  ///
  /// \see DefaultReaderTraits
  /// \see QuotedStringReader
  /// \see \ref GraphWriter
  /// \see \ref graph-io-page
  /// \author Balazs Dezso
  template <typename _Graph, typename _ReaderTraits = DefaultReaderTraits> 
  class GraphReader {
  public:
    
    typedef _Graph Graph;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;

    typedef _ReaderTraits ReaderTraits;
    typedef typename ReaderTraits::Skipper DefaultSkipper;

    /// \brief Construct a new GraphReader.
    ///
    /// Construct a new GraphReader. It reads into the given graph
    /// and it uses the given reader as the default skipper.
    GraphReader(std::istream& _is, Graph& _graph, 
		const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(new LemonReader(_is)), own_reader(true), skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	edgeset_reader(*reader, _graph, nodeset_reader, 
		       std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	edge_reader(*reader, edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Construct a new GraphReader.
    ///
    /// Construct a new GraphReader. It reads into the given graph
    /// and it uses the given reader as the default skipper.
    GraphReader(const std::string& _filename, Graph& _graph, 
		const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(new LemonReader(_filename)), own_reader(true), 
	skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	edgeset_reader(*reader, _graph, nodeset_reader, 
		       std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	edge_reader(*reader, edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Construct a new GraphReader.
    ///
    /// Construct a new GraphReader. It reads into the given graph
    /// and it uses the given reader as the default skipper.
    GraphReader(LemonReader& _reader, Graph& _graph, 
		const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(_reader), own_reader(false), skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	edgeset_reader(*reader, _graph, nodeset_reader, 
		       std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	edge_reader(*reader, edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Destruct the graph reader.
    ///
    /// Destruct the graph reader.
    ~GraphReader() {
      if (own_reader) 
	delete reader;
    }

    /// \brief Give a new node map reading command to the reader.
    ///
    /// Give a new node map reading command to the reader.
    template <typename Map>
    GraphReader& readNodeMap(std::string name, Map& map) {
      nodeset_reader.readNodeMap(name, map);
      return *this;
    }

    template <typename Map>
    GraphReader& readNodeMap(std::string name, const Map& map) {
      nodeset_reader.readNodeMap(name, map);
      return *this;
    }

    /// \brief Give a new node map reading command to the reader.
    ///
    /// Give a new node map reading command to the reader.
    template <typename Reader, typename Map>
    GraphReader& readNodeMap(std::string name, Map& map, 
			     const Reader& reader = Reader()) {
      nodeset_reader.readNodeMap(name, map, reader);
      return *this;
    }

    template <typename Reader, typename Map>
    GraphReader& readNodeMap(std::string name, const Map& map, 
			     const Reader& reader = Reader()) {
      nodeset_reader.readNodeMap(name, map, reader);
      return *this;
    }

    /// \brief Give a new node map skipping command to the reader.
    ///
    /// Give a new node map skipping command to the reader.
    template <typename Reader>
    GraphReader& skipNodeMap(std::string name, 
			     const Reader& reader = Reader()) {
      nodeset_reader.skipNodeMap(name, reader);
      return *this;
    }

    /// \brief Give a new edge map reading command to the reader.
    ///
    /// Give a new edge map reading command to the reader.
    template <typename Map>
    GraphReader& readEdgeMap(std::string name, Map& map) { 
      edgeset_reader.readEdgeMap(name, map);
      return *this;
    }

    template <typename Map>
    GraphReader& readEdgeMap(std::string name, const Map& map) { 
      edgeset_reader.readEdgeMap(name, map);
      return *this;
    }


    /// \brief Give a new edge map reading command to the reader.
    ///
    /// Give a new edge map reading command to the reader.
    template <typename Reader, typename Map>
    GraphReader& readEdgeMap(std::string name, Map& map,
			     const Reader& reader = Reader()) {
      edgeset_reader.readEdgeMap(name, map, reader);
      return *this;
    }

    template <typename Reader, typename Map>
    GraphReader& readEdgeMap(std::string name, const Map& map,
			     const Reader& reader = Reader()) {
      edgeset_reader.readEdgeMap(name, map, reader);
      return *this;
    }

    /// \brief Give a new edge map skipping command to the reader.
    ///
    /// Give a new edge map skipping command to the reader.
    template <typename Reader>
    GraphReader& skipEdgeMap(std::string name, 
			     const Reader& reader = Reader()) {
      edgeset_reader.skipEdgeMap(name, reader);
      return *this;
    }

    /// \brief Give a new labeled node reading command to the reader.
    ///
    /// Give a new labeled node reading command to the reader.
    GraphReader& readNode(std::string name, Node& node) {
      node_reader.readNode(name, node);
      return *this;
    }

    /// \brief Give a new labeled edge reading command to the reader.
    ///
    /// Give a new labeled edge reading command to the reader.
    GraphReader& readEdge(std::string name, Edge& edge) {
      edge_reader.readEdge(name, edge);
      return *this;
    }

    /// \brief Give a new attribute reading command.
    ///
    ///  Give a new attribute reading command.
    template <typename Value>
    GraphReader& readAttribute(std::string name, Value& value) {
      attribute_reader.readAttribute(name, value);
      return *this;
    }
    
    /// \brief Give a new attribute reading command.
    ///
    ///  Give a new attribute reading command.
    template <typename Reader, typename Value>
    GraphReader& readAttribute(std::string name, Value& value, 
			       const Reader& reader) {
      attribute_reader.readAttribute<Reader>(name, value, reader);
      return *this;
    }

    /// \brief Conversion operator to LemonReader.
    ///
    /// Conversion operator to LemonReader. It makes possible to access the
    /// encapsulated \e LemonReader, this way you can attach to this reader
    /// new instances of \e LemonReader::SectionReader. For more details see
    /// the \ref rwbackground "Background of Reading and Writing".
    operator LemonReader&() {
      return *reader;
    }

    /// \brief Executes the reading commands.
    ///
    /// Executes the reading commands.
    void run() {
      reader->run();
    }

    /// \brief Gives back the node by its id.
    ///
    /// It reads an id from the stream and gives back which node belongs to
    /// it. It is possible only if there was read an "id" named node map.
    Node readId(std::istream& is, Node) const {
      return nodeset_reader.readId(is, Node());
    } 

    /// \brief Gives back the edge by its id.
    ///
    /// It reads an id from the stream and gives back which edge belongs to
    /// it. It is possible only if there was read an "id" named edge map.
    Edge readId(std::istream& is, Edge) const {
      return edgeset_reader.readId(is, Edge());
    } 

  private:

    LemonReader* reader;
    bool own_reader;

    DefaultSkipper skipper;

    NodeSetReader<Graph, ReaderTraits> nodeset_reader;
    EdgeSetReader<Graph, ReaderTraits> edgeset_reader;

    NodeReader<Graph> node_reader;
    EdgeReader<Graph> edge_reader;
    
    AttributeReader<ReaderTraits> attribute_reader;
  };


  /// \brief Read a graph from the input.
  ///
  /// It is a helper function to read a graph from the given input
  /// stream. It gives back an GraphReader object and this object
  /// can read more maps, labeled nodes, edges and attributes.
  ///
  /// \warning Do not forget to call the \c run() function.
  ///
  /// \param is The input stream.
  /// \param g The graph.
  template<typename Graph>
  GraphReader<Graph> graphReader(std::istream& is, Graph &g) {
    return GraphReader<Graph>(is, g);
  }

  /// \brief Read a graph from the input.
  ///
  /// It is a helper function to read a graph from the given input
  /// file. It gives back an GraphReader object and this object
  /// can read more maps, labeled nodes, edges and attributes.
  ///
  /// \warning Do not forget to call the \c run() function.
  ///
  /// \param fn The input filename.
  /// \param g The graph.
  template<typename Graph>
  GraphReader<Graph> graphReader(const std::string& fn, Graph &g) {
    return GraphReader<Graph>(fn, g);
  }

  /// \brief The undirected graph reader class.
  ///
  /// The \c UndirGraphReader class provides the graph input. 
  /// Before you read this documentation it might be useful to read the general
  /// description of  \ref graph-io-page "Graph Input-Output".
  ///
  /// If you don't need very sophisticated
  /// behaviour then you can use the versions of the public function
  /// \ref readGraph() to read a graph (or a max flow instance etc).
  ///
  /// The given file format may contain several maps and labeled nodes or 
  /// edges.
  ///
  /// If you read a graph you need not read all the maps and items just those
  /// that you need. The interface of the \c UndirGraphReader is very similar
  /// to the UndirGraphWriter but the reading method does not depend on the
  /// order of the given commands.
  ///
  /// The reader object suppose that each not readed value does not contain 
  /// whitespaces, therefore it has some extra possibilities to control how
  /// it should skip the values when the string representation contains spaces.
  ///
  /// \code
  /// UndirGraphReader<UndirListGraph> reader(std::cin, graph);
  /// \endcode
  ///
  /// The \c readNodeMap() function reads a map from the \c \@nodeset section.
  /// If there is a map that you do not want to read from the file and there is
  /// whitespace in the string represenation of the values then you should
  /// call the \c skipNodeMap() template member function with proper 
  /// parameters.
  ///
  /// \code
  /// reader.readNodeMap("coords", coords);
  ///
  /// reader.readNodeMap<QuotedStringReader>("label", labelMap);
  /// reader.skipNodeMap<QuotedStringReader>("description");
  ///
  /// reader.readNodeMap("color", colorMap);
  /// \endcode
  ///
  /// With the \c readUndirEdgeMap() member function you can give an 
  /// undir edge map reading command similar to the NodeMaps. 
  ///
  /// \code
  /// reader.readUndirEdgeMap("capacity", capacityMap);
  /// \endcode
  ///
  /// The reading of the directed edge maps is just a syntactical sugar.
  /// It reads two undirected edgemaps into a directed edge map. The 
  /// undirected edge maps' name should be start with the \c '+' and the
  /// \c '-' character and the same.
  ///
  /// \code
  /// reader.readEdgeMap("flow", flowMap);
  /// \endcode 
  ///
  /// With \c readNode() and \c readUndirEdge() functions you can read 
  /// labeled Nodes and UndirEdges.
  ///
  /// \code
  /// reader.readNode("source", sourceNode);
  /// reader.readNode("target", targetNode);
  ///
  /// reader.readUndirEdge("observed", undirEdge);
  /// \endcode
  ///
  /// With the \c readAttribute() functions you can read an attribute
  /// in a variable. You can specify the reader for the attribute as
  /// the nodemaps.
  ///
  /// After you give all read commands you must call the \c run() member
  /// function, which execute all the commands.
  ///
  /// \code
  /// reader.run();
  /// \endcode
  ///
  /// \see GraphReader
  /// \see DefaultReaderTraits
  /// \see \ref UndirGraphWriter
  /// \see \ref graph-io-page
  ///
  /// \author Balazs Dezso
  template <typename _Graph, typename _ReaderTraits = DefaultReaderTraits> 
  class UndirGraphReader {
  public:
    
    typedef _Graph Graph;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;
    typedef typename Graph::UndirEdge UndirEdge;

    typedef _ReaderTraits ReaderTraits;
    typedef typename ReaderTraits::Skipper DefaultSkipper;

    /// \brief Construct a new UndirGraphReader.
    ///
    /// Construct a new UndirGraphReader. It reads into the given graph
    /// and it use the given reader as the default skipper.
    UndirGraphReader(std::istream& _is, Graph& _graph, 
		     const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(new LemonReader(_is)), own_reader(true), skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	undir_edgeset_reader(*reader, _graph, nodeset_reader, 
			     std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	undir_edge_reader(*reader, undir_edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Construct a new UndirGraphReader.
    ///
    /// Construct a new UndirGraphReader. It reads into the given graph
    /// and it use the given reader as the default skipper.
    UndirGraphReader(const std::string& _filename, Graph& _graph, 
		     const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(new LemonReader(_filename)), own_reader(true), 
	skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	undir_edgeset_reader(*reader, _graph, nodeset_reader, 
			     std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	undir_edge_reader(*reader, undir_edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Construct a new UndirGraphReader.
    ///
    /// Construct a new UndirGraphReader. It reads into the given graph
    /// and it use the given reader as the default skipper.
    UndirGraphReader(LemonReader& _reader, Graph& _graph, 
		     const DefaultSkipper& _skipper = DefaultSkipper()) 
      : reader(_reader), own_reader(false), skipper(_skipper),
	nodeset_reader(*reader, _graph, std::string(), skipper),
	undir_edgeset_reader(*reader, _graph, nodeset_reader, 
			     std::string(), skipper),
	node_reader(*reader, nodeset_reader, std::string()),
	undir_edge_reader(*reader, undir_edgeset_reader, std::string()),
	attribute_reader(*reader, std::string()) {}

    /// \brief Destruct the graph reader.
    ///
    /// Destruct the graph reader.
    ~UndirGraphReader() {
      if (own_reader) 
	delete reader;
    }

    /// \brief Give a new node map reading command to the reader.
    ///
    /// Give a new node map reading command to the reader.
    template <typename Map>
    UndirGraphReader& readNodeMap(std::string name, Map& map) {
      nodeset_reader.readNodeMap(name, map);
      return *this;
    }

    template <typename Map>
    UndirGraphReader& readNodeMap(std::string name, const Map& map) {
      nodeset_reader.readNodeMap(name, map);
      return *this;
    }

    /// \brief Give a new node map reading command to the reader.
    ///
    /// Give a new node map reading command to the reader.
    template <typename Reader, typename Map>
    UndirGraphReader& readNodeMap(std::string name, Map& map, 
				  const Reader& reader = Reader()) {
      nodeset_reader.readNodeMap(name, map, reader);
      return *this;
    }

    template <typename Reader, typename Map>
    UndirGraphReader& readNodeMap(std::string name, const Map& map, 
				  const Reader& reader = Reader()) {
      nodeset_reader.readNodeMap(name, map, reader);
      return *this;
    }

    /// \brief Give a new node map skipping command to the reader.
    ///
    /// Give a new node map skipping command to the reader.
    template <typename Reader>
    UndirGraphReader& skipNodeMap(std::string name, 
			     const Reader& reader = Reader()) {
      nodeset_reader.skipNodeMap(name, reader);
      return *this;
    }

    /// \brief Give a new undirected edge map reading command to the reader.
    ///
    /// Give a new undirected edge map reading command to the reader.
    template <typename Map>
    UndirGraphReader& readUndirEdgeMap(std::string name, Map& map) { 
      undir_edgeset_reader.readUndirEdgeMap(name, map);
      return *this;
    }

    template <typename Map>
    UndirGraphReader& readUndirEdgeMap(std::string name, const Map& map) { 
      undir_edgeset_reader.readUndirEdgeMap(name, map);
      return *this;
    }


    /// \brief Give a new undirected edge map reading command to the reader.
    ///
    /// Give a new undirected edge map reading command to the reader.
    template <typename Reader, typename Map>
    UndirGraphReader& readUndirEdgeMap(std::string name, Map& map,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.readUndirEdgeMap(name, map, reader);
      return *this;
    }

    template <typename Reader, typename Map>
    UndirGraphReader& readUndirEdgeMap(std::string name, const Map& map,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.readUndirEdgeMap(name, map, reader);
      return *this;
    }

    /// \brief Give a new undirected edge map skipping command to the reader.
    ///
    /// Give a new undirected edge map skipping command to the reader.
    template <typename Reader>
    UndirGraphReader& skipUndirEdgeMap(std::string name,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.skipUndirMap(name, reader);
      return *this;
    }


    /// \brief Give a new edge map reading command to the reader.
    ///
    /// Give a new edge map reading command to the reader.
    template <typename Map>
    UndirGraphReader& readEdgeMap(std::string name, Map& map) { 
      undir_edgeset_reader.readEdgeMap(name, map);
      return *this;
    }

    template <typename Map>
    UndirGraphReader& readEdgeMap(std::string name, const Map& map) { 
      undir_edgeset_reader.readEdgeMap(name, map);
      return *this;
    }


    /// \brief Give a new edge map reading command to the reader.
    ///
    /// Give a new edge map reading command to the reader.
    template <typename Reader, typename Map>
    UndirGraphReader& readEdgeMap(std::string name, Map& map,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.readEdgeMap(name, map, reader);
      return *this;
    }

    template <typename Reader, typename Map>
    UndirGraphReader& readEdgeMap(std::string name, const Map& map,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.readEdgeMap(name, map, reader);
      return *this;
    }

    /// \brief Give a new edge map skipping command to the reader.
    ///
    /// Give a new edge map skipping command to the reader.
    template <typename Reader>
    UndirGraphReader& skipEdgeMap(std::string name,
				       const Reader& reader = Reader()) {
      undir_edgeset_reader.skipEdgeMap(name, reader);
      return *this;
    }

    /// \brief Give a new labeled node reading command to the reader.
    ///
    /// Give a new labeled node reading command to the reader.
    UndirGraphReader& readNode(std::string name, Node& node) {
      node_reader.readNode(name, node);
      return *this;
    }

    /// \brief Give a new labeled edge reading command to the reader.
    ///
    /// Give a new labeled edge reading command to the reader.
    UndirGraphReader& readEdge(std::string name, Edge& edge) {
      undir_edge_reader.readEdge(name, edge);
    }

    /// \brief Give a new labeled undirected edge reading command to the
    /// reader.
    ///
    /// Give a new labeled undirected edge reading command to the reader.
    UndirGraphReader& readUndirEdge(std::string name, UndirEdge& edge) {
      undir_edge_reader.readUndirEdge(name, edge);
    }

    /// \brief Give a new attribute reading command.
    ///
    ///  Give a new attribute reading command.
    template <typename Value>
    UndirGraphReader& readAttribute(std::string name, Value& value) {
      attribute_reader.readAttribute(name, value);
      return *this;
    }
    
    /// \brief Give a new attribute reading command.
    ///
    ///  Give a new attribute reading command.
    template <typename Reader, typename Value>
    UndirGraphReader& readAttribute(std::string name, Value& value, 
			       const Reader& reader) {
      attribute_reader.readAttribute<Reader>(name, value, reader);
      return *this;
    }

    /// \brief Conversion operator to LemonReader.
    ///
    /// Conversion operator to LemonReader. It make possible
    /// to access the encapsulated \e LemonReader, this way
    /// you can attach to this reader new instances of 
    /// \e LemonReader::SectionReader.
    operator LemonReader&() {
      return *reader;
    }

    /// \brief Executes the reading commands.
    ///
    /// Executes the reading commands.
    void run() {
      reader->run();
    }

    /// \brief Gives back the node by its id.
    ///
    /// It reads an id from the stream and gives back which node belongs to
    /// it. It is possible only if there was read an "id" named node map.
    Node readId(std::istream& is, Node) const {
      return nodeset_reader.readId(is, Node());
    } 

    /// \brief Gives back the edge by its id.
    ///
    /// It reads an id from the stream and gives back which edge belongs to
    /// it. It is possible only if there was read an "id" named edge map.
    Edge readId(std::istream& is, Edge) const {
      return undir_edgeset_reader.readId(is, Edge());
    } 

    /// \brief Gives back the undirected edge by its id.
    ///
    /// It reads an id from the stream and gives back which undirected edge 
    /// belongs to it. It is possible only if there was read an "id" named 
    /// edge map.
    UndirEdge readId(std::istream& is, UndirEdge) const {
      return undir_edgeset_reader.readId(is, UndirEdge());
    } 
    

  private:

    LemonReader* reader;
    bool own_reader;

    DefaultSkipper skipper;

    NodeSetReader<Graph, ReaderTraits> nodeset_reader;
    UndirEdgeSetReader<Graph, ReaderTraits> undir_edgeset_reader;

    NodeReader<Graph> node_reader;
    UndirEdgeReader<Graph> undir_edge_reader;
    
    AttributeReader<ReaderTraits> attribute_reader;
  };

  /// \brief Read an undirected graph from the input.
  ///
  /// It is a helper function to read an undirected graph from the given input
  /// stream. It gives back an UndirGraphReader object and this object
  /// can read more maps, labeled nodes, edges, undirected edges and
  /// attributes.
  ///
  /// \warning Do not forget to call the \c run() function.
  ///
  /// \param is The input stream.
  /// \param g The graph.
  template<typename Graph>
  UndirGraphReader<Graph> undirGraphReader(std::istream& is, Graph &g) {
    return GraphReader<Graph>(is, g);
  }

  /// \brief Read an undirected graph from the input.
  ///
  /// It is a helper function to read an undirected graph from the given input
  /// file. It gives back an UndirGraphReader object and this object
  /// can read more maps, labeled nodes, edges, undirected edges and 
  /// attributes.
  ///
  /// \warning Do not forget to call the \c run() function.
  ///
  /// \param fn The input filename.
  /// \param g The graph.
  template<typename Graph>
  UndirGraphReader<Graph> undirGraphReader(const std::string& fn, Graph &g) {
    return GraphReader<Graph>(fn, g);
  }

  /// @}
}

#endif