/* -*- C++ -*-
 * lemon/lemon_writer.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 Format writer.

#ifndef LEMON_LEMON_WRITER_H
#define LEMON_LEMON_WRITER_H

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
#include <map>
#include <memory>

#include <lemon/error.h>
#include <lemon/invalid.h>
#include <lemon/graph_utils.h>
#include <lemon/bits/item_writer.h>
#include <lemon/utility.h>
#include <lemon/maps.h>

#include <lemon/concept_check.h>
#include <lemon/concept/maps.h>


namespace lemon {

  namespace _writer_bits {
    
    template <typename Item>
    class ItemIdWriter {
    public:

      bool isIdWriter() { return true; }

      void writeId(std::ostream&, const Item&) {}
      
      template <class _ItemIdWriter>
      struct Constraints {
	void constraints() {
	  bool b = writer.isIdWriter();
	  ignore_unused_variable_warning(b);
	  writer.writeId(os, item);
	}
	_ItemIdWriter& writer;
	std::ostream& os;
	const Item& item;
      };

    };

    template <typename Item>
    class ItemWriter {
    public:

      void write(std::ostream&, const Item&) {}
      
      template <class _ItemWriter>
      struct Constraints {
	void constraints() {
	  writer.write(os, item);
	}
	_ItemWriter& writer;
	std::ostream& os;
	const Item& item;
      };

    };

  }

  /// \ingroup io_group
  /// \brief Lemon Format writer class.
  /// 
  /// The Lemon Format contains several sections. We do not want to
  /// determine what sections are in a lemon file we give only a framework
  /// to write a section oriented format.
  ///
  /// In the Lemon Format each section starts with a line contains a \c \@
  /// character on the first not white space position. This line is the
  /// header line of the section. Each next lines belong to this section
  /// while it does not starts with \c \@ character. This line can start a 
  /// new section or if it can close the file with the \c \@end line.
  /// The file format ignore the empty lines and it may contain comments
  /// started with a \c # character to the end of the line. 
  ///
  /// The framework provides an abstract LemonWriter::SectionWriter class
  /// what defines the interface of a SectionWriter. The SectionWriter
  /// has the \c header() member function what gives back the header of the
  /// section. After that it will be called the \c write() member which
  /// should write the content of the section.
  ///
  /// \relates GraphWriter
  /// \relates NodeSetWriter
  /// \relates EdgeSetWriter
  /// \relates NodesWriter
  /// \relates EdgesWriter
  /// \relates AttributeWriter
  class LemonWriter {
  public:

    /// \brief Abstract base class for writing a section.
    ///
    /// This class has an \c header() member function what gives back
    /// the header line of the section. The \c write() member should
    /// write the content of the section to the stream.
    class SectionWriter {
      friend class LemonWriter;
    protected:
      /// \brief Constructor for SectionWriter.
      ///
      /// Constructor for SectionWriter. It attach this writer to
      /// the given LemonWriter.
      SectionWriter(LemonWriter& writer) {
	writer.attach(*this);
      }
      
      virtual ~SectionWriter() {}

      /// \brief The header of section.
      ///
      /// It gives back the header of the section.
      virtual std::string header() = 0;

      /// \brief  Writer function of the section.
      ///
      /// Write the content of the section.
      virtual void write(std::ostream& os) = 0;
    };

    /// \brief Constructor for LemonWriter.
    ///
    /// Constructor for LemonWriter which writes to the given stream.
    LemonWriter(std::ostream& _os) 
      : os(&_os), own_os(false) {}

    /// \brief Constructor for LemonWriter.
    ///
    /// Constructor for LemonWriter which writes to the given file.
    LemonWriter(const std::string& filename) 
      : os(0), own_os(true) {
      os = new std::ofstream(filename.c_str());
    }

    /// \brief Desctructor for LemonWriter.
    ///
    /// Desctructor for LemonWriter.
    ~LemonWriter() {
      if (own_os) {
	delete os;
      }
    }

  private:
    LemonWriter(const LemonWriter&);
    void operator=(const LemonWriter&);

    void attach(SectionWriter& writer) {
      writers.push_back(&writer);
    }

  public:

    /// \brief Executes the LemonWriter.
    /// 
    /// It executes the LemonWriter.
    void run() {
      SectionWriters::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	*os << (*it)->header() << std::endl;
	(*it)->write(*os);
      }
      *os << "@end" << std::endl;
    }


  private:

    std::ostream* os;
    bool own_os;

    typedef std::vector<SectionWriter*> SectionWriters;
    SectionWriters writers;

  };

  /// \brief Helper class for implementing the common SectionWriters.
  ///
  /// Helper class for implementing the common SectionWriters.
  class CommonSectionWriterBase : public LemonWriter::SectionWriter {
    typedef LemonWriter::SectionWriter Parent;
  protected:
    
    /// \brief Constructor for CommonSectionWriterBase.
    ///
    /// Constructor for CommonSectionWriterBase. It attach this writer to
    /// the given LemonWriter.
    CommonSectionWriterBase(LemonWriter& _writer) 
      : Parent(_writer) {}

    template <typename _Item>    
    class WriterBase {
    public:
      typedef _Item Item;

      virtual ~WriterBase() {}

      virtual void write(std::ostream& os, const Item& item) = 0;
    };


    template <typename _Item, typename _Map, typename _Writer>
    class MapWriter : public WriterBase<_Item> {
    public:
      typedef _Map Map;
      typedef _Writer Writer;
      typedef typename Writer::Value Value;
      typedef _Item Item;
      
      typename SmartConstReference<Map>::Type map;
      Writer writer;

      MapWriter(const Map& _map, const Writer& _writer) 
	: map(_map), writer(_writer) {}

      virtual ~MapWriter() {}

      virtual void write(std::ostream& os, const Item& item) {
	Value value = map[item];
	writer.write(os, value);
      }

    };


    class ValueWriterBase {
    public:
      virtual ~ValueWriterBase() {}
      virtual void write(std::ostream&) = 0;
    };

    template <typename _Value, typename _Writer>
    class ValueWriter : public ValueWriterBase {
    public:
      typedef _Value Value;
      typedef _Writer Writer;

      ValueWriter(const Value& _value, const Writer& _writer)
 	: value(_value), writer(_writer) {}

      virtual void write(std::ostream& os) {
	writer.write(os, value);
      }
    private:
      const Value& value;
      Writer writer;
    };
    

    template <typename _Item>
    class IdWriterBase {
    public:
      typedef _Item Item;
      virtual ~IdWriterBase() {}
      virtual void write(std::ostream&, const Item&) const = 0;
      virtual bool isIdWriter() const = 0;
    };

    template <typename _Item, typename _BoxedIdWriter>
    class IdWriter : public IdWriterBase<_Item> {
    public:
      typedef _Item Item;
      typedef _BoxedIdWriter BoxedIdWriter;

      const BoxedIdWriter& idWriter;

      IdWriter(const BoxedIdWriter& _idWriter) 
	: idWriter(_idWriter) {}

      virtual void write(std::ostream& os, const Item& item) const {
	idWriter.writeId(os, item);
      }

      virtual bool isIdWriter() const {
	return idWriter.isIdWriter();
      }
    };
  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing a graph's nodeset.
  ///
  /// The lemon format can store multiple graph nodesets with several maps.
  /// The nodeset section's header line is \c \@nodeset \c nodeset_id, but the
  /// \c nodeset_id may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes a node in the nodeset, and
  /// contains the mapped values for each map.
  ///
  /// If the nodeset contains an \c "id" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c writeId() member will be called with a node it will write it's id.
  /// Otherwise if the \c _forceIdMap constructor parameter is true then
  /// the id map will be the id in the graph.
  ///
  /// \relates LemonWriter
  template <typename _Graph, typename _Traits = DefaultWriterTraits>
  class NodeSetWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;

    /// \brief Constructor.
    ///
    /// Constructor for NodeSetWriter. It creates the NodeSetWriter and
    /// attach it into the given LemonWriter. If the \c _forceIdMap
    /// parameter is true then the writer will write own id map when
    /// the user does not give "id" named map.
    NodeSetWriter(LemonWriter& _writer, const Graph& _graph, 
		  const std::string& _id = std::string(), 
		  bool _forceIdMap = true) 
      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap), 
	graph(_graph), id(_id) {}

    /// \brief Destructor.
    ///
    /// Destructor for NodeSetWriter.
    virtual ~NodeSetWriter() {
      typename MapWriters::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	delete it->second;
      }
    }

  private:
    NodeSetWriter(const NodeSetWriter&);
    void operator=(const NodeSetWriter&);
  
  public:

    /// \brief Add a new node map writer command for the writer.
    ///
    /// Add a new node map writer command for the writer.
    template <typename Map>
    NodeSetWriter& writeNodeMap(std::string name, const Map& map) {
      return writeNodeMap<typename Traits::
	template Writer<typename Map::Value>, Map>(name, map);
    }

    /// \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>
    NodeSetWriter& writeNodeMap(std::string name, const Map& map, 
			    const Writer& writer = Writer()) {
      checkConcept<concept::ReadMap<Node, typename Map::Value>, Map>();
      checkConcept<_writer_bits::ItemWriter<typename Map::Value>, Writer>();
      writers.push_back(
	make_pair(name, new MapWriter<Node, Map, Writer>(map, writer)));
      return *this;
    }

  protected:

    /// \brief The header of the section.
    ///
    /// It gives back the header of the section.
    virtual std::string header() {
      return "@nodeset " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      for (int i = 0; i < (int)writers.size(); ++i) {
	if (writers[i].first == "id") {
	  idMap = writers[i].second;
	  forceIdMap = false;
	  break;
	}
      }
      if (forceIdMap) {
	os << "id\t";
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	os << writers[i].first << '\t';
      }
      os << std::endl;
      for (typename Graph::NodeIt it(graph); it != INVALID; ++it) {
	if (forceIdMap) {
	  os << graph.id(it) << '\t';
	}
	for (int i = 0; i < (int)writers.size(); ++i) {
	  writers[i].second->write(os, it);
	  os << '\t';
	}
	os << std::endl;
      }
    }

  public:

    /// \brief Returns true if the nodeset can write the ids of the nodes.
    ///
    /// Returns true if the nodeset can write the ids of the nodes.
    /// It is possible only if an "id" named map was written or the 
    /// \c _forceIdMap constructor parameter was true.
    bool isIdWriter() const {
      return idMap != 0 || forceIdMap;
    }

    /// \brief Write the id of the given node.
    ///
    /// It writes the id of the given node. If there was written an "id"
    /// named map then it will write the map value belongs to the node.
    /// Otherwise if the \c forceId parameter was true it will write
    /// its id in the graph. 
    void writeId(std::ostream& os, const Node& item) const {
      if (forceIdMap) {
	os << graph.id(item);
      } else {
	idMap->write(os, item);
      }
    }

  private:

    typedef std::vector<std::pair<std::string, WriterBase<Node>*> > MapWriters;
    MapWriters writers;

    WriterBase<Node>* idMap;
    bool forceIdMap;
   
    typename SmartConstReference<Graph>::Type graph;   
    std::string id;

  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing a graph's edgesets.
  ///
  /// The lemon format can store multiple graph edgesets with several maps. 
  /// The edgeset section's header line is \c \@edgeset \c edgeset_id, but the
  /// \c edgeset_id may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes a edge in the edgeset. The
  /// line contains the source and the target nodes' id and the mapped 
  /// values for each map.
  ///
  /// If the edgeset contains an \c "id" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c writeId() member will be called with an edge it will write it's id.
  /// Otherwise if the \c _forceIdMap constructor parameter is true then
  /// the id map will be the id in the graph.
  ///
  /// The edgeset writer needs a node id writer to identify which nodes
  /// have to be connected. If a NodeSetWriter can write the nodes' id,
  /// it will be able to use with this class.
  ///
  /// \relates LemonWriter
  template <typename _Graph, typename _Traits = DefaultWriterTraits>
  class EdgeSetWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;

    /// \brief Constructor.
    ///
    /// Constructor for EdgeSetWriter. It creates the EdgeSetWriter and
    /// attach it into the given LemonWriter. It will write node ids by
    /// the \c _nodeIdWriter. If the \c _forceIdMap parameter is true 
    /// then the writer will write own id map if the user does not give 
    /// "id" named map.
    template <typename NodeIdWriter>
    EdgeSetWriter(LemonWriter& _writer, const Graph& _graph, 
		  const NodeIdWriter& _nodeIdWriter, 
		  const std::string& _id = std::string(),
		  bool _forceIdMap = true)
      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap),
	graph(_graph), id(_id) {
      checkConcept<_writer_bits::ItemIdWriter<Node>, NodeIdWriter>();
      nodeIdWriter.reset(new IdWriter<Node, NodeIdWriter>(_nodeIdWriter));
    } 

    /// \brief Destructor.
    ///
    /// Destructor for EdgeSetWriter.
    virtual ~EdgeSetWriter() {
      typename MapWriters::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	delete it->second;
      }
    }

  private:
    EdgeSetWriter(const EdgeSetWriter&);
    void operator=(const EdgeSetWriter&);

  public:

    /// \brief Add a new edge map writer command for the writer.
    ///
    /// Add a new edge map writer command for the writer.
    template <typename Map>
    EdgeSetWriter& writeEdgeMap(std::string name, const Map& map) {
      return writeEdgeMap<typename Traits::
	template Writer<typename Map::Value>, Map>(name, map);
    }

    /// \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>
    EdgeSetWriter& writeEdgeMap(std::string name, const Map& map, 
			    const Writer& writer = Writer()) {
      checkConcept<concept::ReadMap<Edge, typename Map::Value>, Map>();
      checkConcept<_writer_bits::ItemWriter<typename Map::Value>, Writer>();
      writers.push_back(
	make_pair(name, new MapWriter<Edge, Map, Writer>(map, writer)));
      return *this;
    }

  protected:

    /// \brief The header of the section.
    ///
    /// It gives back the header of the section.
    virtual std::string header() {
      return "@edgeset " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      if (!nodeIdWriter->isIdWriter()) {
	throw DataFormatError("Cannot find nodeset or ID map");
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	if (writers[i].first == "id") {
	  idMap = writers[i].second;
	  forceIdMap = false;
	  break;
	}
      }
      os << "\t\t";
      if (forceIdMap) {
	os << "id\t";
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	os << writers[i].first << '\t';
      }
      os << std::endl;
      for (typename Graph::EdgeIt it(graph); it != INVALID; ++it) {
	nodeIdWriter->write(os, graph.source(it));
	os << '\t';
	nodeIdWriter->write(os, graph.target(it));
	os << '\t';
	if (forceIdMap) {
	  os << graph.id(it) << '\t';
	}
	for (int i = 0; i < (int)writers.size(); ++i) {
	  writers[i].second->write(os, it);
	  os << '\t';
	}
	os << std::endl;
      }
    }

  public:

    /// \brief Returns true if the edgeset can write the ids of the edges.
    ///
    /// Returns true if the edgeset can write the ids of the edges.
    /// It is possible only if an "id" named map was written or the 
    /// \c _forceIdMap constructor parameter was true.
    bool isIdWriter() const {
      return forceIdMap || idMap != 0;
    }

    /// \brief Write the id of the given edge.
    ///
    /// It writes the id of the given edge. If there was written an "id"
    /// named map then it will write the map value belongs to the edge.
    /// Otherwise if the \c forceId parameter was true it will write
    /// its id in the graph. 
    void writeId(std::ostream& os, const Edge& item) const {
      if (forceIdMap) {
	os << graph.id(item);
      } else {
	idMap->write(os, item);
      }
    } 

  private:

    typedef std::vector<std::pair<std::string, WriterBase<Edge>*> > MapWriters;
    MapWriters writers;

    WriterBase<Edge>* idMap;
    bool forceIdMap;
   
    typename SmartConstReference<Graph>::Type graph;   
    std::string id;

    std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;
  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing a undirected edgeset.
  ///
  /// The lemon format can store multiple undirected edgesets with several 
  /// maps. The undirected edgeset section's header line is \c \@undiredgeset 
  /// \c undiredgeset_id, but the \c undiredgeset_id may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes an undirected edge in the 
  /// edgeset. The line contains the two connected nodes' id and the mapped 
  /// values for each undirected map.
  ///
  /// The section can handle the directed as a syntactical sugar. Two
  /// undirected edge map describes one directed edge map. This two maps
  /// are the forward map and the backward map and the names of this map
  /// is near the same just with a prefix \c '+' or \c '-' character 
  /// difference.
  ///
  /// If the edgeset contains an \c "id" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c writeId() member will be called with an undirected edge it will 
  /// write it's id. Otherwise if the \c _forceIdMap constructor parameter
  /// is true then the id map will be the id in the graph.
  ///
  /// The undirected edgeset writer needs a node id writer to identify 
  /// which nodes have to be connected. If a NodeSetWriter can write the 
  /// nodes' id, it will be able to use with this class.
  ///
  /// \relates LemonWriter
  template <typename _Graph, typename _Traits = DefaultWriterTraits>
  class UndirEdgeSetWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;
    typedef typename Graph::UndirEdge UndirEdge;

    /// \brief Constructor.
    ///
    /// Constructor for UndirEdgeSetWriter. It creates the UndirEdgeSetWriter
    /// and attach it into the given LemonWriter. It will write node ids by
    /// the \c _nodeIdWriter. If the \c _forceIdMap parameter is true 
    /// then the writer will write own id map if the user does not give 
    /// "id" named map.
    template <typename NodeIdWriter>
    UndirEdgeSetWriter(LemonWriter& _writer, const Graph& _graph, 
		       const NodeIdWriter& _nodeIdWriter, 
		       const std::string& _id = std::string(),
		       bool _forceIdMap = true)
      : Parent(_writer), idMap(0), forceIdMap(_forceIdMap),
	graph(_graph), id(_id) {
      checkConcept<_writer_bits::ItemIdWriter<Node>, NodeIdWriter>();
      nodeIdWriter.reset(new IdWriter<Node, NodeIdWriter>(_nodeIdWriter));
    } 

    /// \brief Destructor.
    ///
    /// Destructor for UndirEdgeSetWriter.
    virtual ~UndirEdgeSetWriter() {
      typename MapWriters::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	delete it->second;
      }
    }

  private:
    UndirEdgeSetWriter(const UndirEdgeSetWriter&);
    void operator=(const UndirEdgeSetWriter&);

  public:

    /// \brief Add a new undirected edge map writer command for the writer.
    ///
    /// Add a new undirected map writer command for the writer.
    template <typename Map>
    UndirEdgeSetWriter& writeUndirEdgeMap(std::string name, const Map& map) {
      return writeUndirEdgeMap<typename Traits::
	template Writer<typename Map::Value>, Map>(name, map);
    }

    /// \brief Add a new undirected map writer command for the writer.
    ///
    /// Add a new undirected map writer command for the writer.
    template <typename Writer, typename Map>
    UndirEdgeSetWriter& writeUndirEdgeMap(std::string name, const Map& map, 
					  const Writer& writer = Writer()) {
      checkConcept<concept::ReadMap<UndirEdge, typename Map::Value>, Map>();
      checkConcept<_writer_bits::ItemWriter<typename Map::Value>, Writer>();
      writers.push_back(
	make_pair(name, new MapWriter<UndirEdge, Map, Writer>(map, writer)));
      return *this;
    }

    /// \brief Add a new directed edge map writer command for the writer.
    ///
    /// Add a new directed map writer command for the writer.
    template <typename Map>
    UndirEdgeSetWriter& writeEdgeMap(std::string name, const Map& map) {
      return writeEdgeMap<typename Traits::
	template Writer<typename Map::Value>, Map>(name, map);
    }

    /// \brief Add a new directed map writer command for the writer.
    ///
    /// Add a new directed map writer command for the writer.
    template <typename Writer, typename Map>
    UndirEdgeSetWriter& writeEdgeMap(std::string name, const Map& map, 
				     const Writer& writer = Writer()) {
      checkConcept<concept::ReadMap<Edge, typename Map::Value>, Map>();
      checkConcept<_writer_bits::ItemWriter<typename Map::Value>, Writer>();
      writeUndirEdge("+" + name, composeMap(forwardMap(graph), map), writer);
      writeUndirEdge("-" + name, composeMap(backwardMap(graph), map), writer);
      return *this;
    }

  protected:

    /// \brief The header of the section.
    ///
    /// It gives back the header of the section.
    virtual std::string header() {
      return "@undiredgeset " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      if (!nodeIdWriter->isIdWriter()) {
	throw DataFormatError("Cannot find nodeset or ID map");
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	if (writers[i].first == "id") {
	  idMap = writers[i].second;
	  forceIdMap = false;
	  break;
	}
      }
      os << "\t\t";
      if (forceIdMap) {
	os << "id\t";
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	os << writers[i].first << '\t';
      }
      os << std::endl;
      for (typename Graph::UndirEdgeIt it(graph); it != INVALID; ++it) {
	nodeIdWriter->write(os, graph.source(it));
	os << '\t';
	nodeIdWriter->write(os, graph.target(it));
	os << '\t';
	if (forceIdMap) {
	  os << graph.id(it) << '\t';
	}
	for (int i = 0; i < (int)writers.size(); ++i) {
	  writers[i].second->write(os, it);
	  os << '\t';
	}
	os << std::endl;
      }
    }

  public:

    /// \brief Returns true if the undirected edgeset can write the ids of 
    /// the edges.
    ///
    /// Returns true if the undirected edgeset can write the ids of the 
    /// undirected edges. It is possible only if an "id" named map was 
    /// written or the \c _forceIdMap constructor parameter was true.
    bool isIdWriter() const {
      return forceIdMap || idMap != 0;
    }

    /// \brief Write the id of the given undirected edge.
    ///
    /// It writes the id of the given undirected edge. If there was written 
    /// an "id" named map then it will write the map value belongs to the 
    /// undirected edge. Otherwise if the \c forceId parameter was true it 
    /// will write its id in the graph. 
    void writeId(std::ostream& os, const UndirEdge& item) const {
      if (forceIdMap) {
	os << graph.id(item);
      } else {
	idMap->write(os, item);
      }
    } 

    /// \brief Write the id of the given edge.
    ///
    /// It writes the id of the given edge. If there was written 
    /// an "id" named map then it will write the map value belongs to the 
    /// edge. Otherwise if the \c forceId parameter was true it 
    /// will write its id in the graph. If the edge is forward map
    /// then its prefix character is \c '+' elsewhere \c '-'.
    void writeId(std::ostream& os, const Edge& item) const {
      if (graph.forward(item)) {
	os << "+ ";
      } else {
	os << "- ";
      }
      if (forceIdMap) {
	os << graph.id(item);
      } else {
	idMap->write(os, item);
      }
    } 

  private:

    typedef std::vector<std::pair<std::string, 
				  WriterBase<UndirEdge>*> > MapWriters;
    MapWriters writers;

    WriterBase<UndirEdge>* idMap;
    bool forceIdMap;
   
    typename SmartConstReference<Graph>::Type graph;   
    std::string id;

    std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;
  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing labeled nodes.
  ///
  /// The nodes section's header line is \c \@nodes \c nodes_id, but the
  /// \c nodes_id may be empty.
  ///
  /// Each line in the section contains the label of the node and 
  /// then the node id. 
  ///
  /// \relates LemonWriter
  template <typename _Graph>
  class NodeWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
    typedef _Graph Graph;
    typedef typename Graph::Node Node;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for NodeWriter. It creates the NodeWriter and
    /// attach it into the given LemonWriter. The given \c _IdWriter
    /// will write the nodes' id what can be a nodeset writer.
    template <typename _IdWriter>
    NodeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
	       const std::string& _id = std::string()) 
      : Parent(_writer), id(_id) {
      checkConcept<_writer_bits::ItemIdWriter<Node>, _IdWriter>();
      idWriter.reset(new IdWriter<Node, _IdWriter>(_idWriter));
    }


    /// \brief Destructor.
    ///
    /// Destructor for NodeWriter.
    virtual ~NodeWriter() {}

  private:
    NodeWriter(const NodeWriter&);
    void operator=(const NodeWriter&);

  public:

    /// \brief Add a node writer command for the NodeWriter.
    ///
    /// Add a node writer command for the NodeWriter.
    void writeNode(const std::string& name, const Node& item) {
      writers.push_back(make_pair(name, &item));
    }

  protected:

    /// \brief Header checking function.
    ///
    /// It gives back true when the header line start with \c \@nodes,
    /// and the header line's id and the writer's id are the same.
    virtual std::string header() {
      return "@nodes " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      if (!idWriter->isIdWriter()) {
	throw DataFormatError("Cannot find nodeset or ID map");
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	os << writers[i].first << ' ';
	idWriter->write(os, *(writers[i].second));
	os << std::endl;
      }
    }
    
  private:

    std::string id;

    typedef std::vector<std::pair<std::string, const Node*> > NodeWriters;
    NodeWriters writers;
    std::auto_ptr<IdWriterBase<Node> > idWriter;
  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing labeled edges.
  ///
  /// The edges section's header line is \c \@edges \c edges_id, but the
  /// \c edges_id may be empty.
  ///
  /// Each line in the section contains the label of the edge and 
  /// then the edge id. 
  ///
  /// \relates LemonWriter
  template <typename _Graph>
  class EdgeWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
    typedef _Graph Graph;
    typedef typename Graph::Edge Edge;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for EdgeWriter. It creates the EdgeWriter and
    /// attach it into the given LemonWriter. The given \c _IdWriter
    /// will write the edges' id what can be a edgeset writer.
    template <typename _IdWriter>
    EdgeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
	       const std::string& _id = std::string()) 
      : Parent(_writer), id(_id) {
      checkConcept<_writer_bits::ItemIdWriter<Edge>, _IdWriter>();
      idWriter.reset(new IdWriter<Edge, _IdWriter>(_idWriter));
    }

    /// \brief Destructor.
    ///
    /// Destructor for EdgeWriter.
    virtual ~EdgeWriter() {}
  private:
    EdgeWriter(const EdgeWriter&);
    void operator=(const EdgeWriter&);

  public:

    /// \brief Add an edge writer command for the EdgeWriter.
    ///
    /// Add an edge writer command for the EdgeWriter.
    void writeEdge(const std::string& name, const Edge& item) {
      writers.push_back(make_pair(name, &item));
    }

  protected:

    /// \brief Header checking function.
    ///
    /// It gives back true when the header line start with \c \@edges,
    /// and the header line's id and the writer's id are the same.
    virtual std::string header() {
      return "@edges " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      if (!idWriter->isIdWriter()) {
	throw DataFormatError("Cannot find edgeset or ID map");
      }
      for (int i = 0; i < (int)writers.size(); ++i) {
	os << writers[i].first << ' ';
	idWriter->write(os, *(writers[i].second));
	os << std::endl;
      }
    }
    
  private:

    std::string id;

    typedef std::vector<std::pair<std::string, const Edge*> > EdgeWriters;
    EdgeWriters writers;

    std::auto_ptr<IdWriterBase<Edge> > idWriter;
  };

  /// \ingroup io_group
  /// \brief SectionWriter for writing labeled undirected edges.
  ///
  /// The undirected edges section's header line is \c \@undiredges 
  /// \c undiredges_id, but the \c undiredges_id may be empty.
  ///
  /// Each line in the section contains the label of the undirected edge and 
  /// then the undirected edge id. 
  ///
  /// \relates LemonWriter
  template <typename _Graph>
  class UndirEdgeWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
    typedef _Graph Graph;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;
    typedef typename Graph::UndirEdge UndirEdge;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for UndirEdgeWriter. It creates the UndirEdgeWriter and
    /// attach it into the given LemonWriter. The given \c _IdWriter
    /// will write the undirected edges' id what can be an undirected 
    /// edgeset writer.
    template <typename _IdWriter>
    UndirEdgeWriter(LemonWriter& _writer, const _IdWriter& _idWriter, 
	       const std::string& _id = std::string()) 
      : Parent(_writer), id(_id) {
      checkConcept<_writer_bits::ItemIdWriter<Edge>, _IdWriter>();
      checkConcept<_writer_bits::ItemIdWriter<UndirEdge>, _IdWriter>();
      undirEdgeIdWriter.reset(new IdWriter<UndirEdge, _IdWriter>(_idWriter));
      edgeIdWriter.reset(new IdWriter<Edge, _IdWriter>(_idWriter));
    }

    /// \brief Destructor.
    ///
    /// Destructor for UndirEdgeWriter.
    virtual ~UndirEdgeWriter() {}
  private:
    UndirEdgeWriter(const UndirEdgeWriter&);
    void operator=(const UndirEdgeWriter&);

  public:

    /// \brief Add an edge writer command for the UndirEdgeWriter.
    ///
    /// Add an edge writer command for the UndirEdgeWriter.
    void writeEdge(const std::string& name, const Edge& item) {
      edgeWriters.push_back(make_pair(name, &item));
    }

    /// \brief Add an undirected edge writer command for the UndirEdgeWriter.
    ///
    /// Add an undirected edge writer command for the UndirEdgeWriter.
    void writeUndirEdge(const std::string& name, const UndirEdge& item) {
      undirEdgeWriters.push_back(make_pair(name, &item));
    }

  protected:

    /// \brief Header checking function.
    ///
    /// It gives back true when the header line start with \c \@undiredges,
    /// and the header line's id and the writer's id are the same.
    virtual std::string header() {
      return "@undiredges " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    virtual void write(std::ostream& os) {
      if (!edgeIdWriter->isIdWriter()) {
	throw DataFormatError("Cannot find undirected edgeset or ID map");
      }
      if (!undirEdgeIdWriter->isIdWriter()) {
	throw DataFormatError("Cannot find undirected edgeset or ID map");
      }
      for (int i = 0; i < (int)undirEdgeWriters.size(); ++i) {
	os << undirEdgeWriters[i].first << ' ';
	undirEdgeIdWriter->write(os, *(undirEdgeWriters[i].second));
	os << std::endl;
      }
      for (int i = 0; i < (int)edgeWriters.size(); ++i) {
	os << edgeWriters[i].first << ' ';
	edgeIdWriter->write(os, *(edgeWriters[i].second));
	os << std::endl;
      }
    }
    
  private:

    std::string id;

    typedef std::vector<std::pair<std::string, 
				  const UndirEdge*> > UndirEdgeWriters;
    UndirEdgeWriters undirEdgeWriters;
    std::auto_ptr<IdWriterBase<UndirEdge> > undirEdgeIdWriter;

    typedef std::vector<std::pair<std::string, const Edge*> > EdgeWriters;
    EdgeWriters edgeWriters;
    std::auto_ptr<IdWriterBase<Edge> > edgeIdWriter;

  };

  /// \ingroup io_group
  /// \brief SectionWriter for attributes.
  ///
  /// The lemon format can store multiple attribute set. Each set has
  /// the header line \c \@attributes \c attributeset_id, but the 
  /// attributeset_id may be empty.
  ///
  /// The attributeset section contains several lines. Each of them starts
  /// with the name of attribute and then the value.
  ///
  /// \relates LemonWriter
  template <typename _Traits = DefaultWriterTraits>
  class AttributeWriter : public CommonSectionWriterBase {
    typedef CommonSectionWriterBase Parent;
    typedef _Traits Traits; 
  public:
    /// \brief Constructor.
    ///
    /// Constructor for AttributeWriter. It creates the AttributeWriter and
    /// attach it into the given LemonWriter.
    AttributeWriter(LemonWriter& _writer, 
		    const std::string& _id = std::string()) 
      : Parent(_writer), id(_id) {}

    /// \brief Destructor.
    ///
    /// Destructor for AttributeWriter.
    virtual ~AttributeWriter() {
      typename Writers::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	delete it->second;
      }
    }

  private:
    AttributeWriter(const AttributeWriter&);
    void operator=(AttributeWriter&);

  public:
    /// \brief Add an attribute writer command for the writer.
    ///
    /// Add an attribute writer command for the writer.
    template <typename Value>
    AttributeWriter& writeAttribute(const std::string& id, 
				    const Value& value) {
      return 
	writeAttribute<typename Traits::template Writer<Value> >(id, value);
    }

    /// \brief Add an attribute writer command for the writer.
    ///
    /// Add an attribute writer command for the writer.
    template <typename Writer, typename Value>
    AttributeWriter& writeAttribute(const std::string& name, 
				    const Value& value,
				    const Writer& writer = Writer()) {
      checkConcept<_writer_bits::ItemWriter<Value>, Writer>();
      writers.push_back(make_pair(name, new ValueWriter<Value, Writer>
      			       (value, writer)));
      return *this;
    }

  protected:

    /// \brief The header of section.
    ///
    /// It gives back the header of the section.
    std::string header() {
      return "@attributes " + id;
    }

    /// \brief  Writer function of the section.
    ///
    /// Write the content of the section.
    void write(std::ostream& os) {
      typename Writers::iterator it;
      for (it = writers.begin(); it != writers.end(); ++it) {
	os << it->first << ' ';
	it->second->write(os);
	os << std::endl;
      }
    }    

  private:
    std::string id;

    typedef std::vector<std::pair<std::string, ValueWriterBase*> > Writers;
    Writers writers;  
  };


}
#endif