/* -*- C++ -*-

  * lemon/lemon_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 Format reader.

 #ifndef LEMON_LEMON_READER_H

 #define LEMON_LEMON_READER_H

 #include <iostream>

 #include <fstream>

 #include <string>

 #include <vector>

 #include <algorithm>

 #include <map>

 #include <memory>

 #include <lemon/error.h>

 #include <lemon/graph_utils.h>

 #include <lemon/utility.h>

 #include <lemon/bits/item_reader.h>

 #include <lemon/concept_check.h>

 #include <lemon/concept/maps.h>

 namespace lemon {

   namespace _reader_bits {

     template <typename Item>

     class ItemIdReader {

     public:

       bool isIdReader() { return true; }

       void readId(std::istream&, Item&) {}

       template <class _ItemIdReader>

       struct Constraints {

 	void constraints() {

 	  bool b = reader.isIdReader();

 	  ignore_unused_variable_warning(b);

 	  Item item;

 	  reader.readId(is, item);

 	}

 	_ItemIdReader& reader;

 	std::istream& is;

       };

     };

     template <typename Item>

     class ItemReader {

     public:

       void read(std::istream&, Item&) {}

       template <class _ItemReader>

       struct Constraints {

 	void constraints() {

 	  Item item;

 	  reader.read(is, item);

 	}

 	_ItemReader& reader;

 	std::istream& is;

       };

     };

     template <typename T>

     bool operator<(T, T) {

       throw DataFormatError("Id is not comparable");

     }

     template <typename T>

     struct Less {

       bool operator()(const T& p, const T& q) const {

 	return p < q;

       }

     };

     template <typename M1, typename M2>

     class WriteComposeMap {

     public:

       typedef True NeedCopy;

       typedef typename M2::Key Key;

       typedef typename M1::Value Value;

       WriteComposeMap(typename SmartParameter<M1>::Type _m1, const M2& _m2) 

 	: m1(_m1), m2(_m2) {}

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

 	m1.set(m2[key], value);

       }

     private:

       typename SmartReference<M1>::Type m1;

       typename SmartConstReference<M2>::Type m2;

     };

     template <typename M1, typename M2>

     WriteComposeMap<M1, M2> writeComposeMap(M1& m1, const M2& m2) {

       return WriteComposeMap<M1, M2>(m1, m2);

     }

     template <typename M1, typename M2>

     WriteComposeMap<M1, M2> writeComposeMap(const M1& m1, const M2& m2) {

       return WriteComposeMap<M1, M2>(m1, m2);

     }

   }

   /// \ingroup io_group

   /// \brief Lemon Format reader 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 read 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 and comment lines. The line is

   /// comment line if it starts with a \c # character. 

   ///

   /// The framework provides an abstract LemonReader::SectionReader class

   /// what defines the interface of a SectionReader. The SectionReader

   /// has the \c header() member function what get a header line string and

   /// decides if it want to process the next section. Several SectionReaders

   /// can be attached to an LemonReader and the first attached what can

   /// process the section will be used. Its \c read() member will called

   /// with a stream contains the section. From this stream the empty and

   /// comment lines are filtered out.

   ///

   /// \relates GraphReader

   /// \relates NodeSetReader

   /// \relates EdgeSetReader

   /// \relates NodesReader

   /// \relates EdgesReader

   /// \relates AttributeReader

   class LemonReader {

   private:

     class FilterStreamBuf : public std::streambuf {

     public:

       typedef std::streambuf Parent;

       typedef Parent::char_type char_type;

       FilterStreamBuf(std::istream& is, int& num) 

 	: _is(is), _base(0), _eptr(0), 

 	  _num(num), skip_state(after_endl) {}

     protected:

       enum skip_state_type {

 	no_skip,

 	after_endl,

 	comment_line

       };

       char_type small_buf[1];

       std::istream& _is;

       char_type* _base;

       char_type* _eptr;

       int& _num;

       skip_state_type skip_state;

       char_type* base() { return _base; }

       char_type* eptr() { return _eptr; }

       int blen() { return _eptr - _base; }

       void setb(char_type* buf, int len) {

 	_base = buf;

 	_eptr = buf + len;

       }

       virtual std::streambuf* setbuf(char *buf, int len) {

 	if (base()) return 0;

 	if (buf != 0 && len >= (int)sizeof(small_buf)) {

 	  setb(buf, len);

 	} else {

 	  setb(small_buf, sizeof(small_buf));

 	}

 	setg(0, 0, 0);

 	return this;

       }

       bool put_char(char c) {

 	switch (skip_state) {

 	case no_skip:

 	  switch (c) {

 	  case '\n': 

 	    skip_state = after_endl;

 	    return true;

 	  default:

 	    return true;

 	  }

 	case after_endl:

 	  switch (c) {

 	  case '@':

 	    return false;

 	  case '\n': 

 	    return false;

 	  case '#':

 	    skip_state = comment_line;

 	    return false;

 	  default:

 	    if (!isspace(c)) {

 	      skip_state = no_skip;

 	      return true;

 	    } else {

 	      return false;

 	    }

 	  }

 	  break;

 	case comment_line:

 	  switch (c) {

 	  case '\n': 

 	    skip_state = after_endl;

 	    return false;

 	  default:

 	    return false;

 	  }

 	}

 	return false;

       }

       virtual int underflow() {

 	char c;

 	if (_is.read(&c, 1)) {

 	  _is.putback(c);

 	  if (c == '@') {

 	    return EOF;

 	  }

 	} else {

 	  return EOF;

 	}

 	char_type *ptr;

 	for (ptr = base(); ptr != eptr(); ++ptr) {

 	  if (_is.read(&c, 1)) {

 	    if (c == '\n') ++_num;

 	    if (put_char(c)) {

 	      *ptr = c;

 	    } else {

 	      if (skip_state == after_endl && c == '@') {

 		_is.putback('@');

 		break;

 	      }

 	      --ptr;

 	    }

 	  } else {

 	    break;

 	  }

 	}

 	setg(base(), base(), ptr);

 	return *base();

       }

       virtual int sync() {

 	return EOF;

       }

     };

   public:

     /// \brief Abstract base class for reading a section.

     ///

     /// This class has an \c header() member function what get a 

     /// header line string and decides if it want to process the next 

     /// section. Several SectionReaders can be attached to an LemonReader 

     /// and the first attached what can process the section will be used. 

     /// Its \c read() member will called with a stream contains the section. 

     /// From this stream the empty lines and comments are filtered out.

     class SectionReader {

       friend class LemonReader;

     protected:

       /// \brief Constructor for SectionReader.

       ///

       /// Constructor for SectionReader. It attach this reader to

       /// the given LemonReader.

       SectionReader(LemonReader& reader) {

 	reader.attach(*this);

       }

       /// \brief Gives back true when the SectionReader can process 

       /// the section with the given header line.

       ///

       /// It gives back true when the SectionReader can process

       /// the section with the given header line.

       virtual bool header(const std::string& line) = 0;

       /// \brief Reader function of the section.

       ///

       /// It reads the content of the section.

       virtual void read(std::istream& is) = 0;

     };

     /// \brief Constructor for LemonReader.

     ///

     /// Constructor for LemonReader which reads from the given stream.

     LemonReader(std::istream& _is) 

       : is(&_is), own_is(false) {}

     /// \brief Constructor for LemonReader.

     ///

     /// Constructor for LemonReader which reads from the given file.

     LemonReader(const std::string& filename) 

       : is(0), own_is(true) {

       is = new std::ifstream(filename.c_str());

     }

     /// \brief Desctructor for LemonReader.

     ///

     /// Desctructor for LemonReader.

     ~LemonReader() {

       if (own_is) {

 	delete is;

       }

     }

   private:

     LemonReader(const LemonReader&);

     void operator=(const LemonReader&);

     void attach(SectionReader& reader) {

       readers.push_back(&reader);

     }

   public:

     /// \brief Executes the LemonReader.

     /// 

     /// It executes the LemonReader.

     void run() {

       int line_num = 0;

       std::string line;

       try {

 	while ((++line_num, getline(*is, line)) && line.find("@end") != 0) {

 	  SectionReaders::iterator it;

 	  for (it = readers.begin(); it != readers.end(); ++it) {

 	    if ((*it)->header(line)) {

 	      char buf[2048];

 	      FilterStreamBuf buffer(*is, line_num);

 	      buffer.pubsetbuf(buf, sizeof(buf));

 	      std::istream is(&buffer);

 	      (*it)->read(is);

 	      break;

 	    }

 	  }

 	}

       } catch (DataFormatError& error) {

 	error.line(line_num);

 	throw error;

       }	

     }

   private:

     std::istream* is;

     bool own_is;

     typedef std::vector<SectionReader*> SectionReaders;

     SectionReaders readers;

   };

   /// \brief Helper class for implementing the common SectionReaders.

   ///

   /// Helper class for implementing the common SectionReaders.

   class CommonSectionReaderBase : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   protected:

     /// \brief Constructor for CommonSectionReaderBase.

     ///

     /// Constructor for CommonSectionReaderBase. It attach this reader to

     /// the given LemonReader.

     CommonSectionReaderBase(LemonReader& _reader) 

       : Parent(_reader) {}

     template <typename _Item>

     class ReaderBase;

     template <typename _Item>

     class InverterBase : public ReaderBase<_Item> {

     public:

       typedef _Item Item;

       virtual void read(std::istream&, const Item&) = 0;

       virtual Item read(std::istream&) const = 0;

       virtual InverterBase<_Item>* getInverter() {

 	return this;

       }

     };

     template <typename _Item, typename _Map, typename _Reader>

     class MapReaderInverter : public InverterBase<_Item> {

     public:

       typedef _Item Item;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Map Map;

       typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

       typename SmartReference<Map>::Type map;

       Reader reader;

       Inverse inverse;

       MapReaderInverter(typename SmartParameter<Map>::Type _map,

 			const Reader& _reader) 

 	: map(_map), reader(_reader) {}

       virtual ~MapReaderInverter() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	map.set(item, value);

 	typename Inverse::iterator it = inverse.find(value);

 	if (it == inverse.end()) {

 	  inverse.insert(std::make_pair(value, item));

 	} else {

 	  throw DataFormatError("Multiple ID occurence");

 	}

       }

       virtual Item read(std::istream& is) const {

 	Value value;

 	reader.read(is, value);	

 	typename Inverse::const_iterator it = inverse.find(value);

 	if (it != inverse.end()) {

 	  return it->second;

 	} else {

 	  throw DataFormatError("Invalid ID error");

 	}

       }      

     };

     template <typename _Item, typename _Reader>

     class SkipReaderInverter : public InverterBase<_Item> {

     public:

       typedef _Item Item;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

       Reader reader;

       SkipReaderInverter(const Reader& _reader) 

 	: reader(_reader) {}

       virtual ~SkipReaderInverter() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	typename Inverse::iterator it = inverse.find(value);

 	if (it == inverse.end()) {

 	  inverse.insert(std::make_pair(value, item));

 	} else {

 	  throw DataFormatError("Multiple ID occurence error");

 	}

       }

       virtual Item read(std::istream& is) const {

 	Value value;

 	reader.read(is, value);	

 	typename Inverse::const_iterator it = inverse.find(value);

 	if (it != inverse.end()) {

 	  return it->second;

 	} else {

 	  throw DataFormatError("Invalid ID error");

 	}

       }

     private:

       Inverse inverse;

     };

     template <typename _Item>    

     class ReaderBase {

     public:

       typedef _Item Item;

       virtual ~ReaderBase() {}

       virtual void read(std::istream& is, const Item& item) = 0;

       virtual InverterBase<_Item>* getInverter() = 0;

     };

     template <typename _Item, typename _Map, typename _Reader>

     class MapReader : public ReaderBase<_Item> {

     public:

       typedef _Map Map;

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Item Item;

       typename SmartReference<Map>::Type map;

       Reader reader;

       MapReader(typename SmartParameter<Map>::Type _map, 

 		const Reader& _reader) 

 	: map(_map), reader(_reader) {}

       virtual ~MapReader() {}

       virtual void read(std::istream& is, const Item& item) {

 	Value value;

 	reader.read(is, value);

 	map.set(item, value);

       }

       virtual InverterBase<_Item>* getInverter() {

 	return new MapReaderInverter<Item, Map, Reader>(map, reader);

       }

     };

     template <typename _Item, typename _Reader>

     class SkipReader : public ReaderBase<_Item> {

     public:

       typedef _Reader Reader;

       typedef typename Reader::Value Value;

       typedef _Item Item;

       Reader reader;

       SkipReader(const Reader& _reader) : reader(_reader) {}

       virtual ~SkipReader() {}

       virtual void read(std::istream& is, const Item&) {

 	Value value;

 	reader.read(is, value);

       }      

       virtual InverterBase<Item>* getInverter() {

 	return new SkipReaderInverter<Item, Reader>(reader);

       }

     };

     template <typename _Item>

     class IdReaderBase {

     public:

       typedef _Item Item;

       virtual Item read(std::istream& is) const = 0;

       virtual bool isIdReader() const = 0;

     };

     template <typename _Item, typename _BoxedIdReader>

     class IdReader : public IdReaderBase<_Item> {

     public:

       typedef _Item Item;

       typedef _BoxedIdReader BoxedIdReader;

       const BoxedIdReader& boxedIdReader;

       IdReader(const BoxedIdReader& _boxedIdReader) 

 	: boxedIdReader(_boxedIdReader) {}

       virtual Item read(std::istream& is) const {

 	Item item;

 	boxedIdReader.readId(is, item);

 	return item;

       }

       virtual bool isIdReader() const {

 	return boxedIdReader.isIdReader();

       }

     };

     class ValueReaderBase {

     public:

       virtual void read(std::istream&) {};

     };

     template <typename _Value, typename _Reader>

     class ValueReader : public ValueReaderBase {

     public:

       typedef _Value Value;

       typedef _Reader Reader;

       ValueReader(Value& _value, const Reader& _reader)

  	: value(_value), reader(_reader) {}

       virtual void read(std::istream& is) {

 	reader.read(is, value);

       }

     private:

       Value& value;

       Reader reader;

     };

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading 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 readId() member will read a value from the given stream it will

   /// give back that node which is mapped to this value.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class NodeSetReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for NodeSetReader. It creates the NodeSetReader and

     /// attach it into the given LemonReader. The nodeset reader will

     /// add the readed nodes to the given Graph. The reader will read

     /// the section when the \c section_id and the \c _id are the same. 

     NodeSetReader(LemonReader& _reader, 

 		  typename SmartParameter<Graph>::Type _graph, 

 		  const std::string& _id = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), id(_id), skipper(_skipper) {} 

     /// \brief Destructor.

     ///

     /// Destructor for NodeSetReader.

     virtual ~NodeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

 	   it != readers.end(); ++it) {

 	delete it->second;

       }

     }

   private:

     NodeSetReader(const NodeSetReader&);

     void operator=(const NodeSetReader&);

   public:

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

     ///

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

     template <typename Map>

     NodeSetReader& readNodeMap(std::string name, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

     template <typename Map>

     NodeSetReader& readNodeMap(std::string name, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

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

     ///

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

     template <typename Reader, typename Map>

     NodeSetReader& readNodeMap(std::string name, Map& map, 

 			       const Reader& reader = Reader()) {

       return _readMap<Reader, Map, typename SmartParameter<Map>::Type>

 	(name, map, reader);

     }

     template <typename Reader, typename Map>

     NodeSetReader& readNodeMap(std::string name, const Map& map, 

 			       const Reader& reader = Reader()) {

       return _readMap<Reader, Map, typename SmartParameter<Map>::Type>

 	(name, map, reader);

     }

   private:

     template <typename Reader, typename Map, typename MapParameter>

     NodeSetReader& _readMap(std::string name, MapParameter map, 

 			    const Reader& reader = Reader()) {

       checkConcept<concept::WriteMap<Node, typename Map::Value>, Map>();

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(

 	make_pair(name, new MapReader<Node, Map, Reader>(map, reader)));

       return *this;

     }

   public:

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

     ///

     /// Add a new node map skipper command for the reader.

     template <typename Reader>

     NodeSetReader& skipNodeMap(std::string name, 

 			   const Reader& reader = Reader()) {

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, new SkipReader<Node, Reader>(reader)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@nodeset,

     /// and the header line's id and the nodeset's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@nodeset" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       std::vector<ReaderBase<Node>* > index;

       std::string line;

       getline(is, line);

       std::istringstream ls(line);	

       while (ls >> id) {

 	typename MapReaders::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  index.push_back(it->second);

 	} else {

 	  index.push_back(&skipper);

 	}

 	if (id == "id" && inverter.get() == 0) {

 	  inverter.reset(index.back()->getInverter());

 	  index.back() = inverter.get();

 	}

       }

       while (getline(is, line)) {	

 	Node node = graph.addNode();

 	std::istringstream ls(line);

 	for (int i = 0; i < (int)index.size(); ++i) {

 	  index[i]->read(ls, node);

 	}

       }

     }

   public:

     /// \brief Returns true if the nodeset can give back the node by its id.

     ///

     /// Returns true if the nodeset can give back the node by its id.

     /// It is possible only if an "id" named map was read.

     bool isIdReader() const {

       return inverter.get() != 0;

     }

     /// \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 map.

     void readId(std::istream& is, Node& node) const {

       node = inverter->read(is);

     } 

   private:

     typedef std::map<std::string, ReaderBase<Node>*> MapReaders;

     MapReaders readers;

     typename SmartReference<Graph>::Type graph;   

     std::string id;

     SkipReader<Node, DefaultSkipper> skipper;

     std::auto_ptr<InverterBase<Node> > inverter;

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading a graph's edgeset.

   ///

   /// 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 an 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 readId() member will read a value from the given stream it will

   /// give back that edge which is mapped to this value.

   ///

   /// The edgeset reader needs a node id reader to identify which nodes

   /// have to be connected. If a NodeSetReader reads an "id" named map,

   /// it will be able to resolve the nodes by ids.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class EdgeSetReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Graph::Edge Edge;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for EdgeSetReader. It creates the EdgeSetReader and

     /// attach it into the given LemonReader. The edgeset reader will

     /// add the readed edges to the given Graph. It will use the given

     /// node id reader to read the source and target nodes of the edges.

     /// The reader will read the section only if the \c _id and the 

     /// \c edgset_id are the same. 

     template <typename NodeIdReader>

     EdgeSetReader(LemonReader& _reader, 

 		  typename SmartParameter<Graph>::Type _graph, 

 		  const NodeIdReader& _nodeIdReader, 

 		  const std::string& _id = std::string(),

 		  const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), id(_id), skipper(_skipper) {

       checkConcept<_reader_bits::ItemIdReader<Node>, NodeIdReader>();

       nodeIdReader.reset(new IdReader<Node, NodeIdReader>(_nodeIdReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for EdgeSetReader.

     virtual ~EdgeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

 	   it != readers.end(); ++it) {

 	delete it->second;

       }

     }

   private:

     EdgeSetReader(const EdgeSetReader&);

     void operator=(const EdgeSetReader&);

   public:

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

     ///

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

     template <typename Map>

     EdgeSetReader& readEdgeMap(std::string name, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

     template <typename Map>

     EdgeSetReader& readEdgeMap(std::string name, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

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

     ///

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

     template <typename Reader, typename Map>

     EdgeSetReader& readEdgeMap(std::string name, Map& map, 

 			   const Reader& reader = Reader()) {

       return _readMap<Reader, Map,

 	typename SmartParameter<Map>::Type>(name, map, reader);

     }

     template <typename Reader, typename Map>

     EdgeSetReader& readEdgeMap(std::string name, const Map& map, 

 			       const Reader& reader = Reader()) {

       return _readMap<Reader, Map,

 	typename SmartParameter<Map>::Type>(name, map, reader);

     }

   private:

     template <typename Reader, typename Map, typename MapParameter>

     EdgeSetReader& _readMap(std::string name, MapParameter map, 

 			    const Reader& reader = Reader()) {

       checkConcept<concept::WriteMap<Edge, typename Map::Value>, Map>();

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(

 	make_pair(name, new MapReader<Edge, Map, Reader>(map, reader)));

       return *this;

     }

   public:

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

     ///

     /// Add a new edge map skipper command for the reader.

     template <typename Reader>

     EdgeSetReader& skipEdgeMap(std::string name, 

 			       const Reader& reader = Reader()) {

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, new SkipReader<Edge, Reader>(reader)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@edgeset,

     /// and the header line's id and the edgeset's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@edgeset" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find nodeset or ID map");

       }

       std::vector<ReaderBase<Edge>* > index;

       std::string line;

       getline(is, line);

       std::istringstream ls(line);	

       while (ls >> id) {

 	typename MapReaders::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  index.push_back(it->second);

 	} else {

 	  index.push_back(&skipper);

 	}

 	if (id == "id" && inverter.get() == 0) {

 	  inverter.reset(index.back()->getInverter());

 	  index.back() = inverter.get();

 	}

       }

       while (getline(is, line)) {	

 	std::istringstream ls(line);

 	Node from = nodeIdReader->read(ls);

 	Node to = nodeIdReader->read(ls);

 	Edge edge = graph.addEdge(from, to);

 	for (int i = 0; i < (int)index.size(); ++i) {

 	  index[i]->read(ls, edge);

 	}

       }

     }

   public:

     /// \brief Returns true if the edgeset can give back the edge by its id.

     ///

     /// Returns true if the edgeset can give back the edge by its id.

     /// It is possible only if an "id" named map was read.

     bool isIdReader() const {

       return inverter.get() != 0;

     }

     /// \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 map.

     void readId(std::istream& is, Edge& edge) const {

       edge = inverter->read(is);

     } 

   private:

     typedef std::map<std::string, ReaderBase<Edge>*> MapReaders;

     MapReaders readers;

     typename SmartReference<Graph>::Type graph;   

     std::string id;

     SkipReader<Edge, DefaultSkipper> skipper;

     std::auto_ptr<InverterBase<Edge> > inverter;

     std::auto_ptr<IdReaderBase<Node> > nodeIdReader;

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading a undirected graph's 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 edge in the edgeset. The

   /// line contains the connected nodes' id and the mapped values for each 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 readId() member will read a value from the given stream it will

   /// give back that undiricted edge which is mapped to this value.

   ///

   /// The undirected edgeset reader needs a node id reader to identify which 

   /// nodes have to be connected. If a NodeSetReader reads an "id" named map,

   /// it will be able to resolve the nodes by ids.

   ///

   /// \relates LemonReader

   template <typename _Graph, typename _Traits = DefaultReaderTraits>

   class UndirEdgeSetReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

   public:

     typedef _Graph Graph;

     typedef _Traits Traits;

     typedef typename Graph::Node Node;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::UndirEdge UndirEdge;

     typedef typename Traits::Skipper DefaultSkipper;

     /// \brief Constructor.

     ///

     /// Constructor for UndirEdgeSetReader. It creates the UndirEdgeSetReader 

     /// and attach it into the given LemonReader. The undirected edgeset 

     /// reader will add the readed undirected edges to the given Graph. It 

     /// will use the given node id reader to read the source and target 

     /// nodes of the edges. The reader will read the section only if the 

     /// \c _id and the \c undiredgset_id are the same. 

     template <typename NodeIdReader>

     UndirEdgeSetReader(LemonReader& _reader, 

 		       typename SmartParameter<Graph>::Type _graph, 

 		       const NodeIdReader& _nodeIdReader, 

 		       const std::string& _id = std::string(),

 		       const DefaultSkipper& _skipper = DefaultSkipper()) 

       : Parent(_reader), graph(_graph), id(_id), skipper(_skipper) {

       checkConcept<_reader_bits::ItemIdReader<Node>, NodeIdReader>();

       nodeIdReader.reset(new IdReader<Node, NodeIdReader>(_nodeIdReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for UndirEdgeSetReader.

     virtual ~UndirEdgeSetReader() {

       for (typename MapReaders::iterator it = readers.begin(); 

 	   it != readers.end(); ++it) {

 	delete it->second;

       }

     }

   private:

     UndirEdgeSetReader(const UndirEdgeSetReader&);

     void operator=(const UndirEdgeSetReader&);

   public:

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

     ///

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

     template <typename Map>

     UndirEdgeSetReader& readUndirEdgeMap(std::string name, Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map, 

 	typename SmartParameter<Map>::Type>(name, map);

     }

     template <typename Map>

     UndirEdgeSetReader& readUndirEdgeMap(std::string name, const Map& map) {

       return _readMap<

 	typename Traits::template Reader<typename Map::Value>, Map, 

 	typename SmartParameter<Map>::Type>(name, map);

     }

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

     ///

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

     template <typename Reader, typename Map>

     UndirEdgeSetReader& readUndirEdgeMap(std::string name, Map& map, 

 					 const Reader& reader = Reader()) {

       return _readMap<Reader, Map, typename SmartParameter<Map>::Type>

 	(name, map, reader);

     }

     template <typename Reader, typename Map>

     UndirEdgeSetReader& readUndirEdgeMap(std::string name, const Map& map, 

 					 const Reader& reader = Reader()) {

       return _readMap<Reader, Map, typename SmartParameter<Map>::Type >

 	(name, map, reader);

     }

   private:

     template <typename Reader, typename Map, typename MapParameter>

     UndirEdgeSetReader& _readMap(std::string name, MapParameter map,

 				 const Reader& reader = Reader()) {

       checkConcept<concept::WriteMap<UndirEdge, typename Map::Value>, Map>();

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(

 	make_pair(name, new MapReader<UndirEdge, Map, Reader>(map, reader)));

       return *this;

     }

   public:

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

     ///

     /// Add a new undirected edge map skipper command for the reader.

     template <typename Reader>

     UndirEdgeSetReader& skipUndirEdgeMap(std::string name, 

 					 const Reader& reader = Reader()) {

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node map: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, 

 			       new SkipReader<UndirEdge, Reader>(reader)));

       return *this;

     }

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

     ///

     /// Add a new directed edge map reader command for the reader.

     template <typename Map>

     UndirEdgeSetReader& readEdgeMap(std::string name, Map& map) {

       return _readDirMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

     template <typename Map>

     UndirEdgeSetReader& readEdgeMap(std::string name, const Map& map) {

       return _readDirMap<

 	typename Traits::template Reader<typename Map::Value>, Map,

 	typename SmartParameter<Map>::Type>(name, map);

     }

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

     ///

     /// Add a new directed edge map reader command for the reader.

     template <typename Reader, typename Map>

     UndirEdgeSetReader& readEdgeMap(std::string name, Map& map, 

 				    const Reader& reader = Reader()) {

       return _readDirMap<Reader, Map, typename SmartParameter<Map>::Type>

 	(name, map, reader);

     }

     template <typename Reader, typename Map>

     UndirEdgeSetReader& readEdgeMap(std::string name, const Map& map, 

 				    const Reader& reader = Reader()) {

       return _readDirMap<Reader, Map, typename SmartParameter<Map>::Type>

 	(name, map, reader);

     }

   private:

     template <typename Reader, typename Map, typename MapParameter>

     UndirEdgeSetReader& _readDirMap(std::string name, MapParameter map,

 				    const Reader& reader = Reader()) { 

       checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();

       checkConcept<concept::WriteMap<Edge, typename Map::Value>, Map>();

       readMap("+" + name, 

 	      _reader_bits::writeComposeMap(map, forwardMap(graph)), reader);

       readMap("-" + name, 

 	      _reader_bits::writeComposeMap(map, backwardMap(graph)), reader);

       return *this;      

     }

   public:

     /// \brief Add a new directed edge map skipper command for the reader.

     ///

     /// Add a new directed edge map skipper command for the reader.

     template <typename Reader>

     UndirEdgeSetReader& skipEdgeMap(std::string name, 

 				    const Reader& reader = Reader()) {

       skipMap("+" + name, reader);

       skipMap("-" + name, reader);

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line starts with \c \@undiredgeset,

     /// and the header line's id and the edgeset's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@undiredgeset" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find nodeset or ID map");

       }

       std::vector<ReaderBase<UndirEdge>* > index;

       std::string line;

       getline(is, line);

       std::istringstream ls(line);	

       while (ls >> id) {

 	typename MapReaders::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  index.push_back(it->second);

 	} else {

 	  index.push_back(&skipper);

 	}

 	if (id == "id" && inverter.get() == 0) {

 	  inverter.reset(index.back()->getInverter());

 	  index.back() = inverter.get();

 	}

       }

       while (getline(is, line)) {	

 	std::istringstream ls(line);

 	Node from = nodeIdReader->read(ls);

 	Node to = nodeIdReader->read(ls);

 	UndirEdge edge = graph.addEdge(from, to);

 	for (int i = 0; i < (int)index.size(); ++i) {

 	  index[i]->read(ls, edge);

 	}

       }

     }

   public:

     /// \brief Returns true if the edgeset can give back the edge by its id.

     ///

     /// Returns true if the edgeset can give back the undirected edge by its 

     /// id. It is possible only if an "id" named map was read.

     bool isIdReader() const {

       return inverter.get() != 0;

     }

     /// \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 map.

     void readId(std::istream& is, UndirEdge& undirEdge) const {

       undirEdge = inverter->read(is);

     } 

     /// \brief Gives back the directed edge by its id.

     ///

     /// It reads an id from the stream and gives back which directed edge 

     /// belongs to it. The directed edge id is the \c '+' or \c '-' character

     /// and the undirected edge id. It is possible only if there was read 

     /// an "id" named map.

     void readId(std::istream& is, Edge& edge) const {

       char c;

       is >> c;

       UndirEdge undirEdge = inverter->read(is);

       if (c == '+') {

 	edge = graph.edgeWithSource(undirEdge, graph.source(undirEdge));

       } else if (c == '-') {

         edge = graph.edgeWithSource(undirEdge, graph.target(undirEdge));

       } else {

 	throw DataFormatError("Wrong id format for edge "

 			      "in undirected edgeset");

       }

     } 

   private:

     typedef std::map<std::string, ReaderBase<UndirEdge>*> MapReaders;

     MapReaders readers;

     typename SmartReference<Graph>::Type graph;   

     std::string id;

     SkipReader<UndirEdge, DefaultSkipper> skipper;

     std::auto_ptr<InverterBase<UndirEdge> > inverter;

     std::auto_ptr<IdReaderBase<Node> > nodeIdReader;

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading 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 name of the node 

   /// and then the node id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class NodeReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

     typedef _Graph Graph;

     typedef typename Graph::Node Node;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for NodeReader. It creates the NodeReader and

     /// attach it into the given LemonReader. It will use the given

     /// node id reader to give back the nodes. The reader will read the 

     /// section only if the \c _id and the \c nodes_id are the same. 

     template <typename _IdReader>

     NodeReader(LemonReader& _reader, const _IdReader& _idReader, 

 	       const std::string& _id = std::string()) 

       : Parent(_reader), id(_id) {

       checkConcept<_reader_bits::ItemIdReader<Node>, _IdReader>();

       nodeIdReader.reset(new IdReader<Node, _IdReader>(_idReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for NodeReader.

     virtual ~NodeReader() {}

   private:

     NodeReader(const NodeReader&);

     void operator=(const NodeReader&);

   public:

     /// \brief Add a node reader command for the NodeReader.

     ///

     /// Add a node reader command for the NodeReader.

     void readNode(const std::string& name, Node& item) {

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for node: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, &item));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@nodes,

     /// and the header line's id and the reader's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@nodes" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!nodeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find nodeset or ID map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename NodeReaders::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  *(it->second) = nodeIdReader->read(ls); 

 	}	

       }

     }

   private:

     std::string id;

     typedef std::map<std::string, Node*> NodeReaders;

     NodeReaders readers;

     std::auto_ptr<IdReaderBase<Node> > nodeIdReader;

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading 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 name of the edge 

   /// and then the edge id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class EdgeReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

     typedef _Graph Graph;

     typedef typename Graph::Edge Edge;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for EdgeReader. It creates the EdgeReader and

     /// attach it into the given LemonReader. It will use the given

     /// edge id reader to give back the edges. The reader will read the 

     /// section only if the \c _id and the \c edges_id are the same. 

     template <typename _IdReader>

     EdgeReader(LemonReader& _reader, const _IdReader& _idReader, 

 	       const std::string& _id = std::string()) 

       : Parent(_reader), id(_id) {

       checkConcept<_reader_bits::ItemIdReader<Edge>, _IdReader>();

       edgeIdReader.reset(new IdReader<Edge, _IdReader>(_idReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for EdgeReader.

     virtual ~EdgeReader() {}

   private:

     EdgeReader(const EdgeReader&);

     void operator=(const EdgeReader&);

   public:

     /// \brief Add an edge reader command for the EdgeReader.

     ///

     /// Add an edge reader command for the EdgeReader.

     void readEdge(const std::string& name, Edge& item) {

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, &item));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@edges,

     /// and the header line's id and the reader's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@edges" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!edgeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find edgeset or ID map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename EdgeReaders::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  *(it->second) = edgeIdReader->read(ls); 

 	}	

       }

     }

   private:

     std::string id;

     typedef std::map<std::string, Edge*> EdgeReaders;

     EdgeReaders readers;

     std::auto_ptr<IdReaderBase<Edge> > edgeIdReader;

   };

   /// \ingroup io_group

   /// \brief SectionReader for reading 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 name of the undirected edge 

   /// and then the undirected edge id. 

   ///

   /// \relates LemonReader

   template <typename _Graph>

   class UndirEdgeReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

     typedef _Graph Graph;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::UndirEdge UndirEdge;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for UndirEdgeReader. It creates the UndirEdgeReader and

     /// attach it into the given LemonReader. It will use the given

     /// undirected edge id reader to give back the edges. The reader will 

     /// read the section only if the \c _id and the \c undiredges_id are 

     /// the same. 

     template <typename _IdReader>

     UndirEdgeReader(LemonReader& _reader, const _IdReader& _idReader, 

 	       const std::string& _id = std::string()) 

       : Parent(_reader), id(_id) {

       checkConcept<_reader_bits::ItemIdReader<UndirEdge>, _IdReader>();

       checkConcept<_reader_bits::ItemIdReader<Edge>, _IdReader>();

       undirEdgeIdReader.reset(new IdReader<UndirEdge, _IdReader>(_idReader));

       edgeIdReader.reset(new IdReader<Edge, _IdReader>(_idReader));

     }

     /// \brief Destructor.

     ///

     /// Destructor for UndirEdgeReader.

     virtual ~UndirEdgeReader() {}

   private:

     UndirEdgeReader(const UndirEdgeReader&);

     void operator=(const UndirEdgeReader&);

   public:

     /// \brief Add an undirected edge reader command for the UndirEdgeReader.

     ///

     /// Add an undirected edge reader command for the UndirEdgeReader.

     void readUndirEdge(const std::string& name, UndirEdge& item) {

       if (undirEdgeReaders.find(name) != undirEdgeReaders.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for undirected edge: " << name;

 	throw IOParameterError(msg.message());

       }

       undirEdgeReaders.insert(make_pair(name, &item));

     }

     /// \brief Add an edge reader command for the UndirEdgeReader.

     ///

     /// Add an edge reader command for the UndirEdgeReader.

     void readEdge(const std::string& name, Edge& item) {

       if (edgeReaders.find(name) != edgeReaders.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for edge: " << name;

 	throw IOParameterError(msg.message());

       }

       edgeReaders.insert(make_pair(name, &item));

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@edges,

     /// and the header line's id and the reader's id are the same.

     virtual bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@undiredges" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     virtual void read(std::istream& is) {

       if (!edgeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find undirected edgeset or ID map");

       }

       if (!undirEdgeIdReader->isIdReader()) {

 	throw DataFormatError("Cannot find undirected edgeset or ID map");

       }

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	{

 	  typename UndirEdgeReaders::iterator it = undirEdgeReaders.find(id);

 	  if (it != undirEdgeReaders.end()) {

 	    *(it->second) = undirEdgeIdReader->read(ls); 

 	    break;

 	  }	

 	} {

 	  typename EdgeReaders::iterator it = edgeReaders.find(id);

 	  if (it != edgeReaders.end()) {

 	    *(it->second) = edgeIdReader->read(ls); 

 	    break;

 	  }	

 	}

       }

     }

   private:

     std::string id;

     typedef std::map<std::string, UndirEdge*> UndirEdgeReaders;

     UndirEdgeReaders undirEdgeReaders;

     std::auto_ptr<IdReaderBase<UndirEdge> > undirEdgeIdReader;

     typedef std::map<std::string, Edge*> EdgeReaders;

     EdgeReaders edgeReaders;

     std::auto_ptr<IdReaderBase<Edge> > edgeIdReader;

   };

   /// \ingroup io_group

   /// \brief SectionReader 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 an attribute and then a the value for the id.

   ///

   /// \relates LemonReader

   template <typename _Traits = DefaultReaderTraits>

   class AttributeReader : public CommonSectionReaderBase {

     typedef CommonSectionReaderBase Parent;

     typedef _Traits Traits; 

   public:

     /// \brief Constructor.

     ///

     /// Constructor for AttributeReader. It creates the AttributeReader and

     /// attach it into the given LemonReader. The reader process a section

     /// only if the \c section_id and the \c _id are the same.

     AttributeReader(LemonReader& _reader, 

 		    const std::string& _id = std::string()) 

       : Parent(_reader), id(_id) {}

     /// \brief Destructor.

     ///

     /// Destructor for AttributeReader.

     virtual ~AttributeReader() {

       for (typename Readers::iterator it = readers.begin(); 

 	   it != readers.end(); ++it) {

 	delete it->second;

       }

     }

   private:

     AttributeReader(const AttributeReader&);

     void operator=(AttributeReader&);

   public:

     /// \brief Add an attribute reader command for the reader.

     ///

     /// Add an attribute reader command for the reader.

     template <typename Value>

     AttributeReader& readAttribute(const std::string& id, Value& value) {

       return readAttribute<typename Traits::template Reader<Value> >

 	(id, value);

     }

     /// \brief Add an attribute reader command for the reader.

     ///

     /// Add an attribute reader command for the reader.

     template <typename Reader, typename Value>

     AttributeReader& readAttribute(const std::string& name, Value& value,

 				   const Reader& reader = Reader()) {

       checkConcept<_reader_bits::ItemReader<Value>, Reader>();

       if (readers.find(name) != readers.end()) {

 	ErrorMessage msg;

 	msg << "Multiple read rule for attribute: " << name;

 	throw IOParameterError(msg.message());

       }

       readers.insert(make_pair(name, new ValueReader<Value, Reader>

       			       (value, reader)));

       return *this;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the header line start with \c \@attributes,

     /// and the header line's id and the attributeset's id are the same.

     bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command;

       std::string name;

       ls >> command >> name;

       return command == "@attributes" && name == id;

     }

     /// \brief Reader function of the section.

     ///

     /// It reads the content of the section.

     void read(std::istream& is) {

       std::string line;

       while (getline(is, line)) {

 	std::istringstream ls(line);

 	std::string id;

 	ls >> id;

 	typename Readers::iterator it = readers.find(id);

 	if (it != readers.end()) {

 	  it->second->read(ls);

 	}

       }

     }    

   private:

     std::string id;

     typedef std::map<std::string, ValueReaderBase*> Readers;

     Readers readers;  

   };

   /// \ingroup io_group

   /// \brief SectionReader for retrieve what is in the file.

   ///

   /// SectionReader for retrieve what is in the file. If you want

   /// to know which sections, maps and items are in the file

   /// use the next code:

   /// \code

   /// LemonReader reader("input.lgf");

   /// ContentReader content(reader);

   /// reader.run();

   /// \endcode

   class ContentReader : public LemonReader::SectionReader {

     typedef LemonReader::SectionReader Parent;

   public:

     /// \brief Constructor.

     ///

     /// Constructor for

     ContentReader(LemonReader& _reader) : Parent(_reader) {}

     /// \brief Desctructor.

     ///

     /// Desctructor.

     virtual ~ContentReader() {}

     /// \brief Gives back how many nodesets are in the file.

     ///

     /// Gives back how many nodesets are in the file.

     int nodeSetNum() const {

       return nodesets.size();

     }

     /// \brief Gives back the name of nodeset on the indiced position.

     ///

     /// Gives back the name of nodeset on the indiced position.

     std::string nodeSetName(int index) const {

       return nodesets[index].name;

     }

     /// \brief Gives back the map names of nodeset on the indiced position.

     ///

     /// Gives back the map names of nodeset on the indiced position.

     const std::vector<std::string>& nodeSetMaps(int index) const {

       return nodesets[index].items;

     }

     /// \brief Gives back how many edgesets are in the file.

     ///

     /// Gives back how many edgesets are in the file.

     int edgeSetNum() const {

       return edgesets.size();

     }

     /// \brief Gives back the name of edgeset on the indiced position.

     ///

     /// Gives back the name of edgeset on the indiced position.

     std::string edgeSetName(int index) const {

       return edgesets[index].name;

     }

     /// \brief Gives back the map names of edgeset on the indiced position.

     ///

     /// Gives back the map names of edgeset on the indiced position.

     const std::vector<std::string>& edgeSetMaps(int index) const {

       return edgesets[index].items;

     }

     /// \brief Gives back how many undirected edgesets are in the file.

     ///

     /// Gives back how many undirected edgesets are in the file.

     int undirEdgeSetNum() const {

       return undiredgesets.size();

     }

     /// \brief Gives back the name of undirected edgeset on the indiced 

     /// position.

     ///

     /// Gives back the name of undirected edgeset on the indiced position.

     std::string undirEdgeSetName(int index) const {

       return undiredgesets[index].name;

     }

     /// \brief Gives back the map names of undirected edgeset on the indiced 

     /// position.

     ///

     /// Gives back the map names of undirected edgeset on the indiced position.

     const std::vector<std::string>& undirEdgeSetMaps(int index) const {

       return undiredgesets[index].items;

     }

     /// \brief Gives back how many labeled nodes section are in the file.

     ///

     /// Gives back how many labeled nodes section are in the file.

     int nodesNum() const {

       return nodes.size();

     }

     /// \brief Gives back the name of labeled nodes section on the indiced 

     /// position.

     ///

     /// Gives back the name of labeled nodes section on the indiced position.

     std::string nodesName(int index) const {

       return nodes[index].name;

     }

     /// \brief Gives back the names of the labeled nodes in the indiced 

     /// section.

     ///

     /// Gives back the names of the labeled nodes in the indiced section.

     const std::vector<std::string>& nodesItems(int index) const {

       return nodes[index].items;

     }

     /// \brief Gives back how many labeled edges section are in the file.

     ///

     /// Gives back how many labeled edges section are in the file.

     int edgesNum() const {

       return edges.size();

     }

     /// \brief Gives back the name of labeled edges section on the indiced 

     /// position.

     ///

     /// Gives back the name of labeled edges section on the indiced position.

     std::string edgesName(int index) const {

       return edges[index].name;

     }

     /// \brief Gives back the names of the labeled edges in the indiced 

     /// section.

     ///

     /// Gives back the names of the labeled edges in the indiced section.

     const std::vector<std::string>& edgesItems(int index) const {

       return edges[index].items;

     }

     /// \brief Gives back how many labeled undirected edges section are 

     /// in the file.

     ///

     /// Gives back how many labeled undirected edges section are in the file.

     int undirEdgesNum() const {

       return undiredges.size();

     }

     /// \brief Gives back the name of labeled undirected edges section 

     /// on the indiced position.

     ///

     /// Gives back the name of labeled undirected edges section on the 

     /// indiced position.

     std::string undirEdgesName(int index) const {

       return undiredges[index].name;

     }

     /// \brief Gives back the names of the labeled undirected edges in 

     /// the indiced section.

     ///

     /// Gives back the names of the labeled undirected edges in the 

     /// indiced section.

     const std::vector<std::string>& undirEdgesItems(int index) const {

       return undiredges[index].items;

     }

     /// \brief Gives back how many attributes section are in the file.

     ///

     /// Gives back how many attributes section are in the file.

     int attributesNum() const {

       return attributes.size();

     }

     /// \brief Gives back the name of attributes section on the indiced 

     /// position.

     ///

     /// Gives back the name of attributes section on the indiced position.

     std::string attributesName(int index) const {

       return attributes[index].name;

     }

     /// \brief Gives back the names of the attributes in the indiced section.

     ///

     /// Gives back the names of the attributes in the indiced section.

     const std::vector<std::string>& attributesItems(int index) const {

       return attributes[index].items;

     }

     const std::vector<std::string>& otherSections() const {

       return sections;

     }

   protected:

     /// \brief Gives back true when the SectionReader can process 

     /// the section with the given header line.

     ///

     /// It gives back true when the section is common section.

     bool header(const std::string& line) {

       std::istringstream ls(line);

       std::string command, name;

       ls >> command >> name;

       if (command == "@nodeset") {

 	current = command;

 	nodesets.push_back(SectionInfo(name));

       } else if (command == "@edgeset") {

 	current = command;

 	edgesets.push_back(SectionInfo(name));

       } else if (command == "@undiredgeset") {

 	current = command;

 	undiredgesets.push_back(SectionInfo(name));

       } else if (command == "@nodes") {

 	current = command;

 	nodes.push_back(SectionInfo(name));

       } else if (command == "@edges") {

 	current = command;

 	edges.push_back(SectionInfo(name));

       } else if (command == "@undiredges") {

 	current = command;

 	undiredges.push_back(SectionInfo(name));

       } else if (command == "@attributes") {

 	current = command;

 	attributes.push_back(SectionInfo(name));

       } else {

 	sections.push_back(line);

 	return false;

       }

       return true;

     }

     /// \brief Retrieve the items from various sections.

     ///

     /// Retrieve the items from various sections.

     void read(std::istream& is) {

       if (current == "@nodeset") {

 	readMapNames(is, nodesets.back().items);

       } else if (current == "@edgeset") {

 	readMapNames(is, edgesets.back().items);

       } else if (current == "@undiredgeset") {

 	readMapNames(is, undiredgesets.back().items);

       } else if (current == "@nodes") {

 	readItemNames(is, nodes.back().items);

       } else if (current == "@edges") {

 	readItemNames(is, edges.back().items);

       } else if (current == "@undiredges") {

 	readItemNames(is, undiredges.back().items);

       } else if (current == "@attributes") {

 	readItemNames(is, attributes.back().items);

       }

     }    

   private:

     void readMapNames(std::istream& is, std::vector<std::string>& maps) {

       std::string line, id;

       std::getline(is, line);

       std::istringstream ls(line);

       while (ls >> id) {

 	maps.push_back(id);

       }

       while (getline(is, line));

     }

     void readItemNames(std::istream& is, std::vector<std::string>& maps) {

       std::string line, id;

       while (std::getline(is, line)) {

 	std::istringstream ls(line);

 	ls >> id;

 	maps.push_back(id);

       }

     }

     struct SectionInfo {

       std::string name;

       std::vector<std::string> items;

       SectionInfo(const std::string& _name) : name(_name) {}

     };

     std::vector<SectionInfo> nodesets;

     std::vector<SectionInfo> edgesets;

     std::vector<SectionInfo> undiredgesets;

     std::vector<SectionInfo> nodes;

     std::vector<SectionInfo> edges;

     std::vector<SectionInfo> undiredges;

     std::vector<SectionInfo> attributes;

     std::vector<std::string> sections;

     std::string current;

   };

 }

 #endif