/* -*- C++ -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2003-2008

  * 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 lemon_io

 ///\file

 ///\brief Lemon Graph Format writer.

 #ifndef LEMON_LGF_WRITER_H

 #define LEMON_LGF_WRITER_H

 #include <iostream>

 #include <fstream>

 #include <sstream>

 #include <algorithm>

 #include <vector>

 #include <functional>

 #include <lemon/assert.h>

 #include <lemon/graph_utils.h>

 namespace lemon {

   namespace _writer_bits {

     template <typename Value>

     struct DefaultConverter {

       std::string operator()(const Value& value) {

 	std::ostringstream os;

 	os << value;

 	return os.str();

       }

     };

     template <typename T>

     bool operator<(const T&, const T&) {

       throw DataFormatError("Label map is not comparable");

     }

     template <typename _Map>

     class MapLess {

     public:

       typedef _Map Map;

       typedef typename Map::Key Item;

     private:

       const Map& _map;

     public:

       MapLess(const Map& map) : _map(map) {}

       bool operator()(const Item& left, const Item& right) {

 	return _map[left] < _map[right];

       }

     };

     template <typename _Graph, bool _dir, typename _Map>

     class GraphArcMapLess {

     public:

       typedef _Map Map;

       typedef _Graph Graph;

       typedef typename Graph::Edge Item;

     private:

       const Graph& _graph;

       const Map& _map;

     public:

       GraphArcMapLess(const Graph& graph, const Map& map) 

 	: _graph(graph), _map(map) {}

       bool operator()(const Item& left, const Item& right) {

 	return _map[_graph.direct(left, _dir)] < 

 	  _map[_graph.direct(right, _dir)];

       }

     };

     template <typename _Item>    

     class MapStorageBase {

     public:

       typedef _Item Item;

     public:

       MapStorageBase() {}

       virtual ~MapStorageBase() {}

       virtual std::string get(const Item& item) = 0;

       virtual void sort(std::vector<Item>&) = 0;

     };

     template <typename _Item, typename _Map, 

 	      typename _Converter = DefaultConverter<typename _Map::Value> >

     class MapStorage : public MapStorageBase<_Item> {

     public:

       typedef _Map Map;

       typedef _Converter Converter;

       typedef _Item Item;

     private:

       const Map& _map;

       Converter _converter;

     public:

       MapStorage(const Map& map, const Converter& converter = Converter()) 

 	: _map(map), _converter(converter) {}

       virtual ~MapStorage() {}

       virtual std::string get(const Item& item) {

 	return _converter(_map[item]);

       }

       virtual void sort(std::vector<Item>& items) {

 	MapLess<Map> less(_map);

 	std::sort(items.begin(), items.end(), less);

       }

     };

     template <typename _Graph, bool _dir, typename _Map, 

 	      typename _Converter = DefaultConverter<typename _Map::Value> >

     class GraphArcMapStorage : public MapStorageBase<typename _Graph::Edge> {

     public:

       typedef _Map Map;

       typedef _Converter Converter;

       typedef _Graph Graph;

       typedef typename Graph::Edge Item;

       static const bool dir = _dir;

     private:

       const Graph& _graph;

       const Map& _map;

       Converter _converter;

     public:

       GraphArcMapStorage(const Graph& graph, const Map& map,  

 			 const Converter& converter = Converter()) 

 	: _graph(graph), _map(map), _converter(converter) {}

       virtual ~GraphArcMapStorage() {}

       virtual std::string get(const Item& item) {

 	return _converter(_map[_graph.direct(item, dir)]);

       }

       virtual void sort(std::vector<Item>& items) {

 	GraphArcMapLess<Graph, dir, Map> less(_graph, _map);

 	std::sort(items.begin(), items.end(), less);

       }

     };

     class ValueStorageBase {

     public:

       ValueStorageBase() {}

       virtual ~ValueStorageBase() {}

       virtual std::string get() = 0;      

     };

     template <typename _Value, typename _Converter = DefaultConverter<_Value> >

     class ValueStorage : public ValueStorageBase {

     public:

       typedef _Value Value;

       typedef _Converter Converter;

     private:

       const Value& _value;

       Converter _converter;

     public:

       ValueStorage(const Value& value, const Converter& converter = Converter())

  	: _value(value), _converter(converter) {}

       virtual std::string get() {

 	return _converter(_value);

       }

     };

     template <typename Value>

     struct MapLookUpConverter {

       const std::map<Value, std::string>& _map;

       MapLookUpConverter(const std::map<Value, std::string>& map) 

 	: _map(map) {}

       std::string operator()(const Value& str) {

 	typename std::map<Value, std::string>::const_iterator it = 

 	  _map.find(str);

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

 	  throw DataFormatError("Item not found");

 	}

 	return it->second;

       }

     };

     template <typename Graph>

     struct GraphArcLookUpConverter {

       const Graph& _graph;

       const std::map<typename Graph::Edge, std::string>& _map;

       GraphArcLookUpConverter(const Graph& graph, 

 			      const std::map<typename Graph::Edge, 

 			                     std::string>& map) 

 	: _graph(graph), _map(map) {}

       std::string operator()(const typename Graph::Arc& val) {

 	typename std::map<typename Graph::Edge, std::string>

 	  ::const_iterator it = _map.find(val);

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

 	  throw DataFormatError("Item not found");

 	}

 	return (_graph.direction(val) ? '+' : '-') + it->second;

       }

     };

     bool isWhiteSpace(char c) {

       return c == ' ' || c == '\t' || c == '\v' || 

         c == '\n' || c == '\r' || c == '\f'; 

     }

     bool isEscaped(char c) {

       return c == '\\' || c == '\"' || c == '\'' || 

 	c == '\a' || c == '\b';

     }

     static void writeEscape(std::ostream& os, char c) {

       switch (c) {

       case '\\':

 	os << "\\\\";

 	return;

       case '\"':

 	os << "\\\"";

 	return;

       case '\a':

 	os << "\\a";

 	return;

       case '\b':

 	os << "\\b";

 	return;

       case '\f':

 	os << "\\f";

 	return;

       case '\r':

 	os << "\\r";

 	return;

       case '\n':

 	os << "\\n";

 	return;

       case '\t':

 	os << "\\t";

 	return;

       case '\v':

 	os << "\\v";

 	return;

       default:

 	if (c < 0x20) {

 	  std::ios::fmtflags flags = os.flags();

 	  os << '\\' << std::oct << static_cast<int>(c);

 	  os.flags(flags);

 	} else {

 	  os << c;

 	}

 	return;

       }     

     }

     bool requireEscape(const std::string& str) {

       if (str.empty() || str[0] == '@') return true;

       std::istringstream is(str);

       char c;

       while (is.get(c)) {

 	if (isWhiteSpace(c) || isEscaped(c)) {

 	  return true;

 	}

       }

       return false;

     }

     std::ostream& writeToken(std::ostream& os, const std::string& str) {

       if (requireEscape(str)) {

 	os << '\"';

 	for (std::string::const_iterator it = str.begin(); 

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

 	  writeEscape(os, *it);

 	}	

 	os << '\"';

       } else {

 	os << str;

       }

       return os;

     }

   }

   /// \ingroup lemon_io

   ///  

   /// \brief LGF writer for directed graphs

   ///

   /// This utility writes an \ref lgf-format "LGF" file.

   ///

   /// The writing method does a batch processing. The user creates a

   /// writer object, then various writing rules can be added to the

   /// writer, and eventually the writing is executed with the \c run()

   /// member function. A map writing rule can be added to the writer

   /// with the \c nodeMap() or \c arcMap() members. An optional

   /// converter parameter can also be added as a standard functor

   /// converting from the value type of the map to std::string. If it

   /// is set, it will determine how the map's value type is written to

   /// the output stream. If the functor is not set, then a default

   /// conversion will be used. The \c attribute(), \c node() and \c

   /// arc() functions are used to add attribute writing rules.

   ///

   ///\code

   ///     DigraphWriter<Digraph>(std::cout, digraph).

   ///       nodeMap("coordinates", coord_map).

   ///       nodeMap("size", size).

   ///       nodeMap("title", title).

   ///       arcMap("capacity", cap_map).

   ///       node("source", src).

   ///       node("target", trg).

   ///       attribute("caption", caption).

   ///       run();

   ///\endcode

   ///

   ///

   /// By default, the writer does not write additional captions to the

   /// sections, but they can be give as an optional parameter of

   /// the \c nodes(), \c arcs() or \c

   /// attributes() functions.

   ///

   /// The \c skipNodes() and \c skipArcs() functions forbid the

   /// writing of the sections. If two arc sections should be written

   /// to the output, it can be done in two passes, the first pass

   /// writes the node section and the first arc section, then the

   /// second pass skips the node section and writes just the arc

   /// section to the stream. The output stream can be retrieved with

   /// the \c ostream() function, hence the second pass can append its

   /// output to the output of the first pass.

   template <typename _Digraph>

   class DigraphWriter {

   public:

     typedef _Digraph Digraph;

     TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);

   private:

     std::ostream* _os;

     bool local_os;

     Digraph& _digraph;

     std::string _nodes_caption;

     std::string _arcs_caption;

     std::string _attributes_caption;

     typedef std::map<Node, std::string> NodeIndex;

     NodeIndex _node_index;

     typedef std::map<Arc, std::string> ArcIndex;

     ArcIndex _arc_index;

     typedef std::vector<std::pair<std::string, 

       _writer_bits::MapStorageBase<Node>* > > NodeMaps;    

     NodeMaps _node_maps; 

     typedef std::vector<std::pair<std::string, 

       _writer_bits::MapStorageBase<Arc>* > >ArcMaps;

     ArcMaps _arc_maps;

     typedef std::vector<std::pair<std::string, 

       _writer_bits::ValueStorageBase*> > Attributes;

     Attributes _attributes;

     bool _skip_nodes;

     bool _skip_arcs;

   public:

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output stream.

     DigraphWriter(std::ostream& is, Digraph& digraph) 

       : _os(&is), local_os(false), _digraph(digraph),

 	_skip_nodes(false), _skip_arcs(false) {}

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output file.

     DigraphWriter(const std::string& fn, Digraph& digraph) 

       : _os(new std::ofstream(fn.c_str())), local_os(true), _digraph(digraph),

 	_skip_nodes(false), _skip_arcs(false) {}

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output file.

     DigraphWriter(const char* fn, Digraph& digraph) 

       : _os(new std::ofstream(fn)), local_os(true), _digraph(digraph),

 	_skip_nodes(false), _skip_arcs(false) {}

     /// \brief Copy constructor

     ///

     /// The copy constructor transfers all data from the other writer,

     /// therefore the copied writer will not be usable more. 

     DigraphWriter(DigraphWriter& other) 

       : _os(other._os), local_os(other.local_os), _digraph(other._digraph),

 	_skip_nodes(other._skip_nodes), _skip_arcs(other._skip_arcs) {

       other._os = 0;

       other.local_os = false;

       _node_index.swap(other._node_index);

       _arc_index.swap(other._arc_index);

       _node_maps.swap(other._node_maps);

       _arc_maps.swap(other._arc_maps);

       _attributes.swap(other._attributes);

       _nodes_caption = other._nodes_caption;

       _arcs_caption = other._arcs_caption;

       _attributes_caption = other._attributes_caption;

     }

     /// \brief Destructor

     ~DigraphWriter() {

       for (typename NodeMaps::iterator it = _node_maps.begin(); 

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

 	delete it->second;

       }

       for (typename ArcMaps::iterator it = _arc_maps.begin(); 

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

 	delete it->second;

       }

       for (typename Attributes::iterator it = _attributes.begin(); 

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

 	delete it->second;

       }

       if (local_os) {

 	delete _os;

       }

     }

   private:

     DigraphWriter& operator=(const DigraphWriter&);

   public:

     /// \name Writing rules

     /// @{

     /// \brief Node map reading rule

     ///

     /// Add a node map reading rule to the writer.

     template <typename Map>

     DigraphWriter& nodeMap(const std::string& caption, const Map& map) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Node>* storage = 

 	new _writer_bits::MapStorage<Node, Map>(map);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node map writing rule

     ///

     /// Add a node map writing rule with specialized converter to the

     /// writer.

     template <typename Map, typename Converter>

     DigraphWriter& nodeMap(const std::string& caption, const Map& map, 

 			   const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Node>* storage = 

 	new _writer_bits::MapStorage<Node, Map, Converter>(map, converter);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc map writing rule

     ///

     /// Add an arc map writing rule to the writer.

     template <typename Map>

     DigraphWriter& arcMap(const std::string& caption, const Map& map) {

       checkConcept<concepts::ReadMap<Arc, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Arc>* storage = 

 	new _writer_bits::MapStorage<Arc, Map>(map);

       _arc_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc map writing rule

     ///

     /// Add an arc map writing rule with specialized converter to the

     /// writer.

     template <typename Map, typename Converter>

     DigraphWriter& arcMap(const std::string& caption, const Map& map, 

 			  const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Arc, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Arc>* storage = 

 	new _writer_bits::MapStorage<Arc, Map, Converter>(map, converter);

       _arc_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Attribute writing rule

     ///

     /// Add an attribute writing rule to the writer.

     template <typename Value>

     DigraphWriter& attribute(const std::string& caption, const Value& value) {

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Value>(value);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Attribute writing rule

     ///

     /// Add an attribute writing rule with specialized converter to the

     /// writer.

     template <typename Value, typename Converter>

     DigraphWriter& attribute(const std::string& caption, const Value& value, 

 			     const Converter& converter = Converter()) {

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Value, Converter>(value, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node writing rule

     ///

     /// Add a node writing rule to the writer.

     DigraphWriter& node(const std::string& caption, const Node& node) {

       typedef _writer_bits::MapLookUpConverter<Node> Converter;

       Converter converter(_node_index);

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Node, Converter>(node, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc writing rule

     ///

     /// Add an arc writing rule to writer.

     DigraphWriter& arc(const std::string& caption, const Arc& arc) {

       typedef _writer_bits::MapLookUpConverter<Arc> Converter;

       Converter converter(_arc_index);

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Arc, Converter>(arc, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \name Select section by name

     /// @{

     /// \brief Set \c \@nodes section to be read

     ///

     /// Set \c \@nodes section to be read

     DigraphWriter& nodes(const std::string& caption) {

       _nodes_caption = caption;

       return *this;

     }

     /// \brief Set \c \@arcs section to be read

     ///

     /// Set \c \@arcs section to be read

     DigraphWriter& arcs(const std::string& caption) {

       _arcs_caption = caption;

       return *this;

     }

     /// \brief Set \c \@attributes section to be read

     ///

     /// Set \c \@attributes section to be read

     DigraphWriter& attributes(const std::string& caption) {

       _attributes_caption = caption;

       return *this;

     }

     /// \name Skipping section

     /// @{

     /// \brief Skip writing the node set

     ///

     /// The \c \@nodes section will be not written to the stream.

     DigraphWriter& skipNodes() {

       LEMON_ASSERT(!_skip_nodes, "Multiple usage of skipNodes() member");

       _skip_nodes = true;

       return *this;

     }

     /// \brief Skip writing arc set

     ///

     /// The \c \@arcs section will be not written to the stream.

     DigraphWriter& skipArcs() {

       LEMON_ASSERT(!_skip_arcs, "Multiple usage of skipArcs() member");

       _skip_arcs = true;

       return *this;

     }

     /// @}

   private:

     void writeNodes() {

       _writer_bits::MapStorageBase<Node>* label = 0;

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       *_os << "@nodes";

       if (!_nodes_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _nodes_caption);

       }

       *_os << std::endl;

       if (label == 0) {

 	*_os << "label" << '\t';

       }

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << '\t';

       }

       *_os << std::endl;

       std::vector<Node> nodes;

       for (NodeIt n(_digraph); n != INVALID; ++n) {

 	nodes.push_back(n);

       }

       if (label == 0) {

 	IdMap<Digraph, Node> id_map(_digraph);

 	_writer_bits::MapLess<IdMap<Digraph, Node> > id_less(id_map);

 	std::sort(nodes.begin(), nodes.end(), id_less);

       } else {

 	label->sort(nodes);

       }

       for (int i = 0; i < static_cast<int>(nodes.size()); ++i) {

 	Node n = nodes[i];

 	if (label == 0) {

 	  std::ostringstream os;

 	  os << _digraph.id(n);

 	  _writer_bits::writeToken(*_os, os.str());

 	  *_os << '\t';

 	  _node_index.insert(std::make_pair(n, os.str()));

 	}

 	for (typename NodeMaps::iterator it = _node_maps.begin();

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

 	  std::string value = it->second->get(n);

 	  _writer_bits::writeToken(*_os, value);

 	  if (it->first == "label") {

 	    _node_index.insert(std::make_pair(n, value));

 	  }

 	  *_os << '\t';

 	}

 	*_os << std::endl;

       }

     }

     void createNodeIndex() {

       _writer_bits::MapStorageBase<Node>* label = 0;

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       if (label == 0) {

 	for (NodeIt n(_digraph); n != INVALID; ++n) {

 	  std::ostringstream os;

 	  os << _digraph.id(n);

 	  _node_index.insert(std::make_pair(n, os.str()));	  

 	}	

       } else {

 	for (NodeIt n(_digraph); n != INVALID; ++n) {

 	  std::string value = label->get(n);	  

 	  _node_index.insert(std::make_pair(n, value));

 	}

       }

     }

     void writeArcs() {

       _writer_bits::MapStorageBase<Arc>* label = 0;

       for (typename ArcMaps::iterator it = _arc_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       *_os << "@arcs";

       if (!_arcs_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _arcs_caption);

       }

       *_os << std::endl;

       *_os << '\t' << '\t';

       if (label == 0) {

 	*_os << "label" << '\t';

       }

       for (typename ArcMaps::iterator it = _arc_maps.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << '\t';

       }

       *_os << std::endl;

       std::vector<Arc> arcs;

       for (ArcIt n(_digraph); n != INVALID; ++n) {

 	arcs.push_back(n);

       }

       if (label == 0) {

 	IdMap<Digraph, Arc> id_map(_digraph);

 	_writer_bits::MapLess<IdMap<Digraph, Arc> > id_less(id_map);

 	std::sort(arcs.begin(), arcs.end(), id_less);

       } else {

 	label->sort(arcs);

       }

       for (int i = 0; i < static_cast<int>(arcs.size()); ++i) {

 	Arc a = arcs[i];

 	_writer_bits::writeToken(*_os, _node_index.

 				 find(_digraph.source(a))->second);

 	*_os << '\t';

 	_writer_bits::writeToken(*_os, _node_index.

 				 find(_digraph.target(a))->second);

 	*_os << '\t';

 	if (label == 0) {

 	  std::ostringstream os;

 	  os << _digraph.id(a);

 	  _writer_bits::writeToken(*_os, os.str());

 	  *_os << '\t';

 	  _arc_index.insert(std::make_pair(a, os.str()));

 	}

 	for (typename ArcMaps::iterator it = _arc_maps.begin();

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

 	  std::string value = it->second->get(a);

 	  _writer_bits::writeToken(*_os, value);

 	  if (it->first == "label") {

 	    _arc_index.insert(std::make_pair(a, value));

 	  }

 	  *_os << '\t';

 	}

 	*_os << std::endl;

       }

     }

     void createArcIndex() {

       _writer_bits::MapStorageBase<Arc>* label = 0;

       for (typename ArcMaps::iterator it = _arc_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       if (label == 0) {

 	for (ArcIt a(_digraph); a != INVALID; ++a) {

 	  std::ostringstream os;

 	  os << _digraph.id(a);

 	  _arc_index.insert(std::make_pair(a, os.str()));	  

 	}	

       } else {

 	for (ArcIt a(_digraph); a != INVALID; ++a) {

 	  std::string value = label->get(a);	  

 	  _arc_index.insert(std::make_pair(a, value));

 	}

       }

     }

     void writeAttributes() {

       if (_attributes.empty()) return;

       *_os << "@attributes";

       if (!_attributes_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _attributes_caption);

       }

       *_os << std::endl;

       for (typename Attributes::iterator it = _attributes.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << ' ';

 	_writer_bits::writeToken(*_os, it->second->get());

 	*_os << std::endl;

       }

     }

   public:

     /// \name Execution of the writer    

     /// @{

     /// \brief Start the batch processing

     ///

     /// This function starts the batch processing

     void run() {

       if (!_skip_nodes) {

 	writeNodes();

       } else {

 	createNodeIndex();

       }

       if (!_skip_arcs) {      

 	writeArcs();

       } else {

 	createArcIndex();

       }

       writeAttributes();

     }

     /// \brief Gives back the stream of the writer

     ///

     /// Gives back the stream of the writer

     std::ostream& ostream() {

       return *_os;

     }

     /// @}

   };

   /// \relates DigraphWriter

   template <typename Digraph>

   DigraphWriter<Digraph> digraphWriter(std::ostream& os, Digraph& digraph) {

     DigraphWriter<Digraph> tmp(os, digraph);

     return tmp;

   }

   /// \relates DigraphWriter

   template <typename Digraph>

   DigraphWriter<Digraph> digraphWriter(const std::string& fn, 

 				       Digraph& digraph) {

     DigraphWriter<Digraph> tmp(fn, digraph);

     return tmp;

   }

   /// \relates DigraphWriter

   template <typename Digraph>

   DigraphWriter<Digraph> digraphWriter(const char* fn, Digraph& digraph) {

     DigraphWriter<Digraph> tmp(fn, digraph);

     return tmp;

   }

   /// \ingroup lemon_io

   ///  

   /// \brief LGF writer for directed graphs

   ///

   /// This utility writes an \ref lgf-format "LGF" file.

   template <typename _Graph>

   class GraphWriter {

   public:

     typedef _Graph Graph;

     TEMPLATE_GRAPH_TYPEDEFS(Graph);

   private:

     std::ostream* _os;

     bool local_os;

     Graph& _graph;

     std::string _nodes_caption;

     std::string _edges_caption;

     std::string _attributes_caption;

     typedef std::map<Node, std::string> NodeIndex;

     NodeIndex _node_index;

     typedef std::map<Edge, std::string> EdgeIndex;

     EdgeIndex _edge_index;

     typedef std::vector<std::pair<std::string, 

       _writer_bits::MapStorageBase<Node>* > > NodeMaps;    

     NodeMaps _node_maps; 

     typedef std::vector<std::pair<std::string, 

       _writer_bits::MapStorageBase<Edge>* > >EdgeMaps;

     EdgeMaps _edge_maps;

     typedef std::vector<std::pair<std::string, 

       _writer_bits::ValueStorageBase*> > Attributes;

     Attributes _attributes;

     bool _skip_nodes;

     bool _skip_edges;

   public:

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output stream.

     GraphWriter(std::ostream& is, Graph& graph) 

       : _os(&is), local_os(false), _graph(graph),

 	_skip_nodes(false), _skip_edges(false) {}

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output file.

     GraphWriter(const std::string& fn, Graph& graph) 

       : _os(new std::ofstream(fn.c_str())), local_os(true), _graph(graph),

 	_skip_nodes(false), _skip_edges(false) {}

     /// \brief Constructor

     ///

     /// Construct a directed graph writer, which writes to the given

     /// output file.

     GraphWriter(const char* fn, Graph& graph) 

       : _os(new std::ofstream(fn)), local_os(true), _graph(graph),

 	_skip_nodes(false), _skip_edges(false) {}

     /// \brief Copy constructor

     ///

     /// The copy constructor transfers all data from the other writer,

     /// therefore the copied writer will not be usable more. 

     GraphWriter(GraphWriter& other) 

       : _os(other._os), local_os(other.local_os), _graph(other._graph),

 	_skip_nodes(other._skip_nodes), _skip_edges(other._skip_edges) {

       other._os = 0;

       other.local_os = false;

       _node_index.swap(other._node_index);

       _edge_index.swap(other._edge_index);

       _node_maps.swap(other._node_maps);

       _edge_maps.swap(other._edge_maps);

       _attributes.swap(other._attributes);

       _nodes_caption = other._nodes_caption;

       _edges_caption = other._edges_caption;

       _attributes_caption = other._attributes_caption;

     }

     /// \brief Destructor

     ~GraphWriter() {

       for (typename NodeMaps::iterator it = _node_maps.begin(); 

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

 	delete it->second;

       }

       for (typename EdgeMaps::iterator it = _edge_maps.begin(); 

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

 	delete it->second;

       }

       for (typename Attributes::iterator it = _attributes.begin(); 

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

 	delete it->second;

       }

       if (local_os) {

 	delete _os;

       }

     }

   private:

     GraphWriter& operator=(const GraphWriter&);

   public:

     /// \name Writing rules

     /// @{

     /// \brief Node map reading rule

     ///

     /// Add a node map reading rule to the writer.

     template <typename Map>

     GraphWriter& nodeMap(const std::string& caption, const Map& map) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Node>* storage = 

 	new _writer_bits::MapStorage<Node, Map>(map);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node map writing rule

     ///

     /// Add a node map writing rule with specialized converter to the

     /// writer.

     template <typename Map, typename Converter>

     GraphWriter& nodeMap(const std::string& caption, const Map& map, 

 			   const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Node>* storage = 

 	new _writer_bits::MapStorage<Node, Map, Converter>(map, converter);

       _node_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge map writing rule

     ///

     /// Add an edge map writing rule to the writer.

     template <typename Map>

     GraphWriter& edgeMap(const std::string& caption, const Map& map) {

       checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Edge>* storage = 

 	new _writer_bits::MapStorage<Edge, Map>(map);

       _edge_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge map writing rule

     ///

     /// Add an edge map writing rule with specialized converter to the

     /// writer.

     template <typename Map, typename Converter>

     GraphWriter& edgeMap(const std::string& caption, const Map& map, 

 			  const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Edge>* storage = 

 	new _writer_bits::MapStorage<Edge, Map, Converter>(map, converter);

       _edge_maps.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc map writing rule

     ///

     /// Add an arc map writing rule to the writer.

     template <typename Map>

     GraphWriter& arcMap(const std::string& caption, const Map& map) {

       checkConcept<concepts::ReadMap<Arc, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Edge>* forward_storage = 

 	new _writer_bits::GraphArcMapStorage<Graph, true, Map>(_graph, map);

       _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

       _writer_bits::MapStorageBase<Edge>* backward_storage = 

 	new _writer_bits::GraphArcMapStorage<Graph, false, Map>(_graph, map);

       _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

       return *this;

     }

     /// \brief Arc map writing rule

     ///

     /// Add an arc map writing rule with specialized converter to the

     /// writer.

     template <typename Map, typename Converter>

     GraphWriter& arcMap(const std::string& caption, const Map& map, 

 			  const Converter& converter = Converter()) {

       checkConcept<concepts::ReadMap<Arc, typename Map::Value>, Map>();

       _writer_bits::MapStorageBase<Edge>* forward_storage = 

 	new _writer_bits::GraphArcMapStorage<Graph, true, Map, Converter>

 	(_graph, map, converter);

       _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

       _writer_bits::MapStorageBase<Edge>* backward_storage = 

 	new _writer_bits::GraphArcMapStorage<Graph, false, Map, Converter>

 	(_graph, map, converter);

       _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

       return *this;

     }

     /// \brief Attribute writing rule

     ///

     /// Add an attribute writing rule to the writer.

     template <typename Value>

     GraphWriter& attribute(const std::string& caption, const Value& value) {

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Value>(value);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Attribute writing rule

     ///

     /// Add an attribute writing rule with specialized converter to the

     /// writer.

     template <typename Value, typename Converter>

     GraphWriter& attribute(const std::string& caption, const Value& value, 

 			     const Converter& converter = Converter()) {

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Value, Converter>(value, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Node writing rule

     ///

     /// Add a node writing rule to the writer.

     GraphWriter& node(const std::string& caption, const Node& node) {

       typedef _writer_bits::MapLookUpConverter<Node> Converter;

       Converter converter(_node_index);

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Node, Converter>(node, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Edge writing rule

     ///

     /// Add an edge writing rule to writer.

     GraphWriter& edge(const std::string& caption, const Edge& edge) {

       typedef _writer_bits::MapLookUpConverter<Edge> Converter;

       Converter converter(_edge_index);

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Edge, Converter>(edge, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \brief Arc writing rule

     ///

     /// Add an arc writing rule to writer.

     GraphWriter& arc(const std::string& caption, const Arc& arc) {

       typedef _writer_bits::GraphArcLookUpConverter<Graph> Converter;

       Converter converter(_graph, _edge_index);

       _writer_bits::ValueStorageBase* storage = 

 	new _writer_bits::ValueStorage<Arc, Converter>(arc, converter);

       _attributes.push_back(std::make_pair(caption, storage));

       return *this;

     }

     /// \name Select section by name

     /// @{

     /// \brief Set \c \@nodes section to be read

     ///

     /// Set \c \@nodes section to be read

     GraphWriter& nodes(const std::string& caption) {

       _nodes_caption = caption;

       return *this;

     }

     /// \brief Set \c \@edges section to be read

     ///

     /// Set \c \@edges section to be read

     GraphWriter& edges(const std::string& caption) {

       _edges_caption = caption;

       return *this;

     }

     /// \brief Set \c \@attributes section to be read

     ///

     /// Set \c \@attributes section to be read

     GraphWriter& attributes(const std::string& caption) {

       _attributes_caption = caption;

       return *this;

     }

     /// \name Skipping section

     /// @{

     /// \brief Skip writing the node set

     ///

     /// The \c \@nodes section will be not written to the stream.

     GraphWriter& skipNodes() {

       LEMON_ASSERT(!_skip_nodes, "Multiple usage of skipNodes() member");

       _skip_nodes = true;

       return *this;

     }

     /// \brief Skip writing edge set

     ///

     /// The \c \@edges section will be not written to the stream.

     GraphWriter& skipEdges() {

       LEMON_ASSERT(!_skip_edges, "Multiple usage of skipEdges() member");

       _skip_edges = true;

       return *this;

     }

     /// @}

   private:

     void writeNodes() {

       _writer_bits::MapStorageBase<Node>* label = 0;

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       *_os << "@nodes";

       if (!_nodes_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _nodes_caption);

       }

       *_os << std::endl;

       if (label == 0) {

 	*_os << "label" << '\t';

       }

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << '\t';

       }

       *_os << std::endl;

       std::vector<Node> nodes;

       for (NodeIt n(_graph); n != INVALID; ++n) {

 	nodes.push_back(n);

       }

       if (label == 0) {

 	IdMap<Graph, Node> id_map(_graph);

 	_writer_bits::MapLess<IdMap<Graph, Node> > id_less(id_map);

 	std::sort(nodes.begin(), nodes.end(), id_less);

       } else {

 	label->sort(nodes);

       }

       for (int i = 0; i < static_cast<int>(nodes.size()); ++i) {

 	Node n = nodes[i];

 	if (label == 0) {

 	  std::ostringstream os;

 	  os << _graph.id(n);

 	  _writer_bits::writeToken(*_os, os.str());

 	  *_os << '\t';

 	  _node_index.insert(std::make_pair(n, os.str()));

 	}

 	for (typename NodeMaps::iterator it = _node_maps.begin();

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

 	  std::string value = it->second->get(n);

 	  _writer_bits::writeToken(*_os, value);

 	  if (it->first == "label") {

 	    _node_index.insert(std::make_pair(n, value));

 	  }

 	  *_os << '\t';

 	}

 	*_os << std::endl;

       }

     }

     void createNodeIndex() {

       _writer_bits::MapStorageBase<Node>* label = 0;

       for (typename NodeMaps::iterator it = _node_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       if (label == 0) {

 	for (NodeIt n(_graph); n != INVALID; ++n) {

 	  std::ostringstream os;

 	  os << _graph.id(n);

 	  _node_index.insert(std::make_pair(n, os.str()));	  

 	}	

       } else {

 	for (NodeIt n(_graph); n != INVALID; ++n) {

 	  std::string value = label->get(n);	  

 	  _node_index.insert(std::make_pair(n, value));

 	}

       }

     }

     void writeEdges() {

       _writer_bits::MapStorageBase<Edge>* label = 0;

       for (typename EdgeMaps::iterator it = _edge_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       *_os << "@edges";

       if (!_edges_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _edges_caption);

       }

       *_os << std::endl;

       *_os << '\t' << '\t';

       if (label == 0) {

 	*_os << "label" << '\t';

       }

       for (typename EdgeMaps::iterator it = _edge_maps.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << '\t';

       }

       *_os << std::endl;

       std::vector<Edge> edges;

       for (EdgeIt n(_graph); n != INVALID; ++n) {

 	edges.push_back(n);

       }

       if (label == 0) {

 	IdMap<Graph, Edge> id_map(_graph);

 	_writer_bits::MapLess<IdMap<Graph, Edge> > id_less(id_map);

 	std::sort(edges.begin(), edges.end(), id_less);

       } else {

 	label->sort(edges);

       }

       for (int i = 0; i < static_cast<int>(edges.size()); ++i) {

 	Edge e = edges[i];

 	_writer_bits::writeToken(*_os, _node_index.

 				 find(_graph.u(e))->second);

 	*_os << '\t';

 	_writer_bits::writeToken(*_os, _node_index.

 				 find(_graph.v(e))->second);

 	*_os << '\t';

 	if (label == 0) {

 	  std::ostringstream os;

 	  os << _graph.id(e);

 	  _writer_bits::writeToken(*_os, os.str());

 	  *_os << '\t';

 	  _edge_index.insert(std::make_pair(e, os.str()));

 	}

 	for (typename EdgeMaps::iterator it = _edge_maps.begin();

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

 	  std::string value = it->second->get(e);

 	  _writer_bits::writeToken(*_os, value);

 	  if (it->first == "label") {

 	    _edge_index.insert(std::make_pair(e, value));

 	  }

 	  *_os << '\t';

 	}

 	*_os << std::endl;

       }

     }

     void createEdgeIndex() {

       _writer_bits::MapStorageBase<Edge>* label = 0;

       for (typename EdgeMaps::iterator it = _edge_maps.begin();

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

         if (it->first == "label") {

 	  label = it->second;

 	  break;

 	}

       }

       if (label == 0) {

 	for (EdgeIt e(_graph); e != INVALID; ++e) {

 	  std::ostringstream os;

 	  os << _graph.id(e);

 	  _edge_index.insert(std::make_pair(e, os.str()));	  

 	}	

       } else {

 	for (EdgeIt e(_graph); e != INVALID; ++e) {

 	  std::string value = label->get(e);	  

 	  _edge_index.insert(std::make_pair(e, value));

 	}

       }

     }

     void writeAttributes() {

       if (_attributes.empty()) return;

       *_os << "@attributes";

       if (!_attributes_caption.empty()) {

 	_writer_bits::writeToken(*_os << ' ', _attributes_caption);

       }

       *_os << std::endl;

       for (typename Attributes::iterator it = _attributes.begin();

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

 	_writer_bits::writeToken(*_os, it->first) << ' ';

 	_writer_bits::writeToken(*_os, it->second->get());

 	*_os << std::endl;

       }

     }

   public:

     /// \name Execution of the writer    

     /// @{

     /// \brief Start the batch processing

     ///

     /// This function starts the batch processing

     void run() {

       if (!_skip_nodes) {

 	writeNodes();

       } else {

 	createNodeIndex();

       }

       if (!_skip_edges) {      

 	writeEdges();

       } else {

 	createEdgeIndex();

       }

       writeAttributes();

     }

     /// \brief Gives back the stream of the writer

     ///

     /// Gives back the stream of the writer

     std::ostream& ostream() {

       return *_os;

     }

     /// @}

   };

   /// \relates GraphWriter

   template <typename Graph>

   GraphWriter<Graph> graphWriter(std::ostream& os, Graph& graph) {

     GraphWriter<Graph> tmp(os, graph);

     return tmp;

   }

   /// \relates GraphWriter

   template <typename Graph>

   GraphWriter<Graph> graphWriter(const std::string& fn, Graph& graph) {

     GraphWriter<Graph> tmp(fn, graph);

     return tmp;

   }

   /// \relates GraphWriter

   template <typename Graph>

   GraphWriter<Graph> graphWriter(const char* fn, Graph& graph) {

     GraphWriter<Graph> tmp(fn, graph);

     return tmp;

   }

 }

 #endif