/* -*- 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 reader.

 #ifndef LEMON_LGF_READER_H

 #define LEMON_LGF_READER_H

 #include <iostream>

 #include <fstream>

 #include <sstream>

 #include <set>

 #include <map>

 #include <lemon/assert.h>

 #include <lemon/graph_utils.h>

 #include <lemon/lgf_writer.h>

 #include <lemon/concept_check.h>

 #include <lemon/concepts/maps.h>

 namespace lemon {

   namespace _reader_bits {

     template <typename Value>

     struct DefaultConverter {

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

 	std::istringstream is(str);

 	Value value;

 	is >> value;

 	char c;

 	if (is >> std::ws >> c) {

 	  throw DataFormatError("Remaining characters in token");

 	}

 	return value;

       }

     };

     template <>

     struct DefaultConverter<std::string> {

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

 	return str;

       }

     };

     template <typename _Item>    

     class MapStorageBase {

     public:

       typedef _Item Item;

     public:

       MapStorageBase() {}

       virtual ~MapStorageBase() {}

       virtual void set(const Item& item, const std::string& value) = 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:

       Map& _map;

       Converter _converter;

     public:

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

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

       virtual ~MapStorage() {}

       virtual void set(const Item& item ,const std::string& value) {

 	_map.set(item, _converter(value));

       }

     };

     class ValueStorageBase {

     public:

       ValueStorageBase() {}

       virtual ~ValueStorageBase() {}

       virtual void set(const std::string&) = 0;

     };

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

     class ValueStorage : public ValueStorageBase {

     public:

       typedef _Value Value;

       typedef _Converter Converter;

     private:

       Value& _value;

       Converter _converter;

     public:

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

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

       virtual void set(const std::string& value) {

 	_value = _converter(value);

       }

     };

     template <typename Value>

     struct MapLookUpConverter {

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

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

         : _map(map) {}

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

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

           _map.find(str);

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

           std::ostringstream msg;

           msg << "Item not found: " << str;

           throw DataFormatError(msg.str().c_str());

         }

         return it->second;

       }

     };

     bool isWhiteSpace(char c) {

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

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

     }

     bool isOct(char c) {

       return '0' <= c && c <='7'; 

     }

     int valueOct(char c) {

       LEMON_ASSERT(isOct(c), "The character is not octal.");

       return c - '0';

     }

     bool isHex(char c) {

       return ('0' <= c && c <= '9') || 

 	('a' <= c && c <= 'z') || 

 	('A' <= c && c <= 'Z'); 

     }

     int valueHex(char c) {

       LEMON_ASSERT(isHex(c), "The character is not hexadecimal.");

       if ('0' <= c && c <= '9') return c - '0';

       if ('a' <= c && c <= 'z') return c - 'a' + 10;

       return c - 'A' + 10;

     }

     bool isIdentifierFirstChar(char c) {

       return ('a' <= c && c <= 'z') ||

 	('A' <= c && c <= 'Z') || c == '_';

     }

     bool isIdentifierChar(char c) {

       return isIdentifierFirstChar(c) ||

 	('0' <= c && c <= '9');

     }

     char readEscape(std::istream& is) {

       char c;

       if (!is.get(c))

 	throw DataFormatError("Escape format error");

       switch (c) {

       case '\\':

 	return '\\';

       case '\"':

 	return '\"';

       case '\'':

 	return '\'';

       case '\?':

 	return '\?';

       case 'a':

 	return '\a';

       case 'b':

 	return '\b';

       case 'f':

 	return '\f';

       case 'n':

 	return '\n';

       case 'r':

 	return '\r';

       case 't':

 	return '\t';

       case 'v':

 	return '\v';

       case 'x':

 	{

 	  int code;

 	  if (!is.get(c) || !isHex(c)) 

 	    throw DataFormatError("Escape format error");

 	  else if (code = valueHex(c), !is.get(c) || !isHex(c)) is.putback(c);

 	  else code = code * 16 + valueHex(c);

 	  return code;

 	}

       default:

 	{

 	  int code;

 	  if (!isOct(c)) 

 	    throw DataFormatError("Escape format error");

 	  else if (code = valueOct(c), !is.get(c) || !isOct(c)) 

 	    is.putback(c);

 	  else if (code = code * 8 + valueOct(c), !is.get(c) || !isOct(c)) 

 	    is.putback(c);

 	  else code = code * 8 + valueOct(c);

 	  return code;

 	}	      

       } 

     }

     std::istream& readToken(std::istream& is, std::string& str) {

       std::ostringstream os;

       char c;

       is >> std::ws;

       if (!is.get(c)) 

 	return is;

       if (c == '\"') {

 	while (is.get(c) && c != '\"') {

 	  if (c == '\\') 

 	    c = readEscape(is);

 	  os << c;

 	}

 	if (!is) 

 	  throw DataFormatError("Quoted format error");

       } else {

 	is.putback(c);

 	while (is.get(c) && !isWhiteSpace(c)) {

 	  if (c == '\\') 

 	    c = readEscape(is);

 	  os << c;

 	}

 	if (!is) {

 	  is.clear();

 	} else {

 	  is.putback(c);

 	}

       }

       str = os.str();

       return is;

     }

     std::istream& readIdentifier(std::istream& is, std::string& str) {

       std::ostringstream os;

       char c;

       is >> std::ws;

       if (!is.get(c))

 	return is;

       if (!isIdentifierFirstChar(c))

 	throw DataFormatError("Wrong char in identifier");

       os << c;

       while (is.get(c) && !isWhiteSpace(c)) {

 	if (!isIdentifierChar(c)) 

 	  throw DataFormatError("Wrong char in identifier");	  

 	os << c;

       }

       if (!is) is.clear();

       str = os.str();

       return is;

     }

   }

   /// \e

   template <typename _Digraph>

   class DigraphReader {

   public:

     typedef _Digraph Digraph;

     GRAPH_TYPEDEFS(typename Digraph);

   private:

     std::istream* _is;

     bool local_is;

     Digraph& _digraph;

     std::string _nodes_caption;

     std::string _arcs_caption;

     std::string _attributes_caption;

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

     NodeIndex _node_index;

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

     ArcIndex _arc_index;

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

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

     NodeMaps _node_maps; 

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

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

     ArcMaps _arc_maps;

     typedef std::multimap<std::string, _reader_bits::ValueStorageBase*> 

       Attributes;

     Attributes _attributes;

     bool _use_nodes;

     bool _use_arcs;

     int line_num;

     std::istringstream line;

   public:

     /// \e

     DigraphReader(std::istream& is, Digraph& digraph) 

       : _is(&is), local_is(false), _digraph(digraph),

 	_use_nodes(false), _use_arcs(false) {}

     /// \e

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

       : _is(new std::ifstream(fn.c_str())), local_is(true), _digraph(digraph),

     	_use_nodes(false), _use_arcs(false) {}

     /// \e

     DigraphReader(const char* fn, Digraph& digraph) 

       : _is(new std::ifstream(fn)), local_is(true), _digraph(digraph),

     	_use_nodes(false), _use_arcs(false) {}

     /// \e

     DigraphReader(DigraphReader& other) 

       : _is(other._is), local_is(other.local_is), _digraph(other._digraph),

 	_use_nodes(other._use_nodes), _use_arcs(other._use_arcs) {

       other.is = 0;

       other.local_is = 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;

     }

     /// \e

     ~DigraphReader() {

       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_is) {

 	delete _is;

       }

     }

   private:

     DigraphReader& operator=(const DigraphReader&);

   public:

     /// \e

     template <typename Map>

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

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

       _reader_bits::MapStorageBase<Node>* storage = 

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

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

       return *this;

     }

     /// \e

     template <typename Map, typename Converter>

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

 			   const Converter& converter = Converter()) {

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

       _reader_bits::MapStorageBase<Node>* storage = 

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

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

       return *this;

     }

     /// \e

     template <typename Map>

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

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

       _reader_bits::MapStorageBase<Arc>* storage = 

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

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

       return *this;

     }

     /// \e

     template <typename Map, typename Converter>

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

 			  const Converter& converter = Converter()) {

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

       _reader_bits::MapStorageBase<Arc>* storage = 

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

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

       return *this;

     }

     /// \e

     template <typename Value>

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

       _reader_bits::ValueStorageBase* storage = 

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

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

       return *this;

     }

     /// \e

     template <typename Value, typename Converter>

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

 			     const Converter& converter = Converter()) {

       _reader_bits::ValueStorageBase* storage = 

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

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

       return *this;

     }

     /// \e

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

       typedef _reader_bits::MapLookUpConverter<Node> Converter;

       Converter converter(_node_index);

       _reader_bits::ValueStorageBase* storage = 

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

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

       return *this;

     }

     /// \e

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

       typedef _reader_bits::MapLookUpConverter<Arc> Converter;

       Converter converter(_arc_index);

       _reader_bits::ValueStorageBase* storage = 

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

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

       return *this;

     }

     /// \e

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

       _nodes_caption = caption;

       return *this;

     }

     /// \e

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

       _arcs_caption = caption;

       return *this;

     }

     /// \e

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

       _attributes_caption = caption;

       return *this;

     }

     /// \e

     template <typename Map>

     DigraphReader& useNodes(const Map& map) {

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

       LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

       _use_nodes = true;

       _writer_bits::DefaultConverter<typename Map::Value> converter;

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

 	_node_index.insert(std::make_pair(converter(map[n]), n));

       }

       return *this;

     }

     /// \e

     template <typename Map, typename Converter>

     DigraphReader& useNodes(const Map& map, 

 			    const Converter& converter = Converter()) {

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

       LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

       _use_nodes = true;

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

 	_node_index.insert(std::make_pair(converter(map[n]), n));

       }

       return *this;

     }

     /// \e

     template <typename Map>

     DigraphReader& useArcs(const Map& map) {

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

       LEMON_ASSERT(!_use_arcs, "Multiple usage of useArcs() member");

       _use_arcs = true;

       _writer_bits::DefaultConverter<typename Map::Value> converter;

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

 	_arc_index.insert(std::make_pair(converter(map[a]), a));

       }

       return *this;

     }

     /// \e

     template <typename Map, typename Converter>

     DigraphReader& useArcs(const Map& map, 

 			    const Converter& converter = Converter()) {

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

       LEMON_ASSERT(!_use_arcs, "Multiple usage of useArcs() member"); 

       _use_arcs = true;

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

 	_arc_index.insert(std::make_pair(converter(map[a]), a));

       }

       return *this;

     }

   private:

     bool readLine() {

       std::string str;

       while(++line_num, std::getline(*_is, str)) {

 	line.clear(); line.str(str);

 	char c;

 	if (line >> std::ws >> c && c != '#') {

 	  line.putback(c);

 	  return true;

 	}

       }

       return false;

     }

     bool readSuccess() {

       return static_cast<bool>(*_is);

     }

     void skipSection() {

       char c;

       while (readSuccess() && line >> c && c != '@') {

 	readLine();

       }

       line.putback(c);

     }

     void readNodes() {

       std::vector<int> map_index(_node_maps.size());

       int map_num, label_index;

       if (!readLine()) 

 	throw DataFormatError("Cannot find map captions");

       {

 	std::map<std::string, int> maps;

 	std::string map;

 	int index = 0;

 	while (_reader_bits::readIdentifier(line, map)) {

 	  if (maps.find(map) != maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of node map: " << map;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  maps.insert(std::make_pair(map, index));

 	  ++index;

 	}

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

 	  std::map<std::string, int>::iterator jt = 

 	    maps.find(_node_maps[i].first);

 	  if (jt == maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Map not found in file: " << _node_maps[i].first;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  map_index[i] = jt->second;

 	}

 	{

 	  std::map<std::string, int>::iterator jt = maps.find("label");

 	  if (jt == maps.end())

 	    throw DataFormatError("Label map not found in file");

 	  label_index = jt->second;

 	}

 	map_num = maps.size();

       }

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::vector<std::string> tokens(map_num);

 	for (int i = 0; i < map_num; ++i) {

 	  if (!_reader_bits::readToken(line, tokens[i])) {

 	    std::ostringstream msg;

 	    msg << "Column not found (" << i + 1 << ")";

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	}

 	if (line >> std::ws >> c)

 	  throw DataFormatError("Extra character on the end of line");

 	Node n;

 	if (!_use_nodes) {

 	  n = _digraph.addNode();

 	  _node_index.insert(std::make_pair(tokens[label_index], n));

 	} else {

 	  typename std::map<std::string, Node>::iterator it =

 	    _node_index.find(tokens[label_index]);

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

 	    std::ostringstream msg;

 	    msg << "Node with label not found: " << tokens[label_index];

 	    throw DataFormatError(msg.str().c_str());	    

 	  }

 	  n = it->second;

 	}

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

 	  _node_maps[i].second->set(n, tokens[map_index[i]]);

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

     }

     void readArcs() {

       std::vector<int> map_index(_arc_maps.size());

       int map_num, label_index;

       if (!readLine()) 

 	throw DataFormatError("Cannot find map captions");

       {

 	std::map<std::string, int> maps;

 	std::string map;

 	int index = 0;

 	while (_reader_bits::readIdentifier(line, map)) {

 	  if (maps.find(map) != maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of arc map: " << map;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  maps.insert(std::make_pair(map, index));

 	  ++index;

 	}

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

 	  std::map<std::string, int>::iterator jt = 

 	    maps.find(_arc_maps[i].first);

 	  if (jt == maps.end()) {

 	    std::ostringstream msg;

 	    msg << "Map not found in file: " << _arc_maps[i].first;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  map_index[i] = jt->second;

 	}

 	{

 	  std::map<std::string, int>::iterator jt = maps.find("label");

 	  if (jt == maps.end())

 	    throw DataFormatError("Label map not found in file");

 	  label_index = jt->second;

 	}

 	map_num = maps.size();

       }

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::string source_token;

 	std::string target_token;

 	if (!_reader_bits::readToken(line, source_token))

 	  throw DataFormatError("Source not found");

 	if (!_reader_bits::readToken(line, target_token))

 	  throw DataFormatError("Source not found");

 	std::vector<std::string> tokens(map_num);

 	for (int i = 0; i < map_num; ++i) {

 	  if (!_reader_bits::readToken(line, tokens[i])) {

 	    std::ostringstream msg;

 	    msg << "Column not found (" << i + 1 << ")";

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	}

 	if (line >> std::ws >> c)

 	  throw DataFormatError("Extra character on the end of line");

 	Arc a;

 	if (!_use_arcs) {

           typename NodeIndex::iterator it;

           it = _node_index.find(source_token);

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

             std::ostringstream msg;

             msg << "Item not found: " << source_token;

             throw DataFormatError(msg.str().c_str());

           }

           Node source = it->second;

           it = _node_index.find(target_token);

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

             std::ostringstream msg;            

             msg << "Item not found: " << target_token;

             throw DataFormatError(msg.str().c_str());

           }                                          

           Node target = it->second;                            

 	  a = _digraph.addArc(source, target);

 	  _arc_index.insert(std::make_pair(tokens[label_index], a));

 	} else {

 	  typename std::map<std::string, Arc>::iterator it =

 	    _arc_index.find(tokens[label_index]);

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

 	    std::ostringstream msg;

 	    msg << "Arc with label not found: " << tokens[label_index];

 	    throw DataFormatError(msg.str().c_str());	    

 	  }

 	  a = it->second;

 	}

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

 	  _arc_maps[i].second->set(a, tokens[map_index[i]]);

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

     }

     void readAttributes() {

       std::set<std::string> read_attr;

       char c;

       while (readLine() && line >> c && c != '@') {

 	line.putback(c);

 	std::string attr, token;

 	if (!_reader_bits::readIdentifier(line, attr))

 	  throw DataFormatError("Attribute name not found");

 	if (!_reader_bits::readToken(line, token))

 	  throw DataFormatError("Attribute value not found");

 	if (line >> c)

 	  throw DataFormatError("Extra character on the end of line");	  

 	{

 	  std::set<std::string>::iterator it = read_attr.find(attr);

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

 	    std::ostringstream msg;

 	    msg << "Multiple occurence of attribute " << attr;

 	    throw DataFormatError(msg.str().c_str());

 	  }

 	  read_attr.insert(attr);

 	}

 	{

 	  typename Attributes::iterator it = _attributes.lower_bound(attr);

 	  while (it != _attributes.end() && it->first == attr) {

 	    it->second->set(token);

 	    ++it;

 	  }

 	}

       }

       if (readSuccess()) {

 	line.putback(c);

       }

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

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

 	if (read_attr.find(it->first) == read_attr.end()) {

 	  std::ostringstream msg;

 	  msg << "Attribute not found in file: " << it->first;

 	  throw DataFormatError(msg.str().c_str());

 	}	

       }

     }

   public:

     /// \e

     void run() {

       LEMON_ASSERT(_is != 0, "This reader assigned to an other reader");

       bool nodes_done = false;

       bool arcs_done = false;

       bool attributes_done = false;

       line_num = 0;      

       readLine();

       while (readSuccess()) {

 	skipSection();

 	try {

 	  char c;

 	  std::string section, caption;

 	  line >> c;

 	  _reader_bits::readIdentifier(line, section);

 	  _reader_bits::readIdentifier(line, caption);

 	  if (line >> c) 

 	    throw DataFormatError("Extra character on the end of line");

 	  if (section == "nodes" && !nodes_done) {

 	    if (_nodes_caption.empty() || _nodes_caption == caption) {

 	      readNodes();

 	      nodes_done = true;

 	    }

 	  } else if ((section == "arcs" || section == "edges") && 

 		     !arcs_done) {

 	    if (_arcs_caption.empty() || _arcs_caption == caption) {

 	      readArcs();

 	      arcs_done = true;

 	    }

 	  } else if (section == "attributes" && !attributes_done) {

 	    if (_attributes_caption.empty() || _attributes_caption == caption) {

 	      readAttributes();

 	      attributes_done = true;

 	    }

 	  } else {

 	    readLine();

 	    skipSection();

 	  }

 	} catch (DataFormatError& error) {

 	  error.line(line_num);

 	  throw;

 	}	

       }

       if (!nodes_done) {

 	throw DataFormatError("Section @nodes not found");

       }

       if (!arcs_done) {

 	throw DataFormatError("Section @arcs not found");

       }

       if (!attributes_done && !_attributes.empty()) {

 	throw DataFormatError("Section @attributes not found");

       }

     }

   };

   template <typename Digraph>

   DigraphReader<Digraph> digraphReader(std::istream& is, Digraph& digraph) {

     return DigraphReader<Digraph>(is, digraph);

   }

   template <typename Digraph>

   DigraphReader<Digraph> digraphReader(const std::string& fn, 

 				       Digraph& digraph) {

     return DigraphReader<Digraph>(fn, digraph);

   }

   template <typename Digraph>

   DigraphReader<Digraph> digraphReader(const char* fn, Digraph& digraph) {

     return DigraphReader<Digraph>(fn, digraph);

   }

 }

 #endif