/* -*- 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;
    TEMPLATE_DIGRAPH_TYPEDEFS(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