/* -*- mode: C++; indent-tabs-mode: nil; -*-

 *

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

 *

 * Copyright (C) 2003-2013

 * 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 \ref lgf-format "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/core.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;

        if (!(is >> value)) {

          throw FormatError("Cannot read token");

        }

        char c;

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

          throw FormatError("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));

      }

    };

    template <typename _GR, bool _dir, typename _Map,

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

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

    public:

      typedef _Map Map;

      typedef _Converter Converter;

      typedef _GR GR;

      typedef typename GR::Edge Item;

      static const bool dir = _dir;

    private:

      const GR& _graph;

      Map& _map;

      Converter _converter;

    public:

      GraphArcMapStorage(const GR& graph, Map& map,

                         const Converter& converter = Converter())

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

      virtual ~GraphArcMapStorage() {}

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

        _map.set(_graph.direct(item, dir), _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,

              typename Map = std::map<std::string, Value> >

    struct MapLookUpConverter {

      const Map& _map;

      MapLookUpConverter(const Map& map)

        : _map(map) {}

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

        typename Map::const_iterator it = _map.find(str);

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

          std::ostringstream msg;

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

          throw FormatError(msg.str());

        }

        return it->second;

      }

    };

    template <typename Value,

              typename Map1 = std::map<std::string, Value>,

              typename Map2 = std::map<std::string, Value> >

    struct DoubleMapLookUpConverter {

      const Map1& _map1;

      const Map2& _map2;

      DoubleMapLookUpConverter(const Map1& map1, const Map2& map2)

        : _map1(map1), _map2(map2) {}

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

        typename Map1::const_iterator it1 = _map1.find(str);

        typename Map2::const_iterator it2 = _map2.find(str);

        if (it1 == _map1.end()) {

          if (it2 == _map2.end()) {

            std::ostringstream msg;

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

            throw FormatError(msg.str());

          } else {

            return it2->second;

          }

        } else {

          if (it2 == _map2.end()) {

            return it1->second;

          } else {

            std::ostringstream msg;

            msg << "Item is ambigous: " << str;

            throw FormatError(msg.str());

          }

        }

      }

    };

    template <typename GR>

    struct GraphArcLookUpConverter {

      const GR& _graph;

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

      GraphArcLookUpConverter(const GR& graph,

                              const std::map<std::string,

                                             typename GR::Edge>& map)

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

      typename GR::Arc operator()(const std::string& str) {

        if (str.empty() || (str[0] != '+' && str[0] != '-')) {

          throw FormatError("Item must start with '+' or '-'");

        }

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

          ::const_iterator it = _map.find(str.substr(1));

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

          throw FormatError("Item not found");

        }

        return _graph.direct(it->second, str[0] == '+');

      }

    };

    inline bool isWhiteSpace(char c) {

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

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

    }

    inline bool isOct(char c) {

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

    }

    inline int valueOct(char c) {

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

      return c - '0';

    }

    inline bool isHex(char c) {

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

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

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

    }

    inline 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;

    }

    inline bool isIdentifierFirstChar(char c) {

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

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

    }

    inline bool isIdentifierChar(char c) {

      return isIdentifierFirstChar(c) ||

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

    }

    inline char readEscape(std::istream& is) {

      char c;

      if (!is.get(c))

        throw FormatError("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 FormatError("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 FormatError("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;

        }

      }

    }

    inline 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 FormatError("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;

    }

    class Section {

    public:

      virtual ~Section() {}

      virtual void process(std::istream& is, int& line_num) = 0;

    };

    template <typename Functor>

    class LineSection : public Section {

    private:

      Functor _functor;

    public:

      LineSection(const Functor& functor) : _functor(functor) {}

      virtual ~LineSection() {}

      virtual void process(std::istream& is, int& line_num) {

        char c;

        std::string line;

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

          if (c == '\n') {

            ++line_num;

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

            getline(is, line);

            ++line_num;

          } else if (!isWhiteSpace(c)) {

            is.putback(c);

            getline(is, line);

            _functor(line);

            ++line_num;

          }

        }

        if (is) is.putback(c);

        else if (is.eof()) is.clear();

      }

    };

    template <typename Functor>

    class StreamSection : public Section {

    private:

      Functor _functor;

    public:

      StreamSection(const Functor& functor) : _functor(functor) {}

      virtual ~StreamSection() {}

      virtual void process(std::istream& is, int& line_num) {

        _functor(is, line_num);

        char c;

        std::string line;

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

          if (c == '\n') {

            ++line_num;

          } else if (!isWhiteSpace(c)) {

            getline(is, line);

            ++line_num;

          }

        }

        if (is) is.putback(c);

        else if (is.eof()) is.clear();

      }

    };

  }

  template <typename DGR>

  class DigraphReader;

  template <typename TDGR>

  DigraphReader<TDGR> digraphReader(TDGR& digraph, std::istream& is = std::cin);

  template <typename TDGR>

  DigraphReader<TDGR> digraphReader(TDGR& digraph, const std::string& fn);

  template <typename TDGR>

  DigraphReader<TDGR> digraphReader(TDGR& digraph, const char *fn);

  /// \ingroup lemon_io

  ///

  /// \brief \ref lgf-format "LGF" reader for directed graphs

  ///

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

  ///

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

  /// reader object, then various reading rules can be added to the

  /// reader, and eventually the reading is executed with the \c run()

  /// member function. A map reading rule can be added to the reader

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

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

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

  /// is set, it will determine how the tokens in the file should be

  /// converted to the value type of the map. If the functor is not set,

  /// then a default conversion will be used. One map can be read into

  /// multiple map objects at the same time. The \c attribute(), \c

  /// node() and \c arc() functions are used to add attribute reading

  /// rules.

  ///

  ///\code

  /// DigraphReader<DGR>(digraph, std::cin).

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

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

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

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

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

  ///   run();

  ///\endcode

  ///

  /// By default, the reader uses the first section in the file of the

  /// proper type. If a section has an optional name, then it can be

  /// selected for reading by giving an optional name parameter to the

  /// \c nodes(), \c arcs() or \c attributes() functions.

  ///

  /// The \c useNodes() and \c useArcs() functions are used to tell the reader

  /// that the nodes or arcs should not be constructed (added to the

  /// graph) during the reading, but instead the label map of the items

  /// are given as a parameter of these functions. An

  /// application of these functions is multipass reading, which is

  /// important if two \c \@arcs sections must be read from the

  /// file. In this case the first phase would read the node set and one

  /// of the arc sets, while the second phase would read the second arc

  /// set into an \e ArcSet class (\c SmartArcSet or \c ListArcSet).

  /// The previously read label node map should be passed to the \c

  /// useNodes() functions. Another application of multipass reading when

  /// paths are given as a node map or an arc map.

  /// It is impossible to read this in

  /// a single pass, because the arcs are not constructed when the node

  /// maps are read.

  template <typename DGR>

  class DigraphReader {

  public:

    typedef DGR Digraph;

  private:

    TEMPLATE_DIGRAPH_TYPEDEFS(DGR);

    std::istream* _is;

    bool local_is;

    std::string _filename;

    DGR& _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;

    bool _skip_nodes;

    bool _skip_arcs;

    int line_num;

    std::istringstream line;

  public:

    /// \brief Constructor

    ///

    /// Construct a directed graph reader, which reads from the given

    /// input stream.

    DigraphReader(DGR& digraph, std::istream& is = std::cin)

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

        _use_nodes(false), _use_arcs(false),

        _skip_nodes(false), _skip_arcs(false) {}

    /// \brief Constructor

    ///

    /// Construct a directed graph reader, which reads from the given

    /// file.

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

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

        _filename(fn), _digraph(digraph),

        _use_nodes(false), _use_arcs(false),

        _skip_nodes(false), _skip_arcs(false) {

      if (!(*_is)) {

        delete _is;

        throw IoError("Cannot open file", fn);

      }

    }

    /// \brief Constructor

    ///

    /// Construct a directed graph reader, which reads from the given

    /// file.

    DigraphReader(DGR& digraph, const char* fn)

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

        _filename(fn), _digraph(digraph),

        _use_nodes(false), _use_arcs(false),

        _skip_nodes(false), _skip_arcs(false) {

      if (!(*_is)) {

        delete _is;

        throw IoError("Cannot open file", fn);

      }

    }

    /// \brief Destructor

    ~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:

    template <typename TDGR>

    friend DigraphReader<TDGR> digraphReader(TDGR& digraph, std::istream& is);

    template <typename TDGR>

    friend DigraphReader<TDGR> digraphReader(TDGR& digraph,

                                             const std::string& fn);

    template <typename TDGR>

    friend DigraphReader<TDGR> digraphReader(TDGR& digraph, const char *fn);

    DigraphReader(DigraphReader& other)

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

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

        _skip_nodes(other._skip_nodes), _skip_arcs(other._skip_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;

    }

    DigraphReader& operator=(const DigraphReader&);

  public:

    /// \name Reading Rules

    /// @{

    /// \brief Node map reading rule

    ///

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

    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;

    }

    /// \brief Node map reading rule

    ///

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

    /// reader.

    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;

    }

    /// \brief Arc map reading rule

    ///

    /// Add an arc map reading rule to the reader.

    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;

    }

    /// \brief Arc map reading rule

    ///

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

    /// reader.

    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;

    }

    /// \brief Attribute reading rule

    ///

    /// Add an attribute reading rule to the reader.

    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;

    }

    /// \brief Attribute reading rule

    ///

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

    /// reader.

    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;

    }

    /// \brief Node reading rule

    ///

    /// Add a node reading rule to reader.

    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;

    }

    /// \brief Arc reading rule

    ///

    /// Add an arc reading rule to reader.

    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;

    }

    /// @}

    /// \name Select Section by Name

    /// @{

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

    ///

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

    DigraphReader& 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

    DigraphReader& 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

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

      _attributes_caption = caption;

      return *this;

    }

    /// @}

    /// \name Using Previously Constructed Node or Arc Set

    /// @{

    /// \brief Use previously constructed node set

    ///

    /// Use previously constructed node set, and specify the node

    /// label map.

    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;

    }

    /// \brief Use previously constructed node set

    ///

    /// Use previously constructed node set, and specify the node

    /// label map and a functor which converts the label map values to

    /// \c std::string.

    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;

    }

    /// \brief Use previously constructed arc set

    ///

    /// Use previously constructed arc set, and specify the arc

    /// label map.

    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;

    }

    /// \brief Use previously constructed arc set

    ///

    /// Use previously constructed arc set, and specify the arc

    /// label map and a functor which converts the label map values to

    /// \c std::string.

    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;

    }

    /// \brief Skips the reading of node section

    ///

    /// Omit the reading of the node section. This implies that each node

    /// map reading rule will be abandoned, and the nodes of the graph

    /// will not be constructed, which usually cause that the arc set

    /// could not be read due to lack of node name resolving.

    /// Therefore \c skipArcs() function should also be used, or

    /// \c useNodes() should be used to specify the label of the nodes.

    DigraphReader& skipNodes() {

      LEMON_ASSERT(!_skip_nodes, "Skip nodes already set");

      _skip_nodes = true;

      return *this;

    }

    /// \brief Skips the reading of arc section

    ///

    /// Omit the reading of the arc section. This implies that each arc

    /// map reading rule will be abandoned, and the arcs of the graph

    /// will not be constructed.

    DigraphReader& skipArcs() {

      LEMON_ASSERT(!_skip_arcs, "Skip arcs already set");

      _skip_arcs = true;

      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();

      }

      if (readSuccess()) {

        line.putback(c);

      }

    }

    void readNodes() {

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

      int map_num, label_index;

      char c;

      if (!readLine() || !(line >> c) || c == '@') {

        if (readSuccess() && line) line.putback(c);

        if (!_node_maps.empty())

          throw FormatError("Cannot find map names");

        return;

      }

      line.putback(c);

      {

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

        std::string map;

        int index = 0;

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

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

            std::ostringstream msg;

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

            throw FormatError(msg.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: " << _node_maps[i].first;

            throw FormatError(msg.str());

          }

          map_index[i] = jt->second;

        }

        {

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

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

            label_index = jt->second;

          } else {

            label_index = -1;

          }

        }

        map_num = maps.size();

      }

      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 FormatError(msg.str());

          }

        }

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

          throw FormatError("Extra character at the end of line");

        Node n;

        if (!_use_nodes) {

          n = _digraph.addNode();

          if (label_index != -1)

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

        } else {

          if (label_index == -1)

            throw FormatError("Label map not found");

          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 FormatError(msg.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;

      char c;

      if (!readLine() || !(line >> c) || c == '@') {

        if (readSuccess() && line) line.putback(c);

        if (!_arc_maps.empty())

          throw FormatError("Cannot find map names");

        return;

      }

      line.putback(c);

      {