/// \ingroup lemon_io

   ///

   /// \brief Reader for the content of the \ref lgf-format "LGF" file 

   ///

   /// This class can be used to read the sections, the map names and

   /// the attributes from a file. Usually, the Lemon programs know

   /// that, which type of graph, which maps and which attributes

   /// should be read from a file, but in general tools (like glemon)

   /// the content of an LGF file should be guessed somehow. This class

   /// reads the graph and stores the appropriate information for

   /// reading the graph.

   ///

   ///\code LgfContent content("graph.lgf"); 

   /// content.run();

   ///

   /// // does it contain any node section and arc section

   /// if (content.nodeSectionNum() == 0 || content.arcSectionNum()) {

   ///   std::cerr << "Failure, cannot find graph" << std::endl;

   ///   return -1;

   /// }

   /// std::cout << "The name of the default node section : " 

   ///           << content.nodeSection(0) << std::endl;

   /// std::cout << "The number of the arc maps : " 

   ///           << content.arcMaps(0).size() << std::endl;

   /// std::cout << "The name of second arc map : " 

   ///           << content.arcMaps(0)[1] << std::endl;

   ///\endcode

   class LgfContent {    

   private:

     std::istream* _is;

     bool local_is;

     std::vector<std::string> _node_sections;

     std::vector<std::string> _edge_sections;

     std::vector<std::string> _attribute_sections;

     std::vector<std::string> _extra_sections;

     std::vector<bool> _arc_sections;

     std::vector<std::vector<std::string> > _node_maps;

     std::vector<std::vector<std::string> > _edge_maps;

     std::vector<std::vector<std::string> > _attributes;

     int line_num;

     std::istringstream line;

   public:

     /// \brief Constructor

     ///

     /// Construct an \e LGF content reader, which reads from the given

     /// input stream.

     LgfContent(std::istream& is) 

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

     /// \brief Constructor

     ///

     /// Construct an \e LGF content reader, which reads from the given

     /// file.

     LgfContent(const std::string& fn) 

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

     /// \brief Constructor

     ///

     /// Construct an \e LGF content reader, which reads from the given

     /// file.

     LgfContent(const char* fn)

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

     /// \brief Copy constructor

     ///

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

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

     LgfContent(LgfContent& other)

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

       other._is = 0;

       other.local_is = false;

       _node_sections.swap(other._node_sections);

       _edge_sections.swap(other._edge_sections);

       _attribute_sections.swap(other._attribute_sections);

       _extra_sections.swap(other._extra_sections);

       _arc_sections.swap(other._arc_sections);

       _node_maps.swap(other._node_maps);

       _edge_maps.swap(other._edge_maps);

       _attributes.swap(other._attributes);

     }

     /// \brief Destructor

     ~LgfContent() {

       if (local_is) delete _is;

     }

     /// \name Node sections

     /// @{

     /// \brief Gives back the number of node sections in the file.

     ///

     /// Gives back the number of node sections in the file.

     int nodeSectionNum() const {

       return _node_sections.size();

     }

     /// \brief Returns the section name at the given position. 

     ///

     /// Returns the section name at the given position. 

     const std::string& nodeSection(int i) const {

       return _node_sections[i];

     }

     /// \brief Gives back the node maps for the given section.

     ///

     /// Gives back the node maps for the given section.

     const std::vector<std::string>& nodeMaps(int i) const {

       return _node_maps[i];

     }

     /// @}

     /// \name Arc sections 

     /// @{

     /// \brief Gives back the number of arc sections in the file.

     ///

     /// Gives back the number of arc sections in the file.

     /// \note It is synonim of \c edgeSectionNum().

     int arcSectionNum() const {

       return _edge_sections.size();

     }

     /// \brief Returns the section name at the given position. 

     ///

     /// Returns the section name at the given position. 

     /// \note It is synonim of \c edgeSection().

     const std::string& arcSection(int i) const {

       return _edge_sections[i];

     }

     /// \brief Gives back the arc maps for the given section.

     ///

     /// Gives back the arc maps for the given section.

     /// \note It is synonim of \c edgeMaps().

     const std::vector<std::string>& arcMaps(int i) const {

       return _edge_maps[i];

     }

     /// \brief Returns true when the section type is \c "@arcs".

     ///

     /// Returns true when the section type is \c "@arcs", and not "@edges".

     bool isArcSection(int i) const {

       return _arc_sections[i];

     }

     /// @}

     /// \name Edge sections   

     /// @{

     /// \brief Gives back the number of edge sections in the file.

     ///

     /// Gives back the number of edge sections in the file.

     int edgeSectionNum() const {

       return _edge_sections.size();

     }

     /// \brief Returns the section name at the given position. 

     ///

     /// Returns the section name at the given position. 

     const std::string& edgeSection(int i) const {

       return _edge_sections[i];

     }

     /// \brief Gives back the edge maps for the given section.

     ///

     /// Gives back the edge maps for the given section.

     const std::vector<std::string>& edgeMaps(int i) const {

       return _edge_maps[i];

     }

     /// \brief Returns true when the section type is \c "@edges".

     ///

     /// Returns true when the section type is \c "@edges", and not "@arcs".

     bool isEdgeSection(int i) const {

       return !_arc_sections[i];

     }

     /// @}

     /// \name Attribute sections   

     /// @{

     /// \brief Gives back the number of attribute sections in the file.

     ///

     /// Gives back the number of attribute sections in the file.

     int attributeSectionNum() const {

       return _attribute_sections.size();

     }

     /// \brief Returns the section name at the given position. 

     ///

     /// Returns the section name at the given position. 

     const std::string& attributeSection(int i) const {

       return _attribute_sections[i];

     }

     /// \brief Gives back the attributes for the given section.

     ///

     /// Gives back the attributes for the given section.

     const std::vector<std::string>& attributes(int i) const {

       return _attributes[i];

     }

     /// @}

     /// \name Extra sections   

     /// @{

     /// \brief Gives back the number of extra sections in the file.

     ///

     /// Gives back the number of extra sections in the file.

     int extraSectionNum() const {

       return _extra_sections.size();

     }

     /// \brief Returns the extra section type at the given position. 

     ///

     /// Returns the section type at the given position. 

     const std::string& extraSection(int i) const {

       return _extra_sections[i];

     }

     /// @}

   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 readMaps(std::vector<std::string>& maps) {

       if (!readLine()) 

 	throw DataFormatError("Cannot find map captions");

       std::string map;

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

 	maps.push_back(map);

       }

     }

     void readAttributes(std::vector<std::string>& attrs) {

       readLine();

       char c;

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

 	line.putback(c);

 	std::string attr;

 	_reader_bits::readToken(line, attr);

 	attrs.push_back(attr);

 	readLine();

       }

       line.putback(c);

     }

   public:

     /// \name Execution of the content reader    

     /// @{

     /// \brief Start the reading

     ///

     /// This function starts the reading

     void run() {

       readLine();

       skipSection();

       while (readSuccess()) {

 	char c;

 	line >> c;

 	std::string section, caption;

 	_reader_bits::readToken(line, section);

 	_reader_bits::readToken(line, caption);

 	if (section == "nodes") {

 	  _node_sections.push_back(caption);

 	  _node_maps.push_back(std::vector<std::string>());

 	  readMaps(_node_maps.back());

 	  readLine(); skipSection();

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

 	  _edge_sections.push_back(caption);

 	  _arc_sections.push_back(section == "arcs");

 	  _edge_maps.push_back(std::vector<std::string>());

 	  readMaps(_edge_maps.back());

 	  readLine(); skipSection();

 	} else if (section == "attributes") {

 	  _attribute_sections.push_back(caption);

 	  _attributes.push_back(std::vector<std::string>());

 	  readAttributes(_attributes.back());

 	} else {

 	  _extra_sections.push_back(section);

 	  readLine(); skipSection();

 	}

       }

     }

     /// @}

   };