#include <lemon/concept_check.h>

 #include <lemon/concepts/maps.h>

     class Section {

     public:

       virtual ~Section() {}

       virtual void process(std::ostream& os) = 0;

     };

     template <typename Functor>

     class LineSection : public Section {

     private:

       Functor _functor;

     public:

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

       virtual ~LineSection() {}

       virtual void process(std::ostream& os) {

         std::string line;

         while (!(line = _functor()).empty()) os << line << std::endl;

       }

     };

     template <typename Functor>

     class StreamSection : public Section {

     private:

       Functor _functor;

     public:

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

       virtual ~StreamSection() {}

       virtual void process(std::ostream& os) {

         _functor(os);

       }

     };

   class SectionWriter;

   SectionWriter sectionWriter(std::istream& is);

   SectionWriter sectionWriter(const std::string& fn);

   SectionWriter sectionWriter(const char* fn);

   /// \ingroup lemon_io

   ///

   /// \brief Section writer class

   ///

   /// In the \ref lgf-format "LGF" file extra sections can be placed,

   /// which contain any data in arbitrary format. Such sections can be

   /// written with this class. A writing rule can be added to the

   /// class with two different functions. With the \c sectionLines()

   /// function a generator can write the section line-by-line, while

   /// with the \c sectionStream() member the section can be written to

   /// an output stream.

   class SectionWriter {

   private:

     std::ostream* _os;

     bool local_os;

     typedef std::vector<std::pair<std::string, _writer_bits::Section*> >

     Sections;

     Sections _sections;

   public:

     /// \brief Constructor

     ///

     /// Construct a section writer, which writes to the given output

     /// stream.

     SectionWriter(std::ostream& os)

       : _os(&os), local_os(false) {}

     /// \brief Constructor

     ///

     /// Construct a section writer, which writes into the given file.

     SectionWriter(const std::string& fn)

       : _os(new std::ofstream(fn.c_str())), local_os(true) {}

     /// \brief Constructor

     ///

     /// Construct a section writer, which writes into the given file.

     SectionWriter(const char* fn)

       : _os(new std::ofstream(fn)), local_os(true) {}

     /// \brief Destructor

     ~SectionWriter() {

       for (Sections::iterator it = _sections.begin();

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

         delete it->second;

       }

       if (local_os) {

         delete _os;

       }

     }

   private:

     friend SectionWriter sectionWriter(std::ostream& os);

     friend SectionWriter sectionWriter(const std::string& fn);

     friend SectionWriter sectionWriter(const char* fn);

     SectionWriter(SectionWriter& other)

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

       other._os = 0;

       other.local_os = false;

       _sections.swap(other._sections);

     }

     SectionWriter& operator=(const SectionWriter&);

   public:

     /// \name Section writers

     /// @{

     /// \brief Add a section writer with line oriented writing

     ///

     /// The first parameter is the type descriptor of the section, the

     /// second is a generator with std::string values. At the writing

     /// process, the returned \c std::string will be written into the

     /// output file until it is an empty string.

     ///

     /// For example, an integer vector is written into a section.

     ///\code

     ///  @numbers

     ///  12 45 23 78

     ///  4 28 38 28

     ///  23 6 16

     ///\endcode

     ///

     /// The generator is implemented as a struct.

     ///\code

     ///  struct NumberSection {

     ///    std::vector<int>::const_iterator _it, _end;

     ///    NumberSection(const std::vector<int>& data)

     ///      : _it(data.begin()), _end(data.end()) {}

     ///    std::string operator()() {

     ///      int rem_in_line = 4;

     ///      std::ostringstream ls;

     ///      while (rem_in_line > 0 && _it != _end) {

     ///        ls << *(_it++) << ' ';

     ///        --rem_in_line;

     ///      }

     ///      return ls.str();

     ///    }

     ///  };

     ///

     ///  // ...

     ///

     ///  writer.sectionLines("numbers", NumberSection(vec));

     ///\endcode

     template <typename Functor>

     SectionWriter& sectionLines(const std::string& type, Functor functor) {

       LEMON_ASSERT(!type.empty(), "Type is empty.");

       _sections.push_back(std::make_pair(type,

         new _writer_bits::LineSection<Functor>(functor)));

       return *this;

     }

     /// \brief Add a section writer with stream oriented writing

     ///

     /// The first parameter is the type of the section, the second is

     /// a functor, which takes a \c std::ostream& parameter. The

     /// functor writes the section to the output stream.

     /// \warning The last line must be closed with end-line character.

     template <typename Functor>

     SectionWriter& sectionStream(const std::string& type, Functor functor) {

       LEMON_ASSERT(!type.empty(), "Type is empty.");

       _sections.push_back(std::make_pair(type,

          new _writer_bits::StreamSection<Functor>(functor)));

       return *this;

     }

     /// @}

   public:

     /// \name Execution of the writer

     /// @{

     /// \brief Start the batch processing

     ///

     /// This function starts the batch processing.

     void run() {

       LEMON_ASSERT(_os != 0, "This writer is assigned to an other writer");

       for (Sections::iterator it = _sections.begin();

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

         (*_os) << '@' << it->first << std::endl;

         it->second->process(*_os);

       }

     }

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

     ///

     /// Returns the stream of the writer

     std::ostream& ostream() {

       return *_os;

     }

     /// @}

   };

   /// \brief Return a \ref SectionWriter class

   ///

   /// This function just returns a \ref SectionWriter class.

   /// \relates SectionWriter

   inline SectionWriter sectionWriter(std::ostream& os) {

     SectionWriter tmp(os);

     return tmp;

   }

   /// \brief Return a \ref SectionWriter class

   ///

   /// This function just returns a \ref SectionWriter class.

   /// \relates SectionWriter

   inline SectionWriter sectionWriter(const std::string& fn) {

     SectionWriter tmp(fn);

     return tmp;

   }

   /// \brief Return a \ref SectionWriter class

   ///

   /// This function just returns a \ref SectionWriter class.

   /// \relates SectionWriter

   inline SectionWriter sectionWriter(const char* fn) {

     SectionWriter tmp(fn);

     return tmp;

   }