// Copyright (C) 2007, 2008, 2009 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation, version 2 of the License.
//
// Olena is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_ACCU_COUNT_HH
# define MLN_ACCU_COUNT_HH

/// \file
///
/// Define an accumulator that counts.

# include <mln/accu/internal/base.hh>
# include <mln/core/concept/meta_accumulator.hh>


namespace mln
{

  // Forward declaration.
  namespace accu { template <typename T> struct count; }


  // Traits.

  namespace trait
  {

    template <typename T>
    struct accumulator_< accu::count<T> >
    {
      typedef accumulator::has_untake::yes    has_untake;
      typedef accumulator::has_set_value::yes has_set_value;
      typedef accumulator::has_stop::no       has_stop;
      typedef accumulator::when_pix::use_pix  when_pix;
    };

  } // end of namespace mln::trait


  namespace accu
  {

    /// \brief Generic counter accumulator.
    /// The parameter \a T is the type to be count.
    ///
    /// \ingroup modaccusiteset
    //
    template <typename T>
    struct count : public mln::accu::internal::base< unsigned , count<T> >
    {
      typedef T argument;

      count();

      /// Manipulators.
      /// \{
      void init();
      void take(const argument&);
      void take(const count<T>& other);

      void untake(const argument&);
      void untake(const count<T>& other);

      /// Force the value of the counter to \a c.
      void set_value(unsigned c);
      /// \}

      /// Get the value of the accumulator.
      unsigned to_result() const;

      /// Check whether this accu is able to return a result.
      /// Always true here.
      bool is_valid() const;

    protected:
      /// The value of the counter.
      unsigned count_;
    };


    namespace meta
    {

      /// Meta accumulator for count.
      struct count : public Meta_Accumulator< count >
      {
	template <typename T>
	struct with
	{
	  typedef accu::count<T> ret;
	};
      };

    } // end of namespace mln::accu::meta



# ifndef MLN_INCLUDE_ONLY

    template <typename T>
    inline
    count<T>::count()
    {
      init();
    }

    template <typename T>
    inline
    void
    count<T>::init()
    {
      count_ = 0;
    }

    template <typename T>
    inline
    void
    count<T>::take(const argument&)
    {
      ++count_;
    }

    template <typename T>
    inline
    void
    count<T>::untake(const argument&)
    {
      mln_precondition(count_ > 0);
      --count_;
    }

    template <typename T>
    inline
    void
    count<T>::take(const count<T>& other)
    {
      count_ += other.count_;
    }

    template <typename T>
    inline
    void
    count<T>::untake(const count<T>& other)
    {
      mln_precondition(other.count_ <= count_);
      count_ -= other.count_;
    }

    template <typename T>
    inline
    unsigned
    count<T>::to_result() const
    {
      return count_;
    }

    template <typename T>
    inline
    void
    count<T>::set_value(unsigned c)
    {
      count_ = c;
    }

    template <typename T>
    inline
    bool
    count<T>::is_valid() const
    {
      return true;
    }

# endif // ! MLN_INCLUDE_ONLY

  } // end of namespace mln::accu

} // end of namespace mln


#endif // ! MLN_ACCU_COUNT_HH