#ifndef PYTHONIC_INCLUDE_ITERTOOLS_IFILTER_HPP
#define PYTHONIC_INCLUDE_ITERTOOLS_IFILTER_HPP

#include "pythonic/include/utils/iterator.hpp"
#include "pythonic/include/itertools/common.hpp"
#include "pythonic/include/utils/functor.hpp"

#include <iterator>
#include <type_traits>

PYTHONIC_NS_BEGIN

namespace itertools
{

  namespace details
  {

    template <typename Operator, typename List0>
    struct ifilter_iterator
        : std::iterator<std::forward_iterator_tag, typename List0::value_type> {
      using sequence_type = typename std::remove_cv<
          typename std::remove_reference<List0>::type>::type;

      Operator op;
      typename List0::iterator iter;
      // FIXME : iter_end should be const because ifilter should be evaluate
      // only once. Some tests doesn't work with it for now because of
      // uncorrect itertools.product implementation
      typename List0::iterator iter_end;

      bool test_filter(std::true_type);
      bool test_filter(std::false_type);

      ifilter_iterator() = default;
      ifilter_iterator(Operator _op, List0 &_seq);
      ifilter_iterator(npos, Operator _op, List0 &_seq);

      typename List0::value_type operator*() const;

      ifilter_iterator &operator++();
      void next_value();

      bool operator==(ifilter_iterator const &other) const;
      bool operator!=(ifilter_iterator const &other) const;
      bool operator<(ifilter_iterator const &other) const;
    };

    // Inherit from iterator_reminder to keep a reference on the iterator
    // && avoid a dangling reference
    // FIXME: It would be better to have a copy only if needed but Pythran
    // typing is ! good enough for this as arguments have
    // remove_cv/remove_ref
    template <typename Operator, typename List0>
    struct ifilter : utils::iterator_reminder<false, List0>,
                     ifilter_iterator<Operator, List0> {

      using value_type = typename List0::value_type;
      using iterator = ifilter_iterator<Operator, List0>;

      iterator end_iter;

      ifilter() = default;
      ifilter(Operator _op, List0 const &_seq);

      iterator &begin();
      iterator const &begin() const;
      iterator const &end() const;
    };
  }

  template <typename Operator, typename List0>
  details::ifilter<typename std::remove_cv<
                       typename std::remove_reference<Operator>::type>::type,
                   typename std::remove_cv<
                       typename std::remove_reference<List0>::type>::type>
  ifilter(Operator &&_op, List0 &&_seq);

  DEFINE_FUNCTOR(pythonic::itertools, ifilter);
}
PYTHONIC_NS_END
#endif
