// Copyright (c) 2011  INRIA Saclay Ile-de-France (France).
// All rights reserved.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/STL_Extension/include/CGAL/type_traits/is_iterator.h $
// $Id: include/CGAL/type_traits/is_iterator.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Marc Glisse


#ifndef CGAL_TYPE_TRAITS_IS_ITERATOR_H
#define CGAL_TYPE_TRAITS_IS_ITERATOR_H

#include <boost/mpl/has_xxx.hpp>
#include <boost/mpl/logical.hpp>

#include <iterator>

namespace CGAL {
namespace internal {

BOOST_MPL_HAS_XXX_TRAIT_DEF(iterator_category)
BOOST_MPL_HAS_XXX_TRAIT_DEF(value_type)
BOOST_MPL_HAS_XXX_TRAIT_DEF(difference_type)
BOOST_MPL_HAS_XXX_TRAIT_DEF(pointer)
BOOST_MPL_HAS_XXX_TRAIT_DEF(reference)

//We request the type to be either a pointer or to
//provide all 5 nested types provided by iterator_traits
template <class T>
struct is_iterator_
  : public std::bool_constant<
             ( has_iterator_category<T>::value &&
               has_value_type<T>::value &&
               has_difference_type<T>::value &&
               has_pointer<T>::value &&
               has_reference<T>::value) ||
               std::is_pointer_v<T> >
{ };

template <class T, class U, bool = is_iterator_<T>::value>
struct is_iterator_type_
  : public boost::mpl::false_
{ };

template <class T,class U>
struct is_iterator_type_<T, U, true>
  : public //std::is_base_of<U,typename std::iterator_traits<T>::iterator_category>
           std::is_convertible<typename std::iterator_traits<T>::iterator_category, U>
{ };

} // namespace internal

// NOTE: we don't want the real std::decay or functions are included
template <class T>
struct is_iterator
  : public internal::is_iterator_<std::remove_cv_t<std::remove_reference_t<T>>>
{ };

template <class T>
inline constexpr bool is_iterator_v = is_iterator<T>::value;

template <class T, class Tag>
struct is_iterator_type
  : public internal::is_iterator_type_<std::remove_cv_t<std::remove_reference_t<T>>, Tag>
{ };

template <class T, class Tag>
inline constexpr bool is_iterator_type_v = is_iterator_type<T,Tag>::value;


template <class T, class U, bool = is_iterator<T>::value>
struct is_iterator_to
  : public boost::mpl::false_
{ };

template <class T, class U>
struct is_iterator_to<T, U, true>
  : public std::is_convertible<typename std::iterator_traits<T>::value_type, U>
{ };

template <class T, class U>
inline constexpr bool is_iterator_to_v = is_iterator_to<T,U>::value;


} // namespace CGAL

#endif // CGAL_IS_ITERATOR_H

