//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_RANGES_ADJACENT_FIND_H
#define _LIBCPP___ALGORITHM_RANGES_ADJACENT_FIND_H

#include <__config>
#include <__functional/identity.h>
#include <__functional/invoke.h>
#include <__functional/ranges_operations.h>
#include <__iterator/concepts.h>
#include <__iterator/projected.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/dangling.h>
#include <__utility/move.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

#if _LIBCPP_STD_VER >= 20

_LIBCPP_BEGIN_NAMESPACE_STD

namespace ranges {
namespace __adjacent_find {
struct __fn {
  template <class _Iter, class _Sent, class _Proj, class _Pred>
  _LIBCPP_HIDE_FROM_ABI constexpr static _Iter
  __adjacent_find_impl(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
    if (__first == __last)
      return __first;

    auto __i = __first;
    while (++__i != __last) {
      if (std::invoke(__pred, std::invoke(__proj, *__first), std::invoke(__proj, *__i)))
        return __first;
      __first = __i;
    }
    return __i;
  }

  template <forward_iterator _Iter,
            sentinel_for<_Iter> _Sent,
            class _Proj                                                                       = identity,
            indirect_binary_predicate<projected<_Iter, _Proj>, projected<_Iter, _Proj>> _Pred = ranges::equal_to>
  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Iter
  operator()(_Iter __first, _Sent __last, _Pred __pred = {}, _Proj __proj = {}) const {
    return __adjacent_find_impl(std::move(__first), std::move(__last), __pred, __proj);
  }

  template <forward_range _Range,
            class _Proj = identity,
            indirect_binary_predicate<projected<iterator_t<_Range>, _Proj>, projected<iterator_t<_Range>, _Proj>>
                _Pred = ranges::equal_to>
  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Range>
  operator()(_Range&& __range, _Pred __pred = {}, _Proj __proj = {}) const {
    return __adjacent_find_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
  }
};
} // namespace __adjacent_find

inline namespace __cpo {
inline constexpr auto adjacent_find = __adjacent_find::__fn{};
} // namespace __cpo
} // namespace ranges

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_STD_VER >= 20

#endif // _LIBCPP___ALGORITHM_RANGES_ADJACENT_FIND_H