// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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
// SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCUDACXX___RANGES_RBEGIN_H
#define _LIBCUDACXX___RANGES_RBEGIN_H

#include <cuda/std/detail/__config>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#include <cuda/std/__concepts/class_or_enum.h>
#include <cuda/std/__concepts/same_as.h>
#include <cuda/std/__iterator/concepts.h>
#include <cuda/std/__iterator/readable_traits.h>
#include <cuda/std/__iterator/reverse_iterator.h>
#include <cuda/std/__ranges/access.h>
#include <cuda/std/__type_traits/is_reference.h>
#include <cuda/std/__type_traits/remove_cvref.h>
#include <cuda/std/__type_traits/remove_reference.h>
#include <cuda/std/__utility/auto_cast.h>

_LIBCUDACXX_BEGIN_NAMESPACE_RANGES

#if _CCCL_STD_VER >= 2017 && !defined(_CCCL_COMPILER_MSVC_2017)

// [ranges.access.rbegin]

_LIBCUDACXX_BEGIN_NAMESPACE_CPO(__rbegin)
template <class _Tp>
void rbegin(_Tp&) = delete;
template <class _Tp>
void rbegin(const _Tp&) = delete;

#  if _CCCL_STD_VER >= 2020
template <class _Tp>
concept __member_rbegin = __can_borrow<_Tp> && __workaround_52970<_Tp> && requires(_Tp&& __t) {
  {
    _LIBCUDACXX_AUTO_CAST(__t.rbegin())
  } -> input_or_output_iterator;
};

template <class _Tp>
concept __unqualified_rbegin =
  !__member_rbegin<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
    {
      _LIBCUDACXX_AUTO_CAST(rbegin(__t))
    } -> input_or_output_iterator;
  };

template <class _Tp>
concept __can_reverse =
  __can_borrow<_Tp> && !__member_rbegin<_Tp> && !__unqualified_rbegin<_Tp> && requires(_Tp&& __t) {
    {
      _CUDA_VRANGES::begin(__t)
    } -> same_as<decltype(_CUDA_VRANGES::end(__t))>;
    {
      _CUDA_VRANGES::begin(__t)
    } -> bidirectional_iterator;
  };
#  else // ^^^ CXX20 ^^^ / vvv CXX17 vvv
template <class _Tp>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __member_rbegin_,
  requires(_Tp&& __t)(requires(__can_borrow<_Tp>),
                      requires(__workaround_52970<_Tp>),
                      requires(input_or_output_iterator<decltype(_LIBCUDACXX_AUTO_CAST(__t.rbegin()))>)));

template <class _Tp>
_LIBCUDACXX_CONCEPT __member_rbegin = _LIBCUDACXX_FRAGMENT(__member_rbegin_, _Tp);

template <class _Tp>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __unqualified_rbegin_,
  requires(_Tp&& __t)(requires(!__member_rbegin<_Tp>),
                      requires(__can_borrow<_Tp>),
                      requires(__class_or_enum<remove_cvref_t<_Tp>>),
                      requires(input_or_output_iterator<decltype(_LIBCUDACXX_AUTO_CAST(rbegin(__t)))>)));

template <class _Tp>
_LIBCUDACXX_CONCEPT __unqualified_rbegin = _LIBCUDACXX_FRAGMENT(__unqualified_rbegin_, _Tp);

template <class _Tp>
_LIBCUDACXX_CONCEPT_FRAGMENT(
  __can_reverse_,
  requires(_Tp&& __t)(requires(__can_borrow<_Tp>),
                      requires(!__member_rbegin<_Tp>),
                      requires(!__unqualified_rbegin<_Tp>),
                      requires(same_as<decltype(_CUDA_VRANGES::end(__t)), decltype(_CUDA_VRANGES::begin(__t))>),
                      requires(bidirectional_iterator<decltype(_CUDA_VRANGES::begin(__t))>)));

template <class _Tp>
_LIBCUDACXX_CONCEPT __can_reverse = _LIBCUDACXX_FRAGMENT(__can_reverse_, _Tp);
#  endif // _CCCL_STD_VER <= 2017

struct __fn
{
  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES(__member_rbegin<_Tp>)
  _CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI _LIBCUDACXX_INLINE_VISIBILITY constexpr auto operator()(_Tp&& __t) const
    noexcept(noexcept(_LIBCUDACXX_AUTO_CAST(__t.rbegin())))
  {
    return _LIBCUDACXX_AUTO_CAST(__t.rbegin());
  }

  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES(__unqualified_rbegin<_Tp>)
  _CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI _LIBCUDACXX_INLINE_VISIBILITY constexpr auto operator()(_Tp&& __t) const
    noexcept(noexcept(_LIBCUDACXX_AUTO_CAST(rbegin(__t))))
  {
    return _LIBCUDACXX_AUTO_CAST(rbegin(__t));
  }

  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES(__can_reverse<_Tp>)
  _CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI _LIBCUDACXX_INLINE_VISIBILITY constexpr auto operator()(_Tp&& __t) const
    noexcept(noexcept(_CUDA_VRANGES::end(__t)))
  {
    return _CUDA_VSTD::make_reverse_iterator(_CUDA_VRANGES::end(__t));
  }

  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES((!__member_rbegin<_Tp> && !__unqualified_rbegin<_Tp> && !__can_reverse<_Tp>) )
  void operator()(_Tp&&) const = delete;
};
_LIBCUDACXX_END_NAMESPACE_CPO

inline namespace __cpo
{
_LIBCUDACXX_CPO_ACCESSIBILITY auto rbegin = __rbegin::__fn{};
} // namespace __cpo

// [range.access.crbegin]

_LIBCUDACXX_BEGIN_NAMESPACE_CPO(__crbegin)
struct __fn
{
  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES(is_lvalue_reference_v<_Tp&&>)
  _CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI _LIBCUDACXX_INLINE_VISIBILITY constexpr auto operator()(_Tp&& __t) const
    noexcept(noexcept(_CUDA_VRANGES::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))))
      -> decltype(_CUDA_VRANGES::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)))
  {
    return _CUDA_VRANGES::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t));
  }

  _LIBCUDACXX_TEMPLATE(class _Tp)
  _LIBCUDACXX_REQUIRES(is_rvalue_reference_v<_Tp&&>)
  _CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI _LIBCUDACXX_INLINE_VISIBILITY constexpr auto operator()(_Tp&& __t) const
    noexcept(noexcept(_CUDA_VRANGES::rbegin(static_cast<const _Tp&&>(__t))))
      -> decltype(_CUDA_VRANGES::rbegin(static_cast<const _Tp&&>(__t)))
  {
    return _CUDA_VRANGES::rbegin(static_cast<const _Tp&&>(__t));
  }
};
_LIBCUDACXX_END_NAMESPACE_CPO

inline namespace __cpo
{
_LIBCUDACXX_CPO_ACCESSIBILITY auto crbegin = __crbegin::__fn{};
} // namespace __cpo

#endif // _CCCL_STD_VER >= 2017 && && !_CCCL_COMPILER_MSVC_2017

_LIBCUDACXX_END_NAMESPACE_RANGES

#endif // _LIBCUDACXX___RANGES_RBEGIN_H