//===----------------------------------------------------------------------===//
//
// 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___UTILITY_INTEGER_SEQUENCE_H
#define _LIBCUDACXX___UTILITY_INTEGER_SEQUENCE_H

#ifndef __cuda_std__
#include <__config>
#endif // __cuda_std__

#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 "../__type_traits/is_integral.h"
#include "../cstddef"

_LIBCUDACXX_BEGIN_NAMESPACE_STD

template <size_t...> struct __tuple_indices {};

template <class _IdxType, _IdxType... _Values>
struct __integer_sequence {
  template <template <class _OIdxType, _OIdxType...> class _ToIndexSeq, class _ToIndexType>
  using __convert = _ToIndexSeq<_ToIndexType, _Values...>;

  template <size_t _Sp>
  using __to_tuple_indices = __tuple_indices<(_Values + _Sp)...>;
};

#if !__has_builtin(__make_integer_seq) || defined(_LIBCUDACXX_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)

namespace __detail {

template<typename _Tp, size_t ..._Extra> struct __repeat;
template<typename _Tp, _Tp ..._Np, size_t ..._Extra> struct __repeat<__integer_sequence<_Tp, _Np...>, _Extra...> {
  typedef _LIBCUDACXX_NODEBUG_TYPE __integer_sequence<_Tp,
                           _Np...,
                           sizeof...(_Np) + _Np...,
                           2 * sizeof...(_Np) + _Np...,
                           3 * sizeof...(_Np) + _Np...,
                           4 * sizeof...(_Np) + _Np...,
                           5 * sizeof...(_Np) + _Np...,
                           6 * sizeof...(_Np) + _Np...,
                           7 * sizeof...(_Np) + _Np...,
                           _Extra...> type;
};

template<size_t _Np> struct __parity;
template<size_t _Np> struct __make : __parity<_Np % 8>::template __pmake<_Np> {};

template<> struct __make<0> { typedef __integer_sequence<size_t> type; };
template<> struct __make<1> { typedef __integer_sequence<size_t, 0> type; };
template<> struct __make<2> { typedef __integer_sequence<size_t, 0, 1> type; };
template<> struct __make<3> { typedef __integer_sequence<size_t, 0, 1, 2> type; };
template<> struct __make<4> { typedef __integer_sequence<size_t, 0, 1, 2, 3> type; };
template<> struct __make<5> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4> type; };
template<> struct __make<6> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4, 5> type; };
template<> struct __make<7> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4, 5, 6> type; };

template<> struct __parity<0> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type> {}; };
template<> struct __parity<1> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 1> {}; };
template<> struct __parity<2> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 2, _Np - 1> {}; };
template<> struct __parity<3> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 3, _Np - 2, _Np - 1> {}; };
template<> struct __parity<4> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
template<> struct __parity<5> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
template<> struct __parity<6> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
template<> struct __parity<7> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 7, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };

} // namespace detail

#endif  // !__has_builtin(__make_integer_seq) || defined(_LIBCUDACXX_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)

#if __has_builtin(__make_integer_seq)
template <size_t _Ep, size_t _Sp>
using __make_indices_imp =
    typename __make_integer_seq<__integer_sequence, size_t, _Ep - _Sp>::template
    __to_tuple_indices<_Sp>;
#else
template <size_t _Ep, size_t _Sp>
using __make_indices_imp =
    typename __detail::__make<_Ep - _Sp>::type::template __to_tuple_indices<_Sp>;

#endif

#if _CCCL_STD_VER > 2011

template<class _Tp, _Tp... _Ip>
struct _LIBCUDACXX_TEMPLATE_VIS integer_sequence
{
    typedef _Tp value_type;
    static_assert( is_integral<_Tp>::value,
                  "std::integer_sequence can only be instantiated with an integral type" );
    static
    _LIBCUDACXX_INLINE_VISIBILITY
    constexpr
    size_t
    size() noexcept { return sizeof...(_Ip); }
};

template<size_t... _Ip>
    using index_sequence = integer_sequence<size_t, _Ip...>;

#if __has_builtin(__make_integer_seq) && !defined(_LIBCUDACXX_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)

template <class _Tp, _Tp _Ep>
using __make_integer_sequence _LIBCUDACXX_NODEBUG_TYPE = __make_integer_seq<integer_sequence, _Tp, _Ep>;

#else

template<typename _Tp, _Tp _Np> using __make_integer_sequence_unchecked _LIBCUDACXX_NODEBUG_TYPE =
  typename __detail::__make<_Np>::type::template __convert<integer_sequence, _Tp>;

template <class _Tp, _Tp _Ep>
struct __make_integer_sequence_checked
{
    static_assert(is_integral<_Tp>::value,
                  "std::make_integer_sequence can only be instantiated with an integral type" );
    static_assert(0 <= _Ep, "std::make_integer_sequence must have a non-negative sequence length");
    // Workaround GCC bug by preventing bad installations when 0 <= _Ep
    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68929
    typedef _LIBCUDACXX_NODEBUG_TYPE __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
};

template <class _Tp, _Tp _Ep>
using __make_integer_sequence _LIBCUDACXX_NODEBUG_TYPE = typename __make_integer_sequence_checked<_Tp, _Ep>::type;

#endif

template<class _Tp, _Tp _Np>
    using make_integer_sequence = __make_integer_sequence<_Tp, _Np>;

template<size_t _Np>
    using make_index_sequence = make_integer_sequence<size_t, _Np>;

template<class... _Tp>
    using index_sequence_for = make_index_sequence<sizeof...(_Tp)>;

#endif // _CCCL_STD_VER > 2011

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___UTILITY_INTEGER_SEQUENCE_H
