//===----------------------------------------------------------------------===//
//
// 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___UTILITY_INTEGER_SEQUENCE_H
#define _LIBCPP___UTILITY_INTEGER_SEQUENCE_H

#include <__config>
#include <__type_traits/is_integral.h>
#include <cstddef>

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

_LIBCPP_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(_LIBCPP_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 _LIBCPP_NODEBUG __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> {};

// clang-format off
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> {}; };
// clang-format on

} // namespace __detail

#endif

#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 _LIBCPP_STD_VER >= 14

template <class _Tp, _Tp... _Ip>
struct _LIBCPP_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 _LIBCPP_HIDE_FROM_ABI 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(_LIBCPP_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)

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

#  else

template <typename _Tp, _Tp _Np>
using __make_integer_sequence_unchecked _LIBCPP_NODEBUG =
    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 _LIBCPP_NODEBUG __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
};

template <class _Tp, _Tp _Ep>
using __make_integer_sequence _LIBCPP_NODEBUG = 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)>;

#  if _LIBCPP_STD_VER >= 20
// Executes __func for every element in an index_sequence.
template <size_t... _Index, class _Function>
_LIBCPP_HIDE_FROM_ABI constexpr void __for_each_index_sequence(index_sequence<_Index...>, _Function __func) {
  (__func.template operator()<_Index>(), ...);
}
#  endif // _LIBCPP_STD_VER >= 20

#endif // _LIBCPP_STD_VER >= 14

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___UTILITY_INTEGER_SEQUENCE_H
