// -*- 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) 2024 NVIDIA CORPORATION & AFFILIATES
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCUDACXX___MEMORY_CONSTRUCT_AT_H
#define _LIBCUDACXX___MEMORY_CONSTRUCT_AT_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/concept_macros.h>
#include <cuda/std/__iterator/access.h>
#include <cuda/std/__memory/addressof.h>
#include <cuda/std/__memory/voidify.h>
#include <cuda/std/__type_traits/enable_if.h>
#include <cuda/std/__type_traits/integral_constant.h>
#include <cuda/std/__type_traits/is_arithmetic.h>
#include <cuda/std/__type_traits/is_array.h>
#include <cuda/std/__type_traits/is_constant_evaluated.h>
#include <cuda/std/__type_traits/is_trivially_constructible.h>
#include <cuda/std/__type_traits/is_trivially_destructible.h>
#include <cuda/std/__type_traits/is_trivially_move_assignable.h>
#include <cuda/std/__type_traits/void_t.h>
#include <cuda/std/__utility/declval.h>
#include <cuda/std/__utility/forward.h>
#include <cuda/std/__utility/move.h>

#if _CCCL_CUDA_COMPILER(CLANG)
#  include <new>
#endif // _CCCL_CUDA_COMPILER(CLANG)

#if _CCCL_STD_VER >= 2020 // need to backfill ::std::construct_at
#  if !_CCCL_COMPILER(NVRTC)
#    include <memory>
#  endif // _CCCL_COMPILER(NVRTC)

#  ifndef __cpp_lib_constexpr_dynamic_alloc
namespace std
{
_CCCL_EXEC_CHECK_DISABLE
template <class _Tp,
          class... _Args,
          class = decltype(::new(_CUDA_VSTD::declval<void*>()) _Tp(_CUDA_VSTD::declval<_Args>()...))>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _Tp* construct_at(_Tp* __location, _Args&&... __args)
{
#    if defined(_CCCL_BUILTIN_ADDRESSOF)
  return ::new (_CUDA_VSTD::__voidify(*__location)) _Tp(_CUDA_VSTD::forward<_Args>(__args)...);
#    else
  return ::new (const_cast<void*>(static_cast<const volatile void*>(__location)))
    _Tp(_CUDA_VSTD::forward<_Args>(__args)...);
#    endif
}
} // namespace std
#  endif // __cpp_lib_constexpr_dynamic_alloc
#endif // _CCCL_STD_VER >= 2020

_LIBCUDACXX_BEGIN_NAMESPACE_STD

// There is a performance issue with placement new, where EDG based compiler insert a nullptr check that is superfluous
// Because this is a noticeable performance regression, we specialize it for certain types
// This is possible because we are calling ::new ignoring any user defined overloads of operator placement new
namespace __detail
{
// We cannot allow narrowing conversions between arithmetic types as the assignment will give errors
template <class _To, class...>
struct __is_narrowing_impl : false_type
{};

template <class _To, class _From>
struct __is_narrowing_impl<_To, _From> : true_type
{};

// This is a bit hacky, but we rely on the fact that arithmetic types cannot have more than one argument to their
// constructor
template <class _To, class _From>
struct __is_narrowing_impl<_To, _From, void_t<decltype(_To{_CUDA_VSTD::declval<_From>()})>> : false_type
{};

template <class _Tp, class... _Args>
using __is_narrowing = _If<_CCCL_TRAIT(is_arithmetic, _Tp), __is_narrowing_impl<_Tp, _Args...>, false_type>;

// The destination type must be trivially constructible from the arguments and also trivially assignable, because we
// technically move assign in the optimization
template <class _Tp, class... _Args>
struct __can_optimize_construct_at
    : integral_constant<bool,
                        _CCCL_TRAIT(is_trivially_constructible, _Tp, _Args...)
                          && _CCCL_TRAIT(is_trivially_move_assignable, _Tp) && !__is_narrowing<_Tp, _Args...>::value>
{};
} // namespace __detail

// construct_at
#if _CCCL_STD_VER >= 2020

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp,
          class... _Args,
          class = decltype(::new(_CUDA_VSTD::declval<void*>()) _Tp(_CUDA_VSTD::declval<_Args>()...))>
_LIBCUDACXX_HIDE_FROM_ABI
_CCCL_CONSTEXPR_CXX20 enable_if_t<!__detail::__can_optimize_construct_at<_Tp, _Args...>::value, _Tp*>
construct_at(_Tp* __location, _Args&&... __args)
{
  _CCCL_ASSERT(__location != nullptr, "null pointer given to construct_at");
  // Need to go through `std::construct_at` as that is the explicitly blessed function
  if (_CUDA_VSTD::is_constant_evaluated())
  {
    return ::std::construct_at(__location, _CUDA_VSTD::forward<_Args>(__args)...);
  }
  return ::new (_CUDA_VSTD::__voidify(*__location)) _Tp(_CUDA_VSTD::forward<_Args>(__args)...);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp,
          class... _Args,
          class = decltype(::new(_CUDA_VSTD::declval<void*>()) _Tp(_CUDA_VSTD::declval<_Args>()...))>
_LIBCUDACXX_HIDE_FROM_ABI
_CCCL_CONSTEXPR_CXX20 enable_if_t<__detail::__can_optimize_construct_at<_Tp, _Args...>::value, _Tp*>
construct_at(_Tp* __location, _Args&&... __args)
{
  _CCCL_ASSERT(__location != nullptr, "null pointer given to construct_at");
  // Need to go through `std::construct_at` as that is the explicitly blessed function
  if (_CUDA_VSTD::is_constant_evaluated())
  {
    return ::std::construct_at(__location, _CUDA_VSTD::forward<_Args>(__args)...);
  }
  *__location = _Tp{_CUDA_VSTD::forward<_Args>(__args)...};
  return __location;
}

#endif // _CCCL_STD_VER >= 2020

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp, class... _Args>
_LIBCUDACXX_HIDE_FROM_ABI
_CCCL_CONSTEXPR_CXX20 enable_if_t<!__detail::__can_optimize_construct_at<_Tp, _Args...>::value, _Tp*>
__construct_at(_Tp* __location, _Args&&... __args)
{
  _CCCL_ASSERT(__location != nullptr, "null pointer given to construct_at");
#if _CCCL_STD_VER >= 2020
  // Need to go through `std::construct_at` as that is the explicitly blessed function
  if (_CUDA_VSTD::is_constant_evaluated())
  {
    return ::std::construct_at(__location, _CUDA_VSTD::forward<_Args>(__args)...);
  }
#endif // _CCCL_STD_VER >= 2020
  return ::new (_CUDA_VSTD::__voidify(*__location)) _Tp(_CUDA_VSTD::forward<_Args>(__args)...);
}

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp, class... _Args>
_LIBCUDACXX_HIDE_FROM_ABI
_CCCL_CONSTEXPR_CXX20 enable_if_t<__detail::__can_optimize_construct_at<_Tp, _Args...>::value, _Tp*>
__construct_at(_Tp* __location, _Args&&... __args)
{
  _CCCL_ASSERT(__location != nullptr, "null pointer given to construct_at");
#if _CCCL_STD_VER >= 2020
  // Need to go through `std::construct_at` as that is the explicitly blessed function
  if (_CUDA_VSTD::is_constant_evaluated())
  {
    return ::std::construct_at(__location, _CUDA_VSTD::forward<_Args>(__args)...);
  }
#endif // _CCCL_STD_VER >= 2020
  *__location = _Tp{_CUDA_VSTD::forward<_Args>(__args)...};
  return __location;
}

// destroy_at

// The internal functions are available regardless of the language version (with the exception of the `__destroy_at`
// taking an array).
template <class _ForwardIterator>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _ForwardIterator __destroy(_ForwardIterator, _ForwardIterator);

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp,
          enable_if_t<!_CCCL_TRAIT(is_array, _Tp), int>                  = 0,
          enable_if_t<!_CCCL_TRAIT(is_trivially_destructible, _Tp), int> = 0>
_LIBCUDACXX_HIDE_FROM_ABI constexpr void __destroy_at(_Tp* __loc)
{
  _CCCL_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
  __loc->~_Tp();
}

_CCCL_EXEC_CHECK_DISABLE
template <class _Tp,
          enable_if_t<!_CCCL_TRAIT(is_array, _Tp), int>                 = 0,
          enable_if_t<_CCCL_TRAIT(is_trivially_destructible, _Tp), int> = 0>
_LIBCUDACXX_HIDE_FROM_ABI constexpr void __destroy_at(_Tp* __loc)
{
  _CCCL_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
  (void) __loc;
}

template <class _Tp, enable_if_t<_CCCL_TRAIT(is_array, _Tp), int> = 0>
_LIBCUDACXX_HIDE_FROM_ABI constexpr void __destroy_at(_Tp* __loc)
{
  _CCCL_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
  _CUDA_VSTD::__destroy(_CUDA_VSTD::begin(*__loc), _CUDA_VSTD::end(*__loc));
}

template <class _ForwardIterator>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _ForwardIterator __destroy(_ForwardIterator __first, _ForwardIterator __last)
{
  for (; __first != __last; ++__first)
  {
    _CUDA_VSTD::__destroy_at(_CUDA_VSTD::addressof(*__first));
  }
  return __first;
}

template <class _BidirectionalIterator>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _BidirectionalIterator
__reverse_destroy(_BidirectionalIterator __first, _BidirectionalIterator __last)
{
  while (__last != __first)
  {
    --__last;
    _CUDA_VSTD::__destroy_at(_CUDA_VSTD::addressof(*__last));
  }
  return __last;
}

template <class _Tp, enable_if_t<!_CCCL_TRAIT(is_array, _Tp), int> = 0>
_LIBCUDACXX_HIDE_FROM_ABI _CCCL_CONSTEXPR_CXX20 void destroy_at(_Tp* __loc)
{
  _CCCL_ASSERT(__loc != nullptr, "null pointer given to destroy_at");
  __loc->~_Tp();
}

template <class _Tp, enable_if_t<_CCCL_TRAIT(is_array, _Tp), int> = 0>
_LIBCUDACXX_HIDE_FROM_ABI _CCCL_CONSTEXPR_CXX20 void destroy_at(_Tp* __loc)
{
  _CUDA_VSTD::__destroy_at(__loc);
}

template <class _ForwardIterator>
_LIBCUDACXX_HIDE_FROM_ABI _CCCL_CONSTEXPR_CXX20 void destroy(_ForwardIterator __first, _ForwardIterator __last) noexcept
{
  (void) _CUDA_VSTD::__destroy(_CUDA_VSTD::move(__first), _CUDA_VSTD::move(__last));
}

template <class _ForwardIterator, class _Size>
_LIBCUDACXX_HIDE_FROM_ABI _CCCL_CONSTEXPR_CXX20 _ForwardIterator destroy_n(_ForwardIterator __first, _Size __n)
{
  for (; __n > 0; (void) ++__first, --__n)
  {
    _CUDA_VSTD::__destroy_at(_CUDA_VSTD::addressof(*__first));
  }
  return __first;
}

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___MEMORY_CONSTRUCT_AT_H
