//===----------------------------------------------------------------------===//
//
// Part of libcu++, the C++ Standard Library for your entire system,
// 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) 2026 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

#ifndef _CUDA_STD_CTIME
#define _CUDA_STD_CTIME

#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/__host_stdlib/time.h>

#if _CCCL_CUDA_COMPILATION()
#  include <cuda/__ptx/instructions/get_sreg.h>
#endif // _CCCL_CUDA_COMPILATION()

#include <cuda/std/__cccl/prologue.h>

#if _CCCL_FREESTANDING()
#  define TIME_UTC 1

#  if _CCCL_HOSTJIT()
using clock_t = long long int;
#  endif // _CCCL_HOSTJIT()
using time_t = long long int;

struct timespec
{
  ::time_t tv_sec;
  long tv_nsec;
};
#endif // _CCCL_FREESTANDING()

_CCCL_BEGIN_NAMESPACE_CUDA_STD

using ::clock_t;
using ::size_t;
using ::time_t;
using ::timespec;

// clock

[[nodiscard]] _CCCL_API inline clock_t clock() noexcept
{
#if _CCCL_HOSTJIT() // host-side `clock` is not supported in freestanding
  NV_IF_ELSE_TARGET(
    NV_IS_HOST, (::cuda::std::terminate();), (return static_cast<clock_t>(::cuda::ptx::get_sreg_clock64());))
#else // ^^^ _CCCL_HOSTJIT() ^^^ / vvv !_CCCL_HOSTJIT() vvv
  NV_IF_ELSE_TARGET(NV_IS_HOST, (return ::clock();), (return static_cast<clock_t>(::cuda::ptx::get_sreg_clock64());))
#endif // !_CCCL_HOSTJIT()
}

// difftime

[[nodiscard]] _CCCL_API constexpr double difftime(time_t __end, time_t __start) noexcept
{
  return static_cast<double>(__end - __start);
}

// time

#if _CCCL_CUDA_COMPILATION()
[[nodiscard]] _CCCL_DEVICE_API inline time_t __cccl_time_impl_device(time_t* __v) noexcept
{
  const auto __t = static_cast<clock_t>(::cuda::ptx::get_sreg_globaltimer() / 1'000'000'000);
  if (__v != nullptr)
  {
    *__v = __t;
  }
  return __t;
}
#endif // _CCCL_CUDA_COMPILATION()

_CCCL_API inline time_t time(time_t* __v) noexcept
{
#if _CCCL_HOSTJIT() // host-side `time` is not supported in freestanding
  NV_IF_ELSE_TARGET(NV_IS_HOST, (::cuda::std::terminate();), (return ::cuda::std::__cccl_time_impl_device(__v);))
#else // ^^^ _CCCL_HOSTJIT() ^^^ / vvv !_CCCL_HOSTJIT() vvv
  NV_IF_ELSE_TARGET(NV_IS_HOST, (return ::time(__v);), (return ::cuda::std::__cccl_time_impl_device(__v);))
#endif // !_CCCL_HOSTJIT()
}

#if !defined(__ANDROID_API__) || __ANDROID_API__ >= 29

// timespec_get

#  if _CCCL_CUDA_COMPILATION()
[[nodiscard]] _CCCL_DEVICE_API inline int __cccl_timespec_get_impl_device(timespec* __ts, int __base) noexcept
{
  if (__ts == nullptr || __base != TIME_UTC)
  {
    return 0;
  }
  const auto __t = ::cuda::ptx::get_sreg_globaltimer();
  __ts->tv_sec   = static_cast<time_t>(__t / 1'000'000'000);
  __ts->tv_nsec  = static_cast<long>(__t % 1'000'000'000);
  return __base;
}
#  endif // _CCCL_CUDA_COMPILATION()

[[nodiscard]] _CCCL_API inline int timespec_get(timespec* __ts, int __base) noexcept
{
#  if _CCCL_HOSTJIT() // host-side `timespec_get` is not supported in freestanding
  NV_IF_ELSE_TARGET(
    NV_IS_HOST, (::cuda::std::terminate();), (return ::cuda::std::__cccl_timespec_get_impl_device(__ts, __base);))
#  else // ^^^ _CCCL_HOSTJIT() ^^^ / vvv !_CCCL_HOSTJIT() vvv
  NV_IF_ELSE_TARGET(NV_IS_HOST,
                    (return ::timespec_get(__ts, __base);),
                    (return ::cuda::std::__cccl_timespec_get_impl_device(__ts, __base);))
#  endif // !_CCCL_HOSTJIT()
}

#endif // !defined(__ANDROID_API__) || __ANDROID_API__ >= 29

_CCCL_END_NAMESPACE_CUDA_STD

#include <cuda/std/__cccl/epilogue.h>

#endif // _CUDA_STD_CTIME