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#pragma once

#include <thrust/detail/config.h>

#if THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP

#  include <thrust/system/hip/config.h>

#  include <thrust/distance.h>
#  include <thrust/iterator/iterator_traits.h>
#  include <thrust/system/hip/detail/async/customization.h>
#  include <thrust/system/hip/detail/util.h>
#  include <thrust/system/hip/future.h>
#  include <thrust/type_traits/remove_cvref.h>

#  include <type_traits> // IWYU pragma: export

// TODO specialize for thrust::plus to use e.g. ExclusiveSum instead of ExcScan
//  - Note that thrust::plus<> is transparent, cub::Sum is not. This should be
//    fixed in CUB first).
//  - Need to check if CUB actually optimizes for sums before putting in effort

THRUST_NAMESPACE_BEGIN
namespace system
{
namespace hip
{
namespace detail
{

template <typename DerivedPolicy,
          typename ForwardIt,
          typename Size,
          typename OutputIt,
          typename InitialValueType,
          typename BinaryOp>
unique_eager_event async_exclusive_scan_n(
  execution_policy<DerivedPolicy>& policy, ForwardIt first, Size n, OutputIt out, InitialValueType init, BinaryOp op)
{
  auto const device_alloc = get_async_device_allocator(policy);
  unique_eager_event ev;

  // Determine temporary device storage requirements.
  size_t tmp_size = 0;
  {
    thrust::hip_rocprim::throw_on_error(
      thrust::hip_rocprim::__scan::invoke_exclusive_scan(
        policy, nullptr, tmp_size, first, out, init, n, op, nullptr, THRUST_HIP_DEBUG_SYNC_FLAG),
      "after determining tmp storage "
      "requirements for exclusive_scan");
  }

  // Allocate temporary storage.
  auto content        = uninitialized_allocate_unique_n<std::uint8_t>(device_alloc, tmp_size);
  void* const tmp_ptr = raw_pointer_cast(content.get());

  // Set up stream with dependencies.
  hipStream_t const user_raw_stream = thrust::hip_rocprim::stream(policy);

  if (thrust::hip_rocprim::default_stream() != user_raw_stream)
  {
    ev = make_dependent_event(
      std::tuple_cat(std::make_tuple(std::move(content), unique_stream(nonowning, user_raw_stream)),
                     extract_dependencies(std::move(thrust::detail::derived_cast(policy)))));
  }
  else
  {
    ev = make_dependent_event(std::tuple_cat(
      std::make_tuple(std::move(content)), extract_dependencies(std::move(thrust::detail::derived_cast(policy)))));
  }

  // Run scan.
  {
    thrust::hip_rocprim::throw_on_error(
      thrust::hip_rocprim::__scan::invoke_exclusive_scan(
        policy, tmp_ptr, tmp_size, first, out, init, n, op, user_raw_stream, THRUST_HIP_DEBUG_SYNC_FLAG),
      "after dispatching exclusive_scan kernel");
  }

  return ev;
}

} // namespace detail
} // namespace hip
} // namespace system

namespace hip_rocprim
{

// ADL entry point.
template <typename DerivedPolicy,
          typename ForwardIt,
          typename Sentinel,
          typename OutputIt,
          typename InitialValueType,
          typename BinaryOp>
auto async_exclusive_scan(
  execution_policy<DerivedPolicy>& policy,
  ForwardIt first,
  Sentinel&& last,
  OutputIt&& out,
  InitialValueType&& init,
  BinaryOp&& op)
  THRUST_RETURNS(thrust::system::hip::detail::async_exclusive_scan_n(
    policy, first, thrust::distance(first, THRUST_FWD(last)), THRUST_FWD(out), THRUST_FWD(init), THRUST_FWD(op)))

} // namespace hip_rocprim

THRUST_NAMESPACE_END

#endif // THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP
