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// TODO: Move into system::hip

#pragma once

#include <thrust/detail/config.h>

#if THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP

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

#  include <thrust/advance.h>
#  include <thrust/distance.h>
#  include <thrust/iterator/iterator_traits.h>
#  include <thrust/system/hip/detail/async/customization.h>
#  include <thrust/system/hip/detail/parallel_for.h>
#  include <thrust/system/hip/future.h>

#  include <type_traits>

THRUST_NAMESPACE_BEGIN

namespace system
{
namespace hip
{
namespace detail
{

template <typename ForwardIt, typename OutputIt, typename UnaryOperation>
struct async_transform_fn
{
  ForwardIt first_;
  OutputIt output_;
  UnaryOperation op_;

  THRUST_HOST_DEVICE async_transform_fn(ForwardIt&& first, OutputIt&& output, UnaryOperation&& op)
      : first_(std::move(first))
      , output_(std::move(output))
      , op_(std::move(op))
  {}

  template <typename Index>
  THRUST_HOST_DEVICE void operator()(Index idx)
  {
    output_[idx] = op_(thrust::raw_reference_cast(first_[idx]));
  }
};

template <typename DerivedPolicy, typename ForwardIt, typename Size, typename OutputIt, typename UnaryOperation>
auto async_transform_n(
  execution_policy<DerivedPolicy>& policy, ForwardIt first, Size n, OutputIt output, UnaryOperation op)
  -> unique_eager_event
{
  unique_eager_event e;

  // 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)
  {
    e = make_dependent_event(std::tuple_cat(std::make_tuple(unique_stream(nonowning, user_raw_stream)),
                                            extract_dependencies(std::move(thrust::detail::derived_cast(policy)))));
  }
  else
  {
    e = make_dependent_event(extract_dependencies(std::move(thrust::detail::derived_cast(policy))));
  }

  if (n == 0)
  {
    e.ready();
    return e;
  }

  // Run transform.

  async_transform_fn<ForwardIt, OutputIt, UnaryOperation> wrapped(std::move(first), std::move(output), std::move(op));

  thrust::hip_rocprim::throw_on_error(
    thrust::hip_rocprim::__parallel_for::parallel_for(n, std::move(wrapped), e.stream().native_handle()),
    "after transform launch");

  return e;
}

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

namespace hip_rocprim
{

// ADL entry point.
template <typename DerivedPolicy, typename ForwardIt, typename Sentinel, typename OutputIt, typename UnaryOperation>
auto async_transform(
  execution_policy<DerivedPolicy>& policy, ForwardIt first, Sentinel last, OutputIt output, UnaryOperation&& op)
  THRUST_RETURNS(thrust::system::hip::detail::async_transform_n(
    policy, first, thrust::distance(first, last), output, THRUST_FWD(op)));

} // namespace hip_rocprim

THRUST_NAMESPACE_END

#endif // THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP
