#define TORCH_ASSERT_ONLY_METHOD_OPERATORS
#include <ATen/Dispatch.h>
#include <ATen/core/Tensor.h>
#include <ATen/cuda/CUDAContext.h>
#include <ATen/cuda/nvrtc_stub/ATenNVRTC.h>
#include <c10/cuda/CUDAGuard.h>

// Two warninngs in Cutlass included header files
C10_DIAGNOSTIC_PUSH_AND_IGNORED_IF_DEFINED("-Wset-but-not-used")
C10_DIAGNOSTIC_PUSH_AND_IGNORED_IF_DEFINED("-Wunused-but-set-parameter")

#if !defined(USE_ROCM) && !defined(_WIN32) && defined(CUDA_VERSION) && \
    CUDA_VERSION >= 12000
#define BUILD_ASYNC_MM_KERNEL
#endif

#if defined(BUILD_ASYNC_MM_KERNEL)

#include <cutlass/core_io.h>
#include <cutlass/cutlass.h>
#include <cutlass/gemm/device/gemm.h>
#include <cutlass/half.h>
#include <cutlass/numeric_types.h>
#include <cutlass/trace.h>
#include <cutlass/util/host_tensor.h>
#include <cute/tensor.hpp>

#include <cutlass/version.h>
#include <cutlass/gemm/collective/collective_builder.hpp>
#include <cutlass/gemm/device/gemm_universal_adapter.h>
#include <cutlass/epilogue/collective/collective_builder.hpp>

#include <cute/atom/mma_atom.hpp>
#include <cutlass/gemm/dispatch_policy.hpp>
#include <cutlass/gemm/kernel/gemm_universal.hpp>
#include <cutlass/util/packed_stride.hpp>

#include <torch/csrc/distributed/c10d/cuda/cutlass/gemm/kernel/persistent_async_input_scheduler.cuh>

C10_DIAGNOSTIC_POP()
C10_DIAGNOSTIC_POP()

namespace {

using namespace cute;

template <typename LayoutB, typename TileShape_MNK, typename ClusterShape_MNK>
at::Tensor async_input_mm_impl(
    at::Tensor a,
    at::Tensor b,
    at::Tensor a_chunk_signals,
    int64_t a_chunk_pivot,
    at::Tensor out) {
  c10::cuda::CUDAGuard guard(a.device());

  using ElementA = cutlass::bfloat16_t;
  using LayoutA = cutlass::layout::RowMajor;
  constexpr int AlignmentA = 128 / cutlass::sizeof_bits<ElementA>::value;

  using ElementB = cutlass::bfloat16_t;
  constexpr int AlignmentB = 128 / cutlass::sizeof_bits<ElementB>::value;

  using ElementC = cutlass::bfloat16_t;
  using LayoutC = cutlass::layout::RowMajor;
  constexpr int AlignmentC = 128 / cutlass::sizeof_bits<ElementC>::value;

  using ElementAccumulator = float;

  using KernelSchedule = cutlass::gemm::KernelTmaWarpSpecializedCooperative;
  using EpilogueSchedule = cutlass::epilogue::TmaWarpSpecializedCooperative;

  using CollectiveEpilogue =
      typename cutlass::epilogue::collective::CollectiveBuilder<
          cutlass::arch::Sm90,
          cutlass::arch::OpClassTensorOp,
          TileShape_MNK,
          ClusterShape_MNK,
          cutlass::epilogue::collective::EpilogueTileAuto,
          ElementAccumulator,
          ElementAccumulator,
          ElementC,
          LayoutC,
          AlignmentC,
          ElementC,
          LayoutC,
          AlignmentC,
          EpilogueSchedule>::CollectiveOp;

  using CollectiveMainloop =
      typename cutlass::gemm::collective::CollectiveBuilder<
          cutlass::arch::Sm90,
          cutlass::arch::OpClassTensorOp,
          ElementA,
          LayoutA,
          AlignmentA,
          ElementB,
          LayoutB,
          AlignmentB,
          ElementAccumulator,
          TileShape_MNK,
          ClusterShape_MNK,
          cutlass::gemm::collective::StageCountAutoCarveout<static_cast<int>(
              sizeof(typename CollectiveEpilogue::SharedStorage))>,
          KernelSchedule>::CollectiveOp;

  using GemmKernel = cutlass::gemm::kernel::GemmUniversal<
      Shape<int, int, int>,
      CollectiveMainloop,
      CollectiveEpilogue,
      cutlass::gemm::PersistentAsyncInputScheduler<KernelSchedule>>;
  using Gemm = cutlass::gemm::device::GemmUniversalAdapter<GemmKernel>;

  using StrideA = typename Gemm::GemmKernel::StrideA;
  using StrideB = typename Gemm::GemmKernel::StrideB;
  using StrideC = typename Gemm::GemmKernel::StrideC;

  TORCH_CHECK(a.dim() == 2 && b.dim() == 2 && out.dim() == 2);
  TORCH_CHECK(a.is_contiguous() && out.is_contiguous());

  if constexpr (std::is_same_v<LayoutB, cutlass::layout::RowMajor>) {
    TORCH_CHECK(b.is_contiguous());
  } else {
    TORCH_CHECK(b.stride(1) == b.size(0));
    TORCH_CHECK(b.stride(0) == 1);
  }
  TORCH_CHECK_EQ(a.scalar_type(), at::kBFloat16);
  TORCH_CHECK_EQ(b.scalar_type(), at::kBFloat16);
  TORCH_CHECK_EQ(out.scalar_type(), at::kBFloat16);

  int M = static_cast<int>(a.sizes()[0]);
  int N = static_cast<int>(b.sizes()[1]);
  int K = static_cast<int>(a.sizes()[1]);
  TORCH_CHECK_EQ(b.sizes()[0], K);
  TORCH_CHECK_EQ(out.sizes()[0], M);
  TORCH_CHECK_EQ(out.sizes()[1], N);

  auto stride_A = cutlass::make_cute_packed_stride(StrideA{}, {M, K, 1});
  auto stride_B = cutlass::make_cute_packed_stride(StrideB{}, {N, K, 1});
  auto stride_C = cutlass::make_cute_packed_stride(StrideC{}, {M, N, 1});

  Gemm gemm;

  typename Gemm::Arguments arguments{
      cutlass::gemm::GemmUniversalMode::kGemm,
      {M, N, K},
      {
          reinterpret_cast<ElementA*>(a.data_ptr<at::BFloat16>()),
          stride_A,
          reinterpret_cast<ElementB*>(b.data_ptr<at::BFloat16>()),
          stride_B,
      },
      {{1, 1},
       reinterpret_cast<ElementC*>(out.data_ptr<at::BFloat16>()),
       stride_C,
       reinterpret_cast<ElementC*>(out.data_ptr<at::BFloat16>()),
       stride_C},
  };

  TORCH_CHECK(
      a_chunk_signals.sizes().size() == 1,
      "async_input_mm: `a_chunk_signals` must be a 1D tensor.");
  size_t num_chunks_M = a_chunk_signals.numel();

  TORCH_CHECK(
      M % num_chunks_M == 0,
      "async_input_mm: `a.shape(0)` must be an interger multiple of `a_chunk_signals.numel()`");
  size_t chunk_size_M = M / num_chunks_M;
  size_t tile_size_M = cute::get<0>(TileShape_MNK{});

  TORCH_CHECK(chunk_size_M % tile_size_M == 0);

  // We want to swizzle within a chunk
  arguments.scheduler.max_swizzle_size = chunk_size_M / tile_size_M;

  // PersistentAsyncInputScheduler currently only supports rastering along N
  using RasterOrderOptions = typename cutlass::gemm::kernel::detail::
      PersistentTileSchedulerSm90::RasterOrderOptions;
  arguments.scheduler.raster_order = RasterOrderOptions::AlongN;

  // Convert the number of chunks to pivot to the number of m idx to pivot
  arguments.scheduler.tile_idx_pivot_m =
      a_chunk_pivot * (chunk_size_M / tile_size_M);
  arguments.scheduler.tiles_per_chunk_m = chunk_size_M / tile_size_M;
  arguments.scheduler.chunk_signals = a_chunk_signals.data_ptr<uint32_t>();

  size_t workspace_size = Gemm::get_workspace_size(arguments);
  cutlass::device_memory::allocation<uint8_t> workspace(workspace_size);

  TORCH_CHECK(gemm.can_implement(arguments) == cutlass::Status::kSuccess);
  TORCH_CHECK(
      gemm.initialize(arguments, workspace.get()) == cutlass::Status::kSuccess);
  TORCH_CHECK(
      gemm(at::cuda::getCurrentCUDAStream()) == cutlass::Status::kSuccess);

  C10_CUDA_KERNEL_LAUNCH_CHECK();
  return out;
}

} // namespace

#endif

namespace c10d::cuda::detail {

#define DISPATCH_LAYOUT_B(is_b_row_major, ...)    \
  if (is_b_row_major) {                           \
    using LayoutB = cutlass::layout::RowMajor;    \
    __VA_ARGS__();                                \
  } else {                                        \
    using LayoutB = cutlass::layout::ColumnMajor; \
    __VA_ARGS__();                                \
  }

at::Tensor async_input_mm_out(
    at::Tensor a,
    at::Tensor b,
    at::Tensor a_chunk_signals,
    int64_t a_chunk_pivot,
    at::Tensor out) {
  TORCH_CHECK(
      a.dim() == 2 && b.dim() == 2 && out.dim() == 2,
      "async_input_mm: `a`, `b` and `out` must be matrices")
  TORCH_CHECK(
      a.is_contiguous() && out.is_contiguous(),
      "async_input_mm: `a` and `out` must be in row-major layout");

  if (!b.is_contiguous()) {
    TORCH_CHECK(b.stride(1) == b.size(0));
    TORCH_CHECK(b.stride(0) == 1);
  }
  TORCH_CHECK_EQ(a.scalar_type(), at::kBFloat16);
  TORCH_CHECK_EQ(b.scalar_type(), at::kBFloat16);
  TORCH_CHECK_EQ(out.scalar_type(), at::kBFloat16);

  int64_t M = a.sizes()[0];
  int64_t N = b.sizes()[1];
  int64_t K = a.sizes()[1];
  TORCH_CHECK_EQ(b.sizes()[0], K);
  TORCH_CHECK_EQ(out.sizes()[0], M);
  TORCH_CHECK_EQ(out.sizes()[1], N);

#if defined(BUILD_ASYNC_MM_KERNEL)
  const bool is_b_row_major = b.is_contiguous();
  DISPATCH_LAYOUT_B(is_b_row_major, [&]() {
    // TODO(yifu): tuning
    async_input_mm_impl<LayoutB, Shape<_128, _256, _64>, Shape<_2, _1, _1>>(
        a, b, a_chunk_signals, a_chunk_pivot, out);
  });
#else
  TORCH_CHECK(
      false, "async_input_mm is not currenlty supported on your device");
#endif
  return out;
}

at::Tensor async_input_mm(
    at::Tensor a,
    at::Tensor b,
    at::Tensor a_chunk_signals,
    int64_t a_chunk_pivot) {
  TORCH_CHECK(
      a.dim() == 2 && b.dim() == 2,
      "async_input_mm: `a`, `b` and `out` must all be a matrix")

  int64_t M = a.sizes()[0];
  int64_t N = b.sizes()[1];
  auto out = a.new_empty({M, N});
  return async_input_mm_out(a, b, a_chunk_signals, a_chunk_pivot, out);
}

} // namespace c10d::cuda::detail