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#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/kernel_hardware_info.hpp"
#include "cutlass/gemm/gemm.h"
#include "cutlass/gemm/dispatch_policy.hpp"

#include "cute/tensor.hpp"

#include "gather_tensor.hpp"

namespace cutlass::gemm::kernel {

///////////////////////////////////////////////////////////////////////////////

template <
  class ProblemShape_,
  class CollectiveMainloop_,
  class CollectiveEpilogue_,
  class GatherA_,
  class GatherB_,
  class TileScheduler_ = void
>
class GemmGather
{
public:
  //
  // Type Aliases
  //
  using ProblemShape = ProblemShape_;
  using TileSchedulerTag = TileScheduler_;
  using TileScheduler = TileScheduler_;
  static_assert(rank(ProblemShape{}) == 3 or rank(ProblemShape{}) == 4,
    "ProblemShape{} should be <M,N,K> or <M,N,K,L>");

  // Mainloop derived types
  using CollectiveMainloop = CollectiveMainloop_;
  using TileShape = typename CollectiveMainloop::TileShape;
  using TiledMma  = typename CollectiveMainloop::TiledMma;
  using ArchTag   = typename CollectiveMainloop::ArchTag;
  using ElementA  = typename CollectiveMainloop::ElementA;
  using StrideA   = typename CollectiveMainloop::StrideA;
  using ElementB  = typename CollectiveMainloop::ElementB;
  using StrideB   = typename CollectiveMainloop::StrideB;
  using DispatchPolicy = typename CollectiveMainloop::DispatchPolicy;
  using ElementAccumulator = typename CollectiveMainloop::ElementAccumulator;
  using MainloopArguments = typename CollectiveMainloop::Arguments;
  using MainloopParams = typename CollectiveMainloop::Params;

  // Epilogue derived types
  using CollectiveEpilogue = CollectiveEpilogue_;
  using ElementC = typename CollectiveEpilogue::ElementC;
  using StrideC  = typename CollectiveEpilogue::StrideC;
  using ElementD = typename CollectiveEpilogue::ElementD;
  using StrideD  = typename CollectiveEpilogue::StrideD;
  using EpilogueArguments = typename CollectiveEpilogue::Arguments;
  using EpilogueParams = typename CollectiveEpilogue::Params;
  static_assert(std::is_same_v<ElementAccumulator, typename CollectiveEpilogue::ElementAccumulator>,
    "Mainloop and epilogue do not agree on accumulator value type.");

  using GatherA = GatherA_;
  using GatherB = GatherB_;

  static constexpr int SharedStorageSize = static_cast<int>(cute::max(
      sizeof(typename CollectiveMainloop::SharedStorage),
      sizeof(typename CollectiveEpilogue::SharedStorage)));

  static constexpr uint32_t MaxThreadsPerBlock = cute::size(TiledMma{});
  static constexpr uint32_t MinBlocksPerMultiprocessor = 1;

  // Device side arguments
  struct Arguments {
    GemmUniversalMode mode{};
    ProblemShape problem_shape{};
    MainloopArguments mainloop{};
    EpilogueArguments epilogue{};
    KernelHardwareInfo hw_info{};
    GatherA gather_A{};
    GatherB gather_B{};
  };

  // Kernel entry point API
  struct Params {
    GemmUniversalMode mode;
    ProblemShape problem_shape;
    MainloopParams mainloop;
    EpilogueParams epilogue;
    GatherA gather_A{};
    GatherB gather_B{};
  };

  //
  // Methods
  //

  // Convert to underlying arguments.
  static
  Params
  to_underlying_arguments(Arguments const& args, void* workspace) {
    (void) workspace;
    return {
      args.mode,
      args.problem_shape,
      CollectiveMainloop::to_underlying_arguments(args.problem_shape, args.mainloop, workspace),
      CollectiveEpilogue::to_underlying_arguments(args.problem_shape, args.epilogue, workspace),
      args.gather_A,
      args.gather_B
    };
  }

  static
  Status
  initialize_workspace(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
    return Status::kSuccess;
  }

  static
  bool
  can_implement(Arguments const& args) {
    return args.mode == GemmUniversalMode::kGemm or
          (args.mode == GemmUniversalMode::kBatched && rank(ProblemShape{}) == 4);
  }

  static
  int
  get_workspace_size(Arguments const& args) {
    return 0;
  }

  static constexpr
  dim3
  get_grid_shape(Params const& params) {
    int batch_count = 1;
    if constexpr (rank(ProblemShape{}) == 4) {
      batch_count = cute::size<3>(params.problem_shape);
    }

    return dim3(
      cute::size(cute::ceil_div(cute::shape<0>(params.problem_shape), cute::shape<0>(TileShape{}))),
      cute::size(cute::ceil_div(cute::shape<1>(params.problem_shape), cute::shape<1>(TileShape{}))),
      batch_count
    );
  }

  static constexpr
  dim3
  get_block_shape() {
    return dim3(MaxThreadsPerBlock, 1, 1);
  }

  CUTLASS_DEVICE
  void
  operator()(Params const& params, char* smem_buf) {
    using namespace cute;
    using X = Underscore;

    // Preconditions
    CUTE_STATIC_ASSERT(is_static<TileShape>::value);

    // Separate out problem shape for convenience
    // Optionally append 1s until problem shape is rank-4 in case its is only rank-3 (MNK)
    auto problem_shape_MNKL = append<4>(params.problem_shape, Int<1>{});
    auto M = get<0>(problem_shape_MNKL);
    auto N = get<1>(problem_shape_MNKL);
    auto K = get<2>(problem_shape_MNKL);
    auto L = get<3>(problem_shape_MNKL);

    // Preconditions
    static_assert(rank(StrideA{}) == 3, "StrideA must be rank-3: [M, K, L]. If batch mode is not needed, set L stride to Int<0>.");
    static_assert(rank(StrideB{}) == 3, "StrideB must be rank-3: [N, K, L]. If batch mode is not needed, set L stride to Int<0>.");
    static_assert(rank(StrideC{}) == 3, "StrideC must be rank-3: [M, N, L]. If batch mode is not needed, set L stride to Int<0>.");
    static_assert(rank(StrideD{}) == 3, "StrideD must be rank-3: [M, N, L]. If batch mode is not needed, set L stride to Int<0>.");

    // Get the appropriate blocks for this thread block -- potential for thread block locality
    int thread_idx = int(threadIdx.x);
    auto blk_shape = TileShape{};                                                                // (BLK_M,BLK_N,BLK_K)
    auto [m_coord, n_coord, l_coord] = blockIdx;
    auto blk_coord_mnkl = make_coord(m_coord, n_coord, _, l_coord);                                        // (m,n,k,l)

    // Represent the full tensors
    Tensor mA_mkl = make_gather_tensor(make_gmem_ptr(params.mainloop.ptr_A), make_shape(M,K,L), params.mainloop.dA, params.gather_A); //(m,k,l)
    Tensor mB_nkl = make_gather_tensor(make_gmem_ptr(params.mainloop.ptr_B), make_shape(N,K,L), params.mainloop.dB, params.gather_B); //(n,k,l)

    // Get batch slice
    Tensor mA_mk = mA_mkl(_,_,l_coord);                                                                        // (m,k)
    Tensor mB_nk = mB_nkl(_,_,l_coord);                                                                        // (n,k)

    // Slice to get the tiles this thread block is responsible for
    Tensor gA = local_tile(mA_mk, blk_shape, take<0,3>(blk_coord_mnkl), Step<_1, X,_1>{});           // (BLK_M,BLK_K,k)
    Tensor gB = local_tile(mB_nk, blk_shape, take<0,3>(blk_coord_mnkl), Step< X,_1,_1>{});           // (BLK_N,BLK_K,k)

    // Compute tile residues for predication
    auto m_max_coord = M - size<0>(gA) * get<0>(blk_coord_mnkl);                             // M - BLK_M * m_coord
    auto n_max_coord = N - size<0>(gB) * get<1>(blk_coord_mnkl);                             // N - BLK_N * n_coord
    auto k_residue   = K - size<1>(gA) * size<2>(gA);                                        // K - BLK_K * k_coord_max
    auto residue_mnk = make_tuple(m_max_coord, n_max_coord, k_residue);

    // Allocate the tiled_mma and the accumulators for the (M,N) blk_shape
    TiledMma tiled_mma;
    Tensor accumulators = partition_fragment_C(tiled_mma, take<0,2>(blk_shape)); // (MMA,MMA_M,MMA_N)
    clear(accumulators);

    auto k_tile_iter  = cute::make_coord_iterator(shape<2>(gA));
    int  k_tile_count = size<2>(gA);

    // Perform the collective scoped MMA
    CollectiveMainloop collective_mma;
    collective_mma(
      accumulators,
      gA,
      gB,
      accumulators,
      k_tile_iter, k_tile_count,
      residue_mnk,
      thread_idx,
      smem_buf
    );

    // Epilogue and write to gD
    CollectiveEpilogue epilogue{params.epilogue};
    epilogue(
      problem_shape_MNKL,
      blk_shape,
      blk_coord_mnkl,
      accumulators,
      tiled_mma,
      residue_mnk,
      thread_idx,
      smem_buf
    );
  }
};

///////////////////////////////////////////////////////////////////////////////

} // namespace cutlass::gemm::kernel