/*
Copyright 2020 The OneFlow Authors. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include "oneflow/user/kernels/communicate_util.h"
#include "oneflow/core/device/nccl_util.h"
#include "oneflow/core/common/balanced_splitter.h"
#include "oneflow/core/common/container_util.h"
#include "oneflow/core/framework/framework.h"
#include "oneflow/core/kernel/new_kernel_util.h"
#include "oneflow/core/job/parallel_desc.h"
#include "oneflow/core/control/global_process_ctx.h"
#include "oneflow/core/framework/placement_sbp_util.h"
#include "oneflow/core/job/nd_sbp_util.h"
#include "oneflow/core/register/tensor_slice_copier.h"

namespace oneflow {

namespace {

Maybe<Symbol<NdSbp>> GetAllSplitNdSbp(int64_t axis, int64_t ndim) {
  NdSbp split_nd_sbp;
  for (int64_t i = 0; i < ndim; ++i) {
    split_nd_sbp.mutable_sbp_parallel()->Add()->mutable_split_parallel()->set_axis(axis);
  }
  return SymbolOf(split_nd_sbp);
}

auto* CachedGetAllSplitNdSbp = DECORATE(&GetAllSplitNdSbp, ThreadLocal);

Maybe<Symbol<NdSbp>> GetAllBroadcastNdSbp(int64_t ndim) {
  NdSbp split_nd_sbp;
  for (int64_t i = 0; i < ndim; ++i) {
    split_nd_sbp.mutable_sbp_parallel()->Add()->mutable_broadcast_parallel();
  }
  return SymbolOf(split_nd_sbp);
}

auto* CachedGetAllBroadcastNdSbp = DECORATE(&GetAllBroadcastNdSbp, ThreadLocal);

class EagerSToBOpKernelCache final : public user_op::OpKernelCache {
 public:
  explicit EagerSToBOpKernelCache(user_op::KernelCacheContext* ctx) { Init(ctx); }
  ~EagerSToBOpKernelCache() override = default;

  const std::vector<std::pair<int64_t, std::shared_ptr<TensorSliceCopier>>>&
  sorted_elem_cnt2in_tensor_slice_copier_pair() const {
    return sorted_elem_cnt2in_tensor_slice_copier_pair_;
  }

  const std::vector<std::pair<int64_t, std::shared_ptr<TensorSliceCopier>>>&
  sorted_elem_cnt2out_tensor_slice_copier_pair() const {
    return sorted_elem_cnt2out_tensor_slice_copier_pair_;
  }

  const std::vector<std::pair<int64_t, int64_t>>& sorted_p2p_pair() const {
    return sorted_p2p_pair_;
  }

 private:
  void Init(user_op::KernelCacheContext* ctx) {
    const std::string& in_parallel_conf_txt = ctx->Attr<std::string>("in_parallel_conf");
    const std::string& out_parallel_conf_txt = ctx->Attr<std::string>("out_parallel_conf");
    const int64_t in_split_axis = ctx->Attr<int64_t>("in_split_axis");
    const Shape& shape = ctx->Attr<Shape>("shape");
    DeviceType device_type = ctx->device_type();
    DataType data_type = ctx->TensorDesc4ArgNameAndIndex("in", 0)->data_type();
    Symbol<ParallelDesc> in_parallel_desc = CHECK_JUST(TxtStringToPlacement(in_parallel_conf_txt));
    Symbol<ParallelDesc> out_parallel_desc =
        CHECK_JUST(TxtStringToPlacement(out_parallel_conf_txt));
    int64_t out_parallel_num = out_parallel_desc->parallel_num();
    int64_t in_parallel_num = in_parallel_desc->parallel_num();

    for (int64_t out_parallel_id = 0; out_parallel_id < out_parallel_num; ++out_parallel_id) {
      int64_t dst = CHECK_JUST(out_parallel_desc->MachineId4ParallelId(out_parallel_id));
      const TensorSliceView& out_slice = GetTensorSliceView4ParallelId(
          *out_parallel_desc->hierarchy(),
          *CHECK_JUST(CachedGetAllBroadcastNdSbp(out_parallel_desc->hierarchy()->NumAxes())), shape,
          out_parallel_id);
      CHECK(!out_slice.IsEmpty());
      for (int64_t in_parallel_id = 0; in_parallel_id < in_parallel_num; ++in_parallel_id) {
        int64_t src = CHECK_JUST(in_parallel_desc->MachineId4ParallelId(in_parallel_id));
        const TensorSliceView& in_slice = GetTensorSliceView4ParallelId(
            *in_parallel_desc->hierarchy(),
            *CHECK_JUST(
                CachedGetAllSplitNdSbp(in_split_axis, in_parallel_desc->hierarchy()->NumAxes())),
            shape, in_parallel_id);
        CHECK(!in_slice.IsEmpty());
        const TensorSliceView& intersection = out_slice.Intersect(in_slice);
        CHECK(!intersection.IsEmpty());
        sorted_p2p_pair_.emplace_back(std::make_pair(src, dst));
        sorted_elem_cnt2in_tensor_slice_copier_pair_.emplace_back(std::make_pair(
            intersection.shape().elem_cnt(),
            std::make_shared<TensorSliceCopier>(intersection, in_slice, data_type, device_type)));
        sorted_elem_cnt2out_tensor_slice_copier_pair_.emplace_back(std::make_pair(
            intersection.shape().elem_cnt(),
            std::make_shared<TensorSliceCopier>(out_slice, intersection, data_type, device_type)));
      }
    }
  }

  std::vector<std::pair<int64_t, std::shared_ptr<TensorSliceCopier>>>
      sorted_elem_cnt2in_tensor_slice_copier_pair_;
  std::vector<std::pair<int64_t, std::shared_ptr<TensorSliceCopier>>>
      sorted_elem_cnt2out_tensor_slice_copier_pair_;
  std::vector<std::pair<int64_t, int64_t>> sorted_p2p_pair_;
};

size_t InferEagerSToBKernelTmpBufferSize(user_op::InferContext* ctx) {
  const user_op::TensorDesc& in_tensor = ctx->InputTensorDesc("in", 0);
  Shape shape = ctx->Attr<Shape>("shape");
  const int64_t in_split_axis = ctx->Attr<int64_t>("in_split_axis");
  const std::string& in_parallel_conf_txt = ctx->Attr<std::string>("in_parallel_conf");
  Symbol<ParallelDesc> in_parallel_desc = CHECK_JUST(TxtStringToPlacement(in_parallel_conf_txt));
  int64_t in_parallel_num = in_parallel_desc->parallel_num();
  if (in_parallel_num > 1) {
    CHECK_LT(in_split_axis, shape.NumAxes());
    BalancedSplitter bs(shape.At(in_split_axis), in_parallel_num);
    shape.Set(in_split_axis, bs.At(0).size());
  }
  size_t tensor_byte_size = shape.elem_cnt() * GetSizeOfDataType(in_tensor.data_type());
  return tensor_byte_size;
}

}  // namespace

class EagerSToBKernel final : public user_op::OpKernel {
 public:
  EagerSToBKernel() = default;
  ~EagerSToBKernel() override = default;

  void InitOpKernelCacheWithFlags(
      user_op::KernelCacheContext* ctx, int8_t flag,
      std::shared_ptr<user_op::OpKernelCache>* cache_ptr) const override {
    if (*cache_ptr == nullptr) { *cache_ptr = std::make_shared<EagerSToBOpKernelCache>(ctx); }
  }

 private:
  void Compute(user_op::KernelComputeContext* ctx, user_op::OpKernelState*,
               const user_op::OpKernelCache* cache) const override {
    auto* kernel_cache = dynamic_cast<const EagerSToBOpKernelCache*>(cache);
    CHECK(kernel_cache != nullptr);
    const user_op::Tensor* in = ctx->Tensor4ArgNameAndIndex("in", 0);
    user_op::Tensor* out = ctx->Tensor4ArgNameAndIndex("out", 0);
    user_op::Tensor* tmp_buffer = ctx->Tensor4ArgNameAndIndex("tmp_buffer", 0);
    const void* in_ptr = in->dptr();
    void* out_ptr = out->mut_dptr();
    void* tmp_buffer_ptr = tmp_buffer->mut_dptr();

    const auto& sorted_elem_cnt2in_tensor_slice_copier_pair =
        kernel_cache->sorted_elem_cnt2in_tensor_slice_copier_pair();
    const auto& sorted_elem_cnt2out_tensor_slice_copier_pair =
        kernel_cache->sorted_elem_cnt2out_tensor_slice_copier_pair();
    const auto& sorted_p2p_pair = kernel_cache->sorted_p2p_pair();
    CHECK_EQ(sorted_elem_cnt2in_tensor_slice_copier_pair.size(), sorted_p2p_pair.size());
    CHECK_EQ(sorted_elem_cnt2out_tensor_slice_copier_pair.size(), sorted_p2p_pair.size());

    DeviceType device_type = ctx->device_type();

    for (int64_t i = 0; i < sorted_p2p_pair.size(); ++i) {
      const auto& p2p_pair = sorted_p2p_pair.at(i);
      int64_t src = p2p_pair.first;
      int64_t dst = p2p_pair.second;
      if (GlobalProcessCtx::Rank() == src) {
        const auto& elem_cnt2tensor_slice_copier_pair =
            sorted_elem_cnt2in_tensor_slice_copier_pair.at(i);
        const auto& elem_cnt = elem_cnt2tensor_slice_copier_pair.first;
        const auto& tensor_slice_copier = elem_cnt2tensor_slice_copier_pair.second;
        tensor_slice_copier->Copy(ctx->stream(), tmp_buffer_ptr, in_ptr);
        CHECK_JUST(Send(reinterpret_cast<const void*>(tmp_buffer_ptr), elem_cnt, in->data_type(),
                        dst, device_type, ctx->stream()));
      }
      if (GlobalProcessCtx::Rank() == dst) {
        const auto& elem_cnt2tensor_slice_copier_pair =
            sorted_elem_cnt2out_tensor_slice_copier_pair.at(i);
        const auto& elem_cnt = elem_cnt2tensor_slice_copier_pair.first;
        const auto& tensor_slice_copier = elem_cnt2tensor_slice_copier_pair.second;
        CHECK_JUST(
            Recv(tmp_buffer_ptr, elem_cnt, out->data_type(), src, device_type, ctx->stream()));
        tensor_slice_copier->Copy(ctx->stream(), out_ptr,
                                  reinterpret_cast<const void*>(tmp_buffer_ptr));
      }
    }
  }
  bool AlwaysComputeWhenAllOutputsEmpty() const override { return false; }
};

REGISTER_USER_KERNEL("eager_s_to_b")
    .SetCreateFn<EagerSToBKernel>()
    .SetIsMatchedHob(HobIsSendAndRecvRegistered())
    .SetInferTmpSizeFn(InferEagerSToBKernelTmpBufferSize);

}  // namespace oneflow
