#ifndef CAFFE2_OPERATORS_ENSURE_CPU_OUTPUT_OP_H_
#define CAFFE2_OPERATORS_ENSURE_CPU_OUTPUT_OP_H_

#include "caffe2/core/context.h"
#include "caffe2/core/operator.h"
#include "caffe2/utils/math.h"

namespace caffe2 {

template <class Context>
class EnsureCPUOutputOp : public Operator<Context> {
 public:
  USE_OPERATOR_CONTEXT_FUNCTIONS;
  template <class... Args>
  explicit EnsureCPUOutputOp(Args&&... args)
      : Operator<Context>(std::forward<Args>(args)...) {}

  bool RunOnDevice() override {
    if (this->InputIsTensorType(0, CPU)) {
      return CopyWithContext<CPUContext>();
    } else if (this->InputIsTensorType(0, Context::GetDeviceType())) {
      // CUDA Context will go this branch
      return CopyWithContext<Context>();
    } else {
      CAFFE_THROW(
          "Unexpected Input Blob: ",
          OperatorBase::Inputs().at(0)->meta().name());
    }
    return true;
  }

 private:
  template <class InputContext>
  bool CopyWithContext() {
    // Output is always on CPU
    auto& input = this->template Input<Tensor>(0, InputContext::GetDeviceType());
    // TODO: is it possible to use OutputTensorCopyFrom?
    auto* output = this->OutputTensor(
        0, input.sizes(), at::dtype(input.dtype()).device(CPU));
    context_.CopyItemsToCPU(
        input.dtype(),
        input.numel(),
        input.raw_data(),
        output->raw_mutable_data(input.dtype()));
    context_.FinishDeviceComputation();
    return true;
  }
};

} // namespace caffe2

#endif // CAFFE2_OPERATORS_ENSURE_CPU_OUTPUT_OP_H_
