/* Copyright (c) 2018 PaddlePaddle 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 <fstream>

#include "paddle/fluid/framework/op_registry.h"
#include "paddle/fluid/platform/device_context.h"

namespace paddle {
namespace operators {

class LoadCombineOp : public framework::OperatorBase {
 public:
  LoadCombineOp(const std::string &type,
                const framework::VariableNameMap &inputs,
                const framework::VariableNameMap &outputs,
                const framework::AttributeMap &attrs)
      : OperatorBase(type, inputs, outputs, attrs) {}

 private:
  void RunImpl(const framework::Scope &scope,
               const platform::Place &place) const override {
    auto filename = Attr<std::string>("file_path");

    std::ifstream fin(filename);
    PADDLE_ENFORCE(static_cast<bool>(fin),
                   "Cannot open file %s for load_combine op", filename);

    auto out_var_names = Outputs("Out");
    PADDLE_ENFORCE_GT(
        static_cast<int>(out_var_names.size()), 0,
        "The number of output variables should be greater than 0.");

    platform::DeviceContextPool &pool = platform::DeviceContextPool::Instance();
    auto &dev_ctx = *pool.Get(place);

    for (size_t i = 0; i < out_var_names.size(); i++) {
      auto *out_var = scope.FindVar(out_var_names[i]);

      PADDLE_ENFORCE(out_var != nullptr, "Output variable %s cannot be found",
                     out_var_names[i]);

      auto *tensor = out_var->GetMutable<framework::LoDTensor>();

      // Error checking
      PADDLE_ENFORCE(static_cast<bool>(fin), "Cannot read more from file %s",
                     filename);

      // Get data from fin to tensor
      DeserializeFromStream(fin, tensor, dev_ctx);

      if (platform::is_gpu_place(place)) {
        // copy CPU to GPU
        framework::LoDTensor cpu_tensor;
        cpu_tensor.ShareDataWith(*tensor);
        cpu_tensor.set_lod(tensor->lod());

        // reset tensor
        out_var->Clear();
        tensor = out_var->GetMutable<framework::LoDTensor>();
        tensor->set_lod(cpu_tensor.lod());
        Copy(cpu_tensor, place, dev_ctx, tensor);
      }
    }
  }
};

class LoadCombineOpProtoMaker : public framework::OpProtoAndCheckerMaker {
 public:
  LoadCombineOpProtoMaker(OpProto *proto, OpAttrChecker *op_checker)
      : OpProtoAndCheckerMaker(proto, op_checker) {
    AddOutput(
        "Out",
        "(vector) The output LoDTensors that will be read from the input file.")
        .AsDuplicable();
    AddAttr<std::string>("file_path",
                         "(string) "
                         "LoDTensors will be loaded from \"file_path\".")
        .AddCustomChecker(
            [](const std::string &path) { return !path.empty(); });
    AddComment(R"DOC(
LoadCombine Operator.

LoadCombine operator loads LoDTensor variables from a file. The file should 
contain one or more LoDTensors serialized using the SaveCombine operator. The 
LoadCombine operator applies a deserialization strategy to appropriately load 
the LodTensors, and this strategy complements the serialization strategy used 
in the SaveCombine operator. Hence, the LoadCombine operator is tightly coupled
with the SaveCombine operator, and can only deserialize one or more LoDTensors 
that were saved using the SaveCombine operator.

)DOC");
  }
};
}  // namespace operators
}  // namespace paddle
namespace ops = paddle::operators;

REGISTER_OPERATOR(load_combine, ops::LoadCombineOp,
                  ops::LoadCombineOpProtoMaker);