// Copyright (c) 2021 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 <string>
#include <vector>

#include "paddle/fluid/framework/generator.h"
#include "paddle/fluid/framework/op_registry.h"
#include "paddle/fluid/framework/operator.h"
#include "paddle/fluid/platform/enforce.h"

namespace paddle {
namespace operators {

template <typename T>
class CPUReadFileKernel : public framework::OpKernel<T> {
 public:
  void Compute(const framework::ExecutionContext& ctx) const override {
    auto filename = ctx.Attr<std::string>("filename");

    std::ifstream input(filename.c_str(),
                        std::ios::in | std::ios::binary | std::ios::ate);
    std::streamsize file_size = input.tellg();

    input.seekg(0, std::ios::beg);

    auto* out = ctx.Output<framework::LoDTensor>("Out");
    std::vector<int64_t> out_shape = {file_size};
    out->Resize(framework::make_ddim(out_shape));

    uint8_t* data = out->mutable_data<T>(ctx.GetPlace());

    input.read(reinterpret_cast<char*>(data), file_size);
  }
};

class ReadFileOp : public framework::OperatorWithKernel {
 public:
  using framework::OperatorWithKernel::OperatorWithKernel;

  void InferShape(framework::InferShapeContext* ctx) const override {
    PADDLE_ENFORCE_EQ(ctx->HasOutput("Out"), true,
                      platform::errors::InvalidArgument(
                          "Output(Out) of ReadFileOp is null."));

    auto out_dims = std::vector<int>(1, -1);
    ctx->SetOutputDim("Out", framework::make_ddim(out_dims));
  }

 protected:
  framework::OpKernelType GetExpectedKernelType(
      const framework::ExecutionContext& ctx) const override {
    return framework::OpKernelType(framework::proto::VarType::UINT8,
                                   platform::CPUPlace());
  }
};

class ReadFileOpMaker : public framework::OpProtoAndCheckerMaker {
 public:
  void Make() override {
    AddOutput("Out", "The output tensor of ReadFile op");
    AddComment(R"DOC(
This operator read a file.
)DOC");
    AddAttr<std::string>("filename", "Path of the file to be readed.")
        .SetDefault({});
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;

REGISTER_OPERATOR(
    read_file, ops::ReadFileOp, ops::ReadFileOpMaker,
    paddle::framework::EmptyGradOpMaker<paddle::framework::OpDesc>,
    paddle::framework::EmptyGradOpMaker<paddle::imperative::OpBase>)

REGISTER_OP_CPU_KERNEL(read_file, ops::CPUReadFileKernel<uint8_t>)