/* Copyright (c) 2016 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 "paddle/fluid/framework/op_registry.h"

namespace paddle {
namespace framework {
class InferShapeContext;
class LoDTensor;
class OpDesc;
class Scope;
}  // namespace framework
namespace imperative {
class OpBase;
}  // namespace imperative
}  // namespace paddle

namespace paddle {
namespace operators {

using LoD = framework::LoD;

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

 protected:
  void RunBase(const framework::Scope &scope,
               const platform::Place &dev_place) const {
    // get device context from pool
    platform::DeviceContextPool &pool = platform::DeviceContextPool::Instance();
    auto &dev_ctx = *pool.Get(dev_place);

    auto &x = scope.FindVar(Input("X"))->Get<framework::LoDTensor>();
    auto &mask = scope.FindVar(Input("Mask"))->Get<framework::LoDTensor>();
    auto &in_true = scope.FindVar(Input("InTrue"))->Get<framework::LoDTensor>();
    auto &in_false =
        scope.FindVar(Input("InFalse"))->Get<framework::LoDTensor>();
    auto *out =
        scope.FindVar(Output("Out"))->GetMutable<framework::LoDTensor>();
    auto level = static_cast<size_t>(Attr<int>("level"));

    PADDLE_ENFORCE_EQ(
        in_true.numel() || in_false.numel(), true,
        platform::errors::InvalidArgument(
            "Input(InTrue) or Input(InFalse) should be initialized."));

    auto &mask_dim = mask.dims();
    std::unique_ptr<framework::LoDTensor> cpu_mask{new framework::LoDTensor()};
    if (platform::is_cpu_place(mask.place())) {
      cpu_mask->ShareDataWith(mask);
    } else if (platform::is_gpu_place(mask.place())) {
#ifdef PADDLE_WITH_CUDA
      framework::TensorCopy(mask, platform::CPUPlace(), dev_ctx,
                            cpu_mask.get());
#else
      PADDLE_THROW(platform::errors::PreconditionNotMet(
          "Not supported GPU, Please recompile or reinstall paddle with CUDA "
          "support."));
#endif
    }
    auto *mask_data = cpu_mask->data<bool>();

    platform::Place place = dev_place;
    int64_t batch_size = in_true.dims()[0] + in_false.dims()[0];
    auto data_type = in_true.IsInitialized() ? in_true.type() : in_false.type();
    int rank;
    framework::DDim in_dims;
    if (in_true.IsInitialized()) {
      rank = in_true.dims().size();
      in_dims = framework::slice_ddim(in_true.dims(), 1, rank);
    } else {
      rank = in_false.dims().size();
      in_dims = framework::slice_ddim(in_false.dims(), 1, rank);
    }

    auto in_dim_vec = framework::vectorize(in_dims);
    in_dim_vec.insert(in_dim_vec.begin(), batch_size);

    framework::DDim out_dims = framework::make_ddim(in_dim_vec);
    out->Resize(out_dims);

    out->mutable_data(place, data_type);

    auto *out_lod = out->mutable_lod();
    out_lod->clear();
    size_t out_offset = 0;

    // Build LoDTensor `out`

    size_t in_true_idx = 0;
    size_t in_false_idx = 0;
    for (size_t i = 0; i < static_cast<size_t>(mask_dim[0]); i++) {
      const framework::LoDTensor *input = nullptr;
      size_t *in_idx = nullptr;
      if (static_cast<int>(mask_data[i]) == 0) {
        input = &in_false;
        in_idx = &in_false_idx;
      } else {
        input = &in_true;
        in_idx = &in_true_idx;
      }
      auto lod_and_offset = framework::GetSubLoDAndAbsoluteOffset(
          input->lod(), *in_idx, (*in_idx) + 1, 0);
      auto &lod_length = lod_and_offset.first;

      framework::AppendLoD(out_lod, lod_length);

      size_t start_offset = lod_and_offset.second.first;
      size_t end_offset = lod_and_offset.second.second;

      PADDLE_ENFORCE_GE(end_offset, start_offset,
                        platform::errors::InvalidArgument(
                            "The end offset less than start offset, end offset "
                            "is %d, start offset is %d.",
                            end_offset, start_offset));
      size_t len = end_offset - start_offset;
      if (len == 0) {
        continue;
      }
      auto slice = out->Slice(out_offset, out_offset + len);
      framework::TensorCopy(input->Slice(start_offset, end_offset), place,
                            dev_ctx, &slice);
      out_offset += len;
      (*in_idx) += 1;
    }

    for (size_t i = 0; i < level; i++) {
      out_lod->insert(out_lod->begin(), x.lod()[i]);
    }
  }

 private:
  void RunImpl(const framework::Scope &scope,
               const platform::Place &dev_place) const override {
    RunBase(scope, dev_place);
  }
};

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

 private:
  void RunImpl(const framework::Scope &scope,
               const platform::Place &dev_place) const override {
    RunBase(scope, dev_place);
    framework::Variable *in_true_var = scope.FindVar(Input("InTrue"));
    framework::Variable *in_false_var = scope.FindVar(Input("InFalse"));
    in_true_var->Clear();
    in_false_var->Clear();
    in_true_var->GetMutable<framework::LoDTensor>();
    in_false_var->GetMutable<framework::LoDTensor>();
  }
};

class MergeLoDTensorOpProtoMaker : public framework::OpProtoAndCheckerMaker {
 public:
  void Make() override {
    AddInput("X",
             "The input LoDTensor, contains complete lod information to "
             "construct the output");
    AddInput("Mask", "A bool column vector which mask the input");
    AddInput("InTrue", "The True branch to be merged");
    AddInput("InFalse", "The False branch to be merged");
    AddOutput("Out", "The merged output LoDTensor");
    AddAttr<int>("level", "(int) the specific lod level to rank.")
        .SetDefault(0)
        .EqualGreaterThan(0);
    AddComment(
        R"DOC(
        Merge True and False branches of LoDTensor into a single Output,
        with a mask at certain lod level. X is used to obtain complete
        lod information. Please refer to SplitLoDTensorOp.)DOC");
  }
};

class MergeLoDTensorInferShape : public framework::InferShapeBase {
 public:
  void operator()(framework::InferShapeContext *context) const override {
    OP_INOUT_CHECK(context->HasInput("X"), "Input", "X", "merge_lod_tensor");
    OP_INOUT_CHECK(context->HasInput("Mask"), "Input", "Mask",
                   "merge_lod_tensor");
    OP_INOUT_CHECK(context->HasInput("InTrue"), "Input", "InTrue",
                   "merge_lod_tensor");
    OP_INOUT_CHECK(context->HasInput("InFalse"), "Input", "InFalse",
                   "merge_lod_tensor");
    OP_INOUT_CHECK(context->HasOutput("Out"), "Output", "Out",
                   "merge_lod_tensor");
    auto mask_dim = context->GetInputDim("Mask");
    PADDLE_ENFORCE_EQ(mask_dim.size(), 2,
                      platform::errors::InvalidArgument(
                          "If you are using IfElse OP:"
                          "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
                          "ie.true_block():\n    out_1 = ie.input(x)\n\n"
                          "Please ensure that the cond is a 2-D tensor and "
                          "the second dim size of cond is 1. "
                          "But now the cond's shape is [%s].\n",
                          mask_dim));
    if (context->IsRuntime() || mask_dim[1] > 0) {
      PADDLE_ENFORCE_EQ(mask_dim[1], 1,
                        platform::errors::InvalidArgument(
                            "If you are using IfElse OP:"
                            "\n\nie = fluid.layers.IfElse(cond=cond)\nwith "
                            "ie.true_block():\n    out_1 = ie.input(x)\n\n"
                            "Please ensure that the cond is a 2-D tensor "
                            "and the second dim size of cond is 1. "
                            "But now the cond's shape is [%s].\n",
                            mask_dim));
    }

    context->SetOutputDim("Out", context->GetInputDim("InTrue"));
  }
};

template <typename T>
class MergeLoDTensorGradMaker : public framework::SingleGradOpMaker<T> {
 public:
  using framework::SingleGradOpMaker<T>::SingleGradOpMaker;

 protected:
  void Apply(GradOpPtr<T> grad_op) const override {
    grad_op->SetType("split_lod_tensor");
    grad_op->SetInput("X", this->OutputGrad("Out"));
    grad_op->SetInput("Mask", this->Input("Mask"));
    grad_op->SetOutput("OutTrue", this->InputGrad("InTrue"));
    grad_op->SetOutput("OutFalse", this->InputGrad("InFalse"));
    grad_op->SetAttrMap(this->Attrs());
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;
REGISTER_OPERATOR(merge_lod_tensor, ops::MergeLoDTensorOp,
                  ops::MergeLoDTensorOpProtoMaker,
                  ops::MergeLoDTensorInferShape,
                  ops::MergeLoDTensorGradMaker<paddle::framework::OpDesc>,
                  ops::MergeLoDTensorGradMaker<paddle::imperative::OpBase>);
REGISTER_OPERATOR(
    merge_lod_tensor_infer, ops::MergeLoDTensorInferOp,
    ops::MergeLoDTensorOpProtoMaker, ops::MergeLoDTensorInferShape,
    paddle::framework::EmptyGradOpMaker<paddle::framework::OpDesc>,
    paddle::framework::EmptyGradOpMaker<paddle::imperative::OpBase>);
