/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.

   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/operators/seq_expand_op.h"

namespace paddle {
namespace operators {

using framework::Tensor;

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

 protected:
  void InferShape(framework::InferShapeContext* ctx) const override {
    PADDLE_ENFORCE(ctx->HasInput("X"));
    PADDLE_ENFORCE(ctx->HasOutput("Out"));
    PADDLE_ENFORCE(ctx->HasInput("Y"));
    framework::DDim out_dim;
    out_dim = ctx->GetInputDim("Y");
    ctx->ShareLoD("Y", "Out");
    ctx->SetOutputDim("Out", out_dim);
  }
};

class SeqExpandOpMaker : public framework::OpProtoAndCheckerMaker {
 public:
  SeqExpandOpMaker(framework::OpProto* proto,
                   framework::OpAttrChecker* op_checker)
      : OpProtoAndCheckerMaker(proto, op_checker) {
    AddInput("X",
             "(Tensor or LoDTensor) The input(X) of this operator can be a "
             "LoDTensor or a base Tensor.");
    AddInput("Y",
             "(LoDTensor)The reference input(Y) of seq_expand op."
             "It must be a LoDTensor with k-level(k>0)."
             "The input(X) will be expanded according to LOD of input(Y)."
             "The element numbers of last level in input(Y) "
             "must be equal to dims[0] of input(X).");
    AddOutput("Out",
              "(LodTensor)The output of seq_expand op."
              "The lod of output will be as same as input(Y)'s lod.");
    AddComment(R"DOC(
Seq Expand Operator.

This operator expands input(X) according to LOD of input(Y).
Following are cases to better explain how this works:
Case 1:

Given 2-level a LoDTensor input(X)
    X.lod = [[0,       2, 3],
             [0, 1,    3, 4]]
    X.data = [a, b, c, d]
    X.dims = [4, 1]
and input(Y)
    Y.lod = [[0,    2,    4],
             [0, 3, 6, 7, 8]]
with condition len(Y.lod[-1]) -1 == X.dims[0]
then we get 2-level LoDTensor
    Out.lod = [[0,                2,    4],
               [0,       3,       6, 7, 8]]
    Out.data = [a, a, a, b, b, b, c, d]
    Out.dims = [8, 1]

Case 2:

Given a 0-level LoDTensor input(X)
    X.data = [a, b, c]
    X.lod = NULL
    X.dims = [3, 1]
and input(Y)
    Y.lod = [[0, 2, 3, 6]]
with condition len(Y.lod[-1]) -1 == X.dims[0]
then we get 1-level LoDTensor
    Out.lod = [[0,    2, 3,      6]]
    Out.data = [a, a, b, c, c, c]
    Out.dims = [6, 1]

Case 3:

Given a 0-level LoDTensor input(X)
    X.data = [[a, b], [c, d], [e, f]]
    X.lod = NULL
    X.dims = [3, 2]
and input(Y)
    Y.lod = [[0, 2, 3, 6]]
with condition len(Y.lod[-1]) -1 == X.dims[0]
then we get 1-level LoDTensor
    Out.lod = [[0,           2,     3,                     6]]
    Out.data = [[a,b], [a,b] [c,d], [e, f], [e, f], [e, f]]
    Out.dims = [6, 2]

Case 4:

Given 2-level a LoDTensor input(X)
    X.lod = [[0,       2, 3],
             [0, 1,    3, 4]]
    X.data = [a, b, c, d]
    X.dims = [4, 1]
and input(Y)
    Y.lod = [[0,    2,    4],
             [0, 3, 6, 6, 8]]
with condition len(Y.lod[-1]) -1 == X.dims[0]
then we get 2-level LoDTensor
    Out.lod = [[0,                2,    4],
               [0,       3,       6, 6, 8]]
    Out.data = [a, a, a, b, b, b, d, d]
    Out.dims = [8, 1]


)DOC");
  }
};

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

 protected:
  void InferShape(framework::InferShapeContext* ctx) const override {
    PADDLE_ENFORCE(ctx->HasInput("X"));
    PADDLE_ENFORCE(ctx->HasInput("Out"));
    PADDLE_ENFORCE(ctx->HasInput(framework::GradVarName("Out")),
                   "The input(Out@GRAD) should not be null");
    auto x_dims = ctx->GetInputDim("X");
    auto x_grad_name = framework::GradVarName("X");
    if (ctx->HasOutput(x_grad_name)) {
      ctx->SetOutputDim(x_grad_name, x_dims);
    }
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;
REGISTER_OP(seq_expand, ops::SeqExpandOp, ops::SeqExpandOpMaker,
            seq_expand_grad, ops::SeqExpandOpGrad);
REGISTER_OP_CPU_KERNEL(
    seq_expand,
    ops::SeqExpandKernel<paddle::platform::CPUDeviceContext, float>);
REGISTER_OP_CPU_KERNEL(
    seq_expand_grad,
    ops::SeqExpandGradKernel<paddle::platform::CPUDeviceContext, float>);