/* Copyright 2015 The TensorFlow 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.
==============================================================================*/

#define EIGEN_USE_THREADS

#include <algorithm>
#include <numeric>
#include <unordered_map>
#include <utility>
#include <vector>

#include "tensorflow/core/framework/op_kernel.h"
#include "tensorflow/core/framework/register_types.h"
#include "tensorflow/core/framework/tensor.h"
#include "tensorflow/core/framework/tensor_util.h"
#include "tensorflow/core/framework/types.h"
#include "tensorflow/core/lib/gtl/inlined_vector.h"
#include "tensorflow/core/util/sparse/sparse_tensor.h"

namespace tensorflow {

template <typename T>
class SparseConcatOp : public OpKernel {
 public:
  explicit SparseConcatOp(OpKernelConstruction* context) : OpKernel(context) {
    OP_REQUIRES_OK(context, context->GetAttr("concat_dim", &concat_dim_attr_));
  }

  void Compute(OpKernelContext* context) override {
    OpInputList inds;
    OP_REQUIRES_OK(context, context->input_list("indices", &inds));
    const int N = inds.size();
    for (int i = 0; i < N; i++) {
      OP_REQUIRES(context, TensorShapeUtils::IsMatrix(inds[i].shape()),
                  errors::InvalidArgument(
                      "Input indices should be a matrix but received shape ",
                      inds[i].shape().DebugString(), " at position ", i));
    }

    OpInputList vals;
    OP_REQUIRES_OK(context, context->input_list("values", &vals));
    OP_REQUIRES(context, vals.size() == N,
                errors::InvalidArgument("Expected ", N, " input values, got ",
                                        vals.size()));
    for (int i = 0; i < N; i++) {
      OP_REQUIRES(context, TensorShapeUtils::IsVector(vals[i].shape()),
                  errors::InvalidArgument(
                      "Input values should be a vector but received shape ",
                      vals[i].shape().DebugString(), " at position ", i));
    }

    OpInputList shapes;
    OP_REQUIRES_OK(context, context->input_list("shapes", &shapes));
    OP_REQUIRES(context, shapes.size() == N,
                errors::InvalidArgument("Expected ", N, " input shapes, got ",
                                        shapes.size()));
    for (int i = 0; i < N; i++) {
      OP_REQUIRES(context, TensorShapeUtils::IsVector(shapes[i].shape()),
                  errors::InvalidArgument(
                      "Input shapes should be a vector but received shape ",
                      shapes[i].shape().DebugString(), " at position ", i));
    }

    const TensorShape input_shape(shapes[0].vec<int64>());
    const int input_rank = input_shape.dims();
    const int concat_dim = (concat_dim_attr_ < 0)
                               ? input_rank + concat_dim_attr_
                               : concat_dim_attr_;
    OP_REQUIRES(context, concat_dim >= 0 && concat_dim < input_rank,
                errors::InvalidArgument("Concat dimension must be in range [",
                                        -input_rank, ", ", input_rank,
                                        "), got ", concat_dim_attr_));
    for (int i = 1; i < N; ++i) {
      const TensorShape current_shape(shapes[i].vec<int64>());
      OP_REQUIRES(
          context, current_shape.dims() == input_rank,
          errors::InvalidArgument(
              "Ranks of all input tensors must match: expected ", input_rank,
              " but got ", current_shape.dims(), " at position ", i));
      for (int j = 0; j < input_rank; ++j) {
        if (j != concat_dim) {
          OP_REQUIRES(
              context, input_shape.dim_size(j) == current_shape.dim_size(j),
              errors::InvalidArgument(
                  "Input shapes must match: expected ", input_shape.dim_size(j),
                  " for dimension ", j, " but got ", current_shape.dim_size(j),
                  " at position ", i));
        }
      }
    }

    // The input and output sparse tensors are assumed to be ordered along
    // increasing dimension number. But in order for concat to work properly,
    // order[0] must be concat_dim. So we will reorder the inputs to the
    // concat ordering, concatenate, then reorder back to the standard order.
    // We make a deep copy of the input tensors to ensure that the in-place
    // reorder doesn't create race conditions for other ops that may be
    // concurrently reading the indices and values tensors.

    gtl::InlinedVector<int64, 8> std_order(input_rank);
    std::iota(std_order.begin(), std_order.end(), 0);

    std::vector<int64> concat_order;
    concat_order.reserve(input_rank);
    concat_order.push_back(concat_dim);
    for (int j = 0; j < input_rank; ++j) {
      if (j != concat_dim) {
        concat_order.push_back(j);
      }
    }

    std::vector<sparse::SparseTensor> sp_inputs;
    for (int i = 0; i < N; ++i) {
      const TensorShape current_shape(shapes[i].vec<int64>());
      sparse::SparseTensor tensor;
      OP_REQUIRES_OK(context,
                     sparse::SparseTensor::Create(
                         tensor::DeepCopy(inds[i]), tensor::DeepCopy(vals[i]),
                         current_shape, std_order, &tensor));
      sp_inputs.push_back(std::move(tensor));
      sp_inputs[i].Reorder<T>(concat_order);
    }

    sparse::SparseTensor concat = sparse::SparseTensor::Concat<T>(sp_inputs);
    concat.Reorder<T>(std_order);

    context->set_output(0, concat.indices());
    context->set_output(1, concat.values());

    Tensor* output_shape_out = nullptr;
    OP_REQUIRES_OK(context,
                   context->allocate_output(2, TensorShape({concat.dims()}),
                                            &output_shape_out));
    auto output_shape = output_shape_out->vec<int64>();
    auto concat_shape = concat.shape();
    for (int j = 0; j < concat.dims(); ++j) {
      output_shape(j) = concat_shape[j];
    }
  }

 private:
  int concat_dim_attr_;
};

/* ===== KERNEL registering COMMENTED, optimized Op kernels would be used. =====
#define REGISTER_KERNELS(type)                                           \
  REGISTER_KERNEL_BUILDER(                                               \
      Name("SparseConcat").Device(DEVICE_CPU).TypeConstraint<type>("T"), \
      SparseConcatOp<type>)

TF_CALL_ALL_TYPES(REGISTER_KERNELS);
#undef REGISTER_KERNELS
================= End of KERNEL registering COMMENTED block. ================ */
}  // namespace tensorflow
