// modify from
// https://github.com/chengdazhi/Deformable-Convolution-V2-PyTorch/blob/mmdetection/mmdet/ops/dcn/src/modulated_dcn_cuda.c

// based on
// author: Charles Shang
// https://github.com/torch/cunn/blob/master/lib/THCUNN/generic/SpatialConvolutionMM.cu

#include <torch/extension.h>
#include <ATen/DeviceGuard.h>

#include <cmath>
#include <vector>

void DeformablePSROIPoolForward(
    const at::Tensor data, const at::Tensor bbox, const at::Tensor trans,
    at::Tensor out, at::Tensor top_count, const int batch, const int channels,
    const int height, const int width, const int num_bbox,
    const int channels_trans, const int no_trans, const float spatial_scale,
    const int output_dim, const int group_size, const int pooled_size,
    const int part_size, const int sample_per_part, const float trans_std);

void DeformablePSROIPoolBackwardAcc(
    const at::Tensor out_grad, const at::Tensor data, const at::Tensor bbox,
    const at::Tensor trans, const at::Tensor top_count, at::Tensor in_grad,
    at::Tensor trans_grad, const int batch, const int channels,
    const int height, const int width, const int num_bbox,
    const int channels_trans, const int no_trans, const float spatial_scale,
    const int output_dim, const int group_size, const int pooled_size,
    const int part_size, const int sample_per_part, const float trans_std);

void deform_psroi_pooling_cuda_forward(
    at::Tensor input, at::Tensor bbox, at::Tensor trans, at::Tensor out,
    at::Tensor top_count, const int no_trans, const float spatial_scale,
    const int output_dim, const int group_size, const int pooled_size,
    const int part_size, const int sample_per_part, const float trans_std) {
  AT_CHECK(input.is_contiguous(), "input tensor has to be contiguous");
  at::DeviceGuard guard(input.device());

  const int batch = input.size(0);
  const int channels = input.size(1);
  const int height = input.size(2);
  const int width = input.size(3);
  const int channels_trans = no_trans ? 2 : trans.size(1);

  const int num_bbox = bbox.size(0);
  if (num_bbox != out.size(0))
    AT_ERROR("Output shape and bbox number wont match: (%d vs %d).",
             out.size(0), num_bbox);

  DeformablePSROIPoolForward(
      input, bbox, trans, out, top_count, batch, channels, height, width,
      num_bbox, channels_trans, no_trans, spatial_scale, output_dim, group_size,
      pooled_size, part_size, sample_per_part, trans_std);
}

void deform_psroi_pooling_cuda_backward(
    at::Tensor out_grad, at::Tensor input, at::Tensor bbox, at::Tensor trans,
    at::Tensor top_count, at::Tensor input_grad, at::Tensor trans_grad,
    const int no_trans, const float spatial_scale, const int output_dim,
    const int group_size, const int pooled_size, const int part_size,
    const int sample_per_part, const float trans_std) {
  AT_CHECK(out_grad.is_contiguous(), "out_grad tensor has to be contiguous");
  AT_CHECK(input.is_contiguous(), "input tensor has to be contiguous");
  at::DeviceGuard guard(input.device());

  const int batch = input.size(0);
  const int channels = input.size(1);
  const int height = input.size(2);
  const int width = input.size(3);
  const int channels_trans = no_trans ? 2 : trans.size(1);

  const int num_bbox = bbox.size(0);
  if (num_bbox != out_grad.size(0))
    AT_ERROR("Output shape and bbox number wont match: (%d vs %d).",
             out_grad.size(0), num_bbox);

  DeformablePSROIPoolBackwardAcc(
      out_grad, input, bbox, trans, top_count, input_grad, trans_grad, batch,
      channels, height, width, num_bbox, channels_trans, no_trans,
      spatial_scale, output_dim, group_size, pooled_size, part_size,
      sample_per_part, trans_std);
}

PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
  m.def("deform_psroi_pooling_cuda_forward", &deform_psroi_pooling_cuda_forward,
        "deform psroi pooling forward(CUDA)");
  m.def("deform_psroi_pooling_cuda_backward",
        &deform_psroi_pooling_cuda_backward,
        "deform psroi pooling backward(CUDA)");
}
