#ifndef CAFFE_SPATIAL_PRODUCT_HPP_
#define CAFFE_SPATIAL_PRODUCT_HPP_

#include <string>
#include <vector>

#include "caffe/blob.hpp"
#include "caffe/common.hpp"
#include "caffe/layer.hpp"
#include "caffe/proto/caffe.pb.h"

namespace caffe {

/**
 * @brief bottom[0] * bottom[1] across channels
 *       bottom[0] dim: NxCxHxW
 *       bottom[1] dim: Nx1xHxW
 *       top[0]    dim: NxCxHxW where each channel is the spatial prodcut between
 *                      C-th channel of bottom[0] and bottom[1]
 */
template <typename Dtype>
class SpatialProductLayer : public Layer<Dtype> {
 public:
  explicit SpatialProductLayer(const LayerParameter& param)
      : Layer<Dtype>(param) {}

  virtual void LayerSetUp(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual void Reshape(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual inline const char* type() const { return "SpatialProduct"; }

  virtual inline int ExactNumBottomBlobs() const { return 2; }
  virtual inline int ExactNumTopBlobs() const { return 1; }

 protected:
  virtual void Forward_cpu(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual void Forward_gpu(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual void Backward_cpu(const vector<Blob<Dtype>*>& top,
      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
  virtual void Backward_gpu(const vector<Blob<Dtype>*>& top,
      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);

  int num_;
  int channels_;
  int height_;
  int width_;

  Blob<Dtype> multiplier_;  // dot multiplier for backward computation of params
  Blob<Dtype> backward_buff_;  // temporary buffer for backward computation
};

}  // namespace caffe

#endif  // CAFFE_SPATIAL_PRODUCT_HPP_