/* Copyright 2018 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.
==============================================================================*/
#ifndef TENSORFLOW_LITE_KERNELS_INTERNAL_REFERENCE_INTEGER_OPS_POOLING_H_
#define TENSORFLOW_LITE_KERNELS_INTERNAL_REFERENCE_INTEGER_OPS_POOLING_H_

#include <limits>
#include "tensorflow/lite/kernels/internal/common.h"

namespace tflite {
namespace reference_integer_ops {

inline void AveragePool(const PoolParams& params,
                        const RuntimeShape& input_shape, const int8* input_data,
                        const RuntimeShape& output_shape, int8* output_data) {
  TFLITE_DCHECK_LE(params.quantized_activation_min,
                   params.quantized_activation_max);
  TFLITE_DCHECK_EQ(input_shape.DimensionsCount(), 4);
  TFLITE_DCHECK_EQ(output_shape.DimensionsCount(), 4);
  const int batches = MatchingDim(input_shape, 0, output_shape, 0);
  const int depth = MatchingDim(input_shape, 3, output_shape, 3);
  const int input_height = input_shape.Dims(1);
  const int input_width = input_shape.Dims(2);
  const int output_height = output_shape.Dims(1);
  const int output_width = output_shape.Dims(2);
  const int stride_height = params.stride_height;
  const int stride_width = params.stride_width;
  for (int batch = 0; batch < batches; ++batch) {
    for (int out_y = 0; out_y < output_height; ++out_y) {
      for (int out_x = 0; out_x < output_width; ++out_x) {
        for (int channel = 0; channel < depth; ++channel) {
          const int in_x_origin =
              (out_x * stride_width) - params.padding_values.width;
          const int in_y_origin =
              (out_y * stride_height) - params.padding_values.height;
          // Compute the boundaries of the filter region clamped so as to
          // ensure that the filter window fits in the input array.
          const int filter_x_start = std::max(0, -in_x_origin);
          const int filter_x_end =
              std::min(params.filter_width, input_width - in_x_origin);
          const int filter_y_start = std::max(0, -in_y_origin);
          const int filter_y_end =
              std::min(params.filter_height, input_height - in_y_origin);
          int32 acc = 0;
          int filter_count = 0;
          for (int filter_y = filter_y_start; filter_y < filter_y_end;
               ++filter_y) {
            for (int filter_x = filter_x_start; filter_x < filter_x_end;
                 ++filter_x) {
              const int in_x = in_x_origin + filter_x;
              const int in_y = in_y_origin + filter_y;
              acc +=
                  input_data[Offset(input_shape, batch, in_y, in_x, channel)];
              filter_count++;
            }
          }
          // Round to the closest integer value.
          acc = acc > 0 ? (acc + filter_count / 2) / filter_count
                        : (acc - filter_count / 2) / filter_count;
          acc = std::max(acc, params.quantized_activation_min);
          acc = std::min(acc, params.quantized_activation_max);
          output_data[Offset(output_shape, batch, out_y, out_x, channel)] =
              static_cast<int8>(acc);
        }
      }
    }
  }
}

inline void MaxPool(const PoolParams& params, const RuntimeShape& input_shape,
                    const int8* input_data, const RuntimeShape& output_shape,
                    int8* output_data) {
  TFLITE_DCHECK_LE(params.quantized_activation_min,
                   params.quantized_activation_max);
  TFLITE_DCHECK_GE(params.quantized_activation_min,
                   std::numeric_limits<int8_t>::min());
  TFLITE_DCHECK_LE(params.quantized_activation_max,
                   std::numeric_limits<int8_t>::max());
  TFLITE_DCHECK_EQ(input_shape.DimensionsCount(), 4);
  TFLITE_DCHECK_EQ(output_shape.DimensionsCount(), 4);
  const int batches = MatchingDim(input_shape, 0, output_shape, 0);
  const int depth = MatchingDim(input_shape, 3, output_shape, 3);
  const int input_height = input_shape.Dims(1);
  const int input_width = input_shape.Dims(2);
  const int output_height = output_shape.Dims(1);
  const int output_width = output_shape.Dims(2);
  const int stride_height = params.stride_height;
  const int stride_width = params.stride_width;
  for (int batch = 0; batch < batches; ++batch) {
    for (int out_y = 0; out_y < output_height; ++out_y) {
      for (int out_x = 0; out_x < output_width; ++out_x) {
        for (int channel = 0; channel < depth; ++channel) {
          const int in_x_origin =
              (out_x * stride_width) - params.padding_values.width;
          const int in_y_origin =
              (out_y * stride_height) - params.padding_values.height;
          // Compute the boundaries of the filter region clamped so as to
          // ensure that the filter window fits in the input array.
          const int filter_x_start = std::max(0, -in_x_origin);
          const int filter_x_end =
              std::min(params.filter_width, input_width - in_x_origin);
          const int filter_y_start = std::max(0, -in_y_origin);
          const int filter_y_end =
              std::min(params.filter_height, input_height - in_y_origin);
          int8_t max = std::numeric_limits<int8_t>::lowest();
          for (int filter_y = filter_y_start; filter_y < filter_y_end;
               ++filter_y) {
            for (int filter_x = filter_x_start; filter_x < filter_x_end;
                 ++filter_x) {
              const int in_x = in_x_origin + filter_x;
              const int in_y = in_y_origin + filter_y;
              max = std::max(
                  max,
                  input_data[Offset(input_shape, batch, in_y, in_x, channel)]);
            }
          }
          max = std::max<int8_t>(max, params.quantized_activation_min);
          max = std::min<int8_t>(max, params.quantized_activation_max);
          output_data[Offset(output_shape, batch, out_y, out_x, channel)] =
              static_cast<int8_t>(max);
        }
      }
    }
  }
}

}  // namespace reference_integer_ops
}  // namespace tflite

#endif  // TENSORFLOW_LITE_KERNELS_INTERNAL_REFERENCE_INTEGER_OPS_POOLING_H_
