/**
 * @license
 * Copyright 2020 Google LLC. 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.
 * =============================================================================
 */
import {Conv2D, Conv2DAttrs} from '../kernel_names';
import {GradConfig, NamedAttrMap} from '../kernel_registry';
import {conv2DBackpropFilter} from '../ops/conv2d_backprop_filter';
import {conv2DBackpropInput} from '../ops/conv2d_backprop_input';
import * as conv_util from '../ops/conv_util';
import {Tensor, Tensor4D} from '../tensor';
import * as util from '../util';

export const conv2DGradConfig: GradConfig = {
  kernelName: Conv2D,
  inputsToSave: ['x', 'filter'],
  gradFunc: (dy: Tensor4D, saved: Tensor[], attrs: NamedAttrMap) => {
    const [x4D, $filter] = saved as [Tensor4D, Tensor4D];
    const {dilations, strides, pad, dataFormat} = attrs as {} as Conv2DAttrs;

    util.assert(
        conv_util.tupleValuesAreOne(dilations),
        () => 'Error in gradient of conv2D: dilation rates greater than 1 ' +
            `are not yet supported in gradients. Got dilations '${dilations}'`);

    return {
      x: () =>
          conv2DBackpropInput(x4D.shape, dy, $filter, strides, pad, dataFormat),
      filter: () =>
          conv2DBackpropFilter(x4D, dy, $filter.shape, strides, pad, dataFormat)
    };
  }
};