/**
 * @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 {ENGINE} from '../engine';
import {Conv3DBackpropInputV2, Conv3DBackpropInputV2Attrs, Conv3DBackpropInputV2Inputs} from '../kernel_names';
import {NamedAttrMap} from '../kernel_registry';
import {Tensor4D, Tensor5D} from '../tensor';
import {NamedTensorMap} from '../tensor_types';
import * as util from '../util';

import {op} from './operation';
import {reshape} from './reshape';

/**
 * Computes the derivative of the input of a 3D convolution.
 *
 * @param xShape The shape of the input: [batch, depth, height, width,
 * in_channels]. If length of 4, batch of 1 is assumed.
 * @param dy The derivative of the output, of rank 5 or rank 4 of shape
 *   `[batch, outDepth, outHeight, outWidth, in_channels]`.
 * If rank 4, batch of 1 is assumed.
 * @param filter The filter, rank 5, of shape
 *     `[filterDepth, filterHeight, filterWidth, inDepth, outDepth]`.
 * @param strides The strides of the convolution: `[strideDepth, strideHeight,
 * strideWidth]`.
 * @param pad The type of padding algorithm used:
 *    - `same` and stride 1: output will be of same size as input,
 *       regardless of filter size.
 *    - `valid`: output will be smaller than input if filter is larger
 *       than 1x1.
 */
function conv3DBackpropInput_<T extends Tensor4D|Tensor5D>(
    xShape:
        [number, number, number, number,
         number]|[number, number, number, number],
    dy: T, filter: Tensor5D, strides: [number, number, number]|number,
    pad: 'valid'|'same'): T {
  util.assert(
      xShape.length === dy.rank,
      () => `Length of inShape ` +
          `(${xShape.length}) and rank of dy (${dy.rank}) must match`);

  let xShape5D = xShape as [number, number, number, number, number];
  let dy5D = dy as Tensor5D;
  let reshapedTo5D = false;
  if (dy.rank === 4) {
    reshapedTo5D = true;
    dy5D = reshape(dy, [1, dy.shape[0], dy.shape[1], dy.shape[2], dy.shape[3]]);
    xShape5D = [1, xShape[0], xShape[1], xShape[2], xShape[3]];
  }

  const inDepth = xShape5D[4];
  const outDepth = dy5D.shape[4];
  util.assert(
      xShape5D.length === 5,
      () =>
          `Error in conv3dDerInput: inShape must be length 5, but got length ` +
          `${xShape5D.length}.`);
  util.assert(
      dy5D.rank === 5,
      () => `Error in conv3dDerInput: dy must be rank 5, but got ` +
          `rank ${dy5D.rank}`);
  util.assert(
      filter.rank === 5,
      () => `Error in conv3dDerInput: filter must be rank 5, but got ` +
          `rank ${filter.rank}`);
  util.assert(
      inDepth === filter.shape[3],
      () => `Error in conv3dDerInput: depth of input (${inDepth}) must ` +
          `match input depth for filter ${filter.shape[3]}.`);
  util.assert(
      outDepth === filter.shape[4],
      () => `Error in conv3dDerInput: depth of output (${outDepth}) must ` +
          `match output depth for filter ${filter.shape[4]}.`);

  const inputs: Conv3DBackpropInputV2Inputs = {dy: dy5D, filter};

  const attrs:
      Conv3DBackpropInputV2Attrs = {pad, strides, inputShape: xShape5D};

  // tslint:disable-next-line: no-unnecessary-type-assertion
  const res = ENGINE.runKernel(
                  Conv3DBackpropInputV2, inputs as {} as NamedTensorMap,
                  attrs as {} as NamedAttrMap) as T;

  if (reshapedTo5D) {
    return reshape(
               res, [res.shape[1], res.shape[2], res.shape[3], res.shape[4]]) as
        T;
  }
  return res;
}

export const conv3DBackpropInput = op({conv3DBackpropInput_});