/**
 * @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 {LRN, LRNAttrs, LRNInputs} from '../kernel_names';
import {NamedAttrMap} from '../kernel_registry';
import {Tensor3D, Tensor4D} from '../tensor';
import {NamedTensorMap} from '../tensor_types';
import {convertToTensor} from '../tensor_util_env';
import {TensorLike} from '../types';
import * as util from '../util';

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

/**
 * Normalizes the activation of a local neighborhood across or within
 * channels.
 *
 * @param x The input tensor. The 4-D input tensor is treated as a 3-D array
 *     of 1D vectors (along the last dimension), and each vector is
 *     normalized independently.
 * @param depthRadius The number of adjacent channels in the 1D normalization
 *     window.
 * @param bias A constant bias term for the basis.
 * @param alpha A scale factor, usually positive.
 * @param beta An exponent.
 *
 * @doc {heading: 'Operations', subheading: 'Normalization'}
 */
function localResponseNormalization_<T extends Tensor3D|Tensor4D>(
    x: T|TensorLike, depthRadius = 5, bias = 1, alpha = 1, beta = 0.5): T {
  const $x = convertToTensor(x, 'x', 'localResponseNormalization');
  util.assert(
      $x.rank === 4 || $x.rank === 3,
      () => `Error in localResponseNormalization: x must be rank 3 or 4 but got
               rank ${$x.rank}.`);
  util.assert(
      util.isInt(depthRadius),
      () => `Error in localResponseNormalization: depthRadius must be an ` +
          `integer but got depthRadius ${depthRadius}.`);

  let x4D = $x as Tensor4D;
  let reshapedTo4D = false;
  if ($x.rank === 3) {
    reshapedTo4D = true;
    x4D = reshape($x, [1, $x.shape[0], $x.shape[1], $x.shape[2]]);
  }

  const inputs: LRNInputs = {x: x4D};

  const attrs: LRNAttrs = {depthRadius, bias, alpha, beta};

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

  if (reshapedTo4D) {
    return reshape(res, [res.shape[1], res.shape[2], res.shape[3]]) as T;
  } else {
    return res;
  }
}

export const localResponseNormalization = op({localResponseNormalization_});