/**
 * @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 {Prod, ProdAttrs, ProdInputs} from '../kernel_names';
import {NamedAttrMap} from '../kernel_registry';
import {Tensor} from '../tensor';
import {NamedTensorMap} from '../tensor_types';
import {convertToTensor} from '../tensor_util_env';
import {TensorLike} from '../types';

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

/**
 * Computes the product of elements across dimensions of a `tf.Tensor`.
 *
 * Reduces the input along the dimensions given in `axes`. Unless `keepDims`
 * is true, the rank of the `tf.Tensor` is reduced by 1 for each entry in
 * `axes`. If `keepDims` is true, the reduced dimensions are retained with
 * length 1. If `axes` has no entries, all dimensions are reduced, and a
 * `tf.Tensor` with a single element is returned.
 *
 * ```js
 * const x = tf.tensor1d([1, 2, 3]);
 *
 * x.prod().print();  // or tf.prod(x)
 * ```
 *
 * ```js
 * const x = tf.tensor2d([1, 2, 3, 4], [2, 2]);
 *
 * const axis = 1;
 * x.prod(axis).print();  // or tf.prod(x, axis)
 * ```
 *
 * @param x The input tensor to compute the product over. If the dtype is `bool`
 *   it will be converted to `int32` and the output dtype will be `int32`.
 * @param axis The dimension(s) to reduce. By default it reduces
 *     all dimensions.
 * @param keepDims If true, retains reduced dimensions with size 1.
 *
 * @doc {heading: 'Operations', subheading: 'Reduction'}
 */
function prod_<T extends Tensor>(
    x: Tensor|TensorLike, axis: number|number[] = null, keepDims = false): T {
  let $x = convertToTensor(x, 'x', 'prod');

  if ($x.dtype === 'bool') {
    // bool is not an allowed type for the underlying kernel.
    $x = cast($x, 'int32');
  }

  const inputs: ProdInputs = {x: $x};
  const attrs: ProdAttrs = {axis, keepDims};

  return ENGINE.runKernel(
      Prod, inputs as {} as NamedTensorMap, attrs as {} as NamedAttrMap);
}

export const prod = op({prod_});