import { extremaBy } from './_extremaby.js';
import { ExtremaOptions } from './extremaoptions.js';
import { equalityComparerAsync } from '../util/comparer.js';

/**
 * Returns the elements in an async-iterable sequence with the maximum key value.
 *
 * @template TSource The type of the elements in the source sequence.
 * @template TKey The type of the key computed for each element in the source sequence.
 * @param {AsyncIterable<TSource>} source An async-iterable sequence to get the maximum elements for.
 * @param {ExtremaOptions<TSource, TKey>} [options] The options which include an optional comparer and abort signal.
 * @returns {Promise<TSource[]>} A promise containing a list of zero or more elements that have a maximum key value.
 */
export function maxBy<TSource, TKey>(
  source: AsyncIterable<TSource>,
  options?: ExtremaOptions<TSource, TKey>
): Promise<TSource[]> {
  const {
    ['comparer']: comparer = equalityComparerAsync,
    ['selector']: selector,
    ['signal']: signal,
  } = options || {};
  return extremaBy(source, selector!, comparer, signal);
}