find.ts

// Copyright (c) 2020 Jozty. All rights reserved. MIT license.

import type { PH, Predicate1 } from './utils/types.ts';
import curryN from './utils/curry_n.ts';
import { dispatch } from './utils/dispatch.ts';
import FindTransformer from './utils/Transformers/find.ts';

// @types
type Find_2<T> = (list: T[]) => T | undefined;

type Find_1<T> = (predicate: Predicate1<T>) => T | undefined;

type Find =
  & (<T>(predicate: Predicate1<T>) => Find_2<T>)
  & (<T>(predicate: PH, list: T[]) => Find_1<T>)
  & (<T>(predicate: Predicate1<T>, list: T[]) => T | undefined);

function _find<T>(predicate: Predicate1<T>, list: T[]) {
  for (let i = 0; i < list.length; i++) {
    if (predicate(list[i])) return list[i];
  }
  return void 0;
}

const dispatched = dispatch(FindTransformer, _find);

/**
 * Returns the first element of the list which matches the predicate, or
 * `undefined` if no element matches.
 *
 * Acts as a transducer if a transformer is passed in place of `list`
 *
 *      const xs = [{a: 1}, {a: 2}, {a: 3}]
 *      Fae.find(Fae.propEq('a', 2))(xs) //=> {a: 2}
 *      Fae.find(Fae.propEq('a', 4))(xs) //=> undefined
 */
export const find: Find = curryN(2, dispatched);