aperture.ts

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

import { dispatch } from './utils/dispatch.ts';
import ApertureTransformer from './utils/Transformers/aperture.ts';
import curryN from './utils/curry_n.ts';
import type { PH } from './utils/types.ts';

// @types
type Aperture_2 = <T>(list: T[]) => T[][];

type Aperture_1<T> = (n: number) => T[][];

type Aperture =
  & ((n: number) => Aperture_2)
  & (<T>(n: PH, list: T[]) => Aperture_1<T>)
  & (<T>(n: number, list: T[]) => T[][]);

function _aperture<T>(n: number, list: T[]) {
  const len = list.length - n + 1;
  const result = new Array(Math.max(0, len));

  for (let i = 0; i < len; i++) {
    result[i] = list.slice(i, i + n);
  }

  return result;
}

const dispatched = dispatch(ApertureTransformer, _aperture);

/**
 * Returns a new list, composed of n-tuples of consecutive elements. If `n` is
 * greater than the length of the list, an empty list is returned.
 *
 * Acts as a transducer if a transformer is passed in place of `list`
 */
export const aperture = curryN(2, dispatched) as Aperture;