lensPath.ts

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

import { Lens, lens, LensGetter, LensSetter } from './lens.ts';
import { assocPath } from './assocPath.ts';
import curryN from './utils/curry_n.ts';
import type { Path } from './paths.ts';
import { path as pth } from './path.ts';

// @types
type LensPath = <T, F>(path: Path) => Lens<T, F>;

function _lensPath<T, F>(path: Path): Lens<T, F> {
  return lens(
    pth(path) as LensGetter<T, F>,
    (assocPath(path) as any) as LensSetter<T, F>,
  );
}

/**
 * Returns a lens whose focus is the specified path.
 *
 *      const xHeadYLens = Fae.lensPath(['x', 0, 'y'])
 *      Fae.view(xHeadYLens, {x: [{y: 2, z: 3}, {y: 4, z: 5}]}) // {x: [{y: 1, z: 3}, {y: 4, z: 5}]}
 */
export const lensPath: LensPath = curryN(1, _lensPath);