// Copyright (c) 2020 Jozty. All rights reserved. MIT license.
import type { Func } from './utils/types.ts';import { getFunctionLength } from './utils/get.ts';import curryN from './utils/curry_n.ts';
/** * Returns a new function much like the supplied one, except that the first two * arguments' order is reversed. The returned function is automatically curried. * But the types are not preserved as of now due to TS limitations. The returned function * will have all unknown in its parameters list and return type. To make it work properly, * you need to use type assertion using `Curry2` or `Curry3`. * * ```ts * import { flip } from './flip.ts' * import { Curry3 } from './utils/types.ts' * * const mergeThree = (a: number, b: number, c: number) => [a].concat(b, c) * * mergeThree(1, 2, 3); // [1, 2, 3] * * const flipped = flip(mergeThree) * * // @ts-expect-error: append should have been type-asserted * flipped(1, 2)(3); // [2, 1, 3] * * const flippedWithTypes = flipped as Curry3<number, number, number, number[]> * * flippedWithTypes(1, 2)(3); // [2, 1, 3] * ``` */export function flip<T, A extends unknown[], R>( fn: (a: T, b: T, ...rest: A) => R,) { return curryN(getFunctionLength(fn), function ( this: any, b: T, a: T, ...rest: A ) { return fn.apply(this, [a, b, ...rest]); }) as Func<unknown[], unknown, unknown>;}