const pipe = (...fns: (() => any)[]) => (...args: any[]) => fns.reduce((p, c) => [c.apply(null, p)], args);
  
const stringToArray = (str: string) => Array.from(str);
const reverseArray = (arr: any[]) => arr.reverse();
const arrayToString = (arr: string[]) => arr.join("");

const reverseString = pipe(stringToArray, reverseArray, arrayToString); // should be (str: string) => string
// same as (str: string) => arrayToString(reverseArray(stringToArray(str)))

declare function pipe(...fns: any[]): any;

import type { Equal, Expect } from '@type-challenges/utils'

const getString = () => "Hello World!";
const reverseString = (str: string) => Array.from(str).reverse().join("");
const getLength = (str: string) => str.length;
const addTen = (n: number) => n + 10;
const timesByTwo = (n: number) => n * 2;

const case1 = pipe();
const case2 = pipe(getString);
const case3 = pipe(getString, reverseString);
const case4 = pipe(reverseString);
const case5 = pipe(getString, reverseString, getLength, addTen, timesByTwo);
const case6 = pipe(addTen, timesByTwo);

type cases = [
  Expect<Equal<typeof case1, Expected1>>,
  Expect<Equal<typeof case2, Expected2>>,
  Expect<Equal<typeof case3, Expected3>>,
  Expect<Equal<typeof case4, Expected4>>,
  Expect<Equal<typeof case5, Expected5>>,
  Expect<Equal<typeof case6, Expected6>>
]

pipe(
  getString,
  // @ts-expect-error
  addTen
);
pipe(
  addTen,
  // @ts-expect-error
  getLength
);
pipe(
  timesByTwo,
  addTen,
  // @ts-expect-error
  reverseString
);

type Expected1 = () => void;
type Expected2 = () => string;
type Expected3 = () => string;
type Expected4 = (str: string) => string;
type Expected5 = () => number;
type Expected6 = (n: number) => number;