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update solution for 33-compose.solution #33

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62 changes: 34 additions & 28 deletions src/06-challenges/33-compose.solution.ts
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Original file line number Diff line number Diff line change
@@ -1,40 +1,36 @@
import { expect, it } from "vitest";
import { Equal, Expect } from "../helpers/type-utils";

export function compose<T1, T2>(func: (t1: T1) => T2): (t1: T1) => T2;
export function compose<T1, T2, T3>(
func1: (t1: T1) => T2,
func2: (t2: T2) => T3
): (t1: T1) => T3;
export function compose<T1, T2, T3, T4>(
func1: (t1: T1) => T2,
func2: (t2: T2) => T3,
func3: (t3: T3) => T4
): (t1: T1) => T4;
export function compose<T1, T2, T3, T4, T5>(
func1: (t1: T1) => T2,
func2: (t2: T2) => T3,
func3: (t3: T3) => T4,
func4: (t4: T4) => T5
): (t1: T1) => T5;
export function compose(...funcs: Array<(input: any) => any>) {
return (input: any) => {
return funcs.reduce((acc, fn) => fn(acc), input);
type middleFuncArray<TInput, TReturn> = Array<(input: TInput) => TReturn>;

type FuncArray<TInputFirst, TReturn, TReturnLast> = [
(input: TInputFirst) => TReturn,
...middleFuncArray<TReturn, TReturn>,
(input: TReturn) => TReturnLast
];

export const compose =
<TInputFirst, TReturn, TReturnLast>(
...funcs: FuncArray<TInputFirst, TReturn, TReturnLast>
) =>
(input: TInputFirst) => {
return funcs.reduce<any>((acc, fn) => fn(acc), input) as TReturnLast;
};
}

const addOne = (num: number) => {
return num + 1;
};

const addTwoAndStringify = compose(addOne, addOne, String);

const stringifyThenAddOne = compose(
// @ts-expect-error
String,
// addOne takes in a number - so it shouldn't be allowed after
// a function that returns a string!
addOne
const addTwoAndStringify = compose(
addOne,
addOne,
addOne,
addOne,
addOne,
addOne,
addOne,
addOne,
String
);

it("Should compose multiple functions together", () => {
Expand All @@ -44,3 +40,13 @@ it("Should compose multiple functions together", () => {

type tests = [Expect<Equal<typeof result, string>>];
});

it("Should error when the input to a function is not typed correctly", () => {
const stringifyThenAddOne = compose(
// addOne takes in a number - so it shouldn't be allowed after
// a function that returns a string!
// @ts-expect-error
String,
addOne
);
});