RocketChat/Rocket.Chat

type Transform<T, U extends T | Promise<Awaited<T>>> = (x: T) => U;

type TransformChain<T, U extends T | Promise<Awaited<T>>> = {
    (x: T): U;
    use(transform: Transform<T, U>): () => void;
};

export const createAsyncTransformChain = <T>(
    ...transforms: Transform<T, Promise<Awaited<T>>>[]
): TransformChain<T, Promise<Awaited<T>>> => {
    let chain = transforms;

    const call = (x: T): Promise<Awaited<T>> => chain.reduce((x, transform) => x.then(transform), Promise.resolve(x));

    const use = (transform: Transform<T, Promise<Awaited<T>>>): (() => void) => {
        chain.push(transform);

        return (): void => {
            chain = chain.filter((t) => t !== transform);
        };
    };

    return Object.assign(call, { use });
};