Continuous effect for effector

ContinuousEffect.ts

import { createEffect, createEvent, Effect, Event } from 'effector';

export interface ContinuousEffect<Params, Done, Payload = Done, Fail = Error> extends Effect<Params, Done, Fail> {
    readonly progress: Event<{params: Params; result: Payload}>
    readonly progressData: Event<Payload>
}

export function createContinuousEffect<Params, Done, Payload = Done, Fail = Error>(
    handler: ((params: Params) => Done | Promise<Done> | Iterator<Payload, Done> | AsyncIterator<Payload, Done>)
) {
    const progress = createEvent<{ params: Params, result: Payload }>();
    const progressData: Event<Payload> = progress.map({
        // @ts-ignore
        named: 'progressData',
        fn: ({ result }: any) => result,
    });

    async function continuousHandler(params: Params): Promise<Done> {
        let maybeIterator = handler(params);

        // Return as is if not iterable
        if (!('next' in maybeIterator)) {
            return maybeIterator;
        }

        // Have to use .next manually because for-await-of won't show a final result.
        while (true) {
            // Can't destructure right here because of typescript troubles
            const next = await maybeIterator.next();
            if (next.done !== true) {
                progress({ params, result: next.value });
            } else {
                return next.value;
            }
        }
    };

    const instance: ContinuousEffect<Params, Done, Payload, Fail> = Object.assign(
        createEffect<typeof continuousHandler, Fail>(continuousHandler),
        { progress, progressData },
    );

    return instance;
}