refetch a resource from the fetcher

export function makeFetcher<T>(source?: IterableSource<T>) {
  if (!source) return () => undefined;
  return createRoot((dispose) => {
    const owner = getOwner();
    const [subscribe, trigger] = createSignal<void>(undefined, { equals: false });

    return async function(): Promise<T | undefined> {
      subscribe();
      while (source && !isIterator(source)) {
        if (isFunction(source)) { source = source(); }
        if (isPromise(source)) { source = await source; }
        if (isGenerator(source)) { source = source[Symbol.iterator](); }
        if (isAsyncGenerator(source)) { source = source[Symbol.asyncIterator](); }
      }
      if (!source) { console.warn('no source'); return undefined; }
      const next = source.next();
      const handler = ({ value, done }: IteratorResult<T>): T => {
        if (!done) runWithOwner(owner, trigger); else dispose();
        return value;
      }
      return isPromise(next) ? next.then(handler) : handler(next);
    }
  });
}