memo.ts

const store = new Map<
  () => unknown,
  ReturnType<typeof Promise.withResolvers>
>();

/**
 * Memoiza função assíncrona, garantindo que mais de 1 chamada concorrente retorne a mesma promessa.
 */
export function memo<T>(f: () => Promise<T>) {
  return async () => {
    let value = store.get(f);

    if (!value) {
      value = Promise.withResolvers<unknown>();
      store.set(f, value);
      value.resolve(await f());
    }

    return (await value.promise) as Promise<T>;
  };
}