export type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (
  k: infer I
) => void
  ? I
  : never;

export type MessageFactoryFn<Group, Event> = UnionToIntersection<
  Event extends { type: string }
    ? Event extends { payload: any }
      ? (
          type: Event['type'],
          payload: Event['payload']
        ) => { event: Group; type: Event['type']; payload: Event['payload'] }
      : (
          type: Event['type'],
          payload?: undefined
        ) => { event: Group; type: Event['type']; payload: undefined }
    : never
>;