export type EventType = string | symbol;
export type Handler<T = unknown> = (event: T) => void;
export type WildcardHandler<T = Record<string, unknown>> = (
  type: keyof T,
  event: T[keyof T],
) => void;
export type EventHandlerList<T = unknown> = Array<Handler<T>>;
export type WildCardEventHandlerList<T = Record<string, unknown>> = Array<
  WildcardHandler<T>
>;
export type EventHandlerMap<Events extends Record<EventType, unknown>> = Map<
  keyof Events | '*',
  EventHandlerList<Events[keyof Events]> | WildCardEventHandlerList<Events>
>;
export interface Emitter<Events extends Record<EventType, unknown>> {
  all: EventHandlerMap<Events>;
  on<Key extends keyof Events>(type: Key, handler: Handler<Events[Key]>): void;
  on(type: '*', handler: WildcardHandler<Events>): void;
  off<Key extends keyof Events>(
    type: Key,
    handler?: Handler<Events[Key]>,
  ): void;
  off(type: '*', handler: WildcardHandler<Events>): void;
  emit<Key extends keyof Events>(type: Key, event: Events[Key]): void;
  emit<Key extends keyof Events>(
    type: undefined extends Events[Key] ? Key : never,
  ): void;
}
/**
 * Mitt: Tiny (~200b) functional event emitter / pubsub.
 * @name mitt
 * @returns {Mitt}
 */
export default function mitt<Events extends Record<EventType, unknown>>(
  all?: EventHandlerMap<Events>,
): Emitter<Events>;
declare global {
  interface Window {
    eventBus: Emitter<any>;
  }
}