import type { Message } from "./Message.js";
import type { Model } from "./common.js";
/**
 * A callback that will be invoked whenever the event is published.
 */
export type EventCallback<T> = (arg?: T, publisher?: Model, eventName?: string) => void | Promise<void>;
/**
 * A named event.
 */
export interface Event<T = void> extends Message {
    /**
     * Publishes the event to all subscribers.
     *
     * @returns A promise that is fulfilled once all subscribers have been
     *   notified.
     */
    publish: (arg: T, publisher?: Model) => Promise<void>;
    /**
     * Subscribes to this event.
     *
     * @param callback A callback that will be invoked whenever the event is
     *   published.
     * @returns A handle that can be used to unsubscribe.
     */
    subscribe: (callback: EventCallback<T>) => IHandle;
}