import { SubscriptionChangeEventHandler } from "../dispatching/SubscriptionChangeEventHandler";
/**
 * Indicates the object implements generic subscriptions.
 *
 * @export
 * @interface ISubscribable
 * @template TEventHandler The type of events to handle.
 */
export interface ISubscribable<TEventHandler> {
    /**
     * Returns the number of subscriptions.
     *
     * @type {number}
     * @memberOf ISubscribable
     */
    readonly count: number;
    /**
     * Subscribe to the event.
     *
     * @param {TEventHandler} fn The event handler that is called when the event is dispatched.
     * @returns {() => void} function that unsubscribes the event handler from the event.
     *
     * @memberOf ISubscribable
     */
    subscribe(fn: TEventHandler): () => void;
    /**
     * Subscribe to the event.
     * @param {TEventHandler} fn The event handler that is called when the event is dispatched.
     * @returns A function that unsubscribes the event handler from the event.
     *
     * @memberOf ISubscribable
     */
    sub(fn: TEventHandler): () => void;
    /**
     * Unsubscribe from the event.
     * @param {TEventHandler} fn The event handler that will be unsubsribed from the event.
     *
     * @memberOf ISubscribable
     */
    unsubscribe(fn: TEventHandler): void;
    /**
     * Unsubscribe from the event.
     * @param {TEventHandler} fn The event handler that will be unsubsribed from the event.
     *
     * @memberOf ISubscribable
     */
    unsub(fn: TEventHandler): void;
    /**
     * Subscribes to the event only once.
     * @param {TEventHandler} fn The event handler that is called when the event is dispatched.
     * @returns A function that unsubscribes the event handler from the event.
     *
     * @memberOf ISubscribable
     */
    one(fn: TEventHandler): () => void;
    /**
     * Checks it the event has a subscription for the specified handler.
     * @param {TEventHandler} fn The event handler.
     *
     * @memberOf ISubscribable
     */
    has(fn: TEventHandler): boolean;
    /**
     * Clears all the subscriptions.
     *
     * @memberOf ISubscribable
     */
    clear(): void;
    /**
     * Triggered when subscriptions are changed (added or removed).
     *
     * @type {ISubscribable<SubscriptionChangeEventHandler>}
     * @memberOf ISubscribable
     */
    readonly onSubscriptionChange: ISubscribable<SubscriptionChangeEventHandler>;
}