import { Signal } from './signal.js';
/**
 * Basic type safe event emitter

 * @example
 * ```ts
 * const ms = new EventEmitter<{ onChange: { id: 'onChange' }; onDelete: { id: 'onDelete' } }>();
 * ms.subscribe('onChange', (event) => {
 *    event.id; // 'onChange'
 * });
 * ms.subscribe('onDelete', (event) => {
 *   event.id; // 'onDelete'
 * });
 *
 * ms.notify('onChange', { id: 'onChange' }); // event is type safe
 * ```
 * @example <caption>payload type mismatch</caption>
 * ```ts
 * ms.notify('onChange', { id: 'onDelete' }); // ERROR!!!
 * ```
 * @example <caption>payload type mismatch</caption>
 * ```ts
 * ms.notify('onSomethingElse', { id: 'onDelete' }); // ERROR!!!
 * ```
 */
export declare class EventEmitter<Events extends object, EventId extends keyof Events = keyof Events> {
    protected events: Map<EventId, Signal<any>>;
    /**
     * Check if an event has subscribers
     * @returns true if event has subscribers
     */
    hasSubscribers: (event: EventId) => boolean;
    /**
     * Subscribe a handler for event
     *
     * @returns unsubscribe fn
     */
    subscribe: <Event extends EventId>(event: Event, handler: (data: Events[Event]) => void) => () => void;
    /**
     * {@inheritDoc EventEmitter.subscribe}
     */
    on: <Event extends EventId>(event: Event, handler: (data: Events[Event]) => void) => () => void;
    /**
     * Adds a handler that will be called at most once.
     *
     * @returns unsubscribe fn
     */
    once: <Event extends EventId>(event: Event, handler: (data: Events[Event]) => void) => () => void;
    /**
     * Unsubscribe a handler from event
     */
    unsubscribe: <Event extends EventId>(event: Event, handler: (data: Events[Event]) => void) => void;
    /**
     * {@inheritDoc EventEmitter.unsubscribe}
     */
    off: <Event extends EventId>(event: Event, handler: (data: Events[Event]) => void) => void;
    /**
     * Drop all subscriptions of a signal
     * @param event - signal id
     */
    delete: <Event extends EventId>(event: Event) => void;
    /**
     * Drop all subscriptions
     */
    clear: () => void;
    /**
     * {@inheritDoc Signal.notify}
     * @param event - eve
     * @param data - event data
     */
    notify: <Event extends EventId>(event: Event, data: Events[Event]) => void;
    /**
     * {@inheritDoc EventEmitter.notify}
     */
    emit: <Event extends EventId>(event: Event, data: Events[Event]) => void;
}
export type IEventEmitter<T extends Record<string, any>> = Pick<EventEmitter<T>, keyof EventEmitter<T>>;
//# sourceMappingURL=event-emitter.d.ts.map