/** A handler invoked when an event fires. May return a promise; rejections are caught and logged. */
export type EventHandler = (...args: any[]) => any;
/**
 * A typed event emitter. Handlers may be sync or async; async rejections and
 * thrown errors are caught and logged rather than propagated. Parameterize with
 * an event-to-args map for type-safe {@link EventEmitter.on}/{@link EventEmitter.emit}.
 */
export declare class EventEmitter<TEvents extends Record<string, any[]> = Record<string, any[]>> {
    private _handlers;
    private _pendingTasks;
    private _closed;
    /** Register `handler` for `event`. Returns the handler so it can be removed later. */
    on<K extends keyof TEvents & string>(event: K, handler: (...args: TEvents[K]) => any): (...args: TEvents[K]) => any;
    on(event: string, handler: EventHandler): EventHandler;
    /** Remove a previously registered `handler` for `event`. */
    off<K extends keyof TEvents & string>(event: K, handler: (...args: TEvents[K]) => any): void;
    off(event: string, handler: EventHandler): void;
    /** Register `handler` to fire at most once for the next `event`. Returns the wrapper handler. */
    once<K extends keyof TEvents & string>(event: K, handler: (...args: TEvents[K]) => any): (...args: TEvents[K]) => any;
    once(event: string, handler: EventHandler): EventHandler;
    /**
     * Fire `event`, synchronously invoking every registered handler with `args`.
     * Handlers added or removed during the call do not affect this emit. Never
     * throws, and does nothing once the emitter is closed.
     */
    emit<K extends keyof TEvents & string>(event: K, ...args: TEvents[K]): void;
    emit(event: string, ...args: any[]): void;
    private _invoke;
    /** Number of handlers registered for `event`. */
    listenerCount<K extends keyof TEvents & string>(event: K): number;
    listenerCount(event: string): number;
    /** Remove all handlers for `event`, or for every event when `event` is omitted. */
    removeAllListeners<K extends keyof TEvents & string>(event?: K): void;
    removeAllListeners(event?: string): void;
    /**
     * Close the emitter: drop all handlers and stop emitting. Waits up to 2 seconds
     * for in-flight async handlers to settle before returning.
     */
    closeEmitter(): Promise<void>;
    /** Whether {@link closeEmitter} has been called. */
    get closed(): boolean;
    private _logError;
}