import { FeatureFlyEvent, EventHandler, EventPayloadMap } from './types';
/**
 * Typed event emitter for FeatureFly SDK.
 * Allows consumers to subscribe to internal SDK events like flag changes,
 * cache hits/misses, circuit breaker state changes, etc.
 */
export declare class EventEmitter {
    private readonly listeners;
    /**
     * Subscribe to an event. Returns an unsubscribe function.
     */
    on<E extends FeatureFlyEvent>(event: E, handler: EventHandler<E>): () => void;
    /**
     * Subscribe to an event once (auto-unsubscribes after first invocation).
     */
    once<E extends FeatureFlyEvent>(event: E, handler: EventHandler<E>): () => void;
    /**
     * Emit an event to all registered listeners.
     */
    emit<E extends FeatureFlyEvent>(event: E, payload: EventPayloadMap[E]): void;
    /**
     * Remove all listeners for a specific event, or all events if no event is specified.
     */
    removeAllListeners(event?: FeatureFlyEvent): void;
    /**
     * Get the count of listeners for a given event.
     */
    listenerCount(event: FeatureFlyEvent): number;
}