/**
 * Simple Event Emitter
 *
 * Lightweight pub/sub system for internal feature communication.
 * Following PostHog's SimpleEventEmitter pattern.
 */
/**
 * Event listener function type
 */
export type EventListener<T = unknown> = (payload: T) => void;
/**
 * Unsubscribe function returned by on()
 */
export type Unsubscribe = () => void;
/**
 * Simple event emitter for internal SDK communication.
 * Features can emit and listen to events without direct coupling.
 *
 * @example
 * ```typescript
 * const emitter = new SimpleEventEmitter();
 *
 * // Subscribe to events
 * const unsubscribe = emitter.on('user:identified', (data) => {
 *   console.log('User identified:', data);
 * });
 *
 * // Emit events
 * emitter.emit('user:identified', { userId: '123' });
 *
 * // Unsubscribe when done
 * unsubscribe();
 * ```
 */
export declare class SimpleEventEmitter {
    private _events;
    private _onceEvents;
    /**
     * Subscribe to an event.
     *
     * @param event - Event name to subscribe to
     * @param listener - Callback function
     * @returns Unsubscribe function
     */
    on<T = unknown>(event: string, listener: EventListener<T>): Unsubscribe;
    /**
     * Subscribe to an event once (auto-unsubscribes after first call).
     *
     * @param event - Event name to subscribe to
     * @param listener - Callback function
     * @returns Unsubscribe function
     */
    once<T = unknown>(event: string, listener: EventListener<T>): Unsubscribe;
    /**
     * Emit an event to all listeners.
     *
     * @param event - Event name to emit
     * @param payload - Data to pass to listeners
     */
    emit<T = unknown>(event: string, payload?: T): void;
    /**
     * Remove all listeners for an event.
     *
     * @param event - Event name (or undefined to remove all)
     */
    off(event?: string): void;
    /**
     * Get the number of listeners for an event.
     *
     * @param event - Event name
     * @returns Number of listeners
     */
    listenerCount(event: string): number;
    /**
     * Check if there are any listeners for an event.
     *
     * @param event - Event name
     * @returns True if there are listeners
     */
    hasListeners(event: string): boolean;
}
/**
 * VTilt SDK Events
 *
 * Standard events emitted by the SDK for internal communication.
 */
export declare const VTiltEvents: {
    readonly INITIALIZED: "sdk:initialized";
    readonly CONFIG_UPDATED: "sdk:config_updated";
    readonly REMOTE_CONFIG_LOADED: "sdk:remote_config_loaded";
    readonly USER_IDENTIFIED: "user:identified";
    readonly USER_RESET: "user:reset";
    readonly USER_PROPERTIES_SET: "user:properties_set";
    readonly SESSION_STARTED: "session:started";
    readonly SESSION_ENDED: "session:ended";
    readonly SESSION_ROTATED: "session:rotated";
    readonly FEATURE_STARTED: "feature:started";
    readonly FEATURE_STOPPED: "feature:stopped";
    readonly CONSENT_UPDATED: "consent:updated";
    readonly EVENT_CAPTURED: "event:captured";
    readonly EVENT_SENT: "event:sent";
    readonly EVENT_FAILED: "event:failed";
    readonly RECORDING_STARTED: "recording:started";
    readonly RECORDING_STOPPED: "recording:stopped";
    readonly ERROR: "error";
};
export type VTiltEventName = (typeof VTiltEvents)[keyof typeof VTiltEvents];