import { StreamingConfig, ILogger } from './types';
import { EventEmitter } from './event-emitter';
/**
 * Server-Sent Events (SSE) client for real-time feature flag updates.
 * Uses fetch-based SSE when apiKey is present (secure), falls back to
 * native EventSource when no apiKey (performance).
 */
export declare class FlagStreamClient {
    private readonly baseUrl;
    private eventSource;
    private sseClient;
    private readonly config;
    private readonly logger;
    private readonly events;
    private reconnectAttempts;
    private reconnectTimer;
    private disposed;
    private lastEventId;
    /** Tracks the last document version received to detect gaps */
    private lastReceivedVersion;
    private apiKey;
    constructor(baseUrl: string, apiKey: string | undefined, config: StreamingConfig, logger: ILogger, events: EventEmitter);
    /**
     * Connect to the SSE endpoint.
     * Uses SSEClient (fetch-based) when apiKey is present for secure auth.
     * Falls back to native EventSource when no apiKey for better performance.
     */
    connect(): void;
    /**
     * Connect using fetch-based SSE client (secure, supports custom headers).
     * Used when apiKey is present to avoid sending credentials in URL.
     */
    private connectWithFetch;
    /**
     * Connect using native EventSource.
     * Used when no apiKey is present for better performance.
     */
    private connectWithEventSource;
    private handleUpdateEvent;
    /**
     * Check if the document version has a gap indicating lost events.
     * Returns true if a gap was detected (events were lost), false otherwise.
     */
    private checkVersionGap;
    /**
     * Extract slugs from SSE message data.
     * Supports formats:
     * - { slug: 'checkout-v2', action: 'updated' } → ['checkout-v2']
     * - { slugs: ['a', 'b'], action: 'batch' } → ['a', 'b']
     * - Legacy messages without slug → undefined (triggers full cache clear)
     */
    private extractSlugsFromMessage;
    private scheduleReconnect;
    /**
     * Disconnect the stream. Automatically reconnects won't trigger unless connect() is called again.
     */
    disconnect(): void;
    /**
     * Checks if the stream is currently connected.
     */
    isConnected(): boolean;
    /**
     * Permanently dispose of the stream client.
     */
    dispose(): void;
}