import http from 'node:http';
export interface StreamEvent {
    type: string;
    data: unknown;
}
/**
 * SSEStream — Server-Sent Events endpoint for real-time dashboard push.
 *
 * Lightweight alternative to ObservationStream (WebSocket). Attaches to an
 * existing http.Server by handling requests to '/sse'. Broadcasts typed
 * events (observation:new, stats:update, etc.) to all connected clients.
 * Heartbeat comment every 30s to keep connections alive.
 */
export declare class SSEStream {
    private clients;
    private heartbeatInterval;
    private static readonly MAX_CLIENTS;
    constructor();
    /**
     * Handle an incoming HTTP request. Returns true if the request was handled
     * (i.e. it was a GET to /sse), false otherwise so the caller can route it
     * elsewhere.
     */
    handleRequest(req: http.IncomingMessage, res: http.ServerResponse): boolean;
    /**
     * Broadcast an event to all connected SSE clients.
     * Format: `event: <type>\ndata: <json>\n\n`
     */
    broadcast(event: StreamEvent): void;
    /**
     * Gracefully stop — clear heartbeat, end all client connections.
     */
    stop(): void;
    /** Number of connected clients (useful for diagnostics). */
    get clientCount(): number;
    private heartbeat;
}
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