import { WebSocket as NodeWebSocket } from 'ws';
import http from 'http';
/**
 * Base broadcast message that plugins may extend.
 * Includes an index signature so plugin-defined keys are allowed.
 */
export interface BroadcastMessage {
    /** At minimum every message must have a type string */
    type: string;
    [key: string]: unknown;
}
/**
 * Core HMR message shape — narrows `type` to known HMR events
 * and adds optional fields. It extends BroadcastMessage so it's
 * assignable to the generic constraint.
 */
export interface HMRMessage extends BroadcastMessage {
    type: 'update' | 'error' | 'reload';
    path?: string;
    message?: string;
    stack?: string;
}
/**
 * BroadcastManager — Shared WebSocket utility for dev, preview, and SSR servers.
 * Generic over message type T which defaults to HMRMessage.
 */
export declare class BroadcastManager<T extends BroadcastMessage = HMRMessage> {
    private wss;
    private clients;
    constructor(server: http.Server);
    broadcast(msg: T): void;
    send(ws: NodeWebSocket, msg: T): void;
    getClientCount(): number;
    close(): void;
}