export type SyncedStateStatus = "connected" | "disconnected" | "reconnecting";
export type StatusChangeCallback = (status: SyncedStateStatus) => void;
export type SyncedStateClient = {
    getState(key: string): Promise<unknown>;
    setState(value: unknown, key: string): Promise<void>;
    subscribe(key: string, handler: (value: unknown) => void): Promise<void>;
    unsubscribe(key: string, handler: (value: unknown) => void): Promise<void>;
};
type Subscription = {
    key: string;
    handler: (value: unknown) => void;
    client: SyncedStateClient;
};
/**
 * Registers a callback that fires when the connection status changes for an endpoint.
 * Returns an unsubscribe function.
 */
export declare const onStatusChange: (endpoint: string, callback: StatusChangeCallback) => (() => void);
declare function getBackoffMs(attempt: number): number;
declare function reconnect(endpoint: string, deadClient: SyncedStateClient): void;
/**
 * Returns a cached client for the provided endpoint, creating it when necessary.
 * The returned client is a proxy that loads `capnweb` lazily on first method
 * call — consumers that never hit `use-synced-state` pay no import cost and
 * don't need `capnweb` installed.
 * @param endpoint Endpoint to connect to.
 * @returns RPC client instance.
 */
export declare const getSyncedStateClient: (endpoint?: string) => SyncedStateClient;
/**
 * Initializes and caches an RPC client instance for the sync state endpoint.
 * The client is wrapped to track subscriptions for cleanup on page reload.
 * @param options Optional endpoint override.
 * @returns Cached client instance or `null` when running without `window`.
 */
export declare const initSyncedStateClient: (options?: {
    endpoint?: string;
}) => SyncedStateClient | null;
/**
 * Injects a client instance for tests and updates the cached endpoint.
 * Also clears the subscription registry for test isolation.
 * @param client Stub client instance or `null` to clear the cache.
 * @param endpoint Endpoint associated with the injected client.
 */
export declare const setSyncedStateClientForTesting: (client: SyncedStateClient | null, endpoint?: string) => void;
export declare const __testing: {
    activeSubscriptions: Set<Subscription>;
    clientCache: Map<string, SyncedStateClient>;
    backoffState: Map<string, {
        attempt: number;
        timer: ReturnType<typeof setTimeout> | null;
    }>;
    statusListeners: Map<string, StatusChangeCallback[]>;
    reconnect: typeof reconnect;
    getBackoffMs: typeof getBackoffMs;
    warmUp(endpoint?: string): Promise<void>;
};
export {};