/**
 * Generic presence tracker — ref-counted online status per stream per identity.
 *
 * Supports multi-tab: each subscribe increments the ref count, each
 * unsubscribe decrements it. An identity is considered online when
 * ref count > 0.
 *
 * ## Usage
 *
 * ```typescript
 * const presence = new PresenceTracker();
 *
 * // On SSE connect:
 * presence.add(game_id, player_id);
 *
 * // On SSE disconnect:
 * presence.remove(game_id, player_id);
 *
 * // Query:
 * presence.online(game_id); // Set<string>
 * ```
 */
export declare class PresenceTracker {
    private streams;
    /** Increment ref count for an identity on a stream. */
    add(streamId: string, identity_id: string): void;
    /** Decrement ref count. Removes the identity when count reaches 0. */
    remove(streamId: string, identity_id: string): void;
    /** Get the set of online identity IDs for a stream. */
    online(streamId: string): Set<string>;
    /** Check if a specific identity is online for a stream. */
    isOnline(streamId: string, identity_id: string): boolean;
    /** @deprecated use `online` — removal in the next major */
    get_online(streamId: string): Set<string>;
    /** @deprecated use `isOnline` — removal in the next major */
    is_online(streamId: string, identity_id: string): boolean;
}
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