export declare class BookmarkManager {
    private readonly bookmarks;
    private counter;
    getBookmark(feed: string): string;
    setBookmark(feed: string, bookmark: string): void;
    advanceBookmark(feed: string): Promise<string>;
    /**
     * If a bookmark is already known for the feed and differs from the provided value,
     * return the known bookmark so callers can synchronize the client.
     * Returns null if no sync is necessary.
     */
    syncBookmarkIfMismatch(feed: string, provided: string): string | null;
}
//# sourceMappingURL=bookmark-manager.d.ts.map