export declare class Domain {
    private validDomainExtensions;
    constructor();
    /**
     * Checks if a string ends with a valid domain extension
     */
    isDomainExtension(input: string): boolean;
    /**
     * Extracts the main domain from a URL or domain string
     */
    domain(urlOrDomain: string | null): string;
    /**
     * Validates input is not null and has minimum length
     */
    private isValidInput;
    /**
     * Extracts hostname from URL or cleans up domain string
     */
    private extractAndCleanDomain;
    /**
     * Removes paths, query parameters, anchors, and handles email domains
     */
    private removeUrlFragments;
    /**
     * Parses the main domain from a cleaned domain string
     */
    private parseMainDomain;
    /**
     * Handles domains with 3 or more parts (subdomains or multi-level extensions)
     */
    private handleComplexDomain;
    /**
     * Gets the last 3 parts of a domain (or all parts if fewer than 3)
     */
    private getLastThreeParts;
    /**
     * Checks if a string is a valid domain extension
     */
    private isValidExtension;
}