export declare const REFERRAL_ERROR_CODE: {
    USER_CODE_IS_SAME_AS_REFERRER_CODE: string;
    MAX_DEPTH_REACHED: string;
    REFERRER_NOT_FOUND: string;
    CIRCULAR_REFERRAL_FOUND: string;
    MISSING_USER_CODE: string;
    MISSING_REFERRER_CODE: string;
    INVALID_MAX_LEVEL: string;
};
export declare function generateReferralCode(): string;
type UserReferralInfo = {
    id: string | number;
    code: string;
    referrerCode: string;
};
export declare function isReferrerValid(userCode: string, referrerCode: string, findUserByCode: (code: string) => Promise<UserReferralInfo | null>, options?: {
    maxDepth: number;
}): Promise<{
    isValid: boolean;
    reason?: string;
}>;
export {};