export declare function generateTwoFactorSecret(): string;
export declare function generateTwoFactorToken(secret: Secret): Promise<Token>;
export declare function verifyTwoFactorCode(token: Token, secret: Secret): Promise<boolean>;
/**
 * Generate an otpauth:// URI for two-factor authentication
 *
 * This URI can be used with any QR code library to generate a scannable
 * QR code for authenticator apps.
 *
 * @param user - User identifier (email or username)
 * @param service - Service name (e.g., 'StacksJS 2FA')
 * @param secret - Optional secret (will be generated if not provided)
 * @returns The otpauth:// URI string
 */
export declare function generateTwoFactorUri(user?: string, service?: string, secret?: Secret): string;
/**
 * Render an otpauth:// URI as a scannable QR code.
 *
 * SVG rather than a data URI: it stays sharp at any size, can be inlined into
 * a server-rendered page or an email, and is a few hundred bytes rather than
 * tens of kilobytes. `ts-qr-codes` is a pure, synchronous string function with
 * no runtime dependencies of its own, so this costs nothing at import time.
 *
 * Every authenticator setup flow needs this. Leaving it to the caller meant
 * each one either shipped an encoder to the browser or, more often, fell back
 * to asking the user to type a 32-character secret by hand.
 */
export declare function twoFactorQrCode(uri: string, size?: number): string;
export type Token = string;
export type Secret = string;