/**
 * Auth class handles authentication with the M-Pesa API
 * by generating access tokens using consumer credentials.
 * This class provides functionality to generate OAuth tokens
 * required for authenticating API requests to the M-Pesa system.
 */
export declare class Auth {
    /** Consumer key provided by M-Pesa developer portal */
    private consumerKey;
    /** Consumer secret provided by M-Pesa developer portal */
    private consumerSecret;
    /**
     * Base URL for the token generation endpoint.
     * Different URLs are used for sandbox and production environments.
     */
    private baseUrl;
    private readonly rateLimiter;
    /**
     * Creates an instance of Auth class
     * @param consumerKey - The consumer key obtained from M-Pesa developer portal
     * @param consumerSecret - The consumer secret obtained from M-Pesa developer portal
     * @param sandbox - Boolean flag to determine environment:
     *                  true for sandbox/testing environment
     *                  false for production environment
     */
    constructor(consumerKey?: string, consumerSecret?: string, sandbox?: boolean);
    /**
     * Generates an access token for M-Pesa API authentication.
     * The method:
     * 1. Combines consumer key and secret
     * 2. Base64 encodes the credentials
     * 3. Makes HTTP GET request to token endpoint
     * 4. Processes the response to extract token
     *
     * @returns Promise containing an object with:
     *          - token: The access token string for API authentication
     *          - expiresIn: Token validity period in seconds
     *
     * @throws MpesaError with specific error codes and messages based on the API response
     * @throws Error for network issues or invalid responses
     *
     * @example
     * ```typescript
     * const auth = new Auth('your-key', 'your-secret');
     * const {token, expiresIn} = await auth.generateToken();
     * ```
     */
    /**
     * Generates an authentication token for M-Pesa API access.
     *
     * This method:
     * 1. Combines the consumer key and secret
     * 2. Base64 encodes the credentials
     * 3. Makes an HTTP GET request to the token endpoint
     * 4. Returns the access token and expiry time
     *
     * @returns Promise containing an object with:
     *          - token: The access token string for API authentication
     *          - expiresIn: Token validity period in seconds
     *
     * @throws {Error} If network connection fails or no response received
     * @throws {Error} If request setup fails
     * @throws {Error} If API returns error response
     */
    generateToken(): Promise<{
        token: string;
        tokenType: string;
        expiresIn: number;
    }>;
}