/**
 * Configuration for {@link buildLimiter}.
 */
export type LimitConfig = {
    /**
     * Maximum and initial total of tokens in this limiter.
     *
     * This must be `>=1` to be valid.
     */
    b: number;
    /**
     * Rate of renewal of tokens, per second.
     *
     * This must be `>0` to be valid.
     */
    r: number;
};
/**
 * Fetches a {@link Promise} which resolves when a token is available.
 *
 * Throws if the {@link AbortSignal} is or becomes aborted before a token is available.
 */
export type Limiter = (signal: AbortSignal) => Promise<void>;
/**
 * Builds a rate-limiter which can be called to consume a token.
 *
 * Throws if the config is invalid (cowardly refuses to make an invalid limiter).
 * Without a passed config, uses a default of 100 tokens, renews at 10/sec.
 */
export declare function buildLimiter(c?: LimitConfig): Limiter;
export interface Backoff {
    readonly delay: number;
    /**
     * Delays by this long.
     * Abandons (but does not throw) if the signal aborts.
     */
    timeout(signal?: AbortSignal): Promise<void>;
    /**
     * Indicate that we've been successful.
     * Resets the delay.
     */
    success(): void;
    /**
     * Indicate that an error has occured here.
     * Increases the delay.
     */
    error(): void;
}
/**
 * Creates a simple backoff helper.
 */
export declare function createBackoff(baseDelay?: number): Backoff;