import type { EmailDriver } from "../types.mjs";
/** Sliding-window rate limiter — queues calls until they fit in the
*  per-second budget. Intentionally simple: single-process only, no
*  cross-instance coordination. For distributed limits, plug a driver
*  that delegates to Redis/QStash. */
export interface RateLimitOptions {
	/** Maximum calls per `windowMs`. */
	perSecond?: number;
	/** Alternative window in milliseconds — defaults to 1000. */
	windowMs?: number;
	/** Hard cap on queued sends before rejecting fast. Default: 1000. */
	maxQueue?: number;
	/** When true, the limiter also honours `Retry-After` from 429
	*  responses by delaying the next attempt by that long. */
	respectRetryAfter?: boolean;
	/** Injected for tests. */
	now?: () => number;
	sleep?: (ms: number) => Promise<void>;
}
/** Provider-aware preset limits. Numbers are conservative — override
*  when your tier is higher. */
export declare const rateLimitPresets: {
	sendgrid: () => RateLimitOptions;
	mailgun: () => RateLimitOptions;
	resend: () => RateLimitOptions;
	postmark: () => RateLimitOptions;
	ses: () => RateLimitOptions;
	brevo: () => RateLimitOptions;
};
/** Wrap a driver so `send()` respects a rate limit. */
export declare function withRateLimit(driver: EmailDriver, options: RateLimitOptions): EmailDriver;