import type { EmailDriver, Result } from "../types.mjs";
/** Backoff strategies.
*  - `exponential` — `initialDelay * 2^attempt` (default).
*  - `constant` — `initialDelay` every time.
*  - `exponential-jitter` — exponential with ±50% uniform noise.
*  - `full-jitter` — random in `[0, exponential]` (AWS recommendation).
*  - `decorrelated-jitter` — `random(initialDelay, prev * 3)`. */
export type RetryBackoff = "exponential" | "constant" | "exponential-jitter" | "full-jitter" | "decorrelated-jitter";
/** Options for `withRetry`. All numeric values are milliseconds unless
*  noted. `respectRetryAfter` honors `error.status === 429` with the
*  matching `Retry-After` surfaced via `error.cause`. */
export interface RetryOptions {
	/** Number of *retry* attempts on top of the initial send. Default: 3. */
	retries?: number;
	/** Initial backoff delay. Default: 250ms. */
	initialDelay?: number;
	/** Maximum backoff delay between attempts. Default: 10_000ms. */
	maxDelay?: number;
	/** Backoff strategy. See `RetryBackoff`. */
	backoff?: RetryBackoff;
	/** Honor a `Retry-After` seconds value when present on 429. Default: true. */
	respectRetryAfter?: boolean;
	/** Override default retryability — by default only `error.retryable === true`. */
	shouldRetry?: (error: NonNullable<Result<never>["error"]>, attempt: number) => boolean;
	/** Route exhausted sends to this driver (dead-letter). Original error
	*  is preserved on `ctx.meta.deadLetterReason`. */
	deadLetter?: EmailDriver;
	/** Injected for tests. Default: `setTimeout`. */
	sleep?: (ms: number, signal?: AbortSignal) => Promise<void>;
	/** Injected for deterministic jitter in tests. Default: `Math.random`. */
	random?: () => number;
}
/** Wrap a driver so every send is retried on transient failures. Returns a
*  regular `EmailDriver` — compose it with `fallback`, `roundRobin`, etc.
*
*  ```ts
*  const driver = withRetry(resend({ apiKey }), { retries: 3 })
*  ```
*/
export declare function withRetry(driver: EmailDriver, options?: RetryOptions): EmailDriver;