import type { WebhookEventBase } from './types.js';
export interface VerifyWebhookOptions {
    /**
     * Maximum drift in seconds between the request timestamp and the
     * verifier's clock. Defaults to 300 (5 minutes) per contract §4.4.
     * Set higher only if your server is reverse-proxied through a queue
     * that may stall messages.
     */
    tolerance?: number;
    /**
     * Override the "now" clock — exposed primarily so tests can pin a
     * deterministic time. Returns unix seconds.
     */
    now?: () => number;
}
/**
 * Verify an incoming webhook delivery using the iSnap signing scheme:
 *
 * - `X-iSnap-Signature` header carries the hex-encoded
 *   `HMAC-SHA256(secret, "<timestamp>.<rawBody>")`
 * - `X-iSnap-Timestamp` header carries the unix-second issuance time
 *
 * Throws `WebhookSignatureError` on missing headers, malformed
 * timestamp, expired timestamp (outside `tolerance`), or signature
 * mismatch. Returns the parsed event envelope on success.
 *
 * `secret` may be a single secret string OR an array — pass `[newSecret,
 * oldSecret]` during the 5-minute rotate-secret grace window so both
 * still validate. The verifier tries each in order and returns on the
 * first match.
 *
 * Headers may be a `Record<string, string>` (e.g. Express's `req.headers`)
 * or a `Headers` instance — both are read case-insensitively.
 *
 * **Consumers MUST dedupe by `event.event_id`** — retries replay the same
 * envelope (same `event_id`, same body, same signature, refreshed
 * timestamp). Without consumer-side dedup, an at-least-once delivery
 * model produces duplicate side-effects on the partner system.
 */
export declare function verifyWebhook(rawBody: string, headers: Record<string, string | string[] | undefined> | Headers, secret: string | readonly string[], options?: VerifyWebhookOptions): WebhookEventBase;
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