import type { Client } from './client.js';
export interface EventNotificationMessage {
    /** Delete handle from the adp-msg-msgid response header. */
    messageId: string;
    /** ADP's response body, untouched (typically an event envelope). */
    payload: unknown;
}
/**
 * ADP's event-notification queue. It serves ONE message at a time: next()
 * returns the head of the queue — the SAME message until it is deleted —
 * and delete(messageId) acknowledges it, making the next one available.
 * Delete after successful processing for at-least-once semantics.
 *
 * Empty values are `null`, not `undefined` (unlike the rest of the
 * library): flow-step results are JSON-serialized, and null survives the
 * round trip while undefined vanishes.
 */
export declare class EventNotifications {
    private readonly client;
    constructor(client: Client);
    /** Head of the queue, or null when the queue is empty. */
    next(): Promise<EventNotificationMessage | null>;
    /** Acknowledge (delete) a message. ADP echoes the deleted record on 200; null otherwise. */
    delete(messageId: string): Promise<unknown>;
}