import type { MailOptions, SendResult, Transport, VerifyResult } from "./core/types.js";
/** Key-value store for idempotency deduplication. */
export interface IdempotencyStore {
    /** Returns true when the key was already recorded. */
    has(key: string): Promise<boolean>;
    /** Record a key, optionally expiring after `ttlMs` milliseconds. */
    set(key: string, ttlMs?: number): Promise<void>;
}
/** In-memory idempotency store with optional TTL expiry. Suitable for single-process use. */
export declare class MemoryIdempotencyStore implements IdempotencyStore {
    private readonly entries;
    /** Returns true when the key exists and has not expired. */
    has(key: string): Promise<boolean>;
    /** Record a key with optional TTL in milliseconds. */
    set(key: string, ttlMs?: number): Promise<void>;
}
/** Options for {@link IdempotencyTransport}. */
export interface IdempotencyTransportOptions {
    /** Store used to track sent keys. Defaults to {@link MemoryIdempotencyStore}. */
    store?: IdempotencyStore;
    /** TTL in milliseconds for recorded keys. Default: 24 hours. */
    ttlMs?: number;
}
/**
 * Transport decorator that skips duplicate sends when an idempotency key
 * was already recorded. Checks the store once before delegating to the inner
 * transport, so retries inside RetryTransport reuse the same key automatically.
 */
export declare class IdempotencyTransport implements Transport {
    /** Transport that performs the actual send when the key is new. */
    private readonly inner;
    readonly provider = "idempotency";
    private readonly store;
    private readonly ttlMs;
    /** Wraps an inner transport with idempotency deduplication. */
    constructor(
    /** Transport that performs the actual send when the key is new. */
    inner: Transport, options?: IdempotencyTransportOptions);
    /** Sends once per idempotency key; returns a synthetic result on duplicate keys. */
    send(options: MailOptions): Promise<SendResult>;
    /** Delegates batch sends to the inner transport when available. */
    sendBatch(messages: MailOptions[]): Promise<SendResult[]>;
    /** Delegates to the inner transport verify or returns a default success result. */
    verify(): Promise<VerifyResult>;
    /** Delegates close to the inner transport if available. */
    close(): Promise<void>;
}