import { Logger } from '../types/logger';
/**
 * Shape of TypeORM's RedisQueryResultCache once the underlying client is
 * materialized. We reach into it via duck-typing because TypeORM does not
 * export the type.
 */
export interface RedisQueryResultCacheLike {
    client?: {
        on?: (event: string, fn: (err: Error) => void) => void;
    };
    clientType?: string;
    __novaErrorHandlerAttached?: boolean;
}
/**
 * TypeORM's RedisQueryResultCache only attaches an `error` listener on the
 * underlying redis client for `clientType === 'redis'`. With `'ioredis'` (what
 * every hapn service uses to talk to ElastiCache Valkey) the client is an
 * EventEmitter that crashes the host process on the first unhandled `error`
 * event — a TLS hiccup or `MOVED` redirect during failover takes down the
 * Lambda even with `ignoreErrors: true` set in TypeORM config.
 *
 * Idempotent: re-running on the same cache is a no-op.
 *
 * Returns true if a handler was attached on this call (useful for tests and
 * for callers that want to observe whether anything happened).
 */
export declare function attachIoredisErrorHandler(cache: RedisQueryResultCacheLike | undefined | null, logger: Logger): boolean;