/**
 * Media handling — download Slack attachments to disk for pi @file processing.
 *
 * The gateway acts as a pure relay: download to disk, pass path to pi via @file,
 * let pi decide how to handle each file type natively.
 * Periodic cleanup removes stale media files.
 */
import { type AttachmentMeta } from '../types.js';
/** A successfully downloaded file */
export interface DownloadedFile {
    filePath: string;
    originalName: string;
    size: number;
    contentType: string;
}
/**
 * Download all attachments to a per-message directory under the channel session.
 * Returns the list of successfully downloaded files.
 *
 * Slack serves attachments from `url_private`, which requires the bot token as
 * a Bearer header. When no explicit `headers` are passed, an Authorization
 * header is injected automatically for Slack-hosted URLs (config bot token).
 */
export declare function downloadAttachments(attachments: AttachmentMeta[], channelFolder: string, messageId: string, signal?: AbortSignal, headers?: Record<string, string>): Promise<DownloadedFile[]>;
/** Start the periodic media cleanup timer */
export declare function startMediaCleanup(): () => void;