import type { Attachment } from '@openacp/plugin-sdk';
/**
 * Check if an attachment exceeds Discord's upload limit.
 */
export declare function isAttachmentTooLarge(size: number): boolean;
/**
 * Classify a MIME contentType string into an Attachment type.
 */
export declare function classifyAttachmentType(contentType: string | null | undefined): Attachment['type'];
/**
 * Build fallback text when message.content is empty but attachments exist.
 * Mirrors Telegram adapter's pattern: [Photo: filename], [Audio: filename], [File: filename]
 */
export declare function buildFallbackText(attachments: Array<{
    type: Attachment['type'];
    fileName: string;
}>): string;
/**
 * Download a file from a Discord attachment URL.
 * Returns the buffer or null on failure.
 */
export declare function downloadDiscordAttachment(url: string, fileName: string): Promise<Buffer | null>;