/**
 * Attachment Manager
 *
 * Manages external file storage for image attachments with content-hash
 * based deduplication. Images are stored in .smartergpt/lex/attachments/
 * with SHA256 hash filenames.
 *
 * This is part of AX-011 to reduce context bloat by storing images
 * externally and returning references instead of base64 inline data.
 */
/**
 * Attachment reference returned by storage operations
 */
export interface AttachmentRef {
    /** Attachment reference ID (att_<short-hash>) */
    ref: string;
    /** MIME type of the attachment */
    mime_type: string;
    /** Size in bytes */
    size_bytes: number;
    /** Relative path from workspace root */
    path: string;
}
/**
 * Attachment Manager - handles external file storage for attachments
 */
export declare class AttachmentManager {
    private attachmentsDir;
    /**
     * Create a new AttachmentManager
     * @param workspaceRoot - Workspace root directory (defaults to cwd)
     */
    constructor(workspaceRoot?: string);
    /**
     * Store an attachment and return its reference
     * @param data - File data as Buffer
     * @param mimeType - MIME type of the attachment
     * @returns Attachment reference
     */
    storeAttachment(data: Buffer, mimeType: string): AttachmentRef;
    /**
     * Get attachment data by reference
     * @param ref - Attachment reference (att_<hash>)
     * @param format - Return format (base64 or path)
     * @returns Attachment data or path
     */
    getAttachment(ref: string, format?: "base64" | "path"): string | null;
    /**
     * Get attachment metadata by reference
     * @param ref - Attachment reference (att_<hash>)
     * @returns Attachment reference metadata or null
     */
    getAttachmentRef(ref: string): AttachmentRef | null;
    /**
     * Find files matching a hash prefix
     * @param prefix - Hash prefix to search for
     * @returns Array of matching filenames
     */
    private findFilesByPrefix;
    /**
     * Get file extension from MIME type
     * @param mimeType - MIME type
     * @returns File extension (including dot)
     */
    private getExtensionFromMimeType;
    /**
     * Get MIME type from file extension
     * @param ext - File extension (including dot)
     * @returns MIME type
     */
    private getMimeTypeFromExtension;
}