/**
 * Shared helpers for caller-provided MIME type hints.
 *
 * A "MIME hint" is a mimetype string the SDK receives alongside a raw Buffer
 * whose original filename is missing (e.g. Slack/Curator file-uploads that
 * arrive as { buffer, filename: "Untitled", mimetype: "text/plain" }). When
 * the filename has no extension and magic-byte detection cannot identify the
 * content, the hint is the only signal we have.
 *
 * Both FileReferenceRegistry.register() and FileDetector.detect() consume
 * these helpers so the trust/normalization rules stay in one place:
 *
 *   - `application/octet-stream` is never trusted — it is the opaque
 *     "I don't know" sentinel and would let a caller hide real content
 *     behind a generic label (a PNG hinted as octet-stream would otherwise
 *     record mimeType="application/octet-stream" instead of "image/png").
 *   - Empty/undefined hints pass through as `undefined`.
 *   - A hint that cannot be classified maps to `null` so the caller falls
 *     back to magic-byte / extension detection instead of synthesising a
 *     wrong type.
 */
import type { FileType } from "../types/index.js";
/**
 * Normalize a caller-provided mimetype hint: strip any `;charset=...`
 * parameter, lowercase, trim. Returns undefined for empty strings or for
 * the opaque `application/octet-stream` sentinel so downstream code can
 * treat the hint as absent instead of trusting it verbatim.
 */
export declare function normalizeMimeHint(raw?: string): string | undefined;
/**
 * Map a normalized mimetype hint to a NeuroLink FileType. Returns null when
 * the mimetype is unknown or too generic to classify confidently.
 */
export declare function mimeHintToFileType(mimetype: string): FileType | null;
/**
 * Map a normalized mimetype hint to the canonical file extension (without
 * leading dot). Returns "" when the mimetype is unknown — caller should
 * then fall back to magic-byte detection.
 */
export declare function mimeHintToExtension(mimetype: string): string;