/**
 * Multipart filename helpers for media-library uploads.
 *
 * Sitecore derives a media item's `Extension` field from the extension of the
 * `file` part in the multipart upload — NOT from the item name (which is
 * intentionally extensionless, see `UploadMediaInput.itemPath`) and NOT from
 * any `uploadMedia` GraphQL mutation input. So if the multipart filename has
 * no extension, the resulting media item's `Extension` field is left empty and
 * the blob won't serve with the right content type — the image reads as broken
 * / "won't upload".
 *
 * This most often bites `external-url` media sources whose URL path tail
 * carries no extension (CDN / query-style URLs like `.../photo-abc123`), and
 * the bare `"media"` fallback. `ensureMediaFileName` guarantees the multipart
 * filename carries an extension, deriving one from the MIME type when the
 * source name lacks one.
 */
/**
 * Best-effort file extension (no dot) for a MIME type. Falls back to the
 * subtype (`image/svg+xml` → `svg`, dropping any `+suffix` and `;params`),
 * then to `png` when nothing usable can be derived.
 */
export declare const extensionForMime: (mimeType: string) => string;
/**
 * Return a multipart filename guaranteed to carry a file extension so Sitecore
 * populates the media item's `Extension` field. When `fileName` already has
 * one it is returned unchanged; otherwise an extension derived from `mimeType`
 * is appended.
 */
export declare const ensureMediaFileName: (fileName: string, mimeType: string) => string;
/**
 * Canonical image MIME type for a file extension (dot optional), or `undefined`
 * when the extension isn't a known image type.
 */
export declare const mimeForExtension: (ext: string) => string | undefined;
/**
 * Resolve the multipart filename AND MIME type for a media upload so Sitecore
 * derives a correct `Extension` and `Mime Type` on the created item.
 *
 * The filename is guaranteed to carry an extension (`ensureMediaFileName`), and
 * the MIME type is then taken from that extension's canonical image type — so a
 * junk `Content-Type` forwarded from an `external-url` CDN (e.g.
 * `application/octet-stream`) is replaced by the type the extension implies.
 * Only when the extension isn't a known image type is the caller-supplied
 * `mimeType` kept (covers non-image media like PDFs).
 */
export declare const resolveMediaUpload: (fileName: string, mimeType: string) => {
    fileName: string;
    mimeType: string;
};