return extensionForMime(mime);

}

function isGenericContainerMime(mime?: string): boolean {

return mime === "application/zip" || mime === "application/octet-stream";

}

function isImageHeaderMime(contentType?: string): boolean {

return normalizeOptionalString(contentType?.split(";")[0])?.startsWith("image/") === true;

}

function resolveSavedMediaExtension(params: {

detectedMime?: string;

headerExt?: string;

contentType?: string;

originalFilename?: string;

}): string {

const trustedHeaderExt =

params.headerExt &&

isGenericContainerMime(params.detectedMime) &&

isImageHeaderMime(params.contentType)

? undefined

: params.headerExt;

return (

trustedHeaderExt ??

extensionForMime(params.detectedMime) ??

safeOriginalFilenameExtension(params.originalFilename) ??

""

);

}

function buildSavedMediaResult(params: {

dir: string;

id: string;

headerMime: contentType,

filePath: originalFilename ?? detectionFilePathHint,

});

const ext =

headerExt ?? extensionForMime(mime) ?? safeOriginalFilenameExtension(originalFilename) ?? "";

const ext = resolveSavedMediaExtension({

detectedMime: mime,

headerExt,

contentType,

originalFilename,

});

const id = buildSavedMediaId({ baseId: uuid, ext, originalFilename });

await writeSavedMediaBuffer({ subdir, id, buffer });

return buildSavedMediaResult({ dir, id, size: buffer.byteLength, contentType: mime });

headerMime: contentType,

filePath: originalFilename ?? detectionFilePathHint,

});

const ext =

headerExt ??

extensionForMime(mime) ??

safeOriginalFilenameExtension(originalFilename) ??

"";

const ext = resolveSavedMediaExtension({

detectedMime: mime,

headerExt,

contentType,

originalFilename,

});

const id = buildSavedMediaId({ baseId, ext, originalFilename });

return { id, size, contentType: mime };

},