export function deriveThumbnailPathFromManualPath(
  manualPath: string | undefined | null
): string | undefined {
  const trimmedPath = String(manualPath || "").trim()
  if (!trimmedPath || /^https?:\/\//i.test(trimmedPath)) {
    return undefined
  }

  if (!trimmedPath.toLowerCase().endsWith(".pdf")) {
    return undefined
  }

  return trimmedPath.replace(/\.pdf$/i, ".jpg")
}