/**
 * Best-effort device / browser label from a User-Agent string.
 * Not for security decisions — display and audit only.
 */
export function parseDeviceFromUserAgent(
  userAgent: string | null | undefined,
): { device: string; userAgent: string | null } {
  const ua = userAgent?.trim() || null;
  if (!ua) {
    return { device: "Unknown device", userAgent: null };
  }

  const os =
    /Windows NT/i.test(ua)
      ? "Windows"
      : /Android/i.test(ua)
        ? "Android"
        : /iPhone|iPad|iPod/i.test(ua)
          ? "iOS"
          : /Mac OS X|Macintosh/i.test(ua)
            ? "macOS"
            : /CrOS/i.test(ua)
              ? "Chrome OS"
              : /Linux/i.test(ua)
                ? "Linux"
                : null;

  const browser =
    /Edg\//i.test(ua)
      ? "Edge"
      : /OPR\/|Opera/i.test(ua)
        ? "Opera"
        : /Firefox\//i.test(ua)
          ? "Firefox"
          : /Chrome\//i.test(ua) && !/Edg\//i.test(ua)
            ? "Chrome"
            : /Safari\//i.test(ua) && !/Chrome\//i.test(ua)
              ? "Safari"
              : /curl\//i.test(ua)
                ? "curl"
                : null;

  const formFactor = /Mobile|Android.*Mobile|iPhone|iPod/i.test(ua)
    ? "Mobile"
    : /iPad|Tablet|Android(?!.*Mobile)/i.test(ua)
      ? "Tablet"
      : "Desktop";

  const parts = [formFactor, os, browser].filter(Boolean);
  return {
    device: parts.length > 0 ? parts.join(" · ") : "Unknown device",
    userAgent: ua.slice(0, 512),
  };
}

export function getRequestUserAgent(request: Request): string | null {
  const ua = request.headers.get("user-agent")?.trim();
  return ua || null;
}