export const DEVICE_FINGERPRINT_KEY = "hyb_oa_device_fingerprint";

function readCookieFingerprint() {
  if (typeof document === "undefined") {
    return null;
  }

  const prefix = `${DEVICE_FINGERPRINT_KEY}=`;
  const item = document.cookie
    .split(";")
    .map((value) => value.trim())
    .find((value) => value.startsWith(prefix));

  if (!item) {
    return null;
  }

  const rawValue = item.slice(prefix.length);
  try {
    const decoded = decodeURIComponent(rawValue);
    return decoded.trim() ? decoded : null;
  } catch {
    return rawValue.trim() ? rawValue : null;
  }
}

function fallbackFingerprint() {
  return `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
}

function generateFingerprint() {
  if (typeof crypto !== "undefined" && "randomUUID" in crypto) {
    return crypto.randomUUID();
  }

  return fallbackFingerprint();
}

export function getDeviceFingerprint() {
  if (typeof window === "undefined") {
    return "server-render";
  }

  const cookieFingerprint = readCookieFingerprint();
  if (cookieFingerprint) {
    window.localStorage.setItem(DEVICE_FINGERPRINT_KEY, cookieFingerprint);
    return cookieFingerprint;
  }

  const existing = window.localStorage.getItem(DEVICE_FINGERPRINT_KEY);
  if (existing) {
    return existing;
  }

  const next = generateFingerprint();
  window.localStorage.setItem(DEVICE_FINGERPRINT_KEY, next);
  return next;
}