<script>
  const VALID_STORE_CODES = ["STORE_NOVA", "STORE_DC", "STORE_TYSONS"];

  // Read URL parameters Meta passes in
  const params = new URLSearchParams(window.location.search);
  const productId = params.get("productId");
  const storeCode = params.get("storeCode");

  // Validate product ID
  if (!productId || !/^[a-zA-Z0-9_-]+$/.test(productId)) {
    window.location.href = "/error?reason=invalid_product";
  }

  // Validate store code if provided
  else if (storeCode && !VALID_STORE_CODES.includes(storeCode)) {
    window.location.href = "/error?reason=invalid_store";
  }

  // All good — redirect to your Squarespace shop page
  else {
    let redirectUrl = `/shop?productId=${productId}`;
    if (storeCode) redirectUrl += `&storeCode=${storeCode}`;
    window.location.href = redirectUrl;
  }
</script>