export const getQueryParam = (paramName: string) => {
  const search = window.location.search;
  const params = new URLSearchParams(search);
  return params.get(paramName);
};

export const parseQueryParams = () => {
  const params = new URLSearchParams(window.location.search);
  const result: Record<string, string> = {};

  for (const [key, value] of params.entries()) {
    result[key] = value;
  }

  return result;
}

// Params that should NOT be included in state (they are passed separately)
const EXCLUDED_STATE_PARAMS = [
  "paywallId",
  "placementId", 
  "productId",
  "jwtToken",
  "price",
  "currency",
  "fb_pixels",
  "sessionId",
  "state",
  // Tracking cookies (passed separately)
  "_fbc",
  "_fbp",
  "_ym_uid",
  "_ym_d",
  "_ym_isad",
  "_ym_visorc",
  "yandexuid",
  "ymex",
];

/**
 * Get current query params that should be passed between screens and to payment
 * Includes ALL params except internal ones (productId, placementId, etc.)
 * Works with utm_*, fbclid, gclid, and any other marketing params
 */
export const getCurrentQueryParams = (): Record<string, string> => {
  if (typeof window === "undefined") return {};

  const params = parseQueryParams();
  const utmParams: Record<string, string> = {};

  for (const [key, value] of Object.entries(params)) {
    const isExcluded =
      EXCLUDED_STATE_PARAMS.includes(key) ||
      key.startsWith("_ga") ||
      key.startsWith("_gid");

    if (!isExcluded && value) {
      utmParams[key] = value;
    }
  }

  return utmParams;
};

/**
 * Encode params as base64 JSON for state parameter
 * Uses URL-safe base64 encoding
 */
export const encodeStateParam = (params: Record<string, string>): string => {
  if (Object.keys(params).length === 0) return "";

  try {
    const json = JSON.stringify(params);
    // Use btoa for base64, replace unsafe chars for URL
    const base64 = btoa(json)
      .replace(/\+/g, "-")
      .replace(/\//g, "_")
      .replace(/=+$/, "");
    return base64;
  } catch {
    return "";
  }
};

/**
 * Get base64-encoded state parameter with current query params
 */
export const getStateParamForRedirect = (): string => {
  const params = getCurrentQueryParams();
  return encodeStateParam(params);
};

// Backward compatibility alias
export const getCurrentUtmParams = getCurrentQueryParams;