const parseCacheControl = (str: string | null): Map<string, string> => {
  const map = new Map<string, string>();
  if (!str) {
    return map;
  }
  for (let directive of str.split(",")) {
    let [key, value] = directive.trim().split("=");
    key = key.toLowerCase();
    if (value) {
      value = value.toLowerCase();
    }
    map.set(key, value);
  }
  return map;
};

export const getMaxAge = (str: string | null): number => {
  const map = parseCacheControl(str);
  if (map) {
    let age = map.get("s-maxage") || map.get("max-age") || "";
    if (age.startsWith('"') && age.endsWith('"')) {
      age = age.slice(1, -1);
    }
    const n = parseInt(age, 10);
    if (!isNaN(n)) {
      return n;
    }
  }
  return 0;
};