/**
 * @fileoverview Utility for extracting and normalizing domain names from URLs.
 * Handles subdomains and TLD cleaning for source attribution.
 */
/**
 * Extract TLD and hostname from domain in Regex. There's [two or more part 
 * TLDs](https://en.wikipedia.org/wiki/List_of_Internet_top-level_domains)
 * so it is hard to tell if host.secondTLD.tld or host.tld is correct way
 * to get root domain (e.g. abc.go.jp, abc.co.uk) 
 * @param {string} domain 
 * @returns {string} rootDomain 
 */
export function convertURLToDomain(domain) {
  var tldRegExp = new RegExp(
    "(?=[^^]).(fr|de|cz|at|com|wiki|co|edu|gov|info|mil|id|" +
    "gv|tv|int|name|net|org|pro|ac|me|ltd|parliament)(.|$).*$"
  );
  var match =
    domain.match(tldRegExp) ||
    domain.match(/(?=[^^])\.[^a-z]{1,2}\.[^\.]{2,4}$/) ||
    domain.match(/\.[^\.]{2,}$/);
  var tld = match && match.index;
  var domainWithoutSuffix = domain.substring(0, tld);

  // Get the main domain part, handling subdomains
  if (domainWithoutSuffix.includes(".")) {
    // Split by dots and get the last two parts for domains like en.wikipedia.org
    const parts = domainWithoutSuffix.split(".");
    if (parts.length >= 2) {
      domainWithoutSuffix = parts.slice(-2).join(".");
    } else {
      domainWithoutSuffix = parts[parts.length - 1];
    }
  }
  return domainWithoutSuffix;
}


/**
 * Checks if a string is a valid URL.
 * @param {string} string 
 * @returns {boolean} true if the string is a valid URL
 * @private
 */
export function isURLValid(string) {
  return /^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/
    .test(string);
}