/**
 * The X username alone, as the server keeps it: from "@shop", "shop" or the
 * address of the profile. Empty for an empty field, null for anything that
 * is no username (up to 15 letters, digits or underscores).
 */
export const xHandle = (value: string): string | null => {
  const typed = value.trim();
  const profile = typed.match(
    /^(?:https?:\/\/)?(?:www\.|mobile\.)?(?:x|twitter)\.com\/@?([^/?#\s]+)/i
  );
  const handle = (profile ? profile[1] : typed).replace(/^@+/, '');
  if (handle === '') {
    return '';
  }
  return /^[A-Za-z0-9_]{1,15}$/.test(handle) ? handle : null;
};

export const X_HANDLE_ERROR =
  'The username, up to 15 letters, digits or underscores; the address of the profile works too.';