public static function countries($longlist = false, $hydrate = false)
    {
        $list = $longlist ? 'longlist' : 'shortlist';

        if (! isset(static::$countries[$list])) {
            static::$countries[$list] = json_decode(static::getFile(__DIR__.'/../resources/data/'.$list.'.json'), true);
        }

        return $hydrate ? array_map(function ($country) {
            return new Country($country);
        }, static::$countries[$list]) : static::$countries[$list];
    }