public function getCurrenciesForCountry(string $countryCode) : array
    {
        if ($this->countryToCurrency === null) {
            $this->countryToCurrency = require __DIR__ . '/../data/country-to-currency.php';
        }

        $result = [];

        if (isset($this->countryToCurrency[$countryCode])) {
            foreach ($this->countryToCurrency[$countryCode] as $currencyCode) {
                $result[] = $this->getCurrency($currencyCode);
            }
        }

        return $result;
    }