protected function validateDecimal($value, string $parameter, array $args = [], array $rules = null, array $context = null): ?string
    {
        if (count($args) == 0) {
            throw new ValidatorConfigException("Validator 'decimal' must have argument in validator list for parameter {$parameter}");
        }

        $decimals = (int)$args[0];

        if ($decimals <= 0) {
            throw new ValidatorConfigException("Validator 'decimal' has invalid value which is lower or equal to zero; for parameter={$parameter}");
        }

        if ($decimals > 100) {
            throw new ValidatorConfigException("Validator 'decimal' can't have that large argument; parameter={$parameter}");
        }

        //$value = $this->getValue($parameter);

        if ($value === null) {
            return null;
        }

        if (!is_scalar($value)) {
            return Message::getMessage(Message::PRIMITIVE, [
                'param' => $parameter
            ]);
        }

        $value = trim((string)$value);

        if ($value === '') {
            return null;
        }

        if (!is_numeric($value)) {
            return Message::getMessage(Message::NUMERIC, [
                'param' => $parameter,
                'value' => $value
            ]);
        }

        $parts = explode('.', $value);

        if (count($parts) == 1) {
            return null; // value is not decimal, it's probably integer, so it's ok
        }

        $valueDecimals = $parts[1];

        if (strlen($valueDecimals) > $decimals) {
            return Message::getMessage(Message::DECIMAL, [
                'param' => $parameter,
                'value' => $value,
                'decimals' => $decimals
            ]);
        }

        return null;
    }