class ConfigurationResolver

class ConfigurationResolver implements ConfigurationResolverInterface {
    public function has(string $name) : bool {
        return $this->getVariable($name) !== null;
    }
    public function getString(string $name) : ?string {
        return $this->getVariable($name);
    }
    public function getBoolean(string $name) : ?bool {
        $value = $this->getVariable($name);
        if ($value === null) {
            return null;
        }
        return $value === 'true';
    }
    public function getInt(string $name) : ?int {
        $value = $this->getVariable($name);
        if ($value === null) {
            return null;
        }
        if (filter_var($value, FILTER_VALIDATE_INT) === false) {
            
            //log warning
            return null;
        }
        return (int) $value;
    }
    public function getList(string $name) : array {
        $value = $this->getVariable($name);
        if ($value === null) {
            return [];
        }
        return explode(',', $value);
    }
    private function getVariable(string $name) : ?string {
        $value = $_SERVER[$name] ?? null;
        if ($value !== false && !self::isEmpty($value)) {
            assert(is_string($value));
            return $value;
        }
        $value = getenv($name);
        if ($value !== false && !self::isEmpty($value)) {
            return $value;
        }
        $value = ini_get($name);
        if ($value !== false && !self::isEmpty($value)) {
            return $value;
        }
        return null;
    }
    private static function isEmpty($value) : bool {
        return $value === false || $value === null || $value === '';
    }

}