private function parse20VersionConstraint(array $data)
    {
        static $dep20toOperatorMap = array('has' => '==', 'min' => '>=', 'max' => '<=', 'exclude' => '!=');

        $versions = array();
        $values = array_intersect_key($data, $dep20toOperatorMap);
        if (0 == count($values)) {
            return '*';
        }
        if (isset($values['min']) && isset($values['exclude']) && $data['min'] == $data['exclude']) {
            $versions[] = '>' . $this->parseVersion($values['min']);
        } elseif (isset($values['max']) && isset($values['exclude']) && $data['max'] == $data['exclude']) {
            $versions[] = '<' . $this->parseVersion($values['max']);
        } else {
            foreach ($values as $op => $version) {
                if ('exclude' == $op && is_array($version)) {
                    foreach ($version as $versionPart) {
                        $versions[] = $dep20toOperatorMap[$op] . $this->parseVersion($versionPart);
                    }
                } else {
                    $versions[] = $dep20toOperatorMap[$op] . $this->parseVersion($version);
                }
            }
        }

        return implode(',', $versions);
    }