String stackName = request.getStackName();
String stackVersion = request.getStackVersion();
if (stackVersion != null) {
StackInfo stackInfo = this.ambariMetaInfo.getStackInfo(stackName, stackVersion);
response = Collections.singleton(stackInfo.convertToResponse());
} else {
Set<StackInfo> stackInfos = this.ambariMetaInfo.getStackInfos(stackName);
response = new HashSet<StackVersionResponse>();
for (StackInfo stackInfo: stackInfos) {
response.add(stackInfo.convertToResponse());