Email-To-Case custom email handler - updates

The handler is working really well. But with a few minor issues.

extractRef

1. Update the code in extractRef to check for null.
2. Allow for more variations of Case in subject line

patternString = '.*case\\s*[;:=#]?\\s*([0-9]+).*';

private String extractRef(String emailSubject)
{
 String itemRef = null;
// add test for null
 if(emailSubject == null)
  return null;
 String target = emailSubject.toLowerCase();
 String patternString;
 Pattern thePattern;
 Matcher matcher;
 
/*  Take the text between the period and ":ref"  For example in the ref [ ref:00D7JFzw.5007H3Rh8:ref ] extract 5007H3Rh8
 Take that text and remove the 5007. For example H3Rh8 
 Append H3Rh8 to https://na5.salesforce.com/5007000000  to produce https://na5.salesforce.com/5007000000H3Rh8.   This is your link to get to the case.
*/  
 patternString = '.*ref:(.{8}).(.{4})(.+):ref.*';
 thePattern = Pattern.compile(patternString);
 matcher = thePattern.matcher(emailSubject); // do not change to lower case for this test because Id's are case sensitive
  
 if (matcher.matches()) {
  String caseId = matcher.group(2) + '000000' + matcher.group(3);
  if(TRACE) system.debug(Logginglevel.ERROR,'extractRef "' + caseId + '"');    
  Case[] matchingCases = [Select CaseNumber from Case where Id = :caseId];
  if(matchingCases.size() == 1) {
   Case theCase = matchingCases[0];
   itemRef = theCase.CaseNumber;
  }    
 }  
 if(itemRef == null) {
  // extract the Case Number from the email Subject
  // Re: Test two numbers Case: 30088 and Case: 30089'
  // returns 30089, the last pattern matched
// Change the pattern to allow for more variations:
  patternString = '.*case\\s*[;:=#]?\\s*([0-9]+).*';
  thePattern = Pattern.compile(patternString);
  matcher = thePattern.matcher(target);
  
  if (matcher.matches()) {
   itemRef = matcher.group(1);
   if(TRACE) system.debug('Extracted case number ' + itemRef); 
  }
 }

 return itemRef; 
}