LimitCases

trigger LimitCases on Case (before insert) {

    //Extract the custom setting value into a variable
    Max_Cases__c maxCase = Max_Cases__c.getInstance('maxcases');
    Decimal maxNoCases   = maxCase.MaxCases__c;
    
        System.debug('The max no. of cases setting is:' + maxNoCases);
        
    //1. Create a set of all Owner Id's whose cases are being fed for import
    Map<Id,Integer> ownerCasesMap = new Map<Id,Integer>();
    Set<String> ownerIds = new Set<String>();
    
        for(Case newCase: Trigger.new) {
                System.debug('Creating a set of Owner Ids');
                ownerIds.add(newCase.OwnerId);
                ownerCasesMap.put(newCase.OwnerId,0);
                
                }

   
     
    /*2. Create a user Map just to obtain the Owner Name using their Id
         Add all userIds to a map with 0 number of cases as initial values 
         Salesforce doesn't allow doing Owner.name for some incomprehensible reason! */
  
           Map<Id,User> userMap = new Map<Id,User>();
           List<User> userM =[SELECT Id, Name FROM User WHERE Id IN: ownerIds];
           for(User ownerUser:userM) {
           userMap.put(ownerUser.Id, ownerUser);
           }
      
     
   //3. Use AggregateResults to get a count of all Cases pertaining to the above owners
    
    System.debug('Creating a list of grouped results[AggregateResults] now');
    List<AggregateResult> groupedResults= [SELECT OwnerId , count(Id) FROM Case
                                           WHERE OwnerId IN:ownerIds 
                                           AND CreatedDate= THIS_MONTH     
                                           GROUP BY OwnerId];
                                           
                                                         
    //4. Use the previously created Map to store Owner Id and the number of Cases from above
        
    for(AggregateResult countCase: groupedResults) {
    
      
    System.debug('Entered the AggregateResult For loop');
    
        if(countCase!=null) {     
              
        System.debug('Owner Id:' + countCase.get('OwnerId'));
        System.debug('Count is' + countCase.get('expr0'));
        
        //Map now has key-> Owner Id, value-> Case count
        //This will replace the owners previous put in the Map with new values and not put anything for NULL
        //This way users who didn't create any cases this month are retained in the previously created map
        
       ownerCasesMap.put((Id)countCase.get('OwnerId'), (Integer)countCase.get('expr0'));
        }
      }
        
      
       
       //Go through every Case being inserted , find the case count from above and compare to maxCases
              
       for(Case newCase: Trigger.new) {
           
           System.debug('Entered the main Case Trigger.new!');
       
           //Get the number of cases associated with the Owner Id of this case    
           Integer numCases  = ownerCasesMap.get(newCase.OwnerId);
           
           System.debug('Number of Cases created so far by this owner:'+ numCases);
           
           //Do not allow the user to create a case if the limit is reached
           if(numCases>=maxNoCases) {
           System.debug('Entered the if loop in order to show the error since numCases>=maxNoCases' );
           newCase.addError('Too many cases created this month for user' + ' ' + userMap.get(newCase.OwnerId).Name + '(' + newCase.OwnerId + '):' + ' ' + maxNoCases);
           }                  
           
               else {
               System.debug('Entered the else loop in order to let the user create the case' );
           
               ownerCasesMap.put(newCase.OwnerId, ownerCasesMap.get(newCase.OwnerId) + 1);
               System.debug('Number of cases for this owner has been incremented in the map' );
               System.debug('Number of cases for this owner: ' + userMap.get(newCase.OwnerId).Name + 'is: ' +ownerCasesMap.get(newCase.OwnerId));
           
           }
           
         }
          
          System.debug('Case has been inserted' );
      }