trigger PopulateAccount on Account (before insert, before update) {

if(Trigger.isBefore && (Trigger.isInsert || Trigger.isUpdate)){
//Find Ownership according to the Salesperson_Code__c
    Set<Integer> SAPID = new set<Integer>();
    Set<String> SAPIDOwner = new set<String>();
    Map<Integer,User> userIdObj = new map<Integer,User>();
    Map<String,User> ownerIdObj = new map<String,User>();
    if (trigger.isBefore && trigger.isUpdate){
        for (Account acc:trigger.New){
            if((trigger.oldMap.get(acc.Id).ownerId != trigger.newMap.get(acc.Id).ownerId) && (acc.ownerId != null)){
                SAPIDOwner.add(acc.ownerId);
            } else {
                if(acc.Salesperson_Code__c != null){
                    SAPID.add(acc.Salesperson_Code__c.intValue());
                }
            }
        }
    }else{
        for(Account acc:trigger.New){
            if(acc.Salesperson_Code__c == null){
                SAPIDOwner.add(acc.ownerId);//Admin?
            }else{
                if(acc.Salesperson_Code__c != null){
                    SAPID.add(acc.Salesperson_Code__c.intValue());
                }
            }
        }
    }
    if(SAPID.size() > 0){
        for (User userSAP : [SELECT Id,Salesperson_Code__c  FROM user WHERE Salesperson_Code__c =:SAPID]){
            userIdObj.put(userSAP.Salesperson_Code__c.intValue(),userSAP);
        }
    }
    if(SAPIDOwner.size() > 0){
        for (User ownerObj: [SELECT Id,Salesperson_Code__c  FROM user WHERE Id =:SAPIDOwner]){
            ownerIdObj.put(ownerObj.Id,ownerObj);
        }
        if(ownerIdObj.size()>0){
            for(Account acc1:trigger.New){
                acc1.Salesperson_Code__c = ownerIdObj.get(acc1.ownerID).Salesperson_Code__c;
            }

        }
    }else{
        if(userIdObj.size() > 0){
            for(Account acc1:trigger.New){
                if(acc1.Salesperson_Code__c != null){
                    if(userIdObj.get(acc1.Salesperson_Code__c.intValue()) != null){
                        acc1.ownerID = userIdObj.get(acc1.Salesperson_Code__c.intValue()).Id;
                }
            }

        }
    }else{
        List<User> users = [SELECT Id,username FROM user];
        User SAPIntegration = new User();
        for (User SAP:users){
            if (SAP.username == 'admin@company.com'){
                SAPIntegration = SAP; break;
            }
        }
        if(SAPIntegration.username == 'manuele@aircobrands.com.au'){
            for (Account acc1:trigger.New){
                acc1.ownerId = SAPIntegration.Id;
            }
        }
    }
    }

}
//END Find Ownership according to the Salesperson_Code__c
}//END of trigger