trigger StockItemTrigger on Stock_Item__c (before insert, before delete) {
    //Instantiate StockItemHandler
    //Before Insert Handling

    if(Trigger.isInsert && Trigger.isBefore) {
        //call the class in your handler for before insert
        Map<String, Stock_Item__c> stockItemMap =new Map<String, Stock_Item__c>();
        for (Stock_Item__c a : Trigger.new) {
            if ((a.Item_Name__c !=null) &&
                (System.Trigger.isInsert ||
                 (a.Item_Name__c !=
                  System.Trigger.oldMap.get(a.Id).Item_Name__c))){
                      // Make sure another new name isn't also a duplicate;
                      if (stockItemMap.containsKey(a.Item_Name__c)){
                          a.Item_Name__c.addError('Another Stock Item exists with this name.');
                      }else{
                          stockItemMap.put(a.Item_Name__c, a);
                      }
                  }
        }
        // Find all the names in the database that have the same name as any of the stock items being inserted.;
        for (Stock_Item__c a : [SELECT Item_Name__c FROM Stock_Item__c WHERE Item_Name__c IN :stockItemMap.KeySet()]){
            Stock_Item__c newa = stockItemMap.get(a.Item_Name__c);
            newa.Item_Name__c.addError('A stock item with the same name already exists');

        }

    }

    //Before Delete Handling
    if(Trigger.isDelete && Trigger.isBefore) {
        //call the class in your handler for before delete
        //Create methods here to handle the before insert, before delete and utility processes described in the requirements
        //They should accept lists of Stock_Item__c records from the trigger
        //List<Stock_Item__c> availableStock = [SELECT Id, Name, OwnerId, Item_Name__c , Stock_on_Hand__c FROM Stock_Item__c WHERE Stock_on_Hand__c != 0];
        //create a list to hold any new cases we may create

        List<Case> newCases = new List<Case>();
        //Now go through each Stock Item and see if they need a case
        Map<String, Stock_Item__c> stockItemMap =new Map<String, Stock_Item__c>();
        for (Stock_Item__c a: Trigger.old) {
            if (a.Stock_on_Hand__c != 0) {
                System.debug('zeroStockonHand');
                Case cse = new Case();
                cse.Status = 'New';
                cse.Origin = 'Stock Item Issue';
                cse.Subject = 'Stock Item '+ 'Stock Item Name ' + a.Item_Name__c + '+,is not at 0 but is being deleted';
                cse.Description = 'Stock Item Name ' + a.Item_Name__c + ', Stock Id ' + a.Name + ', Stock Item SF Id ' + a.Id + '. Stock on hand ' + a.Stock_on_Hand__c;
                newCases.add(cse);

            }

        }



        insert newCases;



    }

}