Update transaction to reflect items with no errors from Pi

Author: sameetandpotatoes

models/transaction.rb

@@ -40,10 +40,13 @@ def vend
         result = JSON.parse(response.body)
         errors = ""
         result["items"].each do |item_json|
+          item_idx = items_locations.index(item_json['location'])
           if item_json['error']
             errors += "#{item_json['location']}: #{item_json['error']}\n"
+            # Remove item from transaction
+            items_except_error = self.items.reject { |i| i.vend_location.pretty_location == item_json['location'] }
+            self.update(items: items_except_error)
           else
-            item_idx = items_locations.index(item_json['location'])
             self.items[item_idx].location.quantity -= 1
             self.items[item_idx].location.save
           end

routes/transaction.rb

@@ -40,21 +40,25 @@ def self.registered(app)
         )
 
         begin
+          # Vending a transaction will remove items that could not be vended so that user
+          # could be billed for correct amount according to what was actually bought
           error_message = transaction.vend
-          old_balance = user.balance
 
-          unless error_message
-            user.set_balance(user.balance - total_credits_needed, "Merch Transaction: #{items.map(&:name).join(", ")}")
-            
-            if user.balance == old_balance # Transaction failed (quietly)
-              transaction.destroy
-              halt 500, Errors::BALANCE_ERROR
-            end
+          old_balance = user.balance
+          transaction_name = "Merch Transaction: #{items.map(&:name).join(", ")}"
+          user.set_balance(user.balance - transaction.amount, transaction_name)
 
-            ResponseFormat.data(transaction)
-          else
-            halt 500, ResponseFormat.error(error_message)
+          # Transaction failed (quietly)
+          if user.balance == old_balance
+            transaction.destroy
+            halt 500, Errors::BALANCE_ERROR
           end
+          
+          # Attach transaction which contains successful items only + error_message for failed items
+          response = ResponseFormat.data(transaction)
+          JSON.parse(response)['error'] = error_message
+
+          response
         rescue Exception => e
           halt 500, ResponseFormat.error(e.message)
         end