Makes it invalid for a user to re-enter a voucher code they already have.

registrasion/controllers/cart.py

@@ -125,18 +125,25 @@ class CartController(object):
     def apply_voucher(self, voucher_code):
         ''' Applies the voucher with the given code to this cart. '''
 
-        # TODO: is it valid for a cart to re-add a voucher that they have?
-
         # Is voucher exhausted?
         active_carts = rego.Cart.reserved_carts()
 
         # Try and find the voucher
         voucher = rego.Voucher.objects.get(code=voucher_code.upper())
 
+        # It's invalid for a user to enter a voucher that's exhausted
         carts_with_voucher = active_carts.filter(vouchers=voucher)
         if len(carts_with_voucher) >= voucher.limit:
             raise ValidationError("This voucher is no longer available")
 
+        # It's not valid for users to re-enter a voucher they already have
+        user_carts_with_voucher = rego.Cart.objects.filter(
+            user=self.cart.user,
+            vouchers=voucher,
+        )
+        if len(user_carts_with_voucher) > 0:
+            raise ValidationError("You have already entered this voucher.")
+
         # If successful...
         self.cart.vouchers.add(voucher)
         self.end_batch()

registrasion/tests/test_voucher.py

@@ -7,6 +7,7 @@ from django.db import IntegrityError
 
 from registrasion import models as rego
 from registrasion.controllers.cart import CartController
+from registrasion.controllers.invoice import InvoiceController
 
 from test_cart import RegistrationCartTestCase
 
@@ -16,11 +17,11 @@ UTC = pytz.timezone('UTC')
 class VoucherTestCases(RegistrationCartTestCase):
 
     @classmethod
-    def new_voucher(self, code="VOUCHER"):
+    def new_voucher(self, code="VOUCHER", limit=1):
         voucher = rego.Voucher.objects.create(
             recipient="Voucher recipient",
             code=code,
-            limit=1
+            limit=limit,
         )
         voucher.save()
         return voucher
@@ -107,3 +108,21 @@ class VoucherTestCases(RegistrationCartTestCase):
         voucher = self.new_voucher(code="VOUCHeR")
         current_cart = CartController.for_user(self.USER_1)
         current_cart.apply_voucher(voucher.code.lower())
+
+    def test_voucher_can_only_be_applied_once(self):
+        voucher = self.new_voucher(limit=2)
+        current_cart = CartController.for_user(self.USER_1)
+        current_cart.apply_voucher(voucher.code)
+        with self.assertRaises(ValidationError):
+            current_cart.apply_voucher(voucher.code)
+
+    def test_voucher_can_only_be_applied_once_across_multiple_carts(self):
+        voucher = self.new_voucher(limit=2)
+        current_cart = CartController.for_user(self.USER_1)
+        current_cart.apply_voucher(voucher.code)
+
+        inv = InvoiceController.for_cart(current_cart.cart)
+        inv.pay("Hello!", inv.invoice.value)
+
+        with self.assertRaises(ValidationError):
+            current_cart.apply_voucher(voucher.code)