Merge branch 'category_user_limits'

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/controllers/product.py

@@ -1,6 +1,7 @@
 import itertools
 
 from django.db.models import Q
+from django.db.models import Sum
 from registrasion import models as rego
 
 from conditions import ConditionController
@@ -28,11 +29,13 @@ class ProductController(object):
         if products is not None:
             all_products = itertools.chain(all_products, products)
 
-        return [
+        out = [
             product
             for product in all_products
             if cls(product).can_add_with_enabling_conditions(user, 0)
         ]
+        out.sort(key=lambda product: product.order)
+        return out
 
     def user_can_add_within_limit(self, user, quantity):
         ''' Return true if the user is able to add _quantity_ to their count of
@@ -40,17 +43,25 @@ class ProductController(object):
 
         carts = rego.Cart.objects.filter(user=user)
         items = rego.ProductItem.objects.filter(
-            product=self.product,
+            cart=carts,
-            cart=carts)
+        )
 
-        count = 0
+        prod_items = items.filter(product=self.product)
-        for item in items:
+        cat_items = items.filter(product__category=self.product.category)
-            count += item.quantity
 
-        if quantity + count > self.product.limit_per_user:
+        prod_count = prod_items.aggregate(Sum("quantity"))["quantity__sum"]
-            return False
+        cat_count = cat_items.aggregate(Sum("quantity"))["quantity__sum"]
-        else:
+
+        prod_limit = self.product.limit_per_user
+        prod_met = prod_limit is None or quantity + prod_count <= prod_limit
+
+        cat_limit = self.product.category.limit_per_user
+        cat_met = cat_limit is None or quantity + cat_count <= cat_limit
+
+        if prod_met and cat_met:
             return True
+        else:
+            return False
 
     def can_add_with_enabling_conditions(self, user, quantity):
         ''' Returns true if the user is able to add _quantity_ to their count

registrasion/forms.py

@@ -3,51 +3,133 @@ import models as rego
 from django import forms
 
 
-def ProductsForm(products):
+# Products forms -- none of these have any fields: they are to be subclassed
+# and the fields added as needs be.
 
-    PREFIX = "product_"
+class _ProductsForm(forms.Form):
 
-    def field_name(product):
+    PRODUCT_PREFIX = "product_"
-        return PREFIX + ("%d" % product.id)
 
-    class _ProductsForm(forms.Form):
+    ''' Base class for product entry forms. '''
+    def __init__(self, *a, **k):
+        if "product_quantities" in k:
+            initial = self.initial_data(k["product_quantities"])
+            k["initial"] = initial
+            del k["product_quantities"]
+        super(_ProductsForm, self).__init__(*a, **k)
 
-        def __init__(self, *a, **k):
+    @classmethod
-            if "product_quantities" in k:
+    def field_name(cls, product):
-                initial = _ProductsForm.initial_data(k["product_quantities"])
+        return cls.PRODUCT_PREFIX + ("%d" % product.id)
-                k["initial"] = initial
-                del k["product_quantities"]
-            super(_ProductsForm, self).__init__(*a, **k)
 
-        @classmethod
+    @classmethod
-        def initial_data(cls, product_quantities):
+    def set_fields(cls, category, products):
-            ''' Prepares initial data for an instance of this form.
+        ''' Sets the base_fields on this _ProductsForm to allow selecting
-            product_quantities is a sequence of (product,quantity) tuples '''
+        from the provided products. '''
-            initial = {}
+        pass
-            for product, quantity in product_quantities:
-                initial[field_name(product)] = quantity
 
-            return initial
+    @classmethod
+    def initial_data(cls, product_quantites):
+        ''' Prepares initial data for an instance of this form.
+        product_quantities is a sequence of (product,quantity) tuples '''
+        return {}
 
-        def product_quantities(self):
+    def product_quantities(self):
-            ''' Yields a sequence of (product, quantity) tuples from the
+        ''' Yields a sequence of (product, quantity) tuples from the
-            cleaned form data. '''
+        cleaned form data. '''
-            for name, value in self.cleaned_data.items():
+        return iter([])
-                if name.startswith(PREFIX):
-                    product_id = int(name[len(PREFIX):])
-                    yield (product_id, value, name)
 
-    for product in products:
 
-        help_text = "$%d -- %s" % (product.price, product.description)
+class _QuantityBoxProductsForm(_ProductsForm):
+    ''' Products entry form that allows users to enter quantities
+    of desired products. '''
 
-        field = forms.IntegerField(
+    @classmethod
-            label=product.name,
+    def set_fields(cls, category, products):
-            help_text=help_text,
+        for product in products:
+            help_text = "$%d -- %s" % (product.price, product.description)
+
+            field = forms.IntegerField(
+                label=product.name,
+                help_text=help_text,
+            )
+            cls.base_fields[cls.field_name(product)] = field
+
+    @classmethod
+    def initial_data(cls, product_quantities):
+        initial = {}
+        for product, quantity in product_quantities:
+            initial[cls.field_name(product)] = quantity
+
+        return initial
+
+    def product_quantities(self):
+        for name, value in self.cleaned_data.items():
+            if name.startswith(self.PRODUCT_PREFIX):
+                product_id = int(name[len(self.PRODUCT_PREFIX):])
+                yield (product_id, value, name)
+
+
+class _RadioButtonProductsForm(_ProductsForm):
+    ''' Products entry form that allows users to enter quantities
+    of desired products. '''
+
+    FIELD = "chosen_product"
+
+    @classmethod
+    def set_fields(cls, category, products):
+        choices = []
+        for product in products:
+
+            choice_text = "%s -- $%d" % (product.name, product.price)
+            choices.append((product.id, choice_text))
+
+        cls.base_fields[cls.FIELD] = forms.TypedChoiceField(
+            label=category.name,
+            widget=forms.RadioSelect,
+            choices=choices,
+            empty_value=0,
+            coerce=int,
         )
-        _ProductsForm.base_fields[field_name(product)] = field
 
-    return _ProductsForm
+    @classmethod
+    def initial_data(cls, product_quantities):
+        initial = {}
+
+        for product, quantity in product_quantities:
+            if quantity > 0:
+                initial[cls.FIELD] = product.id
+                break
+
+        return initial
+
+    def product_quantities(self):
+        ours = self.cleaned_data[self.FIELD]
+        choices = self.fields[self.FIELD].choices
+        for choice_value, choice_display in choices:
+            yield (
+                choice_value,
+                1 if ours == choice_value else 0,
+                self.FIELD,
+            )
+
+
+def ProductsForm(category, products):
+    ''' Produces an appropriate _ProductsForm subclass for the given render
+    type. '''
+
+    # Each Category.RENDER_TYPE value has a subclass here.
+    RENDER_TYPES = {
+        rego.Category.RENDER_TYPE_QUANTITY: _QuantityBoxProductsForm,
+        rego.Category.RENDER_TYPE_RADIO: _RadioButtonProductsForm,
+    }
+
+    # Produce a subclass of _ProductsForm which we can alter the base_fields on
+    class ProductsForm(RENDER_TYPES[category.render_type]):
+        pass
+
+    ProductsForm.set_fields(category, products)
+    return ProductsForm
 
 
 class ProfileForm(forms.ModelForm):

registrasion/migrations/0007_auto_20160326_2105.py

@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('registrasion', '0006_category_required'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='category',
+            name='limit_per_user',
+            field=models.PositiveIntegerField(null=True, verbose_name='Limit per user', blank=True),
+        ),
+        migrations.AlterField(
+            model_name='product',
+            name='limit_per_user',
+            field=models.PositiveIntegerField(null=True, verbose_name='Limit per user', blank=True),
+        ),
+    ]

registrasion/models.py

@@ -132,6 +132,10 @@ class Category(models.Model):
     name = models.CharField(max_length=65, verbose_name=_("Name"))
     description = models.CharField(max_length=255,
                                    verbose_name=_("Description"))
+    limit_per_user = models.PositiveIntegerField(
+        null=True,
+        blank=True,
+        verbose_name=_("Limit per user"))
     required = models.BooleanField(blank=True)
     order = models.PositiveIntegerField(verbose_name=("Display order"))
     render_type = models.IntegerField(choices=CATEGORY_RENDER_TYPES,
@@ -153,6 +157,7 @@ class Product(models.Model):
                                 decimal_places=2,
                                 verbose_name=_("Price"))
     limit_per_user = models.PositiveIntegerField(
+        null=True,
         blank=True,
         verbose_name=_("Limit per user"))
     reservation_duration = models.DurationField(
@@ -172,9 +177,13 @@ class Voucher(models.Model):
     def __str__(self):
         return "Voucher for %s" % self.recipient
 
+    @classmethod
+    def normalise_code(cls, code):
+        return code.upper()
+
     def save(self, *a, **k):
         ''' Normalise the voucher code to be uppercase '''
-        self.code = self.code.upper()
+        self.code = self.normalise_code(self.code)
         super(Voucher, self).save(*a, **k)
 
     recipient = models.CharField(max_length=64, verbose_name=_("Recipient"))

registrasion/templatetags/registrasion_tags.py

@@ -8,16 +8,19 @@ register = template.Library()
 
 ProductAndQuantity = namedtuple("ProductAndQuantity", ["product", "quantity"])
 
+
 @register.assignment_tag(takes_context=True)
 def available_categories(context):
     ''' Returns all of the available product categories '''
     return rego.Category.objects.all()
 
+
 @register.assignment_tag(takes_context=True)
 def invoices(context):
     ''' Returns all of the invoices that this user has. '''
     return rego.Invoice.objects.filter(cart__user=context.request.user)
 
+
 @register.assignment_tag(takes_context=True)
 def items_pending(context):
     ''' Returns all of the items that this user has in their current cart,
@@ -29,6 +32,7 @@ def items_pending(context):
     )
     return all_items
 
+
 @register.assignment_tag(takes_context=True)
 def items_purchased(context):
     ''' Returns all of the items that this user has purchased '''

registrasion/tests/test_cart.py

@@ -32,69 +32,43 @@ class RegistrationCartTestCase(SetTimeMixin, TestCase):
             email='test2@example.com',
             password='top_secret')
 
-        cls.CAT_1 = rego.Category.objects.create(
-            name="Category 1",
-            description="This is a test category",
-            order=10,
-            render_type=rego.Category.RENDER_TYPE_RADIO,
-            required=False,
-        )
-        cls.CAT_1.save()
-
-        cls.CAT_2 = rego.Category.objects.create(
-            name="Category 2",
-            description="This is a test category",
-            order=10,
-            render_type=rego.Category.RENDER_TYPE_RADIO,
-            required=False,
-        )
-        cls.CAT_2.save()
-
         cls.RESERVATION = datetime.timedelta(hours=1)
 
-        cls.PROD_1 = rego.Product.objects.create(
+        cls.categories = []
-            name="Product 1",
+        for i in xrange(2):
-            description="This is a test product. It costs $10. "
+            cat = rego.Category.objects.create(
-                        "A user may have 10 of them.",
+                name="Category " + str(i + 1),
-            category=cls.CAT_1,
+                description="This is a test category",
-            price=Decimal("10.00"),
+                order=i,
-            reservation_duration=cls.RESERVATION,
+                render_type=rego.Category.RENDER_TYPE_RADIO,
-            limit_per_user=10,
+                required=False,
-            order=10,
+            )
-        )
+            cat.save()
-        cls.PROD_1.save()
+            cls.categories.append(cat)
 
-        cls.PROD_2 = rego.Product.objects.create(
+        cls.CAT_1 = cls.categories[0]
-            name="Product 2",
+        cls.CAT_2 = cls.categories[1]
-            description="This is a test product. It costs $10. "
-                        "A user may have 10 of them.",
-            category=cls.CAT_1,
-            price=Decimal("10.00"),
-            limit_per_user=10,
-            order=10,
-        )
-        cls.PROD_2.save()
 
-        cls.PROD_3 = rego.Product.objects.create(
+        cls.products = []
-            name="Product 3",
+        for i in xrange(4):
-            description="This is a test product. It costs $10. "
+            prod = rego.Product.objects.create(
-                        "A user may have 10 of them.",
+                name="Product 1",
-            category=cls.CAT_2,
+                description="This is a test product.",
-            price=Decimal("10.00"),
+                category=cls.categories[i / 2],  # 2 products per category
-            limit_per_user=10,
+                price=Decimal("10.00"),
-            order=10,
+                reservation_duration=cls.RESERVATION,
-        )
+                limit_per_user=10,
-        cls.PROD_3.save()
+                order=1,
+            )
+            prod.save()
+            cls.products.append(prod)
 
-        cls.PROD_4 = rego.Product.objects.create(
+        cls.PROD_1 = cls.products[0]
-            name="Product 4",
+        cls.PROD_2 = cls.products[1]
-            description="This is a test product. It costs $5. "
+        cls.PROD_3 = cls.products[2]
-                        "A user may have 10 of them.",
+        cls.PROD_4 = cls.products[3]
-            category=cls.CAT_2,
+
-            price=Decimal("5.00"),
+        cls.PROD_4.price = Decimal("5.00")
-            limit_per_user=10,
-            order=10,
-        )
         cls.PROD_4.save()
 
     @classmethod
@@ -205,7 +179,7 @@ class BasicCartTests(RegistrationCartTestCase):
         current_cart.set_quantity(self.PROD_1, 2)
         self.assertEqual(2, get_item().quantity)
 
-    def test_add_to_cart_per_user_limit(self):
+    def test_add_to_cart_product_per_user_limit(self):
         current_cart = CartController.for_user(self.USER_1)
 
         # User should be able to add 1 of PROD_1 to the current cart.
@@ -231,3 +205,86 @@ class BasicCartTests(RegistrationCartTestCase):
         # Second user should not be affected by first user's limits
         second_user_cart = CartController.for_user(self.USER_2)
         second_user_cart.add_to_cart(self.PROD_1, 10)
+
+    def set_limits(self):
+        self.CAT_2.limit_per_user = 10
+        self.PROD_2.limit_per_user = None
+        self.PROD_3.limit_per_user = None
+        self.PROD_4.limit_per_user = 6
+
+        self.CAT_2.save()
+        self.PROD_2.save()
+        self.PROD_3.save()
+        self.PROD_4.save()
+
+    def test_per_user_product_limit_ignored_if_blank(self):
+        self.set_limits()
+
+        current_cart = CartController.for_user(self.USER_1)
+        # There is no product limit on PROD_2, and there is no cat limit
+        current_cart.add_to_cart(self.PROD_2, 1)
+        # There is no product limit on PROD_3, but there is a cat limit
+        current_cart.add_to_cart(self.PROD_3, 1)
+
+    def test_per_user_category_limit_ignored_if_blank(self):
+        self.set_limits()
+        current_cart = CartController.for_user(self.USER_1)
+        # There is no product limit on PROD_2, and there is no cat limit
+        current_cart.add_to_cart(self.PROD_2, 1)
+        # There is no cat limit on PROD_1, but there is a prod limit
+        current_cart.add_to_cart(self.PROD_1, 1)
+
+    def test_per_user_category_limit_only(self):
+        self.set_limits()
+
+        current_cart = CartController.for_user(self.USER_1)
+
+        # Cannot add to cart if category limit is filled by one product.
+        current_cart.set_quantity(self.PROD_3, 10)
+        with self.assertRaises(ValidationError):
+            current_cart.set_quantity(self.PROD_4, 1)
+
+        # Can add to cart if category limit is not filled by one product
+        current_cart.set_quantity(self.PROD_3, 5)
+        current_cart.set_quantity(self.PROD_4, 5)
+        # Cannot add to cart if category limit is filled by two products
+        with self.assertRaises(ValidationError):
+            current_cart.add_to_cart(self.PROD_3, 1)
+
+        current_cart.cart.active = False
+        current_cart.cart.save()
+
+        current_cart = CartController.for_user(self.USER_1)
+        # The category limit should extend across carts
+        with self.assertRaises(ValidationError):
+            current_cart.add_to_cart(self.PROD_3, 10)
+
+    def test_per_user_category_and_product_limits(self):
+        self.set_limits()
+
+        current_cart = CartController.for_user(self.USER_1)
+
+        # Hit both the product and category edges:
+        current_cart.set_quantity(self.PROD_3, 4)
+        current_cart.set_quantity(self.PROD_4, 6)
+        with self.assertRaises(ValidationError):
+            # There's unlimited PROD_3, but limited in the category
+            current_cart.add_to_cart(self.PROD_3, 1)
+
+        current_cart.set_quantity(self.PROD_3, 0)
+        with self.assertRaises(ValidationError):
+            # There's only 6 allowed of PROD_4
+            current_cart.add_to_cart(self.PROD_4, 1)
+
+        # The limits should extend across carts...
+        current_cart.cart.active = False
+        current_cart.cart.save()
+
+        current_cart = CartController.for_user(self.USER_1)
+        current_cart.set_quantity(self.PROD_3, 4)
+
+        with self.assertRaises(ValidationError):
+            current_cart.set_quantity(self.PROD_3, 5)
+
+        with self.assertRaises(ValidationError):
+            current_cart.set_quantity(self.PROD_4, 1)

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)

registrasion/views.py

@@ -93,113 +93,141 @@ def product_category(request, category_id):
     PRODUCTS_FORM_PREFIX = "products"
     VOUCHERS_FORM_PREFIX = "vouchers"
 
+    # Handle the voucher form *before* listing products.
+    # Products can change as vouchers are entered.
+    v = handle_voucher(request, VOUCHERS_FORM_PREFIX)
+    voucher_form, voucher_handled = v
+
     category_id = int(category_id)  # Routing is [0-9]+
     category = rego.Category.objects.get(pk=category_id)
-    current_cart = CartController.for_user(request.user)
 
-    attendee = rego.Attendee.get_instance(request.user)
-
-    products = rego.Product.objects.filter(category=category)
-    products = products.order_by("order")
     products = ProductController.available_products(
         request.user,
-        products=products,
+        category=category,
     )
-    ProductsForm = forms.ProductsForm(products)
 
-    if request.method == "POST":
+    p = handle_products(request, category, products, PRODUCTS_FORM_PREFIX)
-        cat_form = ProductsForm(
+    products_form, discounts, products_handled = p
-            request.POST,
-            request.FILES,
-            prefix=PRODUCTS_FORM_PREFIX)
-        voucher_form = forms.VoucherForm(
-            request.POST,
-            prefix=VOUCHERS_FORM_PREFIX)
 
-        if (voucher_form.is_valid() and
+    if request.POST and not voucher_handled and not products_form.errors:
-                voucher_form.cleaned_data["voucher"].strip()):
+        # Only return to the dashboard if we didn't add a voucher code
-            # Apply voucher
+        # and if there's no errors in the products form
-            # leave
-            voucher = voucher_form.cleaned_data["voucher"]
-            try:
-                current_cart.apply_voucher(voucher)
-            except Exception as e:
-                voucher_form.add_error("voucher", e)
-            # Re-visit current page.
-        elif cat_form.is_valid():
-            try:
-                handle_valid_cat_form(cat_form, current_cart)
-            except ValidationError:
-                pass
 
-            # If category is required, the user must have at least one
+        attendee = rego.Attendee.get_instance(request.user)
-            # in an active+valid cart
+        if category_id > attendee.highest_complete_category:
+            attendee.highest_complete_category = category_id
+            attendee.save()
+        return redirect("dashboard")
 
-            if category.required:
-                carts = rego.Cart.reserved_carts()
-                carts = carts.filter(user=request.user)
-                items = rego.ProductItem.objects.filter(
-                    product__category=category,
-                    cart=carts,
-                )
-                if len(items) == 0:
-                    cat_form.add_error(
-                        None,
-                        "You must have at least one item from this category",
-                    )
-
-            if not cat_form.errors:
-                if category_id > attendee.highest_complete_category:
-                    attendee.highest_complete_category = category_id
-                    attendee.save()
-                return redirect("dashboard")
-
-    else:
-        # Create initial data for each of products in category
-        items = rego.ProductItem.objects.filter(
-            product__category=category,
-            cart=current_cart.cart,
-        )
-        quantities = []
-        for product in products:
-            # Only add items that are enabled.
-            try:
-                quantity = items.get(product=product).quantity
-            except ObjectDoesNotExist:
-                quantity = 0
-            quantities.append((product, quantity))
-
-        cat_form = ProductsForm(
-            prefix=PRODUCTS_FORM_PREFIX,
-            product_quantities=quantities,
-        )
-
-        voucher_form = forms.VoucherForm(prefix=VOUCHERS_FORM_PREFIX)
-
-    discounts = discount.available_discounts(request.user, [], products)
     data = {
         "category": category,
         "discounts": discounts,
-        "form": cat_form,
+        "form": products_form,
         "voucher_form": voucher_form,
     }
 
     return render(request, "product_category.html", data)
 
 
+def handle_products(request, category, products, prefix):
+    ''' Handles a products list form in the given request. Returns the
+    form instance, the discounts applicable to this form, and whether the
+    contents were handled. '''
+
+    current_cart = CartController.for_user(request.user)
+
+    ProductsForm = forms.ProductsForm(category, products)
+
+    # Create initial data for each of products in category
+    items = rego.ProductItem.objects.filter(
+        product__in=products,
+        cart=current_cart.cart,
+    )
+    quantities = []
+    for product in products:
+        # Only add items that are enabled.
+        try:
+            quantity = items.get(product=product).quantity
+        except ObjectDoesNotExist:
+            quantity = 0
+        quantities.append((product, quantity))
+
+    products_form = ProductsForm(
+        request.POST or None,
+        product_quantities=quantities,
+        prefix=prefix,
+    )
+
+    if request.method == "POST" and products_form.is_valid():
+        try:
+            if products_form.has_changed():
+                set_quantities_from_products_form(products_form, current_cart)
+        except ValidationError:
+            # There were errors, but they've already been added to the form.
+            pass
+
+        # If category is required, the user must have at least one
+        # in an active+valid cart
+        if category.required:
+            carts = rego.Cart.objects.filter(user=request.user)
+            items = rego.ProductItem.objects.filter(
+                product__category=category,
+                cart=carts,
+            )
+            if len(items) == 0:
+                products_form.add_error(
+                    None,
+                    "You must have at least one item from this category",
+                )
+    handled = False if products_form.errors else True
+
+    discounts = discount.available_discounts(request.user, [], products)
+
+    return products_form, discounts, handled
+
+
 @transaction.atomic
-def handle_valid_cat_form(cat_form, current_cart):
+def set_quantities_from_products_form(products_form, current_cart):
-    for product_id, quantity, field_name in cat_form.product_quantities():
+    for product_id, quantity, field_name in products_form.product_quantities():
         product = rego.Product.objects.get(pk=product_id)
         try:
             current_cart.set_quantity(product, quantity, batched=True)
         except ValidationError as ve:
-            cat_form.add_error(field_name, ve)
+            products_form.add_error(field_name, ve)
-    if cat_form.errors:
+    if products_form.errors:
         raise ValidationError("Cannot add that stuff")
     current_cart.end_batch()
 
 
+def handle_voucher(request, prefix):
+    ''' Handles a voucher form in the given request. Returns the voucher
+    form instance, and whether the voucher code was handled. '''
+
+    voucher_form = forms.VoucherForm(request.POST or None, prefix=prefix)
+    current_cart = CartController.for_user(request.user)
+
+    if (voucher_form.is_valid() and
+            voucher_form.cleaned_data["voucher"].strip()):
+
+        voucher = voucher_form.cleaned_data["voucher"]
+        voucher = rego.Voucher.normalise_code(voucher)
+
+        if len(current_cart.cart.vouchers.filter(code=voucher)) > 0:
+            # This voucher has already been applied to this cart.
+            # Do not apply code
+            handled = False
+        else:
+            try:
+                current_cart.apply_voucher(voucher)
+            except Exception as e:
+                voucher_form.add_error("voucher", e)
+            handled = True
+    else:
+        handled = False
+
+    return (voucher_form, handled)
+
+
 @login_required
 def checkout(request):
     ''' Runs checkout for the current cart of items, ideally generating an