self.extend_reservation()

        self.cart.revision += 1

        self.cart.save()

    @transaction.atomic

    def set_quantities(self, product_quantities):

        ''' Sets the quantities on each of the products on each of the

        products specified. Raises an exception (ValidationError) if a limit

        is violated. `product_quantities` is an iterable of (product, quantity)

        pairs. '''

        items_in_cart = rego.ProductItem.objects.filter(cart=self.cart)

        product_quantities = list(product_quantities)

        # n.b need to add have the existing items first so that the new

        # items override the old ones.

        all_product_quantities = dict(itertools.chain(

            ((i.product, i.quantity) for i in items_in_cart.all()),

            product_quantities,

        )).items()

        # Validate that the limits we're adding are OK

        self._test_limits(all_product_quantities)

        to_remove = []

        for voucher in self.cart.vouchers.all():

            try:

                self._test_voucher(voucher)

            except ValidationError as ve:

                to_remove.append(voucher)

        for voucher in to_remove:

            self.cart.vouchers.remove(voucher)

        # Fix products and discounts

        items = rego.ProductItem.objects.filter(cart=self.cart)

        products = set(i.product for i in items)

        available = set(ProductController.available_products(

            self.cart.user,

            products=products,

        ))

        not_available = products - available

        zeros = [(product, 0) for product in not_available]

        self.set_quantities(zeros)

    @transaction.atomic

    def recalculate_discounts(self):

        ''' Calculates all of the discounts available for this product.

        '''

        # Delete the existing entries.

        rego.DiscountItem.objects.filter(cart=self.cart).delete()

        products = [i.product for i in product_items]

        discounts = discount.available_discounts(self.cart.user, [], products)

        # The highest-value discounts will apply to the highest-value

        # products first.

        product_items = self.cart.productitem_set.all()

        product_items = product_items.order_by('product__price')

        product_items = reversed(product_items)

        for item in product_items:

            self._add_discount(item.product, item.quantity, discounts)

    def _add_discount(self, product, quantity, discounts):

        ''' Applies the best discounts on the given product, from the given

        discounts.'''

        def matches(discount):

            ''' Returns True if and only if the given discount apples to

            our product. '''

        self.category = category

    @classmethod

    def available_categories(cls, user, products=AllProducts):

        ''' Returns the categories available to the user. Specify `products` if

        you want to restrict to just the categories that hold the specified

        products, otherwise it'll do all. '''

        # STOPGAP -- this needs to be elsewhere tbqh

        from product import ProductController

        if products is AllProducts:

        available = ProductController.available_products(

            user,

            products=products,

        )

        return set(i.category for i in available)

    def user_quantity_remaining(self, user):

        ''' Returns the number of items from this category that the user may

        add in the current cart. '''

import itertools

from collections import defaultdict

from collections import namedtuple

from django.db.models import Sum

from django.utils import timezone

from registrasion import models as rego

ConditionAndRemainder = namedtuple(

    "ConditionAndRemainder",

        if products is not None and product_quantities is not None:

            raise ValueError("Please specify only products or "

                             "product_quantities")

        elif products is None:

            products = set(i[0] for i in product_quantities)

            quantities = dict((product, quantity)

                              for product, quantity in product_quantities)

        elif product_quantities is None:

            products = set(products)

            quantities = {}

        # Get the conditions covered by the products themselves

            for product in products

        # All mandatory conditions on a product need to be met

        mandatory = defaultdict(lambda: True)

        # At least one non-mandatory condition on a product must be met

        # if there are no mandatory conditions

        non_mandatory = defaultdict(lambda: False)

        messages = {}

        for condition in all_conditions:

            cond = cls.for_condition(condition)

            remainder = cond.user_quantity_remaining(user)

            # Get all products covered by this condition, and the products

            # from the categories covered by this condition

            cond_products = condition.products.all()

            from_category = rego.Product.objects.filter(

                category__in=condition.categories.all(),

            ).all()

            # Remove the products that we aren't asking about

            if quantities:

                consumed = sum(quantities[i] for i in all_products)

            else:

                consumed = 1

            met = consumed <= remainder

            if not met:

                items = ", ".join(str(product) for product in all_products)

                base = cls.MESSAGE[remainder == 0][len(all_products) == 1]

                message = base % {"items": items, "remainder": remainder}

from registrasion import models as rego

from django.db.models import Sum

class DiscountAndQuantity(object):

    def __init__(self, discount, clause, quantity):

        self.discount = discount

        self.clause = clause

        self.quantity = quantity

    def __repr__(self):

            self.discount, self.clause, self.quantity,

        )

def available_discounts(user, categories, products):

    ''' Returns all discounts available to this user for the given categories

    and products. The discounts also list the available quantity for this user,

    not including products that are pending purchase. '''

    # discounts that match provided categories

    category_discounts = rego.DiscountForCategory.objects.filter(

        category__in=categories

    )

    # discounts that match provided products

    product_discounts = rego.DiscountForProduct.objects.filter(

        product__in=products

    )

    # discounts that match categories for provided products

    product_category_discounts = rego.DiscountForCategory.objects.filter(

        category__in=(product.category for product in products)

    )

    # (Not relevant: discounts that match products in provided categories)

    # The set of all potential discounts

    potential_discounts = set(itertools.chain(

        product_discounts,

    ))

    discounts = []

    # Markers so that we don't need to evaluate given conditions more than once

    accepted_discounts = set()

    failed_discounts = set()

    for discount in potential_discounts:

        real_discount = rego.DiscountBase.objects.get_subclass(

            pk=discount.discount.pk,

        )

        cond = ConditionController.for_condition(real_discount)

        # Count the past uses of the given discount item.

        # If this user has exceeded the limit for the clause, this clause

        # is not available any more.

        past_uses = rego.DiscountItem.objects.filter(

            cart__user=user,

            cart__active=False,  # Only past carts count

            cart__released=False,  # You can reuse refunded discounts

        )

        agg = past_uses.aggregate(Sum("quantity"))

        past_use_count = agg["quantity__sum"]

        if past_use_count is None:

            past_use_count = 0

        if past_use_count >= discount.quantity:

            # This clause has exceeded its use count

            pass

        elif real_discount not in failed_discounts:

            # This clause is still available

            if real_discount in accepted_discounts or cond.is_met(user):

    @classmethod

    def available_products(cls, user, category=None, products=None):

        ''' Returns a list of all of the products that are available per

        enabling conditions from the given categories.

        TODO: refactor so that all conditions are tested here and

        can_add_with_enabling_conditions calls this method. '''

        if category is None and products is None:

            raise ValueError("You must provide products or a category")

        if category is not None:

            all_products = rego.Product.objects.filter(category=category)

        else:

            all_products = []

        if products is not None:

        passed_limits = set(

            product

            for product in all_products

            if cls(product).user_quantity_remaining(user) > 0

        )

        failed_and_messages = ConditionController.test_enabling_conditions(

            user, products=passed_limits

        )

        failed_conditions = set(i[0] for i in failed_and_messages)

        out = list(passed_limits - failed_conditions)

        out.sort(key=lambda product: product.order)

        return out

    ''' 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,

    and is awaiting payment. '''

    all_items = rego.ProductItem.objects.filter(

        cart__user=context.request.user,

        cart__active=True,

    return all_items

@register.assignment_tag(takes_context=True)

def items_purchased(context, category=None):

    ''' Returns all of the items that this user has purchased, optionally

    from the given category. '''

    all_items = rego.ProductItem.objects.filter(

        cart__user=context.request.user,

        cart__active=False,

    if category:

        all_items = all_items.filter(product__category=category)

    out = []

    return out

@register.filter

def multiply(value, arg):

    ''' Multiplies value by arg '''

    return value * arg

            return next_step

        if last_category == 0:

            # Only display the first Category

            title = "Select ticket type"

            current_step = 2

            cats = [cats[0]]

        else:

            # Set title appropriately for remaining categories

            current_step = 3

            title = "Additional items"

        for category in cats:

            prefix = "category_" + str(category.id)

            p = handle_products(request, category, products, prefix)

            products_form, discounts, products_handled = p

            section = GuidedRegistrationSection(

                title=category.name,

                description=category.description,

                discounts=discounts,

                form=products_form,

            )

            if products:

    ''' 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 = []

    products_form = ProductsForm(

        request.POST or None,

        product_quantities=quantities,

        prefix=prefix,

    )

    if request.method == "POST" and products_form.is_valid():

        if products_form.has_changed():

            set_quantities_from_products_form(products_form, current_cart)

        # If category is required, the user must have at least one

                    "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

def set_quantities_from_products_form(products_form, current_cart):

    quantities = list(products_form.product_quantities())

    product_quantities = [

    ]

    field_names = dict(

        (i[0][0], i[1][2]) for i in zip(product_quantities, quantities)

    )

    try:

        current_cart.set_quantities(product_quantities)

    except CartValidationError as ve:

        for ve_field in ve.error_list:

            product, message = ve_field.message

            if product in field_names:

                field = field_names[product]