import collections
import datetime
import discount
import itertools
from django.core.exceptions import ObjectDoesNotExist
from django.core.exceptions import ValidationError
from django.db import transaction
from django.db.models import Max
from django.utils import timezone
from registrasion import models as rego
from registrasion.exceptions import CartValidationError
from category import CategoryController
from conditions import ConditionController
from product import ProductController
class CartController(object):
def __init__(self, cart):
self.cart = cart
@classmethod
def for_user(cls, user):
''' Returns the user's current cart, or creates a new cart
if there isn't one ready yet. '''
try:
existing = rego.Cart.objects.get(user=user, active=True)
except ObjectDoesNotExist:
existing = rego.Cart.objects.create(
user=user,
time_last_updated=timezone.now(),
reservation_duration=datetime.timedelta(),
)
existing.save()
return cls(existing)
def extend_reservation(self):
''' Updates the cart's time last updated value, which is used to
determine whether the cart has reserved the items and discounts it
holds. '''
reservations = [datetime.timedelta()]
# If we have vouchers, we're entitled to an hour at minimum.
if len(self.cart.vouchers.all()) >= 1:
reservations.append(rego.Voucher.RESERVATION_DURATION)
# Else, it's the maximum of the included products
items = rego.ProductItem.objects.filter(cart=self.cart)
agg = items.aggregate(Max("product__reservation_duration"))
product_max = agg["product__reservation_duration__max"]
if product_max is not None:
reservations.append(product_max)
self.cart.time_last_updated = timezone.now()
self.cart.reservation_duration = max(reservations)
def end_batch(self):
''' Performs operations that occur occur at the end of a batch of
product changes/voucher applications etc.
THIS SHOULD BE PRIVATE
'''
self.recalculate_discounts()
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)
for product, quantity in product_quantities:
product_item = rego.ProductItem.objects.get(
cart=self.cart,
product=product,
product_item.quantity = quantity
product_item.save()
rego.ProductItem.objects.create(
quantity=quantity,
items_in_cart.filter(quantity=0).delete()
self.end_batch()
def _test_limits(self, product_quantities):
''' Tests that the quantity changes we intend to make do not violate
the limits and enabling conditions imposed on the products. '''
errors = []
# Test each product limit here
if quantity < 0:
# TODO: batch errors
raise ValidationError("Value must be zero or greater.")
errors.append((product, "Value must be zero or greater."))
prod = ProductController(product)
limit = prod.user_quantity_remaining(self.cart.user)
if quantity > limit:
raise ValidationError(
errors.append((
product,
"You may only have %d of product: %s" % (
limit, product.name,
limit, product,
))
# Collect by category
by_cat = collections.defaultdict(list)
by_cat[product.category].append((product, quantity))
# Test each category limit here
for cat in by_cat:
ctrl = CategoryController(cat)
for category in by_cat:
ctrl = CategoryController(category)
limit = ctrl.user_quantity_remaining(self.cart.user)
# Get the amount so far in the cart
to_add = sum(i[1] for i in by_cat[cat])
to_add = sum(i[1] for i in by_cat[category])
if to_add > limit:
category,
"You may only have %d items in category: %s" % (
limit, cat.name,
limit, category.name,
# Test the enabling conditions
errs = ConditionController.test_enabling_conditions(
self.cart.user,
product_quantities=product_quantities,
if errs:
raise ValidationError("An enabling condition failed")
errors.append(
("enabling_conditions", "An enabling condition failed")
if errors:
raise CartValidationError(errors)
def apply_voucher(self, voucher_code):
''' Applies the voucher with the given code to this cart. '''
# 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,
released=False,
vouchers=voucher,
if len(user_carts_with_voucher) > 0:
raise ValidationError("You have already entered this voucher.")
# If successful...
self.cart.vouchers.add(voucher)
def validate_cart(self):
''' Determines whether the status of the current cart is valid;
this is normally called before generating or paying an invoice '''
# TODO: validate vouchers
product_quantities = list((i.product, i.quantity) for i in items)
self._test_limits(product_quantities)
# Validate the discounts
discount_items = rego.DiscountItem.objects.filter(cart=self.cart)
seen_discounts = set()
for discount_item in discount_items:
discount = discount_item.discount
if discount in seen_discounts:
continue
seen_discounts.add(discount)
real_discount = rego.DiscountBase.objects.get_subclass(
pk=discount.pk)
cond = ConditionController.for_condition(real_discount)
if not cond.is_met(self.cart.user):
raise ValidationError("Discounts are no longer available")
def recalculate_discounts(self):
''' Calculates all of the discounts available for this product.
NB should be transactional, and it's terribly inefficient.
# Delete the existing entries.
rego.DiscountItem.objects.filter(cart=self.cart).delete()
product_items = self.cart.productitem_set.all()
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 = 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. '''
if isinstance(discount.clause, rego.DiscountForCategory):
return discount.clause.category == product.category
else:
return discount.clause.product == product
def value(discount):
''' Returns the value of this discount clause
as applied to this product '''
if discount.clause.percentage is not None:
return discount.clause.percentage * product.price
return discount.clause.price