new file 100644
import datetime
import itertools
from django.core.exceptions import ObjectDoesNotExist
from django.core.exceptions import ValidationError
from django.db.models import Avg, Min, Max, Sum
from django.utils import timezone
from registrasion import models as rego
from conditions import ConditionController
from product import ProductController
class CartController(object):
def __init__(self, cart):
self.cart = cart
@staticmethod
def for_user(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 CartController(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 add_to_cart(self, product, quantity):
''' Adds _quantity_ of the given _product_ to the cart. Raises
ValidationError if constraints are violated.'''
prod = ProductController(product)
# TODO: Check enabling conditions for product for user
if not prod.can_add_with_enabling_conditions(self.cart.user, quantity):
raise ValidationError("Not enough of that product left (ec)")
if not prod.user_can_add_within_limit(self.cart.user, quantity):
raise ValidationError("Not enough of that product left (user)")
# Try to update an existing item within this cart if possible.
product_item = rego.ProductItem.objects.get(
cart=self.cart,
product=product)
product_item.quantity += quantity
product_item = rego.ProductItem.objects.create(
product=product,
quantity=quantity,
product_item.save()
self.recalculate_discounts()
self.extend_reservation()
self.cart.revision += 1
self.cart.save()
def apply_voucher(self, voucher):
''' Applies the given voucher 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()
carts_with_voucher = active_carts.filter(vouchers=voucher)
if len(carts_with_voucher) >= voucher.limit:
raise ValidationError("This voucher is no longer available")
# 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 '''
is_reserved = self.cart in rego.Cart.reserved_carts()
# TODO: validate vouchers
for item in items:
# per-user limits are tested at add time, and are unliklely to change
prod = ProductController(item.product)
# If the cart is not reserved, we need to see if we can re-reserve
quantity = 0 if is_reserved else item.quantity
raise ValidationError("Products are no longer available")
# 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)
quantity = 0 if is_reserved else discount_item.quantity
if not cond.is_met(self.cart.user, quantity):
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()
for item in self.cart.productitem_set.all():
self._add_discount(item.product, item.quantity)
def _add_discount(self, product, quantity):
''' Calculates the best available discounts for this product.
NB this will be super-inefficient in aggregate because discounts will be
re-tested for each product. We should work on that.'''
discounts = prod.available_discounts(self.cart.user)
discounts.sort(key=lambda discount: discount.value)
for discount in reversed(discounts):
if quantity == 0:
break
# Get the count of past uses of this discount condition
# as this affects the total amount we're allowed to use now.
past_uses = rego.DiscountItem.objects.filter(
cart__active=False,
discount=discount.discount,
agg = past_uses.aggregate(Sum("quantity"))
past_uses = agg["quantity__sum"]
if past_uses is None:
past_uses = 0
if past_uses == discount.condition.quantity:
# Get a provisional instance for this DiscountItem
# with the quantity set to as much as we have in the cart
discount_item = rego.DiscountItem.objects.create(
# Truncate the quantity for this DiscountItem if we exceed quantity
ours = discount_item.quantity
allowed = discount.condition.quantity - past_uses
if ours > allowed:
discount_item.quantity = allowed
# Update the remaining quantity.
quantity = ours - allowed
else:
quantity = 0
discount_item.save()