import datetime import discount from django.core.exceptions import ObjectDoesNotExist from django.core.exceptions import ValidationError from django.db.models import Max 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 end_batch(self): ''' Performs operations that occur occur at the end of a batch of product changes/voucher applications etc. ''' self.recalculate_discounts() self.extend_reservation() self.cart.revision += 1 self.cart.save() def set_quantity(self, product, quantity, batched=False): ''' Sets the _quantity_ of the given _product_ in the cart to the given _quantity_. ''' if quantity < 0: raise ValidationError("Cannot have fewer than 0 items in cart.") try: product_item = rego.ProductItem.objects.get( cart=self.cart, product=product) old_quantity = product_item.quantity if quantity == 0: product_item.delete() return except ObjectDoesNotExist: if quantity == 0: return product_item = rego.ProductItem.objects.create( cart=self.cart, product=product, quantity=0, ) old_quantity = 0 # Validate the addition to the cart adjustment = quantity - old_quantity prod = ProductController(product) if not prod.can_add_with_enabling_conditions( self.cart.user, adjustment): raise ValidationError("Not enough of that product left (ec)") if not prod.user_can_add_within_limit(self.cart.user, adjustment): raise ValidationError("Not enough of that product left (user)") product_item.quantity = quantity product_item.save() if not batched: self.end_batch() def add_to_cart(self, product, quantity): ''' Adds _quantity_ of the given _product_ to the cart. Raises ValidationError if constraints are violated.''' try: product_item = rego.ProductItem.objects.get( cart=self.cart, product=product) old_quantity = product_item.quantity except ObjectDoesNotExist: old_quantity = 0 self.set_quantity(product, old_quantity + quantity) 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, 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() 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 items = rego.ProductItem.objects.filter(cart=self.cart) for item in items: # NOTE: 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 if not prod.can_add_with_enabling_conditions( self.cart.user, 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() 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 = 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. ''' 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 else: return discount.clause.price discounts = [i for i in discounts if matches(i)] discounts.sort(key=value) for candidate in reversed(discounts): if quantity == 0: break elif candidate.quantity == 0: # This discount clause has been exhausted by this cart continue # 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( product=product, cart=self.cart, discount=candidate.discount, quantity=quantity, ) # Truncate the quantity for this DiscountItem if we exceed quantity ours = discount_item.quantity allowed = candidate.quantity if ours > allowed: discount_item.quantity = allowed # Update the remaining quantity. quantity = ours - allowed else: quantity = 0 candidate.quantity -= discount_item.quantity discount_item.save()