294 lines
10 KiB
Python
294 lines
10 KiB
Python
import collections
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import datetime
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import discount
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import itertools
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from django.core.exceptions import ObjectDoesNotExist
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from django.core.exceptions import ValidationError
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from django.db import transaction
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from django.db.models import Max, Sum
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from django.utils import timezone
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from registrasion import models as rego
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from category import CategoryController
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from conditions import ConditionController
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from product import ProductController
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class CartController(object):
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def __init__(self, cart):
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self.cart = cart
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@classmethod
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def for_user(cls, user):
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''' Returns the user's current cart, or creates a new cart
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if there isn't one ready yet. '''
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try:
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existing = rego.Cart.objects.get(user=user, active=True)
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except ObjectDoesNotExist:
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existing = rego.Cart.objects.create(
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user=user,
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time_last_updated=timezone.now(),
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reservation_duration=datetime.timedelta(),
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)
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existing.save()
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return cls(existing)
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def extend_reservation(self):
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''' Updates the cart's time last updated value, which is used to
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determine whether the cart has reserved the items and discounts it
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holds. '''
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reservations = [datetime.timedelta()]
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# If we have vouchers, we're entitled to an hour at minimum.
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if len(self.cart.vouchers.all()) >= 1:
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reservations.append(rego.Voucher.RESERVATION_DURATION)
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# Else, it's the maximum of the included products
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items = rego.ProductItem.objects.filter(cart=self.cart)
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agg = items.aggregate(Max("product__reservation_duration"))
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product_max = agg["product__reservation_duration__max"]
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if product_max is not None:
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reservations.append(product_max)
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self.cart.time_last_updated = timezone.now()
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self.cart.reservation_duration = max(reservations)
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def end_batch(self):
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''' Performs operations that occur occur at the end of a batch of
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product changes/voucher applications etc.
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THIS SHOULD BE PRIVATE
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'''
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self.recalculate_discounts()
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self.extend_reservation()
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self.cart.revision += 1
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self.cart.save()
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@transaction.atomic
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def set_quantities(self, product_quantities):
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''' Sets the quantities on each of the products on each of the
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products specified. Raises an exception (ValidationError) if a limit
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is violated. `product_quantities` is an iterable of (product, quantity)
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pairs. '''
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items_in_cart = rego.ProductItem.objects.filter(cart=self.cart)
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product_quantities = list(product_quantities)
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# n.b need to add have the existing items first so that the new
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# items override the old ones.
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all_product_quantities = dict(itertools.chain(
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((i.product, i.quantity) for i in items_in_cart.all()),
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product_quantities,
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)).items()
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# Validate that the limits we're adding are OK
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self._test_limits(all_product_quantities)
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for product, quantity in product_quantities:
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try:
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product_item = rego.ProductItem.objects.get(
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cart=self.cart,
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product=product,
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)
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product_item.quantity = quantity
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product_item.save()
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except ObjectDoesNotExist:
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rego.ProductItem.objects.create(
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cart=self.cart,
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product=product,
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quantity=quantity,
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)
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items_in_cart.filter(quantity=0).delete()
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self.end_batch()
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def _test_limits(self, product_quantities):
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''' Tests that the quantity changes we intend to make do not violate
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the limits and enabling conditions imposed on the products. '''
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# Test each product limit here
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for product, quantity in product_quantities:
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if quantity < 0:
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# TODO: batch errors
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raise ValidationError("Value must be zero or greater.")
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prod = ProductController(product)
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limit = prod.user_quantity_remaining(self.cart.user)
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if quantity > limit:
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# TODO: batch errors
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raise ValidationError(
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"You may only have %d of product: %s" % (
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limit, product.name,
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)
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)
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# Collect by category
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by_cat = collections.defaultdict(list)
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for product, quantity in product_quantities:
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by_cat[product.category].append((product, quantity))
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# Test each category limit here
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for cat in by_cat:
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ctrl = CategoryController(cat)
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limit = ctrl.user_quantity_remaining(self.cart.user)
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# Get the amount so far in the cart
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to_add = sum(i[1] for i in by_cat[cat])
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if to_add > limit:
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# TODO: batch errors
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raise ValidationError(
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"You may only have %d items in category: %s" % (
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limit, cat.name,
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)
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)
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# Test the enabling conditions
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errs = ConditionController.test_enabling_conditions(
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self.cart.user,
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product_quantities=product_quantities,
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)
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if errs:
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# TODO: batch errors
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raise ValidationError("An enabling condition failed")
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def apply_voucher(self, voucher_code):
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''' Applies the voucher with the given code to this cart. '''
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# Is voucher exhausted?
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active_carts = rego.Cart.reserved_carts()
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# Try and find the voucher
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voucher = rego.Voucher.objects.get(code=voucher_code.upper())
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# It's invalid for a user to enter a voucher that's exhausted
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carts_with_voucher = active_carts.filter(vouchers=voucher)
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if len(carts_with_voucher) >= voucher.limit:
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raise ValidationError("This voucher is no longer available")
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# It's not valid for users to re-enter a voucher they already have
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user_carts_with_voucher = rego.Cart.objects.filter(
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user=self.cart.user,
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released=False,
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vouchers=voucher,
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)
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if len(user_carts_with_voucher) > 0:
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raise ValidationError("You have already entered this voucher.")
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# If successful...
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self.cart.vouchers.add(voucher)
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self.end_batch()
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def validate_cart(self):
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''' Determines whether the status of the current cart is valid;
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this is normally called before generating or paying an invoice '''
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is_reserved = self.cart in rego.Cart.reserved_carts()
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# TODO: validate vouchers
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items = rego.ProductItem.objects.filter(cart=self.cart)
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product_quantities = list((i.product, i.quantity) for i in items)
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self._test_limits(product_quantities)
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# Validate the discounts
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discount_items = rego.DiscountItem.objects.filter(cart=self.cart)
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seen_discounts = set()
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for discount_item in discount_items:
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discount = discount_item.discount
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if discount in seen_discounts:
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continue
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seen_discounts.add(discount)
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real_discount = rego.DiscountBase.objects.get_subclass(
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pk=discount.pk)
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cond = ConditionController.for_condition(real_discount)
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if not cond.is_met(self.cart.user):
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raise ValidationError("Discounts are no longer available")
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def recalculate_discounts(self):
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''' Calculates all of the discounts available for this product.
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NB should be transactional, and it's terribly inefficient.
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'''
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# Delete the existing entries.
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rego.DiscountItem.objects.filter(cart=self.cart).delete()
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product_items = self.cart.productitem_set.all()
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products = [i.product for i in product_items]
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discounts = discount.available_discounts(self.cart.user, [], products)
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# The highest-value discounts will apply to the highest-value
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# products first.
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product_items = self.cart.productitem_set.all()
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product_items = product_items.order_by('product__price')
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product_items = reversed(product_items)
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for item in product_items:
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self._add_discount(item.product, item.quantity, discounts)
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def _add_discount(self, product, quantity, discounts):
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''' Applies the best discounts on the given product, from the given
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discounts.'''
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def matches(discount):
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''' Returns True if and only if the given discount apples to
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our product. '''
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if isinstance(discount.clause, rego.DiscountForCategory):
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return discount.clause.category == product.category
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else:
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return discount.clause.product == product
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def value(discount):
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''' Returns the value of this discount clause
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as applied to this product '''
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if discount.clause.percentage is not None:
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return discount.clause.percentage * product.price
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else:
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return discount.clause.price
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discounts = [i for i in discounts if matches(i)]
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discounts.sort(key=value)
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for candidate in reversed(discounts):
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if quantity == 0:
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break
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elif candidate.quantity == 0:
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# This discount clause has been exhausted by this cart
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continue
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# Get a provisional instance for this DiscountItem
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# with the quantity set to as much as we have in the cart
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discount_item = rego.DiscountItem.objects.create(
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product=product,
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cart=self.cart,
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discount=candidate.discount,
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quantity=quantity,
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)
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# Truncate the quantity for this DiscountItem if we exceed quantity
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ours = discount_item.quantity
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allowed = candidate.quantity
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if ours > allowed:
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discount_item.quantity = allowed
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# Update the remaining quantity.
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quantity = ours - allowed
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else:
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quantity = 0
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candidate.quantity -= discount_item.quantity
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discount_item.save()
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