295 lines
9.3 KiB
Python
295 lines
9.3 KiB
Python
import itertools
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from django.db.models import Case
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from django.db.models import F, Q
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from django.db.models import Sum
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from django.db.models import Value
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from django.db.models import When
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from django.utils import timezone
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from registrasion.models import commerce
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from registrasion.models import conditions
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from registrasion.models import inventory
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_BIG_QUANTITY = 99999999 # A big quantity
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class ConditionController(object):
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''' Base class for testing conditions that activate Flag
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or Discount objects. '''
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def __init__(self, condition):
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self.condition = condition
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@staticmethod
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def _controllers():
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return {
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conditions.CategoryFlag: CategoryConditionController,
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conditions.IncludedProductDiscount: ProductConditionController,
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conditions.ProductFlag: ProductConditionController,
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conditions.TimeOrStockLimitDiscount:
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TimeOrStockLimitDiscountController,
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conditions.TimeOrStockLimitFlag:
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TimeOrStockLimitFlagController,
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conditions.VoucherDiscount: VoucherConditionController,
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conditions.VoucherFlag: VoucherConditionController,
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}
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@staticmethod
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def for_type(cls):
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return ConditionController._controllers()[cls]
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@staticmethod
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def for_condition(condition):
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try:
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return ConditionController.for_type(type(condition))(condition)
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except KeyError:
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return ConditionController()
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@classmethod
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def pre_filter(cls, queryset, user):
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''' Returns only the flag conditions that might be available for this
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user. It should hopefully reduce the number of queries that need to be
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executed to determine if a flag is met.
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If this filtration implements the same query as is_met, then you should
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be able to implement ``is_met()`` in terms of this.
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Arguments:
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queryset (Queryset[c]): The canditate conditions.
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user (User): The user for whom we're testing these conditions.
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Returns:
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Queryset[c]: A subset of the conditions that pass the pre-filter
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test for this user.
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'''
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# Default implementation does NOTHING.
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return queryset
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def passes_filter(self, user):
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''' Returns true if the condition passes the filter '''
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cls = type(self.condition)
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qs = cls.objects.filter(pk=self.condition.id)
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return self.condition in self.pre_filter(qs, user)
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def user_quantity_remaining(self, user, filtered=False):
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''' Returns the number of items covered by this flag condition the
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user can add to the current cart. This default implementation returns
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a big number if is_met() is true, otherwise 0.
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Either this method, or is_met() must be overridden in subclasses.
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'''
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return _BIG_QUANTITY if self.is_met(user, filtered) else 0
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def is_met(self, user, filtered=False):
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''' Returns True if this flag condition is met, otherwise returns
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False.
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Either this method, or user_quantity_remaining() must be overridden
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in subclasses.
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Arguments:
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user (User): The user for whom this test must be met.
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filter (bool): If true, this condition was part of a queryset
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returned by pre_filter() for this user.
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'''
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return self.user_quantity_remaining(user, filtered) > 0
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class IsMetByFilter(object):
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def is_met(self, user, filtered=False):
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''' Returns True if this flag condition is met, otherwise returns
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False. It determines if the condition is met by calling pre_filter
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with a queryset containing only self.condition. '''
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if filtered:
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return True # Why query again?
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return self.passes_filter(user)
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class RemainderSetByFilter(object):
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def user_quantity_remaining(self, user, filtered=True):
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''' returns 0 if the date range is violated, otherwise, it will return
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the quantity remaining under the stock limit.
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The filter for this condition must add an annotation called "remainder"
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in order for this to work.
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'''
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if filtered:
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if hasattr(self.condition, "remainder"):
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return self.condition.remainder
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# Mark self.condition with a remainder
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qs = type(self.condition).objects.filter(pk=self.condition.id)
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qs = self.pre_filter(qs, user)
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if len(qs) > 0:
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return qs[0].remainder
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else:
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return 0
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class CategoryConditionController(IsMetByFilter, ConditionController):
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@classmethod
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def pre_filter(self, queryset, user):
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''' Returns all of the items from queryset where the user has a
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product from a category invoking that item's condition in one of their
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carts. '''
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items = commerce.ProductItem.objects.filter(cart__user=user)
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items = items.exclude(cart__status=commerce.Cart.STATUS_RELEASED)
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items = items.select_related("product", "product__category")
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categories = [item.product.category for item in items]
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return queryset.filter(enabling_category__in=categories)
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class ProductConditionController(IsMetByFilter, ConditionController):
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''' Condition tests for ProductFlag and
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IncludedProductDiscount. '''
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@classmethod
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def pre_filter(self, queryset, user):
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''' Returns all of the items from queryset where the user has a
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product invoking that item's condition in one of their carts. '''
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items = commerce.ProductItem.objects.filter(cart__user=user)
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items = items.exclude(cart__status=commerce.Cart.STATUS_RELEASED)
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items = items.select_related("product", "product__category")
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products = [item.product for item in items]
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return queryset.filter(enabling_products__in=products)
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class TimeOrStockLimitConditionController(
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RemainderSetByFilter,
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ConditionController,
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):
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''' Common condition tests for TimeOrStockLimit Flag and
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Discount.'''
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@classmethod
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def pre_filter(self, queryset, user):
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''' Returns all of the items from queryset where the date falls into
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any specified range, but not yet where the stock limit is not yet
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reached.'''
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now = timezone.now()
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# Keep items with no start time, or start time not yet met.
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queryset = queryset.filter(Q(start_time=None) | Q(start_time__lte=now))
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queryset = queryset.filter(Q(end_time=None) | Q(end_time__gte=now))
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# Filter out items that have been reserved beyond the limits
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quantity_or_zero = self._calculate_quantities(user)
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remainder = Case(
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When(limit=None, then=Value(_BIG_QUANTITY)),
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default=F("limit") - Sum(quantity_or_zero),
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)
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queryset = queryset.annotate(remainder=remainder)
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queryset = queryset.filter(remainder__gt=0)
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return queryset
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@classmethod
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def _relevant_carts(cls, user):
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reserved_carts = commerce.Cart.reserved_carts()
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reserved_carts = reserved_carts.exclude(
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user=user,
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status=commerce.Cart.STATUS_ACTIVE,
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)
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return reserved_carts
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class TimeOrStockLimitFlagController(
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TimeOrStockLimitConditionController):
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@classmethod
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def _calculate_quantities(cls, user):
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reserved_carts = cls._relevant_carts(user)
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# Calculate category lines
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item_cats = F('categories__product__productitem__product__category')
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reserved_category_products = (
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Q(categories=item_cats) &
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Q(categories__product__productitem__cart__in=reserved_carts)
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)
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# Calculate product lines
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reserved_products = (
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Q(products=F('products__productitem__product')) &
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Q(products__productitem__cart__in=reserved_carts)
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)
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category_quantity_in_reserved_carts = When(
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reserved_category_products,
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then="categories__product__productitem__quantity",
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)
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product_quantity_in_reserved_carts = When(
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reserved_products,
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then="products__productitem__quantity",
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)
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quantity_or_zero = Case(
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category_quantity_in_reserved_carts,
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product_quantity_in_reserved_carts,
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default=Value(0),
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)
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return quantity_or_zero
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class TimeOrStockLimitDiscountController(TimeOrStockLimitConditionController):
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@classmethod
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def _calculate_quantities(cls, user):
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reserved_carts = cls._relevant_carts(user)
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quantity_in_reserved_carts = When(
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discountitem__cart__in=reserved_carts,
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then="discountitem__quantity"
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)
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quantity_or_zero = Case(
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quantity_in_reserved_carts,
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default=Value(0)
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)
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return quantity_or_zero
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class VoucherConditionController(IsMetByFilter, ConditionController):
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''' Condition test for VoucherFlag and VoucherDiscount.'''
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@classmethod
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def pre_filter(self, queryset, user):
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''' Returns all of the items from queryset where the user has entered
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a voucher that invokes that item's condition in one of their carts. '''
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carts = commerce.Cart.objects.filter(
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user=user,
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)
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vouchers = [cart.vouchers.all() for cart in carts]
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return queryset.filter(voucher__in=itertools.chain(*vouchers))
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