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