99 lines
3.5 KiB
Python
99 lines
3.5 KiB
Python
import itertools
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from conditions import ConditionController
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from registrasion.models import commerce
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from registrasion.models import conditions
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from django.db.models import Sum
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class DiscountAndQuantity(object):
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def __init__(self, discount, clause, quantity):
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self.discount = discount
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self.clause = clause
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self.quantity = quantity
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def __repr__(self):
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return "(discount=%s, clause=%s, quantity=%d)" % (
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self.discount, self.clause, self.quantity,
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)
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def available_discounts(user, categories, products):
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''' Returns all discounts available to this user for the given categories
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and products. The discounts also list the available quantity for this user,
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not including products that are pending purchase. '''
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# discounts that match provided categories
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category_discounts = conditions.DiscountForCategory.objects.filter(
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category__in=categories
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)
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# discounts that match provided products
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product_discounts = conditions.DiscountForProduct.objects.filter(
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product__in=products
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)
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# discounts that match categories for provided products
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product_category_discounts = conditions.DiscountForCategory.objects.filter(
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category__in=(product.category for product in products)
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)
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# (Not relevant: discounts that match products in provided categories)
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product_discounts = product_discounts.select_related(
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"product",
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"product__category",
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)
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all_category_discounts = category_discounts | product_category_discounts
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all_category_discounts = all_category_discounts.select_related(
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"category",
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)
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# The set of all potential discounts
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potential_discounts = set(itertools.chain(
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product_discounts,
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all_category_discounts,
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))
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discounts = []
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# Markers so that we don't need to evaluate given conditions more than once
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accepted_discounts = set()
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failed_discounts = set()
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for discount in potential_discounts:
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real_discount = conditions.DiscountBase.objects.get_subclass(
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pk=discount.discount.pk,
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)
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cond = ConditionController.for_condition(real_discount)
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# Count the past uses of the given discount item.
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# If this user has exceeded the limit for the clause, this clause
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# is not available any more.
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past_uses = commerce.DiscountItem.objects.filter(
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cart__user=user,
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cart__active=False, # Only past carts count
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cart__released=False, # You can reuse refunded discounts
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discount=real_discount,
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)
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agg = past_uses.aggregate(Sum("quantity"))
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past_use_count = agg["quantity__sum"]
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if past_use_count is None:
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past_use_count = 0
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if past_use_count >= discount.quantity:
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# This clause has exceeded its use count
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pass
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elif real_discount not in failed_discounts:
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# This clause is still available
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if real_discount in accepted_discounts or cond.is_met(user):
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# This clause is valid for this user
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discounts.append(DiscountAndQuantity(
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discount=real_discount,
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clause=discount,
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quantity=discount.quantity - past_use_count,
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))
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accepted_discounts.add(real_discount)
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else:
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# This clause is not valid for this user
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failed_discounts.add(real_discount)
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return discounts
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