238 lines
8.4 KiB
Python
238 lines
8.4 KiB
Python
import datetime
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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.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 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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@staticmethod
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def for_user(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 CartController(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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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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def set_quantity(self, product, quantity, batched=False):
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''' Sets the _quantity_ of the given _product_ in the cart to the given
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_quantity_. '''
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if quantity < 0:
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raise ValidationError("Cannot have fewer than 0 items in cart.")
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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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old_quantity = product_item.quantity
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if quantity == 0:
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product_item.delete()
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return
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except ObjectDoesNotExist:
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if quantity == 0:
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return
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product_item = rego.ProductItem.objects.create(
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cart=self.cart,
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product=product,
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quantity=0,
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)
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old_quantity = 0
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# Validate the addition to the cart
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adjustment = quantity - old_quantity
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prod = ProductController(product)
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if not prod.can_add_with_enabling_conditions(
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self.cart.user, adjustment):
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raise ValidationError("Not enough of that product left (ec)")
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if not prod.user_can_add_within_limit(self.cart.user, adjustment):
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raise ValidationError("Not enough of that product left (user)")
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product_item.quantity = quantity
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product_item.save()
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if not batched:
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self.end_batch()
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def add_to_cart(self, product, quantity):
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''' Adds _quantity_ of the given _product_ to the cart. Raises
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ValidationError if constraints are violated.'''
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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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old_quantity = product_item.quantity
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except ObjectDoesNotExist:
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old_quantity = 0
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self.set_quantity(product, old_quantity + quantity)
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def apply_voucher(self, voucher):
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''' Applies the given voucher to this cart. '''
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# TODO: is it valid for a cart to re-add a voucher that they have?
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# Is voucher exhausted?
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active_carts = rego.Cart.reserved_carts()
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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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# 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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for item in items:
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# NOTE: per-user limits are tested at add time
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# and are unliklely to change
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prod = ProductController(item.product)
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# If the cart is not reserved, we need to see if we can re-reserve
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quantity = 0 if is_reserved else item.quantity
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if not prod.can_add_with_enabling_conditions(
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self.cart.user, quantity):
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raise ValidationError("Products are no longer available")
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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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quantity = 0 if is_reserved else discount_item.quantity
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if not cond.is_met(self.cart.user, quantity):
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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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# 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)
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def _add_discount(self, product, quantity):
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''' Calculates the best available discounts for this product.
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NB this will be super-inefficient in aggregate because discounts will
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be re-tested for each product. We should work on that.'''
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prod = ProductController(product)
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discounts = prod.available_discounts(self.cart.user)
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discounts.sort(key=lambda discount: discount.value)
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for discount in reversed(discounts):
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if quantity == 0:
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break
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# Get the count of past uses of this discount condition
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# as this affects the total amount we're allowed to use now.
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past_uses = rego.DiscountItem.objects.filter(
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discount=discount.discount,
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)
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agg = past_uses.aggregate(Sum("quantity"))
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past_uses = agg["quantity__sum"]
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if past_uses is None:
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past_uses = 0
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if past_uses == discount.condition.quantity:
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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=discount.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 = discount.condition.quantity - past_uses
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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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discount_item.save()
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