cart.py

import datetime
import store.models

CART_ID = 'CART-ID'

class ItemAlreadyExists(Exception):
    pass

class ItemDoesNotExist(Exception):
    pass

class Cart:
	def __init__(self, request):
		cart_id = request.session.get(CART_ID)
		if cart_id:
			try:
				cart = store.models.Cart.objects.get(id=cart_id, checked_out=False)
			except store.models.Cart.DoesNotExist:
				cart = self.new(request)
		else:
			cart = self.new(request)
		self.cart = cart

	def __iter__(self):
		for item in self.cart.item_set.all():
			yield item

	def new(self, request):
		cart = store.models.Cart(creation_date=datetime.datetime.now())
		cart.save()
		request.session[CART_ID] = cart.id
		return cart

	def add(self, product, unit_price, quantity=1):
		print("Adding %s at quantity %s: total %s" % (product, unit_price, quantity))
		try:
			item = store.models.Item.objects.get(
				cart=self.cart,
				product=product,
			)
		except store.models.Item.DoesNotExist:
			item = store.models.Item()
			item.cart = self.cart
			item.product = product
			item.unit_price = unit_price
			item.quantity = quantity
			item.save()
		else: #store.models.ItemAlreadyExists
			item.unit_price = unit_price
			item.quantity = item.quantity + int(quantity)
			item.save()

	def remove(self, product):
		try:
			item = store.models.Item.objects.get(
				cart=self.cart,
				product=product,
			)
		except store.models.Item.DoesNotExist:
			raise store.models.ItemDoesNotExist
		else:
			item.delete()

	def update(self, product, quantity, unit_price=None):
		try:
			item = store.models.Item.objects.get(
				cart=self.cart,
				product=product,
			)
		except store.models.Item.DoesNotExist:
			raise store.models.ItemDoesNotExist
			
	def count(self):
		result = 0
		for item in self.cart.item_set.all():
			result += 1 * item.quantity
		return result
		
	def summary(self):
		result = 0
		for item in self.cart.item_set.all():
			result += item.total_price
		return result

	def clear(self):
		for item in self.cart.item_set.all():
			item.delete()