from registrasion.models import commerce from registrasion.models import inventory from django.db.models import Case from django.db.models import F, Q from django.db.models import Sum from django.db.models import When from django.db.models import Value class AllProducts(object): pass class CategoryController(object): def __init__(self, category): self.category = category @classmethod def available_categories(cls, user, products=AllProducts): ''' Returns the categories available to the user. Specify `products` if you want to restrict to just the categories that hold the specified products, otherwise it'll do all. ''' # STOPGAP -- this needs to be elsewhere tbqh from product import ProductController if products is AllProducts: products = inventory.Product.objects.all().select_related( "category", ) available = ProductController.available_products( user, products=products, ) return set(i.category for i in available) @classmethod def user_remainders(cls, user): ''' Return: Mapping[int->int]: A dictionary that maps the category ID to the user's remainder for that category. ''' categories = inventory.Category.objects.all() cart_filter = ( Q(product__productitem__cart__user=user) & Q(product__productitem__cart__status=commerce.Cart.STATUS_PAID) ) quantity = When( cart_filter, then='product__productitem__quantity' ) quantity_or_zero = Case( quantity, default=Value(0), ) remainder = Case( When(limit_per_user=None, then=Value(99999999)), default=F('limit_per_user') - Sum(quantity_or_zero), ) categories = categories.annotate(remainder=remainder) return dict((cat.id, cat.remainder) for cat in categories)