from sqlalchemy.sql import desc, func

from models import Location, Order, OrderItem, Product, User


class FatModel:
    @classmethod
    def all(cls):
        return cls.query.all()

    @classmethod
    def amount(cls):
        return cls.query.count()


class FatLocation(Location, FatModel):
    pass


class FatOrder(Order, FatModel):

    # It's hard to add the unique user constraint,
    #  as DISTINCT seems to apply after a GROUP BY and aggregate
    # So DISTINCT ... count(user_id) ... will count all users,
    #  even if they get reduced by the disctinct afterwards.
    @classmethod
    def items_per_order(cls):
        return Order.query.\
            join(OrderItem).\
            group_by(Order.id).\
            with_entities(Order.id, func.count(OrderItem.user_id).label('total'))


class FatUser(User, FatModel):
    pass


class FatOrderItem(OrderItem, FatModel):
    pass


class FatProduct(Product, FatModel):
    @classmethod
    def top4(cls):
        top4 = OrderItem.query\
            .join(Product)\
            .join(Location)\
            .group_by(Product.id)\
            .with_entities(Product.name,
                           Location.name,
                           func.count(Product.id).label('count')
                           )\
            .order_by(desc('count'))\
            .limit(4)
        for top in top4:
            print(top)