example-code-2e/10-dp-1class-func/promotions.py

from decimal import Decimal
from strategy import Order

def fidelity_promo(order: Order) -> Decimal:  # <3>
    """5% discount for customers with 1000 or more fidelity points"""
    if order.customer.fidelity >= 1000:
        return order.total() * Decimal('0.05')
    return Decimal(0)


def bulk_item_promo(order: Order) -> Decimal:
    """10% discount for each LineItem with 20 or more units"""
    discount = Decimal(0)
    for item in order.cart:
        if item.quantity >= 20:
            discount += item.total() * Decimal('0.1')
    return discount


def large_order_promo(order: Order) -> Decimal:
    """7% discount for orders with 10 or more distinct items"""
    distinct_items = {item.product for item in order.cart}
    if len(distinct_items) >= 10:
        return order.total() * Decimal('0.07')
    return Decimal(0)