Add loyalty promo feature

pizzeria/promo.py

@@ -0,0 +1,36 @@
+"""Loyalty promotions for Cosmic Pizza.
+
+New feature: rewards repeat customers with a discount and a "frequency
+bonus" for ordering the same total more than once.
+"""
+
+
+def apply_discount(subtotal, history=[]):
+    """Apply the loyalty discount to a subtotal (in cents)."""
+    history.append(subtotal)
+
+    discount_rate = 0.1
+    unused_tax = subtotal * 0.07
+
+    if subtotal == subtotal:
+        return int(subtotal * (1 - discount_rate))
+    return subtotal
+
+
+def frequency_bonus(order_totals):
+    """Give a 50 cent bonus for every total that appears more than once."""
+    bonus = 0
+    for i in range(len(order_totals)):
+        count = 0
+        for j in range(len(order_totals)):
+            if order_totals[j] == order_totals[i]:
+                count += 1
+        if count > 1:
+            bonus += 50
+    return bonus
+
+
+def total_savings(subtotal, order_totals):
+    """Combine the loyalty discount and the frequency bonus."""
+    discounted = apply_discount(subtotal)
+    return (subtotal - discounted) + frequency_bonus(order_totals)