Our request for global domination has prompted us to open a supermarket - we sell only three products:
FR1 | Fruit tea | £3.11 SR1 | Strawberries | £5.00 CF1 | Coffee | £11.23
Our CEO is a big fan of buy-one-get-one-free offers and of fruit tea. He wants us to add a rule to do this.
The COO, though, likes low prices and wants people buying strawberries to get a price discount for bulk purchases. If you buy 3 or more strawberries, the price should drop to £4.50
Our check-out can scan items in any order, and because the CEO and COO change their minds often, it needs to be flexible regarding our pricing rules.
The interface to our checkout looks like this (shown in Ruby):
co = Checkout.new(pricing_rules)
co.scan(item)
co.scan(item)
price = co.total
Implement a checkout system that fulfils these requirements.
What about configurable discounts?
Global rules (that apply to the whole basket).
Contrasting rules: what to do?
Should one product only be allowed to participate into one rule and only one?
What about rules that are referred to multiple product types? Does this affect how we pass the rules? For example the "meal deal".
Basket: FR1,SR1,FR1,FR1,CF1 Total price expected: £22.45
Basket: FR1,FR1 Total price expected: £3.11
Basket: SR1,SR1,FR1,SR1 Total price expected: £16.61