The problem

TextMaster's quest for global domination has prompted us to open a supermarket - we sell only three products:

+--------------|--------------|---------+
| Product Code |     Name     |  Price  |
+--------------|--------------|---------+
|     FR1      |   Fruit tea  |  $3.11  |
|     AP1      |   Apple      |  $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 apple to get a price discount for bulk purchases. If you buy 3 or more apples, 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:

co = Checkout.new(pricing_rules)
co.scan(item)
co.scan(item)
price = co.total

Implement a checkout system that fulfils these requirements in Ruby.

Here are some test data:

Basket: FR1, AP1, FR1, CF1 Total price expected: $22.25 Basket: FR1, FR1 Total price expected: $3.11 Basket: AP1, AP1, FR1, AP1 Total price expected: $16.61

PS: Here at TextMaster, we love specs ;)

Submitting your solution

Please send a zip archive containing your code and any relevant materials in an email along with your resume and motivations to jobs+ror@textmaster.com, please add tech-test@textmaster.com in CC. Please do not put your solutions on GitHub.

The purpose of this test is to verify your abilities to code and see how you architect an application.

Finally, please note that even if you have questions about the test we will not answer them, do what you think is best.