clojure solution to checkout-kata

core.clj

(ns lean-challenge.core
  (:use [midje.sweet]))

; ==== application core
(defn cost [fruit] 
  ({"b" 150 "a" 100 "p" 100 "m" 100 "c" 75} fruit))

(defn csv-to-col [s]
  (seq (.split s ",")))

(defn discount [fruits]
  (+ 
    (* 20 (quot (count (filter #{"c"} fruits)) 2))
    (* 50 (quot (count (filter #{"m"} fruits)) 2))
    (* 100 (quot (count (filter #{"p"} fruits)) 3))
    (* 100 (quot (count (filter #{"p" "a" "m"} fruits)) 4))
    (* 200 (quot (count fruits) 5))
    (* (cost "b") (quot (count (filter #{"b"} fruits)) 2))))
(defn basket-price [fruits]
  (- (reduce + (map cost fruits)) 
     (discount fruits)))


; === facts about the application
(fact
  (cost "b" ) => 150
  (cost "a" ) => 100
  (cost "c" ) => 75)

(fact "adds up the cost of all fruits in the basket"
      (basket-price '("a" "c" "b")) => 325)

(fact "discount for every two lots of cherries"
      (basket-price '("c" "c")) => (- 150 20)
      (basket-price '("c" "c" "c" "c")) => (- 300 40))
(fact "buy two bananas get one for free"
      (basket-price '("b" "b")) => (cost "b"))
(fact "3 pommes are 200"
      (basket-price '("p" "p" "p")) => 200
      (basket-price '("m" "m")) => 150)
(fact "global discounts"
      (basket-price '("a", "a" "b", "c" "b" "b")) => 375
      (basket-price '("a", "a" "m", "p" )) => 300)
(fact 
  (csv-to-col "a,b,c") => '("a" "b" "c"))



; ===== To run in repl just (use 'lean-challange/core)
; when you're ready for the next client : enter an empty line
(loop [item (read-line) items []]
  (println (basket-price (concat (csv-to-col item) items)))
  (if (empty? item)
    item
    (recur (read-line) (concat (csv-to-col item) items))))