The Bike Rental Code

bikes.clj

(ns bikes.core
  (:gen-class)
  (:require [clj-time.core :as t]))

(defrecord Bike [model price id])
(defrecord Store [bikes currentRentals rentHistory])
(defrecord Rental [bikeId rentedOn returnedOn rent])

(defn find-rental-for-bike
  [store bike]
  (first (filter (fn [history] (= (.id bike) (.bikeId history))) (.currentRentals store))))

(defn get-bike
  [allBikes bikeId]
  (first (filter (fn [bike] (= (.id bike) bikeId)) allBikes)))

(defn do-rent
  [store bike]
  (let [otherBikes (filter (fn [b] (not= b bike)) (.bikes store))
        newRentals (conj (.currentRentals store) (Rental. (.id bike) (t/now) nil 0))]
    (Store. otherBikes newRentals (.rentHistory store))))

(defn find-cost
  [bike rentedOn returnedOn]
  (* (t/in-days (t/interval rentedOn returnedOn)) (.price bike)))

(defn do-return
  [store bike]
  (let [rental (find-rental-for-bike store bike)
        returnDate (t/now)
        returnedRental (Rental. (.bikeId rental) (.rentedOn rental) returnDate (find-cost bike (.rentedOn rental) returnDate))
        newCurrentRentals (filter (fn [r] (not= r rental)) (.currentRentals store))
        newBikes (conj (.bikes store) (first (filter (fn [rental] (= (.bikeId rental) (.id bike))) (.currentRentals store))))
        newHistory (conj (.rentHistory store) returnedRental)]
    (Store. newBikes newCurrentRentals newHistory)))

(defn -main
  [& args]
  (let [bikes [(Bike. "Thunderbird 350" 1000 1)
               (Bike. "Classic 500" 900 2)
               (Bike. "Himalayan" 1000 3)]
        store (Store. bikes [] [])
        bike (get-bike bikes 1)
        store1 (do-rent store bike)
        bike2 (get-bike bikes 2)
        store2 (do-rent store1 bike2)
        store3 (do-return store2 bike2)
        store4 (do-return store3 bike)]
    (do (println store1)
        (println store2)
        (println store3)
        (println store4))))