7 languages in 7 weeks, Clojure day 3, sleeping barber

barber.clj

(def cut-count (atom 0))
(def client-count (atom 0))

(def cutting (atom false))
(def client-approaching (atom false))
(def client-queue (atom []))

(defn cut [client-id]
  (reset! cutting true)
  (future
    (Thread/sleep 20)
    (reset! cut-count (inc @cut-count))
    (reset! cutting false)))

(defn incomming-client [queue client-id]
  (if (< (count queue) 3)
    (conj queue client-id)
    queue))

(defn remove-first-client [queue]
  (if (> (count queue) 0)
    (rest queue)
    queue))

(defn cut-next-client []
  (if (and (not @cutting) (> (count @client-queue) 0))
    (let [client-id (first @client-queue)]
      (swap! client-queue remove-first-client)
      (cut client-id))))

(defn queue-clients []
  (if (not @client-approaching)
    (do
      (reset! client-approaching true)
      (future
        (Thread/sleep (+ 10 (rand-int 20)))
        (reset! client-count (inc @client-count))
        (swap! client-queue incomming-client @client-count)
        (reset! client-approaching false)))))

(defn get-time [] (System/currentTimeMillis))
(defn time-up? [start-time] (> (System/currentTimeMillis) (+ start-time 10000)))

(defn start-loop [start-time]
  (println "starting at" start-time)
  (while (not (time-up? start-time))
    (do
      (cut-next-client)
      (queue-clients)))
  (println "time elapsed " (- (get-time) start-time))
  (println "clients cut: " @cut-count ", overall clients: " @client-count))

(start-loop (get-time))