Core.aysnc exercise

burgershop.clj

(ns burgershop
  (:require [clojure.core.async :as a]))

;; This exercise simulates a burger shop.

;; Workers for a burger shop 
;; They take one item from in channel, do some operations (put bun/split bun/etc) and put the result in next channel
;; Running flag for system to stop
(defn w1 [out running?]
  (a/go-loop []
    (a/>! out ["bun" (System/currentTimeMillis)])
    (a/<! (a/timeout 100))
    (if @running?
      (recur)
      (a/close! out))))

(defn w2 [in out]
  (a/go-loop [x (a/<! in)]
    (if x
      (do
        (a/<! (a/timeout 500))
        (a/>! out (conj x "split-bun"))
        (recur (a/<! in)))
      (a/close! out))))

(defn w3 [in out]
  (a/go-loop [x (a/<! in)]
    (if x
      (do
        (a/<! (a/timeout 2000))
        (a/>! out (conj x "put-patty"))
        (recur (a/<! in)))
      (a/close! out))))

(defn w4 [in]
  (a/go-loop [x (a/<! in)]
    (when x
      (println (conj x "assemble-burger") (- (System/currentTimeMillis) (second x)))
      (recur (a/<! in)))))

;; 3 Queues being shared with 4 workers
(defn system [running?]
  (let [q1 (a/chan 1)
        q2 (a/chan 1)
        q3 (a/chan 1)]
    (w1 q1 running?)
    ;; Increase workers for performance
    (dotimes [_ 5]
      (w2 q1 q2))
    (dotimes [_ 20]
      (w3 q2 q3))
    (w4 q3)))

(comment

  (def running? (atom true))
  (system running?)
  (reset! running? false)
  
  )