core.clj

(ns brave.core
  (:require [clojure.core.async :as a
             :refer [thread go <! >! <!! >!! put! take! chan go-loop alts! timeout close!]]))


;; -== From brave clojure ==- 
(defn hotdog-machine
  "A hotdog vending machine returns a vector
  with two channels: input and output. Money
  should be deposited into the input channel 
  and the output channel will be used for 
  delivery."
  [hotdogs]
  (let [in  (chan)
        out (chan)]
    (go-loop [dogs hotdogs]
      (if (< 0 dogs)
        (let [deposit (<! in)]
          (if (= 3 deposit)
            (do
              (>! out :hotdog)
              (recur (dec dogs)))
            (do
              (>! out deposit)
              (recur dogs))))
        (do
          (close! in)
          (close! out))))
    [in out]))

;; -== My Experiments ==- 


(defn follow!
  "Follows orders received on the orders channel.
  Echoes each command with the name of the subordinate then takes some
  time to accomplish it before actioning the next command."
  [orders subordinate task-delay]
  (let [in (chan)]
    ;; follow orders
    (a/tap orders in)

    ;; execute
    (go-loop [n 1]
      (when-let [comm (<! in)]
        (let [ack (str n "-" subordinate " " comm ", aye!")]
          (println ack)
          (Thread/sleep (* task-delay 3))
          (recur (inc n)))))
    in))

(def captain
  "This channel is where the orders to the crew go in"
  (chan 10))

(def orders
  "This is the order multiplexer that allows one order
  from the captain to be delivered to multiple subordinates"
  (a/mult captain))

(def xo
  "The executive officer just repeats orders, so there is very
  little delay."
  (follow! orders :xo 1))

(def cob
  "The chief of the boat actually does stuff, so it takes him
  a little longer before he's ready to perform the next task."
  (follow! orders :chief 1000))

(defn give-orders!
  "Puts orders on a channel"
  [ch]
  (a/onto-chan ch [:dive :all-ahead-flank :make-your-depth-60-meters :all-ahead-stop]))

(defn -main
  "Application entry point"
  [& args]
  (give-orders! captain))