queue.cljs

(ns hack.queue)

(defn log [form]
  (.log js/console (pr-str form)))

(defprotocol Queue
  (pop [this])
  (empty? [this])
  (peek [this])
  (append [this x]))

(defn make-queue []
  (let [q (atom [])]
    (reify Queue
      (pop [this]
        (let [x (first @q)]
          (swap! q (fn [v] (vec (next v))))
          x))
      (peek [this]
        (first @q))
      (empty? [this]
        (not (boolean (seq @q))))
      (append [this x]
        (swap! q conj x)))))

(comment
  
  (def queue (make-queue))
  
  (append queue "Hello")
  (peek queue)
  (empty? queue)
  (pop queue)
  (empty? queue)
  )

;; Loop

(defprotocol Loop
  (start [this])
  (continue [this])
  (stop [this]))

(defn make-loop [poll process queue]
  (let [state (atom {:running false
                     :timeout nil})]
    (reify Loop
      
      (start [this]
        (swap! state assoc-in [:running] true)
        (continue this))
      
      (continue [this]
        (when (:running @state)
          (when (:timeout @state)
            (.clearTimeout js/window (:timeout @state))
            (swap! state assoc-in [:timeout] nil))
          (poll queue)
          (if-not (empty? queue)
            (do (process (pop queue))
                (swap! state assoc-in [:timeout] (.setTimeout js/window (fn [] (continue this)) 10)))
            (swap! state assoc-in [:timeout] (.setTimeout js/window (fn [] (continue this)) 1000)))))
      
      (stop [this]
        (swap! state assoc-in [:running] false)))))

(defn process-next-message [msg]
  (log "processing next message...")
  (log msg))

(defn poll [queue]
  (log "Polling...")
  (log queue))

(comment
  
  (def loop (make-loop poll process-next-message queue))
  (start loop)
  (append queue "Hello")
  (stop loop)
  )