(ns scheduled-agent
  (:import java.util.concurrent.Executors
           java.util.concurrent.TimeUnit)
  (:use clojure.stacktrace))

(defn- runnable-proxy [f]
  (proxy [Runnable] [] (run [] (f))))

(defn scheduled-agent
  [func period init]
  (let [pool  (Executors/newScheduledThreadPool 1)
        r     (ref init)
        pfunc (runnable-proxy (fn []
                                (try
                                 (dosync
                                  (ref-set r (func (ensure r))))
                                 (catch Exception e
                                   (print-stack-trace e 5)))))
        future (.scheduleWithFixedDelay pool pfunc 0 period TimeUnit/SECONDS)]
    {:pool pool
     :data r
     :future future
     :func pfunc
     :period period
     :init init}))

(defn cancel [{f :future}]
  (.cancel f false))

(defn poll [{d :data}]
  @d)