logic.clj

(ns net.higher-order.integration.circuit-breaker.atomic
  (:use net.higher-order.integration.circuit-breaker.states))

(def default-policy (TransitionPolicy 5 5000))
(def initial-state (ClosedState default-policy 0))

(defn make-circuit-breaker 
  ([] (atom initial-state))
  ([s] (atom s)))

(def transition-by!)

(defn wrap-with [f state]
  (fn [& args]
    (let [s (transition-by! on-before-call state)]
      (if (proceed s)
	(try
	 (let [res (apply f args)]
	   (do (transition-by! on-success state)
	       res))
	 (catch Exception e
	   (do
	     (transition-by! on-error state)
	     (throw e))))
	(throw (RuntimeException. "OpenCircuit"))))))

(defn wrap [f]
  (let [state (make-circuit-breaker)]
    [(wrap-with f state) state]))

(defn transition-by! [f state]
  (loop [s @state
	 t (f s)]
    (if (or (identical? s t) 
	    (compare-and-set! state s t))
      t
      (let [s1 @state]
	(recur s1 (f s1))))))