shen-tian

(def firebase-push-id!
    (let [last-push-time (atom nil)
          saved-random   (atom nil)]
      (fn firebase-push-id-inner
        ([] (firebase-push-id-inner nil))
        ([millis]
         (locking last-push-time
           (let [push-chars  "-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz"
                 now         (or millis (.getTime (js/Date.)))
                 duplicate?  (= now @last-push-time)