Exploring core.async, core.match and David Nolens async-tests repository.

debounce.cljs

(defn debounce
  ([source msecs edge]
     (debounce (chan) source msecs edge))
  ([sink source msecs edge]
     (go (loop [state ::init last nil chans [source]]
           (let [[_ timer] chans
                 [v c] (alts! chans)]
             (match [state c edge]
               [::init       source :leading] (do (>! sink v)
                                                  (recur ::debouncing nil (conj chans (timeout msecs))))
               
               [::init       source :falling] (recur ::debouncing v (conj chans (timeout msecs)))

               [::debouncing source _       ] (recur ::debouncing v (conj (pop chans) (timeout msecs)))

               [_            timer  :falling] (do (>! sink last)
                                                  (recur ::init nil (pop chans)))

               [_            timer  :leading] (recur ::init nil (pop chans))))))
     sink))