jit-memoize.clj

(defn jit-memoize [query-fn]
  (let [cache-agent (agent {})]
    (letfn
        [(add-listener [queries parameter callback]
           (if-let [listeners (queries parameter)]
             (assoc queries parameter
                    (cons callback listeners))
             (add-query queries parameter callback)))
         (add-query [queries parameter callback]
           (future (send cache-agent
                         deliver-result parameter
                         (try (query-fn parameter)
                              (catch Exception e
                                [::error e]))))
           (assoc queries parameter (cons callback nil)))
         (deliver-result [queries parameter value]
           (future-call
            dorun (map #(try (% value)
                             (catch Exception e
                               (log/error e "When delivering result" value
                                          "for (" query-fn parameter ")")))
                       (queries parameter)))
           (dissoc queries parameter))]
      (fn query
        ([parameter]
           (let [result (promise)]
             (query parameter
                    #(deliver result %)
                    #(deliver result [::error %]))
             (match @result
                    [::error ex] (throw ex)
                    val val)))
        ([parameter on-result on-error]
           (send cache-agent add-listener parameter
                 #(match %
                         [::error ex] (on-error ex)
                         val (on-result)))
           nil)))))