Let's say I want an interceptor that will check a cache for some value args that should already be in the context map. if it exists, the val for that args key should be the response. Otherwise, continue the interceptor chain, and when there is a response cache it.

(def cache (atom {}))

{:enter (fn [{:keys [args] :as ctx}]
          (if (contains? @cache args)
            (chain/terminate ctx)
            ctx))
 :leave (fn [{:keys [response args] :as ctx}]
          (if response
            (do (swap! cache assoc args response) ctx)
            (assoc ctx :response (get @cache))))}