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helo.clj

;; Straighforward
(defn handle-helo
  [session command]
  [(-> session
       (reset-session)
       (assoc :client-host (:domain command)))
   {:code 250 :text (:server-host session)}])

;; State monad style
;; Not sure if command needs to be closed over, though.
(defn handle-helo
  [command]
  (fn [session]
    [{:code 250 :text (:server-host session)}
     (-> session (reset-session) (assoc :client-host (:domain command)))]))

;; This only makes sense if handle-reply returns something useful in this context
(defn handle-helo
  [handle-reply command]
  (fn [session]
    (handle-reply {:code 250 :text (:server-host session)})
    (-> session (reset-session) (assoc :client-host (:domain command)))))

(defn handle-helo
  [session command]
  (-> session
      (reset-session)
      (assoc :client-host (:domain command))
      (assoc :reply {:code 250 :text (:server-host session)})))