Brainstorming middleware ordering... Wider application though.

gistfile1.clj

;; 0. Given that `app` is a RING handler

;; 1. We have 6 functions: 3 to modify requests, 3 to modify responses

;; 1.1. Request modifiers
(defn modify-request-first [handler]
  (fn [request]
    (println "modify-request-first") ; "println" is a placeholder for real code
    (handler request)))

(defn modify-request-second [handler]
  (fn [request]
    (println "modify-request-second")
    (handler request)))

(defn modify-request-third [handler]
  (fn [request]
    (println "modify-request-third")
    (handler request)))

;; 1.2. Response modifiers
(defn modify-response-first [handler]
  (fn [request]
    (let [response (handler request)]
      (println "modify-response-first")
      response)))

(defn modify-response-second [handler]
  (fn [request]
    (let [response (handler request)]
      (println "modify-response-second")
      response)))

(defn modify-response-third [handler]
  (fn [request]
    (let [response (handler request)]
      (println "modify-response-third")
      response)))

;; 2. We want to get this order at output
; modify-request-first
; modify-request-second
; modify-request-third
; modify-response-first
; modify-response-second
; modify-response-third

;; 3. How function calls should be ordered?

;; 3.1. Request modifiers: outer is first
(def app
  (modify-request-first
    (modify-request-second
      (modify-request-third app))))

;; 3.2. Requires bottom-up order with TF macro
(def app
    (-> app
      modify-request-third
      modify-request-second
      modify-request-first))

;; 3.3. Response modifiers: inner is first
(def app
  (modify-response-third
    (modify-response-second
      (modify-response-first app))))

;; 3.4. Requires top-down order with TF macro
(def app
  (-> app
      modify-response-first
      modify-response-second
      modify-response-third))

;; 4.1. The Full Set ^_^ in wrap-style
(def app
  (modify-response-third
    (modify-response-second
      (modify-response-first
        (modify-request-first
          (modify-request-second
            (modify-request-third app)))))))

;; 4.2. And in TF style
(def app
  (-> app
      modify-request-third
      modify-request-second
      modify-request-first
      modify-response-first
      modify-response-second
      modify-response-third))

;; 5. Conclusion: you cannot order handlers which do both request and response handlings in general case!