path.clj

;; "to help support nested routes and mounted applications within applications"

; we have some sub-apps we want to be active at different contexts
(defn blog-app [req] ...)
(defn forum-app [req] ...)
(defn core-app [req] ...)

; a heler function for setting up context keys
(defn in-context [context req]
  (assoc req
    :context context
    :path-info (.substring (:uri req) (.length context))))

; naive implementation
(defn app [{:keys [uri] :as req}]
  (cond
    (.startsWith uri "/blog")
      (blog-app (in-context req "/blog"))
    (.startsWith uri "/forum")
      (forum-app (in-context req "/forum"))
    :else
      (core-app (in-context req ""))))

; extract the pattern
(defn mount [mount-spec]
  (fn [{:keys [uri] :as req}]
    (some
      (fn [[context app]]
        (if (.startsWith uri context)
          (app (in-context req context))))
      mount-spec)))

; mountable apps in current ring architecture
(def app
  (mount
    [["/blog"  blog-app]
     ["/forum" forum-app]
     [""       core-app]]))


;; "application deployment in context"

; our app
(defn app [req] ...)

; middleware to set up context keys
(defn wrap-context [handler context]
  (fn [req]
    (handler (in-context req context))))

; our app deployed in specified context
(def deployed-app
  (-> app
    (wrap-context "/app/context")))