gistfile1.clj

(:use [ring.util.codec :only [url-encode]])

(def utmac  "MO-XXXXXXXX-X") ;; Use MO instead of UA

(defn- new-uuid []
      (java.util.UUID/randomUUID))

(defn md5
  "Generate a md5 checksum for the given string"
  [token]
  (let [hash-bytes
         (doto (java.security.MessageDigest/getInstance "MD5")
               (.reset)
               (.update (.getBytes token)))]
       (.toString
         (new java.math.BigInteger 1 (.digest hash-bytes)) ; Positive and the size of the number
         16)))

(defn- visitor-id 
  []
  (let [message (str "Java" (new-uuid))
        md5-string (md5 message)]
    (str "0x" (subs md5-string 0 16))))

(defn- make-query-string [m]
  (->> (for [[k v] m]
         (str (url-encode k) "=" (url-encode (str v))))
       (interpose "&")
       (apply str)))

(defn make-ga-url [utmp ip]
  (let [gif-url "http://www.google-analytics.com/__utm.gif?"
        url-map (atom {})
          add-key (fn [k v]
                      (swap! url-map assoc (name k) v))]
      (add-key :utmac )
      (add-key :utmn (rand-int 0x7fffffff))
      (add-key :utmr "-")
      (add-key :utmp utmp)
      (add-key :utmdebug 1)
      (add-key :guid "ON")
      (add-key :utmwv "4.4sh")
      (add-key :utmcc "__utma=999.999.999.999.999.1")
      (add-key :utmvid (visitor-id))
      (add-key :utmip ip)
      (str gif-url (make-query-string @url-map))))

(defn wrap-ga
  [handler]
  (fn [request]    
   (let [utmp  (str (:uri request) "?" (:query-string request))
         ip (:remote-addr request)
         url (make-ga-url utmp ip)]
     (slurp url)
     (handler request))))