nth auth code in clojure

;;;
;;; auth.clj
;;;
;;; Perform various miracles involving OAuth authentication.
;;;
;;; Looks for a serialized oauth object.  If it finds one, returns
;;; an object of type Twitter to the caller.  If it doesn't find one,
;;; it sends the user off to twitter for a pin, accepts the pin,
;;; serializes the object, and returns Twitter to the caller (I think).
;;;
;;; Fails catastrophically if you screw up the pin.  Checks that the pin
;;; is seven digits (which might not be carved in stone).
;;;
;;; Written and maintained by Stephen Ramsay
;;;
;;; Last Modified: Wed Mar 17 23:49:56 CDT 2010

(ns gropius.sramsay.nth
  (:import
     (twitter4j Twitter)
     (twitter4j TwitterFactory)
     (twitter4j.http RequestToken)
     (twitter4j.http AccessToken)

     (java.io File)
     (java.io InputStream)
     (java.io BufferedReader)
     (java.io FileOutputStream)
     (java.io FileInputStream)
     (java.io ObjectOutputStream)
     (java.io ObjectInputStream)
     (java.io InputStreamReader)))

(System/setProperty "twitter4j.oauth.consumerKey" "SECRET STUFF")
(System/setProperty "twitter4j.oauth.consumerSecret" "MORE SECRET STUFF")

(def twitter (.getInstance (new TwitterFactory)))

;;
;; Magical serialization functions
;;

(defn serialize [object filename]
  (let [os (new FileOutputStream filename)]
    (with-open [oo (new ObjectOutputStream os)]
      (.writeObject oo object))))

(defn deserialize [filename]
  (let [is (new FileInputStream filename)]
    (with-open [oi (new ObjectInputStream is)]
      (cast twitter4j.http.AccessToken (.readObject oi)))))

;;
;; Sort out authentication
;;

(defn get-auth []
  (if (.exists (new File "oauth.ser")) ; If we have a serialized OAuth object
    (.setOAuthAccessToken twitter (deserialize "oauth.ser")) ; Go with that.
    (do ; Otherwise, give the user a URL and have them give you the pin
      (def request_token (.getOAuthRequestToken twitter))
      (println "Open the following URL to grant this program access to your account.")
      (println (.getAuthorizationURL request_token))
      (println "After doing that, you may enter your PIN: ")
      (def pin (read-line))
      (if (re-matches #"[0-9]{7}" pin) ; 7-digit number, right?
        (do
          (serialize (.getOAuthAccessToken twitter request_token pin) "oauth.ser")
        (do
          (println "That pin doesn't seem to be correct.") ; Should do something
          (System/exit 0))))))                             ; nicer here
  twitter) ; Return the twitter object