(ns cookie-login
  (:use compojure))

(defn clear-login-token [token-key]
  "Creates an expiration cookie for a given cookie name."
  (set-cookie token-key "dummy"
              :expires "Thu, 01-Jan-1970 00:00:01 GMT"))

(defn handle-request-with-login-token
  "Validates login token, handles request, and updates cookies and session
  repository. If token is invalid or an exception is raised while reading it, 
  the token cookie is expired."
  [handler request expiry token-key token-maker token-reader]
  (if-let [session-info (token-reader (get-in request [:cookies token-key]))]
    (let [response (handler (merge-with merge
                                        request
                                        {:session session-info}))
          ; Session variable priority:
          ; 1) variables set by handler
          ; 2) session variables from token-reader
          ; 3) variables from repository          
          session-map (merge (request :session)
                             session-info
                             (response :session))]
      (merge-with merge
                  response
                  {:session session-map}
                  (token-maker session-info expiry)))
    (merge (handler request)
           (clear-login-token token-key))))

; Default expiration is a week.
(def *default-login-token-expiry* (* 1000 60 60 24 7))
(def *default-login-token-key* :login-token)

(defn with-cookie-login
  "Middleware to support automatic cookie login. Must be placed after 
   the with-session middleware!

   Accepts five configuration options:
   - token-key:
        The cookie name to store the login-token under.
        Defaults to 'login-token'.
   - expiry:
        The number of milliseconds a login token is valid for.
        Defaults to one week.
   - is-logged-in?:        
        Function to apply to request's session map to determine whether to
        process login token or not. If a truthy value is returned,
        then the next handler is called without further processing.
   - token-maker:
        Function to generate new login token from session map and 
        milliseconds until login token expiry.
   - token-reader:
        Function to generate session map from login token. Should return nil
        if login token is invalid.
" 
  [handler options]
  (let [token-key     (or (options :default-token-key) *default-login-token-key*)
        expiry        (or (options :expiry) *default-login-token-expiry*)
        is-logged-in? (options :is-logged-in?)
        token-maker   (options :token-maker)
        token-reader  (options :token-reader)]
    (fn [request]
      (if (or (is-logged-in? (request :session))
              (not (get-in request [:cookies token-key])))
        (handler request)
        (handle-request-with-login-token
          handler
          request
          expiry
          token-key
          token-maker
          token-reader)))))