Some error handling

Author: j0ni

src/chat_server/core.clj

@@ -6,37 +6,50 @@
 
 (def clients (ref []))
 
-(defn write-line [client message]
+(defn write-line
+  "Write a single message to a client, returning the client."
+  [client message]
   (socket/write-line (:socket client) message)
   client)
 
 (defn error
+  "Write an error to a socket, returning nil."
   [socket message]
   (socket/write-line socket (str "ERROR: " message)))
 
 (defn nick-exists?
+  "Return truthy if a nick is already in use, otherwise nil."
   [nick]
   (let [nicks (map #(-> % deref :nick) @clients)]
     (some #{nick} nicks)))
 
-(defn set-nick [client nick]
+(defn set-nick
+  "Set the nick of an existing client. This function is transactional."
+  [client nick]
   (dosync
    (if (nick-exists? nick)
      (error (:socket @client) "nick already exists")
      (send-off client assoc :nick nick))))
 
-(defn send-message [client message]
+(defn send-message
+  "Send a message to all clients but the originating one."
+  [client message]
   (doseq [d-client @clients]
     (when-not (= client d-client)
       (send-off d-client write-line (str (:nick @client) ": " message)))))
 
 (defn terminate-client!
+  "Close the socket and remove the client from the list."
   [client]
-  (socket/close-socket (:socket @client))
-  (dosync
-   (alter clients (partial remove #{client}))))
+  (try
+    (socket/close-socket (:socket @client))
+    (dosync
+     (alter clients (partial remove #{client})))
+    (catch Throwable e
+      (println (.getMessage e)))))
 
 (defn listen-client
+  "Listen for and dispatch incoming messages from a client."
   [client]
   (let [{:keys [socket nick channels] :or {channels []}} @client]
     (loop [line (socket/read-line socket)]
@@ -49,13 +62,27 @@
       (when-not (.isClosed socket)
         (recur (socket/read-line socket))))))
 
+(defn handle-client-error
+  "Handle a client error."
+  [the-agent exception]
+  (let [s (:socket @the-agent)
+        msg (.getMessage exception)]
+    (when-not (.isClosed s)
+      (error s msg))
+    (println msg)
+    (terminate-client! the-agent)))
+
 (defn new-client
+  "Takes a freshly opened socket connection, creates a new client and
+  calls the dispatcher."
   [s]
   (loop [line (socket/read-line s)]
     (if-let [[_ nick] (re-matches #"USER (.*)" line)]
       (if-let [client (dosync
                        (when-not (nick-exists? nick)
-                         (let [client (agent {:socket s :nick nick :channels []})]
+                         (let [client (agent {:socket s :nick nick :channels []}
+                                             :error-mode :continue
+                                             :error-handler handle-client-error)]
                            (alter clients conj client)
                            client)))]
         (listen-client client)