Merge pull request #1 from j0ni/agents

Agents

.gitignore

@@ -0,0 +1,2 @@
+target/
+.nrepl-port

src/chat_server/core.clj

@@ -1,41 +1,95 @@
 (ns chat-server.core
  (:require [clj-sockets.core :as socket]
- [chat-server.repl :as repl])
+ [chat-server.repl :as repl]
+ [clojure.string :as string])
  (:gen-class))
 
-(def clients (ref {}))
+(def clients (ref []))
 
+(defn write-line
+ "Write a single message to a client, returning the client."
+ [client message]
+ (socket/write-line (:socket client) message)
+ client)
 
-(defn serve-client
- [nick client]
- (doseq [line (socket/read-lines client)]
- (println "got message from user:" line)
- (let [other-clients (vals (dissoc @clients nick))]
- (case
- (first (clojure.string/split line #" "))
- ;; Instructor Note: explain why a doall is needed here
- "MSG" (doall (map #(socket/write-line % (str nick ": " (subs line 4))) other-clients))
+(defn error
+ "Write an error to a socket, returning nil."
+ [socket message]
+ (socket/write-line socket (str "ERROR: " message)))
 
- ;;TODO: Process other kinds of command here
+(defn nick-exists?
+ "Return truthy if a nick is already in use, otherwise nil."
+ [nick]
+ (let [nicks (map #(-> % deref :nick) @clients)]
+ (some #{nick} nicks)))
 
- ;; else
- (socket/write-line client "ERROR: I don't understand")))))
+(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 new-client
+(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]
+ (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 [command (socket/read-line client)]
- (println "got message:" command)
- (if-let [[_ nick] (re-matches #"USER (.*)" command)]
- ;; Instructor note: explain why we have to use a transaction here to make sure checking if user exists and adding them happens atomically
- (if (dosync
- (when-not (get @clients nick)
- (alter clients assoc nick client)))
-
- (serve-client nick client)
-
- (do
- (socket/write-line client "ERROR: Nick already taken")
- (socket/close-socket client))))))
+ (let [{:keys [socket nick channels] :or {channels []}} @client]
+ (loop [line (socket/read-line socket)]
+ (let [[command & words] (string/split line #" ")]
+ (case command
+ "USER" (set-nick client (string/join "-" words))
+ "MSG" (send-message client (string/join " " words))
+ "QUIT" (terminate-client! client)
+ (error socket "I don't understand")))
+ (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 []}
+ :error-mode :continue
+ :error-handler handle-client-error)]
+ (alter clients conj client)
+ client)))]
+ (listen-client client)
+ (do (error s "nick is already taken, try another")
+ (recur (socket/read-line s))))
+ (do (error s "first set a nick with USER")
+ (recur (socket/read-line s))))))
 
 (defn -main
  "The hello world of chat servers"