/** Simple Chat Server to go with our Trivial Chat Client.
 *
 * Does not implement any form of "anonymous nicknames" - probably
 * a good thing, given how a few people have abused anonymous 
 * chat rooms in the past.
 */
public class ChatServer {
    /** What I call myself in system messages */
    protected final static String CHATMASTER_ID = "ChatMaster";
    /** What goes between any handle and the message */
    protected final static String SEP = ": ";
    /** The Server Socket */
    protected ServerSocket servSock;
    /** The list of my current clients */
    protected ArrayList clients;
    /** Debugging state */
    private boolean DEBUG = false;

    /** Main just constructs a ChatServer, which should never return */
    public static void main(String[] argv) {
        System.out.println("DarwinSys Chat Server 0.1 starting...");
        ChatServer w = new ChatServer(  );
        w.runServer(  );            // should never return.
        System.out.println("**ERROR* Chat Server 0.1 quitting");
    }

    /** Construct (and run!) a Chat Service */
    ChatServer(  ) {
        clients = new ArrayList(  );
        try {
            servSock = new ServerSocket(Chat.PORTNUM);
            System.out.println("DarwinSys Chat Server Listening on port " +
                Chat.PORTNUM);
        } catch(IOException e) {
            log("IO Exception in ChatServer.<init>");
            System.exit(0);
        }
    }

    public void runServer(  ) {
        try {
            while (true) {
                Socket us = servSock.accept(  );
                String hostName = us.getInetAddress().getHostName(  );
                System.out.println("Accepted from " + hostName);
                ChatHandler cl = new ChatHandler(us, hostName);
                synchronized (clients) {
                    clients.add(cl);
                    cl.start(  );
                    if (clients.size(  ) == 1)
                        cl.send(CHATMASTER_ID, 
                    else {
                        cl.send(CHATMASTER_ID, "Welcome! you're the latest of " +
                            clients.size(  ) + " users.");
                    }
                }
            }
        } catch(IOException e) {
            log("IO Exception in runServer: " + e);
            System.exit(0);
        }
    }

    protected void log(String s) {
        System.out.println(s);
    }

    /** Inner class to handle one conversation */
    protected class ChatHandler extends Thread {
        /** The client socket */
        protected Socket clientSock;
        /** BufferedReader for reading from socket */
        protected BufferedReader is;
        /** PrintWriter for sending lines on socket */
        protected PrintWriter pw;
        /** The client's host */
        protected String clientIP;
        /** String handle */
        protected String login;

        /* Construct a Chat Handler */
        public ChatHandler(Socket sock, String clnt) throws IOException {
            clientSock = sock;
            clientIP = clnt;
            is = new BufferedReader(
                new InputStreamReader(sock.getInputStream(  )));
            pw = new PrintWriter(sock.getOutputStream(  ), true);
        }

        /** Each ChatHandler is a Thread, so here's the run(  ) method,
         * which handles this conversation.
         */
        public void run(  ) {
            String line;
            try {
                while ((line = is.readLine(  )) != null) {
                    char c = line.charAt(0);
                    line = line.substring(1);
                    switch (c) {
                    case Chat.CMD_LOGIN:
                        if (!Chat.isValidLoginName(line)) {
                            send(CHATMASTER_ID, "LOGIN " + line + " invalid");
                            log("LOGIN INVALID from " + clientIP);
                            continue;
                        }
                        login = line;
                        broadcast(CHATMASTER_ID, login + 
                            " joins us, for a total of " + 
                            clients.size(  ) + " users");
                        break;
                    case Chat.CMD_MESG:
                        if (login == null) {
                            send(CHATMASTER_ID, "please login first");
                            continue;
                        }
                        int where = line.indexOf(Chat.SEPARATOR);
                        String recip = line.substring(0, where);
                        String mesg = line.substring(where+1);
                        log("MESG: " + login + "-->" + recip + ": "+ mesg);
                        ChatHandler cl = lookup(recip);
                        if (cl == null)
                            psend(CHATMASTER_ID, recip + " not logged in.");
                        else
                            cl.psend(login, mesg);
                        break;
                    case Chat.CMD_QUIT:
                        broadcast(CHATMASTER_ID, "Goodbye to " 
                        close(  );
                        return;        // END OF THIS CHATHANDLER
                        
                    case Chat.CMD_BCAST:
                        if (login != null)
                            broadcast(login, line);
                        else
                            log("B<L FROM " + clientIP);
                        break;
                    default:
                        log("Unknown cmd " + c + " from " + login + "@" + clientIP);
                    }
                }
            } catch (IOException e) {
                log("IO Exception: " + e);
            } finally {
                // the sock ended, so we're done, bye now
                // Can NOT send a good-bye message, until we have
                // a simple command-based protocol in place.
                System.out.println(login + SEP + "All Done");
                synchronized(clients) {
                    clients.remove(this);
                    if (clients.size(  ) == 0) {
                        System.out.println(CHATMASTER_ID + SEP +
                            "Im so lonely I could cry...");
                    } else if (clients.size(  ) == 1) {
                        ChatHandler last = (ChatHandler)clients.get(0);
                        last.send(CHATMASTER_ID,
                            "Hey, you're talking to yourself again");
                    } else {
                        broadcast(CHATMASTER_ID,
                            "There are now " + clients.size(  ) + " users");
                    }
                }
            }
        }

        protected void close(  ) {
            if (clientSock == null) {
                log("close when not open");
                return;
            }
            try {
                clientSock.close(  );
                clientSock = null;
            } catch (IOException e) {
                log("Failure during close to " + clientIP);
            }
        }

        /** Send one message to this user */
        public void send(String sender, String mesg) {
            pw.println(sender + SEP + mesg);
        }

        /** Send a private message */
        protected void psend(String sender, String msg) {
            send("<*" + sender + "*>", msg);
        }
        
        /** Send one message to all users */
        public void broadcast(String sender, String mesg) {
            System.out.println("Broadcasting " + sender + SEP + mesg);
            for (int i=0; i<clients.size(  ); i++) {
                ChatHandler sib = (ChatHandler)clients.get(i);
                if (DEBUG)
                    System.out.println("Sending to " + sib);
                sib.send(sender, mesg);
            }
            if (DEBUG) System.out.println("Done broadcast");
        }

        protected ChatHandler lookup(String nick) {
            synchronized(clients) {
                for (int i=0; i<clients.size(  ); i++) {
                    ChatHandler cl = (ChatHandler)clients.get(i);
                    if (cl.login.equals(nick))
                        return cl;
                }
            }
            return null;
        }

        /** Present this ChatHandler as a String */
        public String toString(  ) {
            return "ChatHandler[" + login + "]";
        }
    }
}