//////////////////////////
//ChatMidlet.java
//importing some java package
//////////////////////////
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;
/////////////
//ChatMidlet extending abstract MIDlet class with CommandListener and Runnable Thread
/////////////
public class ChatMidlet extends MIDlet implements Runnable, CommandListener {
    //declaring some displayable
    private Display display;
    private Form mainform, newChat, composeMessage;
    private TextField listeningPort, message, location, nickname;
    private Command ok, start, exit, cancel, reply, send;
    private Ticker ticker;
    private List ChatSession;
    //flags
    String msgSend, destination, nick;
/////////////
//Constructor
/////////////
public ChatMidlet() {

    ///New Chat Form
    newChat = new Form("BlueChat Initilization...");
    ChatSession = new List("BlueChat Messages", List.IMPLICIT);
    listeningPort = new TextField("Create new chat session over datagram port(this serves as the listening port):","",5, TextField.NUMERIC);
    nickname = new TextField("Nickname:","",100, TextField.ANY);
    message = new TextField("Message:","",100, TextField.ANY);
    location = new TextField("Send to (IP address:port):","",50, TextField.ANY);

    ///Commands
    exit = new Command("Exit", Command.EXIT, 1);
    send = new Command("Send", Command.SCREEN, 1);
    start = new Command("Start", Command.SCREEN , 1);
    cancel = new Command("Cancel", Command.CANCEL, 1);
    reply = new Command("Reply", Command.SCREEN , 1);
    ok = new Command("Ok", Command.SCREEN , 1);

    ///Compose message
    composeMessage = new Form("BlueChat: Compose Message");
    composeMessage.append(location);
    composeMessage.append(message);
    composeMessage.addCommand(send);
    composeMessage.addCommand (cancel);
    composeMessage.setCommandListener(this);

    ///Main Form
    mainform = new Form("BlueChat");
    //Appending image/logo in the main form
    try
    {
        Image img = Image.createImage("/bluechatlogo.jpg");
        //Image img = Image.createImage("/bluechatlogo.png");
        ImageItem image = new ImageItem("\n\n\n\n", img, Item.LAYOUT_CENTER, "BlueChat");
        mainform.append(image);
    } catch (Exception e){e.printStackTrace();}
    mainform.addCommand(ok);
    mainform.addCommand(exit);
    mainform.setCommandListener(this);
    }
/////////////
//Start up function
/////////////
    public void startApp()
    {
        if (display == null)
        {
            display = Display.getDisplay(this);
            display.setCurrent(mainform);
        }
    }
/////////////
//Pause application function
/////////////
    public void pauseApp() {  }
/////////////
//Destroy application function
/////////////
    public void destroyApp(boolean unconditional){  }
/////////////
//Command action function which works with the CommandListener interface
/////////////
public void commandAction(Command c, Displayable d) {
    //Exit Command
    if (c == exit){ notifyDestroyed(); }
    //Okay Command
    if (c == ok)
    {
        newChat.append(listeningPort);
        newChat.append(nickname);
        newChat.addCommand(start);
        newChat.addCommand(exit);
        newChat.setCommandListener (this);
        display.setCurrent(newChat);
    }
    //Start Command
    if (c == start)
    {
        nick = nickname.getString();
        ticker=new Ticker("You are listening to port "+listeningPort.getString()+ ", "+nick);
        ChatSession.setTicker(ticker);
        ChatSession.addCommand(reply);
        ChatSession.addCommand(exit);
        ChatSession.setCommandListener(this);
        display.setCurrent(ChatSession);
        new Thread( this ).start();
    }
    //Cancel Command
    if (c == cancel)
    {
        display.setCurrent(ChatSession);
    }
    //Reply Message Command
    if (c == reply)
    {
        int pointer = ChatSession.getSelectedIndex();
        String[] stringMsg;
        String wholeMsg, locationOfSender="";
        if(pointer >= 0)
        {
            wholeMsg = ChatSession.getString (pointer);
            stringMsg = split(wholeMsg, '(');
            locationOfSender = stringMsg[1];
            stringMsg = split(locationOfSender, ')');
            locationOfSender = stringMsg[0].trim();
        }
        location.setString(""+locationOfSender);
        message.setString ("");
        nickname.setString("");
        display.setCurrent(composeMessage);
    }
    //Send Message Command
    if (c == send)
    {
        msgSend = message.getString();
        destination = location.getString();
        new Thread( this ).start();
        send(msgSend);
    }
    }
/////////////
//Send Message function using datagram connection
/////////////
void send(String msg)  {
    UDPDatagramConnection datagramcon = null;
    String localhost = "datagram://localhost:777";
    try
    {
        datagramcon = (UDPDatagramConnection) Connector.open(localhost);
        msg="From: " + nick + " (" + datagramcon.getLocalAddress()+":"+listeningPort.getString()+")\nMessage: "+ msg;
        int length = msg.length();
        byte[] MessageToSend = msg.getBytes();
        Datagram data = datagramcon.newDatagram (MessageToSend, length, "datagram://"+destination);
        datagramcon.send (data);
    }
    catch (Exception e)
    {
        System.out.println("Failed to send message: " + e);
    }
    finally
    {
        if (datagramcon != null)
        {
            try { datagramcon .close(); } catch (Exception error) { System.out.println ("Failed to close Connector: " + error); }
        }
    }
    }
/////////////
//Split String Utility to parse IP and port number of the sender
// Utility routine to split a string into two from http://java.sun.com/developer/J2METechTips/2002/tt0131.html
/////////////
static String[] split( String in, char ch ){
        String[] result = new String[2];
        int      pos = in.indexOf( ch );

        if( pos != -1 ){
            result[0] = in.substring( 0, pos ).trim();
            result[1] = in.substring( pos+1 ).trim();
        } else {
            result[0] = in.trim();
        }

        return result;
    }
/////////////
//Thread Runnable implementing UDPDtagramConnection serves as a listener for incoming messages
/////////////
public void run()
{
    UDPDatagramConnection datagramListener = null;
    Datagram msg = null;
    try
    {
        datagramListener = (UDPDatagramConnection) Connector.open("datagram://:"+listeningPort.getString());
        String msgReceive;
        while(true)
        {
            msg = datagramListener.newDatagram(datagramListener.getMaximumLength());
            try
            {
                datagramListener.receive (msg);
            } catch (Exception e) { }
            String data = new String(msg.getData(), 0, msg.getLength());
            ChatSession.append(data.trim(),null);
        }
    }
    catch (Exception e) { }
    finally
    {
        if (datagramListener != null)
        {
            try
            {
                datagramListener.close();
            }
            catch (Exception error) { System.out.println("Failed to close Connector: " + error); }
        }
    }
    }
}