import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;

/**
 * GUITail is a small application (GUI of-course) that 
 * has a textfield for file input.  It then prints out all
 * the contents of the file, and tails it (watches it grow).
 * NOTE: This written entirely with swing components.
 * It does not have threads, but does use inner classes.
 * 
 * Questions, comments, etc, please email me.
 * @author Nick 
 * (see http://illx.org for more details)
 */
public class GUItail {
    JTextArea jt = null;
    boolean Break = true;
    public JTextField tf;
    public JLabel errorLabel;
    public int c = 0;
    public String MyFile;
    
    public static void main(String[] args) {
        GUItail gt = new GUItail();
        gt.go();
    }
    
    public void go() {
        JFrame f = new JFrame();
        f.setTitle("Nick's Java GUITail (http://illx.org)");
        JPanel mp = new JPanel(); //main panel
        JPanel bp = new JPanel(); //bottom panel
        
        errorLabel = new JLabel("");
        
        jt = new JTextArea(30,70);
        
        tf = new JTextField("enter filename here", 20);
        tf.addMouseListener(new MListener());

        JButton start = new JButton("Start");
        start.addActionListener(new GUItail.StartListener());
        JButton stop = new JButton("Stop");
        stop.addActionListener(new GUItail.StopListener());

        bp.add(BorderLayout.NORTH, tf);
        bp.add(BorderLayout.WEST, start);
        bp.add(BorderLayout.EAST, stop);

        
        JScrollPane scroller = new JScrollPane(jt);
        scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
        scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scroller.setAutoscrolls(true);
        
        mp.add(scroller);
        
        f.getContentPane().add(BorderLayout.NORTH, mp);
        f.getContentPane().add(BorderLayout.CENTER, errorLabel);
        f.getContentPane().add(BorderLayout.SOUTH, bp);
        
        f.setSize(800,550);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    //this classes whole existence is to clear the JTextField
    // when clicked on!!
    public class MListener implements MouseListener {
        public void mouseEntered(MouseEvent me) { }
        public void mouseExited(MouseEvent me) { }
        public void mouseReleased(MouseEvent me) { }
        public void mousePressed(MouseEvent me) { }

        public void mouseClicked(MouseEvent me) {
            if(c == 0) {
                tf.setText("");
                c++;
            }
        }
    }
    
    public class StartListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            jt.setText("");
            Break = true;
            Thread t = new Thread(new Runnable() {
		public void run() {
                    tail();
                }
	    });
            t.start();
        }
    }
    
    public class StopListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            Break = false;
            jt.append("*** Stopped watching '"+MyFile+"' ***");
        }
    }
     
    public void tail() {
        try {
            MyFile = tf.getText();
            if(MyFile.equals("")) {
                errorLabel.setText("Error! You need to enter a filename");
            }
            else {
            File f = new File(MyFile);    
            FileReader fileReader = new FileReader(f);
            BufferedReader r = new BufferedReader(fileReader);

            String line = null;
            while(Break == true) {
                int c = r.read();
                char aRc = (char)c;
                
                if (c != -1) {
                    line = r.readLine();
                    jt.append(aRc+line+"\n");
                }
                else {
                    try {Thread.sleep(500);} catch (InterruptedException e) {}
                }
            }
            r.close();
            }
        }
        catch(Exception e) {
            errorLabel.setText(e.getMessage());
        }
    }
}