import java.awt.*;
import java.awt.event.*;

// Auxiliary class to buffer key events.
// You are not supposed to understand this yet!

class KeyBuffer extends KeyAdapter {

    static int K = 1000;  
    int in, out, no = 0;

    char[] buf = new char[K];

    synchronized public void keyPressed(KeyEvent e) {
	char c = e.getKeyChar();
	e.consume();
	if (c != KeyEvent.CHAR_UNDEFINED && no < K) { 
	    buf[in++] = c;
	    in = in % K;
	    no++;
	    notify();
	}
    }

    synchronized public char Get() {
	while (no==0) try{ wait();} catch (Exception e){}
	char c = buf[out++];
	out = out % K;
	no--;
	return c;
    }

}

// Class that provides a GUI for the lab

public class TaskDisplay extends Frame{

    public TextField[] tf;
    TextArea    txt;

    static final int width      =   40;
    static final int minhistory = 1000;
  
    private KeyBuffer kb;

    public TaskDisplay(String name, int n) {
    
	super(name);

	int lines = 0;
    
	kb = new KeyBuffer();
    
	addWindowListener(
			  new WindowAdapter(){
			      public void windowClosing(WindowEvent e) {
				  System.exit(0);
			      }
			  });

	// Create 'n' TextFields
    
	if (n > 0) tf = new TextField[n];

	setFont(new Font("Monospaced",Font.BOLD,12));

	setLayout(new GridBagLayout());
	GridBagConstraints c = new GridBagConstraints();

	c.gridx = 0; c.gridy = GridBagConstraints.RELATIVE;
	c.insets = new Insets(5,5,5,5);

	for (int i = 0; i < tf.length; i++) {
	    c.gridx = 0; 
	    Label l = new Label("Task " + i);
	    add(l,c);
	    c.gridx = 1;
	    tf[i] = new TextField(width);
	    tf[i].setEditable(false);
	    tf[i].setForeground(Color.blue);
	    tf[i].setBackground(Color.white);

	    add(tf[i], c);
	}

	txt = new TextArea("",8,width,TextArea.SCROLLBARS_VERTICAL_ONLY);
	txt.addKeyListener(kb);
	txt.setEditable(false);
	txt.setBackground(Color.white);
	c.gridx = 0; c.gridwidth = 2;  c.fill = GridBagConstraints.HORIZONTAL;
	add(txt,c);

	pack();
	setVisible(true);
	txt.requestFocus();
    }

    public void println(String s) {
	txt.setCaretPosition(10000);       // set caret at end
	int last = txt.getCaretPosition();
	if (last > 2*minhistory) txt.replaceRange("",0,last-minhistory);
	txt.append(s+"\n");
    }

    public char getKey() {
	return kb.Get();
    }

}