//CirclesQ.java
//add a LinkedList queue
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.LinkedList;

public class CirclesQ extends JApplet implements ActionListener {

    public static final int STARTINGCIRCLES=12;
    public static final int DELAYDIFF=50;
    public static final String delayLabelPrefix="Delay in ms: ";

    private JTextField numCirclesText;
    private JLabel delayLabel;
    private int circles=STARTINGCIRCLES;
    private int animationDelay = 1000;  // millisecond delay
    private Timer animationTimer;     // Timer drives animation
    private LinkedList queue;  //Colors of the rings

    public void init() {
	JButton fasterButton;
	JButton slowerButton;

	queue = new LinkedList();
	//fill the queue of Colors
	for (int i=0; i<circles; i++)
	    queue.addLast( new Color((int)(Math.random()*256),
				     (int)(Math.random()*256),
				     (int)(Math.random()*256)));

	Container container = getContentPane();
	container.setLayout( new FlowLayout());

	numCirclesText = new JTextField( "12" , 3 );
	container.add( numCirclesText);
	numCirclesText.addActionListener( 
	   new ActionListener() {
	       public void actionPerformed (ActionEvent event) {
		   int prevCircles = circles;
		   try {		   
		       circles = Integer.parseInt(numCirclesText.getText());
		   } 
		   catch (NumberFormatException e) {
		       numCirclesText.setText( "1" );    //change garbage to 1
		       circles = 1;
		   }
		   if (circles < 1) {
		       numCirclesText.setText( "1" );    //change <=0 to 1
		       circles = 1;
		   }
		   //if more new circles:  enqueue circles-prevCircles new Colors
		   if (prevCircles < circles)
		       for (int i=prevCircles; i<circles; i++)
			   queue.addLast( new Color((int)(Math.random()*256),
						    (int)(Math.random()*256),
						    (int)(Math.random()*256)));
		   else
		       //dequeue prevCircles-circles outer Colors at front of queue
		       for (int i=prevCircles; i>circles; i--)
			   queue.removeFirst();   //dequeue

		   if ( ! animationTimer.isRunning() )  
		       animationTimer.restart();
		   repaint();
	       }
	   }
	);

	fasterButton = new JButton( "Faster!" );
	container.add( fasterButton );
	fasterButton.addActionListener(
           new ActionListener() {
	       public void actionPerformed( ActionEvent event ) {
		   if (animationDelay > DELAYDIFF)
		       animationDelay -= DELAYDIFF;
		   restartAnimation();
		   delayLabel.setText( delayLabelPrefix + animationDelay );
	       }
	   }
	);

	slowerButton = new JButton( "Slower!" );
	container.add( slowerButton );
	slowerButton.addActionListener(
           new ActionListener() {
	       public void actionPerformed( ActionEvent event ) {
		   animationDelay += DELAYDIFF;
		   restartAnimation();
		   delayLabel.setText( delayLabelPrefix + animationDelay );
	       }
	   }
	);

	delayLabel = new JLabel( delayLabelPrefix + animationDelay );
	container.add( delayLabel );

    }


    public void start() {
	startAnimation();  // begin animation
    }


    public void paint( Graphics g )
    {
	super.paint( g );
	
	int x1=0, y1=30, width, height, gap, appletSize;

	appletSize = Math.min(getWidth(),getHeight());
	//width = getWidth()-10;
	//height = getHeight()-30;
	width = appletSize-20;
	height = appletSize-20;
	gap = appletSize/circles/2;
	
	queue.removeFirst();      //dequeue
	queue.addLast( new Color((int)(Math.random()*256),     //enqueue
				 (int)(Math.random()*256),
				 (int)(Math.random()*256)));  

	for (int i=0; i<circles; i++) {

	    g.setColor( (Color)queue.get(i) );    //*****
	    g.fillOval(x1,y1,width,height);

	    x1 += gap; 
	    y1 += gap; 
	    width -= 2*gap;
	    height -= 2*gap;
	}
    }


    
    //timer's event handler
    public void actionPerformed (ActionEvent event) {
	//	circles = Integer.parseInt(numCirclesText.getText());
	if ( ! animationTimer.isRunning() )  //sometimes stops?
	    animationTimer.restart();
	repaint();
    }



   // start or restart animation
   public void startAnimation()
   {
      if ( animationTimer == null ) {
         animationTimer = new Timer( animationDelay, this );
         animationTimer.start();
      }
      else 
         if ( ! animationTimer.isRunning() )
            animationTimer.restart();
   }

   // stop animation timer
   public void stopAnimation()
   {
      animationTimer.stop();
   }


   public void restartAnimation()
   {
      stopAnimation();
      animationTimer = null;
      startAnimation();
   }

}