import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.net.*;

/**
 * This class defines the applet, and sets up the Model and View objects.
 * If we had user controls (such as Start and Stop buttons, or a speed
 * control), this is where they would be defined and handled.<p>
 * This example is more complex than it needs to be, because it enforces
 * a strict separation between the model (the part that does the actual
 * computation), the display, and the controls in the user interface (of
 * which there are none). This is called the MVC (Model-View-Controller)
 * pattern, and while it may be overkill for this example, MVC provides an
 * excellent basis for more complex animations.
 */
public class Controller extends Applet {

	// Declare components here, where they are visible to inner classes
	Panel buttonPanel = new Panel ();
	Button runButton = new Button ("  Start  ");

  // Create the model and the view
  Thread animation;
  Model model = new Model();
  View view = new View();

  // Define the images that will be used
  Image graveyard, skull;
  
  /**
   * Lays out the applet components, starts a new thread for the
   * view to do its animation, and gives the model, view, and
   * controller access to one another.
   */
  public void init() {

    // Lay out components
    setLayout(new BorderLayout());
    this.add(BorderLayout.CENTER, view);
    buttonPanel.add (runButton);
    buttonPanel.setBackground(Color.black);
    this.add (BorderLayout.SOUTH, buttonPanel);
    
    // Get applet parameters and put them where they belong
    view.delay = Integer.valueOf(getParameter("delay")).intValue();
    
    // Tell the view about the model and the controller
    view.model = model;
    view.controller = this;
    
    // Get everything set up for the view BEFORE starting its Thread
    loadImages();
    view.alive = true;
    view.okToRun = false;
    
    // Give the view its own thread in which to do the animation
    animation = new Thread(view);
    animation.start();
    
    // Attach actions to components
    runButton.addActionListener (new ActionListener () {
      public void actionPerformed (ActionEvent event) {
        if (view.okToRun) {
          view.okToRun = false;
          showStatus ("Animation is stopped.");
          runButton.setLabel ("  Start  ");
        }
        else {
          view.okToRun = true;
          showStatus ("Animation is running.");
          runButton.setLabel ("  Stop   ");
       }
      }});
  }
  
  /**
   * Finds the size of the canvas (this can't be done in init()
   * because the canvas isn't ready yet) and gives the animation
   * permission to run.
   */
  public void start() {
    Dimension viewSize = view.getSize();
    
    model.imageWidth = 100;
    model.imageHeight = 100;
    model.xLimit = viewSize.width - model.imageWidth;
    model.yLimit = viewSize.height - model.imageHeight;
  }
  
  /**
   * Withdraws permission for the animation to run.
   */
  public void stop() {
    view.okToRun = false;
  }
  
  /**
   * Tells the animation thread to stop running.
   */
  public void destroy() {
    view.alive = false;
  }
  
  /**
   * Loads in the images we will use in this animation. There is an easier
   * way to do this in Java 2, but this method also works with any Java.
   */
   void loadImages() {

    // Create a MediaTracker to wait for the images to be loaded
    MediaTracker tracker = new MediaTracker(this);     

    // Declare variables for the URLs
    URL appletLocation = getCodeBase();
    URL imageURL = null;
System.out.println(appletLocation);

    try {
    
      // Start loading the graveyard image
      imageURL = new URL(appletLocation +  "/images/boothill-blue.jpg");
      graveyard = getImage(imageURL);
      tracker.addImage(graveyard, 0);
      
      // Start loading the skull image
      imageURL = new URL(appletLocation +  "/images/t-skull-0.gif");
      skull = getImage(imageURL);
      tracker.addImage(skull, 0);
     }
     catch (MalformedURLException e) { e.printStackTrace(); }
     
     // Wait for the images to be loaded; does no error checking
    try { tracker.waitForAll(5000); }
    catch (InterruptedException e) {}
   }
}

// -------------------------------------------------------------------------------------  

/**
 * This class models the action of a bouncing image. It is important to note
 * that this class is <i>independent</i> of the GUI. For this animation, the
 * Model does need to know the size of the box that the image is bouncing
 * around in, and this is set from outside. Similarly, it provides a
 * makeOneStep() method so that the model can be controlled from outside the
 * class; but neither of these requires the model to know anything at all
 * about the rest of the program
 */
class Model {
  int imageWidth, imageHeight;
  int xPosition = 0;
  int yPosition = 0;
  int xLimit, yLimit;
  int xDelta = 4;
  int yDelta = 3;
  
  /**
   * Moves the image one step, by adding xDelta and yDelta to its xPosition
   * and yPosition, respectively, and checking for bounces off the "walls".
   */
  void makeOneStep() {
    xPosition += xDelta;
    if(xPosition < 0 || xPosition >= xLimit) {
      xDelta = -xDelta;
      xPosition += xDelta;
    }
    yPosition += yDelta;
    if(yPosition < 0 || yPosition >= yLimit) {
      yDelta = -yDelta;
      yPosition += yDelta;
     }
  }
}

// -------------------------------------------------------------------------------------  

/**
 * This class runs in a separate (animation) thread and controls all the
 * painting.
 */
class View extends Canvas implements Runnable {
  Controller controller;
  Model model;
  Dimension size = getSize();
  int delay = 1000;
  int stepNumber = 0;
  boolean alive, okToRun;
  Image offscreenImage = null;
  Graphics offscreenGraphics = null;

  /**
   * Sets up an (almost) infinite loop to do the animation, and every
   * delay milliseconds asks the model to update itself, then draws the
   * result.
   */
  public void run() {
  
    // "alive" will be true until the Applet is destroyed
    while(alive) {
    
      // "okToRun" will be true if the Applet is started and not stopped
      if(okToRun) {
        model.makeOneStep();
        repaint(); // Note: uses Graphics for this Canvas, not for the Applet
      }
      
      // Control the speed of execution
      try { Thread.sleep(delay); }
      catch(InterruptedException e) {}
    }
  }
  
  /**
   * To avoid flicker, this method paints into the Graphics
   * of an offscreen Image.
   */
  public void update(Graphics g) {
  
    // Don't do anything without permission from the controller
    if (!okToRun) return;
    
    // Create the offscreen Graphics
    if (offscreenImage == null) {
      offscreenImage = createImage(getSize().width, getSize().height);
      offscreenGraphics = offscreenImage.getGraphics();
    }
    // Paint into the offscreen Graphics
    background(offscreenGraphics);
    paint(offscreenGraphics);
    
    // Copy the offscreen onto the screen
    g.drawImage(offscreenImage, 0, 0, null);
  }
  
  /**
   * Repaints the canvas based on information that it gets from the model.
   */
  public void paint(Graphics g) {
  
    // Don't do anything without permission from the controller
    if (!okToRun) return;
    
    // Draw the skull
    g.drawImage(controller.skull, model.xPosition, model.yPosition, null);
    
    // Display steps and position in the status line;
    // this is a good place to put debugging information.
    if(++stepNumber % 10 == 0)
      controller.showStatus("Step " + stepNumber + ", x = " + model.xPosition +
                            ", y = " + model.yPosition);
  }
  
  /**
   * Paints a background on the given Graphics.
   */
   void background(Graphics g) {
     g.drawImage(controller.graveyard, 0, 0, null);
   }
}