// rough demo of reading an image from a file, handling mouse clicks,
// and displaying the image wherever the mouse is clicked.
//
// optional parameters to applet
//    image - name of png, gif, or jpg file in directory with file
//    height - applet height between 150 and 500
//    width - applet window width between 150 and 500
//    example in HTML:
//        <applet code="MovingPicture.class" width=400 height=350>
//        <param name="width" value="400"> 
//        <param name="height" value="350"> 
//        <param name="image" value="MaceWhenua.png">
//        </applet>
//    
// Beth Katz, March 2008

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

public class MovingPicture extends JApplet implements MouseListener {
    
    // default values
    private static final long serialVersionUID = 1L;
    private final int APPLET_WIDTH_DEFAULT = 320;
    private final int APPLET_HEIGHT_DEFAULT = 320;
    private final int IMAGE_HEIGHT = 80;
    private final int IMAGE_WIDTH = 80;
    private final String IMAGE_DEFAULT = "sunflower.jpg";

    // instance variables 
    private Image theImage;
    private int imageX, imageY;
    private int appletWidth;
    private int appletHeight;
    
    /*
     * initializes the applet - sets image, adjusts sizes
     * these will read some parameters from the HTML request
     */
    public void init( ) {
        loadImage( );
        appletWidth = APPLET_WIDTH_DEFAULT;
        appletHeight = APPLET_HEIGHT_DEFAULT;
        adjustAppletSize( );
        setSize(appletWidth, appletHeight);
        setImageLoc(appletWidth/2, appletHeight/2);
        addMouseListener(this);
    }

    /*
     * loads the image (from parameter if provided)
     *   really gets the name of the image but doesn't load
     */
    public void loadImage( ) {
        String s = getParameter("image");
        String imageName = (s != null) ? s : IMAGE_DEFAULT;
        theImage = getImage(getDocumentBase( ), imageName);
    }

    /*
     * adjusts applet dimensions if good parameters are supplied 
     */
    public void adjustAppletSize( ) {
        String h = getParameter("height");
        String w = getParameter("width");
        if (h != null && w != null) {
            int height = Integer.parseInt(h);
            int width = Integer.parseInt(w);
            if (150 <= height && height <= 500) {
                appletHeight = height;
            }
            if (150 <= width && width <= 500) {
                appletWidth = width;
            }
        }
    }
    
    /*
     * changes location where image will be displayed
     * so that it is centered at xLoc,yLoc
     */
    public void setImageLoc(int xLoc, int yLoc) {
        int x = xLoc - (IMAGE_WIDTH / 2);
        int y = yLoc - (IMAGE_HEIGHT / 2);
        imageX = x > 0 ? x : 0;
        imageY = y > 0 ? y : 0;
    }

    /*
     * draws the image at imageX,imageY after clearing the applet area
     */
    public void drawPictures(Graphics page) {
        page.clearRect(0, 0, appletWidth, appletHeight);
        page.drawImage(theImage, imageX, imageY,
                       IMAGE_WIDTH, IMAGE_HEIGHT, this);
    }

    /*
     * called to paint the applet area
     */
    public void paint (Graphics page) {
        drawPictures(page);    
    }
                   
    /**     
     * Handles the mouse click event by changing where image is displayed
     * @param me the mouse event containing location and modifier keys
     */
    public void mouseClicked(MouseEvent me) { 
    setImageLoc(me.getX( ), me.getY( ));
        // System.out.println("Mouse click at " + me.getX( ) + "," + me.getY( )); 
        repaint( );          
    }       

    ///////// these are not used here but are needed for mouse listener ///////
    /**
     * Handles the mouse entered event by printing a message.
     * @param me the mouse event containing location and modifier keys
     */     
    public void mouseEntered(MouseEvent e) {
    }               
                    
    /**                     
     * Handles the mouse exited event by printing a message.
     * @param me the mouse event containing location and modifier keys
     */             
     public void mouseExited(MouseEvent e) {
      }                      
   
     /**             
      * Handles the mouse down event by printing a message..
      * @param me the mouse event containing location and modifier keys
      */     
     public void mousePressed(MouseEvent me) {
      }       
                     
     /**     
      * Handles the mouse up event by printing a message.     
      * @param me the mouse event containing location and modifier keys
     */                 
     public void mouseReleased(MouseEvent me) {
      }
}