import java.applet.Applet;
import java.awt.Image;
import java.awt.Graphics;
import java.awt.image.MemoryImageSource;
import java.awt.Dimension;
import java.awt.AWTEvent;


public class Fairy extends Applet implements Runnable {
	int width, height;
	int[] pixels;
	private Image image = null;
	private MemoryImageSource imageSource = null;

	public void init(){
		Dimension size = getSize();
		width = size.width;
		height = size.height;
		pixels = new int[ width*height ];
		imageSource = new MemoryImageSource( width, height, pixels, 0, width );
		imageSource.setAnimated( true );
		imageSource.setFullBufferUpdates( true );
		image = createImage( imageSource );
	}

	public void drawDust( float x, float y, float radius, float a, int r, int g, int b ){
		
		int min_x = (int)Math.max( 0, x - radius),
			min_y = (int)Math.max( 0, y - radius),
			max_x = (int)Math.min( width-1, x + radius +1.0f),
			max_y = (int)Math.min( height-1, y + radius +1.0f);

		float radiusSq = radius*radius;
		float halfARadiusSqInv = (0.75f*a)/radiusSq;
		for ( int i = min_x; i <= max_x; i++ ){
			float dx = i - x;
			float dxSq = dx*dx;
			for ( int j = min_y; j <= max_y; j++ ){
				float dy = j - y;
				float distSq = dxSq + dy*dy;
				if ( radiusSq >= distSq ){
					float alpha = (radiusSq - distSq)*halfARadiusSqInv;
					float oneMinusAlpha = 1.0f - alpha;
					int index = j*width + i;
					int pixel = pixels[ index ];
					int red = (pixel & 0x00FF0000) >> 16;
					int green = (pixel & 0x0000FF00) >> 8;
					int blue = (pixel & 0x000000FF);

					red = (int)(red*oneMinusAlpha + r*alpha);
					green = (int)(green*oneMinusAlpha + g*alpha);
					blue = (int)(blue*oneMinusAlpha + b*alpha);
					
					pixels[ index ] = 0xFF000000 | (red << 16 ) | (green << 8) | blue;					
				}
			}
		}

	}

	private int mouse_x, mouse_y;
	
	public void processMouseMotionEvent( java.awt.event.MouseEvent me ) {
		if ( me.getID() == me.MOUSE_MOVED || me.getID() == me.MOUSE_DRAGGED ) {
			mouse_x = me.getX();
			mouse_y = me.getY();
			mouse_in = true;
		}
	}
	
	private boolean mouse_in = false;
	
	public void processMouseEvent( java.awt.event.MouseEvent me ) {
		if ( me.getID() == me.MOUSE_ENTERED ) {
			mouse_in = true;
		} 
		else if ( me.getID() == me.MOUSE_EXITED ) {
			mouse_in = false;
			mouse_x = (int)((width/2)/* + 0.5*width*(0.5-Math.random())*/);
			mouse_y = (int)((height/2)/* + 0.5*height*(0.5-Math.random())*/);
		}
	}		
	
	private volatile boolean running = true;

	public void start(){
		running = true;
		(new Thread( this )).start();
	}

	private long num = (long)(Integer.MAX_VALUE*Math.random());
	
	private int randomInt(){
		num = (num * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
        return (int)(num >>> (48 - 32));
	}
	
	private int n = 0;
	
	private float random(){
		return ((n = randomInt()) < 0?-n:n)/(float)(Integer.MAX_VALUE);
	}

	public void run(){
		int num_particles = 70;
		enableEvents( AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK );
		mouse_x = width/2;
		mouse_y = height/2;
		
		Thread.currentThread().setPriority( Thread.MIN_PRIORITY );
		float[] x = new float[ num_particles ];
		float[] y = new float[ num_particles ];
		float[] time = new float[ num_particles ];
		int[] red = new int[ num_particles ];
		int[] green = new int[ num_particles ];
		int[] blue = new int[ num_particles ];
		for ( int i = 0; i < num_particles; i++ ) {
			x[ i ] = (float)(width/2 + 40*(0.5-random()));
			y[ i ] = (float)(height/2 + 40*(0.5-random()));
			time[ i ] = (float)random();
			int r1 = 127 + (int)(128*random());
			red[ i ] = r1;
			green[ i ] = r1;
			blue[ i ] = 127;
		}
		float xf = width/2;
		float yf = height/2;
	
		while ( running ) {
			
			long start = System.currentTimeMillis();
			
			for ( int i = pixels.length-1; i >= 0; --i ) {
				 int pixel = pixels[ i ];
				 int r = (0x00FF0000 & pixel) >> 16;
				 r = 5*r/8;
				 r = r < 0? 0 : r;
				 int g = (0x0000FF00 & pixel) >> 8;
				 g = 5*g/8;
				 g = g < 0? 0 : g;
				 int b = (0x000000FF & pixel);
				 b = 5*b/8;
				 b = b < 0? 0 : b;
				 
				 pixels[ i ] = 0xFF000000 | (r << 16) | (g << 8) | b;
			}
			
			
			for ( int i = 0; i < num_particles; i++ ) {
				float t = time[ i ];
				if ( t > 0.9f ) {
					t = 9.0f*(1.0f - t);
				}
	
				drawDust( x[ i ], y[ i ], 5.0f*t + 2.0f, t, red[ i ], green[ i ], blue[ i ] );
				x[ i ] += 3*(0.5 - random());
				y[ i ] += 1 + 2*(random() -0.1);
				time[ i ] -= 0.01;
				if ( time[ i ] < 0.0f ) { 
					x[ i ] = (float)(xf + 40*(0.5-random()));
					y[ i ] = (float)(yf + 40*(0.5-random()));
					time[ i ] = 1.0f;
					int r1 = 127 + (int)(128*random());
					red[ i ] = r1;
					green[ i ] = mouse_in? r1/2 : r1;
					blue[ i ] = 127;
				}	
			}
			
			float speed = mouse_in? 1.0f : 0.2f;
			
			xf += speed*10.0f*(float)(0.5-random());
			yf += speed*10.0f*(float)(0.5-random());
			
			if ( !mouse_in ) {
				mouse_x += (int)(7*random()) -3;
				mouse_y += (int)(7*random()) -3;			
			}	
			float dx = 0.1f*speed;
			xf = (1.0f-dx)*xf + mouse_x*dx;
			yf = (1.0f-dx)*yf + mouse_y*dx;			  
			
			drawDust( xf, yf, (float)(10 + speed*10*(0.5-random())), 0.8f, 255, 255, 255 );
			if ( mouse_in ) {
				drawDust( xf, yf, (float)(30 + 4*(0.5-random())), 0.7f, 250, 150, 128 );
			}
			else {	
				drawDust( xf, yf, (float)(30 + 2*(0.5-random())), 0.7f, 250, 250, 128 );
			}
				
			long stop = System.currentTimeMillis();	
			/*drawDust( xf -6, yf -5, 10, 1.0f, 255, 255, 255 );
			drawDust( xf +6, yf -5, 10, 1.0f, 255, 255, 255 );
			drawDust( xf -5, yf +6, 8, 1.0f, 255, 255, 255 );
			drawDust( xf +5, yf +6, 8, 1.0f, 255, 255, 255 );*/
			
			imageSource.newPixels();
			image.flush();
			repaint();
			long spare = start + 40 - stop;
			//System.out.print( spare );
			//System.out.println();
			spare = spare < 5? 5 : spare;
			try {
				Thread.sleep( spare );
			}
			catch( Exception e ) {}
			
	
		}
		
	}

	public void stop(){
		running = false;
	}

	public void update( Graphics g ){
		g.drawImage( image, 0, 0, this );
	}

}