/* 
 * Liny.java - A cute bouncing lines demo that runs on HotJava
 *  
 *    This was a quick hack from C code, no comments yet...
 *    It would appear that I need to redraw if the applet is
 *    scrolled around on the screen, but I'm not sure yet.
 *
 *   $Id$
 *   $Log$
 *
 */

import java.awt.*;
import java.applet.*;

/* Beginning of liny class */
public class Liny extends java.applet.Applet implements Runnable {
  Thread animate=null;
  int lx[][] = new int[40][257];
  int ly[][] = new int[40][257]; 
  int dx[] = new int[40]; 
  int dy[] = new int[40]; 
  int xx[] = new int[40]; 
  int yy[] = new int[40]; 
  Color pal[] = new Color[257];

  int z, numlins, traces;
  int maxx, maxy, minx, miny;
  int i, ii, iii, gravity, randon;
  int q;
  float a1, a2;

  int rand() {
    return (int) (Math.random() * 30000);
  }

  Color HSItoRGB(double h, double s, double i) {
    double rv, gv, bv;
    double PI, t;
    Color col;
    int r, g, b;

    PI=3.1415926;

    t = 2 * PI * h;
    rv=1.0 + s * Math.sin(t - 2.0 * PI / 3.0);
    gv=1.0 + s * Math.sin(t);
    bv=1.0 + s * Math.sin(t + 2.0 * PI / 3.0);
 
    t=255.9999999 * i / 2;
 
    r = (int) (rv * t);
    g = (int) (gv * t);
    b = (int) (bv * t);

    col = new Color(r, g, b);       

    return col;
  }

  public void init() {
    int red, green, blue;
    double hue;
    Dimension mydim;

    setSize(500, 500);
    mydim = getSize();

    setBackground(Color.black);

    numlins=3;
    traces=130;
    gravity=0;
    randon=0;

    if (getParameter("lines")!=null) {
      Integer lines=new Integer(getParameter("lines"));
      numlins=lines.intValue();
    }

    if (getParameter("traces")!=null) {
      Integer ntraces=new Integer(getParameter("traces"));
      traces=ntraces.intValue();
    }

    if (getParameter("gravity")!=null) {
      Integer grav=new Integer(getParameter("gravity"));
      gravity=grav.intValue();
    }

    if (getParameter("random")!=null) {
      Integer randn=new Integer(getParameter("random"));
      randon=randn.intValue();
    }

    if (traces>255) traces=255;
    if (numlins>40) numlins=39;
   
    maxx=mydim.width - 21;
    maxy=mydim.height - 21;
    minx=20;
    miny=20;
  
    for (i=0; i<=numlins+1; i++) {
      xx[i]=rand() % maxx; 
      yy[i]=rand() % maxy;
      dx[i]=rand() % 20 - 10; 
      dy[i]=rand() % 20 - 10;
    }
   
    for (i=0; i<=numlins; i++) {
      for (z=0; z<=traces; z++) {
        lx[i][z]=xx[i];
        ly[i][z]=yy[i];
      }
      dx[i] = rand() % 10 - 2;
      dy[i] = rand() % 10 - 2;
    }
    q=1;

  for (i=1; i<(traces + 1); i++) {
      hue=(i/(traces * 1.0));
      pal[i] = HSItoRGB(hue, 0.95, 1.0); 
    }
    pal[0]=Color.black; 
  }
  
  public void run() {
    while (true) {
      try { Thread.sleep(8); } catch(InterruptedException e) {} 

      for (i=1; i<=numlins; i++) {
        xx[i]=xx[i]+dx[i];
        yy[i]=yy[i]+dy[i];
        if (xx[i]>maxx) dx[i]= -(Math.abs(dx[i]));
        if (xx[i]<minx) dx[i]=   Math.abs(dx[i]);
        if (yy[i]>maxy) dy[i]= -(Math.abs(dy[i]));
        if (yy[i]<miny) dy[i]=   Math.abs(dy[i]);
      }

      repaint();

      for (i=1; i<=numlins; i++) {
        lx[i][q]=xx[i];
        ly[i][q]=yy[i];
      }

      if (gravity == 1) {
        for (i=1; i<=numlins; i++) {
          ii=i-1;
          iii=i+1;
          if (i==1) ii=numlins;
          if (i==numlins) iii=1;
          dx[i]=dx[i] + ((xx[ii]+xx[iii] - 2*xx[i])/412);
          dy[i]=dy[i] + ((yy[ii]+yy[iii] - 2*yy[i])/412);
        }
      }

      if (randon == 1) {
        if ((rand()%100) > 97) {
           i=rand() % numlins + 1;
           dx[i]=dx[i] + rand() % 5 - 2;
           dy[i]=dy[i] + rand() % 5 - 2;
        }
      }
 
      for (i=1; i<=numlins; i++) {
        if (dx[i] < -15) dx[i] = -15;
        if (dx[i] >  15) dx[i] =  15;
        if (dy[i] < -15) dy[i] = -15;
        if (dy[i] >  15) dy[i] =  15;
      }
    } /* infinite loop */
  }

  public void start() {
    if (animate == null) {
      animate = new Thread(this);
      animate.start();
    }
  }

  public void stop() {
    if (animate != null) {
      animate.stop();
      animate=null;
    }
  }

  public synchronized void paint(Graphics g) {
    int num;
    Dimension mydim = getSize();

    g.setColor(pal[(q % traces) + 1]); 

    for (i=1; i<numlins; i++)
      g.drawLine(xx[i], yy[i], xx[i+1], yy[i+1]);

    g.drawLine(xx[numlins], yy[numlins], xx[1], yy[1]);

    q=(q+1) % traces;

    g.setColor(Color.black);

    for (i=1; i<numlins; i++)
      g.drawLine(lx[i][q], ly[i][q], lx[i+1][q], ly[i+1][q]);
  
    g.drawLine(lx[numlins][q], ly[numlins][q], lx[1][q], ly[1][q]);
  }

  public synchronized void update(Graphics g) {
    paint(g);
  }

} /* end of liny class */