// tunnel.java  click on points, connect the dots

import java.awt.*;
import java.awt.event.*;

public class tunnel extends Frame
{
  int x, y, z, b;
  double xp[] = new double[1000];
  double yp[] = new double[1000];
  double zp[] = new double[1000];
  int npts = 16;
  int nrngs = 8;
  int width = 400;
  int height = 400;
    int n, nold, nring, ngrp;
  double xmin = -1.0;
  double xmax =  1.0;
  double ymin = -1.0;
  double ymax =  1.0;
  double zmin =  2.0;
  double zmax, znext, zinc=0.5;
  // set up double buffering for smooth "run"
  Image dbImage;
  Graphics dbg; // double buffered graphics
  int speed = 100; // millisecond delay

  tunnel()
  {
    double ang;

    setTitle("tunnel");
    setSize(width,height);
    setBackground(Color.white);
    setForeground(Color.black);
    addWindowListener(new WindowAdapter()
    {
      public void windowClosing(WindowEvent e)
      {
        System.exit(0);
      }
    });
    n = 0;
    znext = zmin;
    // draw one ring
    for(int i=0; i<npts; i++)
    {
      ang = ((double)i/(double)(npts/2))*Math.PI;
      xp[n] = Math.sin(ang);
      yp[n] = Math.cos(ang);
      zp[n] = znext;
      n++;
      ang = ((double)(i+1)/(double)(npts/2))*Math.PI;
      xp[n] = Math.sin(ang);
      yp[n] = Math.cos(ang);
      zp[n] = znext;
      n++;
    }
    xp[n-1] = xp[n-2*npts];
    yp[n-1] = yp[n-2*npts];
    System.out.println("one ring n="+n);
    nring = n;
    for(int j=0; j<nrngs; j++)
    {
      znext += zinc;
      // copy ring at znext
      for(int i=0; i<nring; i++)
      {
        xp[n] = xp[n-nring];
        yp[n] = yp[n-nring];
        zp[n] = znext;
        n++;
      }
    }
    System.out.println("all rings n="+n);
    ngrp = n;

    nold = 0;
    for(int j=0; j<nrngs; j++)
    {
      // connect rings
      for(int i=0; i<npts; i++)
      {
        xp[n] = xp[n-ngrp];
        yp[n] = yp[n-ngrp];
        zp[n] = zp[n-ngrp];
        n++;
        xp[n] = xp[n-1-ngrp+nring];
        yp[n] = yp[n-1-ngrp+nring];
        zp[n] = zp[n-1-ngrp+nring];
        n++;
      }
    }
    System.out.println("n="+n);

    setVisible(true);
    this.addMouseListener (new mousePressHandler());
    znext = 0.0;
    new do_scan().start();
  }

  class mousePressHandler extends MouseAdapter
  {
    public void mousePressed (MouseEvent e)
    {
      x = e.getX();
      y = e.getY();
      b = e.getButton();
      xp[n]=x;
      yp[n]=y;
      if(b==3 && n>0)
      {

      }
      else
      {
        n++;
      }
      requestFocus();
      System.out.println("at x="+x+"   y="+y+"   b="+b); // debug print
      repaint();
    }
  }

  // this is the key to double buffering, repaint() calls update, not paint
  public void update(Graphics g)
  {
    // initialize Double Buffers
    if(dbImage==null)
    {
      dbImage = createImage(this.getSize().width, this.getSize().height);
      dbg = dbImage.getGraphics();
    } // only first time

    // clear Image in RAM, dbg is off screen buffer
    dbg.setColor(Color.white);
    dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);

    paint(dbg); // now call paint to render in dbg
    g.drawImage(dbImage, 0, 0, this); // display rendered image, very fast
  } // end update

  public class do_scan extends Thread
  {
    do_scan()
    {
      System.out.println("do_scan znext="+znext);
    }

    public void run()
    {
      for(int iii=0; iii<80; iii++)
      {
	znext = znext + zinc/8.0;
	repaint();
        try
	{
	  sleep(speed); // milliseconds delay
	}
        catch(InterruptedException excp)
	{
	  System.out.println("caught Exception");
	} // end try catch
      } // end iii
    } // end run
  } // end class do_scan

  public void paint(Graphics g)
  {
    int xs, ys, xs2, ys2;
    double znow1, znow2;

    // draw a boundary
    g.setColor(Color.black);
    g.setColor(Color.red);
    for(int i=0; i<n; i++)
    {
      znow1 = zp[i]-znext;
      if(znow1<0.5) continue;
      xs = (int)((double)width*(xp[i]/znow1-xmin)/(xmax-xmin));
      ys = (int)((double)height*(yp[i]/znow1-ymin)/(ymax-ymin));
      g.drawOval(xs, ys, 2, 2);
    }
    g.setColor(Color.blue);
    for(int i=0; i<n; i+=2)
    {
      znow1 = zp[i]-znext;
      znow2 = zp[i+1]-znext;
      if(znow1<0.5 || znow2<0.5) continue;
      xs =  (int)((double)width*(xp[i]/znow1-xmin)/(xmax-xmin));
      ys =  (int)((double)height*(yp[i]/znow1-ymin)/(ymax-ymin));
      xs2 = (int)((double)width*(xp[i+1]/znow2-xmin)/(xmax-xmin));
      ys2 = (int)((double)height*(yp[i+1]/znow2-ymin)/(ymax-ymin));
      g.drawLine(xs, ys, xs2, ys2);
    }
  }

  public static void main(String args[])
  {
    new tunnel();
  }
}