// July 2002, java applet by Oliver Knill  for the CCP project
// Green's Theorem and the Planimeter by Oliver Knill and Dale Winter
// Harvard University, Nov 15, 2002. See
// http://math.duke.edu/education/ccp/materials/mvcalc/green
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License of the Free Software Foundation for
// details.  Compile with 
// javac -O instrument.java comment.java wheel.java curve.java planimeter.java

import java.lang.Math;
import java.awt.*;

class wheel {

private int h,w;               // width and height taken over 
private int x,y;               // location of pointer
private int x_old,y_old;       // old location of pointer
public  int c_old,d_old;       // old location of pointer
private int x1,y1;             // location of pointer
private int a1,b1;             // variables in calculation of vector field
private double aa1,bb1;        // variables in calculucation of vector field
private int c1,d1;             // location of vector field end point
private double u1,v1;          // coordinate of (x,) with respect to center
private double r1;             // distance from center
private double l=(int) w/4;    // length of planimter arm
private int x_wheel, y_wheel;  // location of wheel on screen
private int ccos, ssin;        // cos and sin of wheel rotation angle 
private int i;                 // index
private int gear=200;          // gear factor to turn wheel, bigger -> wheel slower
private int spines=7;          // symmetry of wheel
private double sum, sum_old;   // integration sum
private boolean active1;       // true during measurement
private int wheel_radius;      // wheel radius
private Color wheel_color;     // wheel color
private int left_border=80;    // border,where wheel no more displayed
private boolean found=false;   // line integral found? 
private boolean counting=false;// summing up? 
private boolean moved=false;   // moved a bit on the curve?


public wheel(int width,int height) {
  this.w = width;   this.h = height;
  l=(int) w/4;
  x_wheel=25; y_wheel=25; 
  sum=0; sum_old=0; 
  active1=false; 
  found=false; 
  counting=false;
  moved=false;
  wheel_radius=22;
  wheel_color=new Color(255,0,255);
}

public void read_pointer(int x, int y) { this.x = x; this.y = y; }
public boolean sum_found()    { return found; } 
public boolean sum_counting() { return counting; } 

public double update( Graphics g, boolean status) {
  active1=status;  
  if (sum==0)  { ccos=1; ssin=0; x_old=x; y_old=y; sum=0.00001; sum_old=sum;}
  if (active1) { wheel_color=new Color(255,0,255); } else { wheel_color=new Color(255,127,255); }

  if (x_old>left_border) {

  for (i=0; i<spines; i++) {
    ccos=(int) (wheel_radius*Math.cos(sum_old/gear+6.283*i/spines));
    ssin=(int) (wheel_radius*Math.sin(sum_old/gear+6.283*i/spines));
    g.setColor(new Color(0,0,0));
    g.drawLine(x_wheel,y_wheel,x_wheel+ccos,y_wheel+ssin);
    g.drawLine(x_old,y_old,x_old+ccos,y_old+ssin);
    g.drawOval(x_wheel+ccos-3,y_wheel+ssin-3,6,6);
  }

  g.setColor(new Color(0,0,0));
  g.drawOval(x_wheel-1,y_wheel-1,2,2);
  g.drawOval(x_wheel-2,y_wheel-2,4,4);
  g.drawOval(x_wheel-3,y_wheel-3,6,6);

  }

  x1=x; y1=y; 
  u1  = (x1-w/2);   v1 = (y1-h/2);
  r1 = Math.sqrt(u1*u1+v1*v1);
  if (r1>(2*l)) { r1=2*l; }; if (r1==0) {r1=1; }
  aa1 = r1/2; bb1=Math.sqrt( l*l-r1*r1/4 );
  a1  = (int) (w/2+( aa1*u1 + bb1*v1)/r1);
  b1  = (int) (h/2+(-bb1*u1 + aa1*v1)/r1);
  c1  = (int) (x1+15*(y1-b1)/l);
  d1  = (int) (y1-15*(x1-a1)/l);

  sum-=(x1-x_old)*(c1-x1)+(y1-y_old)*(d1-y1);

  if (x1>left_border) {

  for (i=0; i<spines; i++) {
    ccos=(int) (wheel_radius*Math.cos(sum/gear+6.283*i/spines)); 
    ssin=(int) (wheel_radius*Math.sin(sum/gear+6.283*i/spines)); 
    g.setColor(wheel_color);
    g.drawLine(x_wheel,y_wheel,x_wheel+ccos,y_wheel+ssin);
    g.drawLine(x1,y1,x1+ccos,y1+ssin);
    g.setColor(new Color(255,0,127));
    g.drawOval(x_wheel+ccos-3,y_wheel+ssin-3,6,6);
  }

  g.setColor(new Color(255,200,255));
  g.drawOval(x_wheel-1,y_wheel-1,2,2);
  g.drawOval(x_wheel-2,y_wheel-2,4,4);
  g.drawOval(x_wheel-3,y_wheel-3,6,6);

  }

  x_old=x1; y_old=y1;
  c_old=c1; d_old=d1;
  sum_old=sum; 

  if ( (x<50) && (y>50) ) {                                                      // reset if over menu
      counting=false; found=false; moved=false;
      sum=0.0000001; 
  } 

  if ( (Math.abs(x-430)>10) || (Math.abs(y-200)>10) && (counting)) {             // check whether moved on curve
    moved=true;
  }
 

  if ( (Math.abs(x-430)<3) && (Math.abs(y-200)<3) && (!found) && (!counting)) {  // reset if first time zero
    sum_old=sum; sum=0.0000001; 
    counting=true; moved=false; 
  }

  if ( (Math.abs(x-430)<3) && (Math.abs(y-200)<3) 
                           && (counting) && (moved) ) { 
      found=true; counting=false; 
  }                                                                             // stop counting if second time zero and moved

  return sum; 
}

}