import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import Line.*;
import Circle.*;

public class vecnodyncirc extends Applet
{
    /* All of the below values can be changed, and any
    changes will be updated further on in the code 
    automatically.  However, you must be sure that if
    the value is initialized as a double, the new value
    you assign it is also a double NOTE: Certain variables
    have minimum values which they shouldn't fall below.
    For example, the minimum x-value of the applet is 22, 
    because the program is told not to draw anything
    that goes beyond that point.  Therefore, if you set
    the initial x position to below 22, you will probably
    see nothing when the applet is run.  The minimum and
    maximum x/y values are sxpos,sypos,lxpos, and lypos,
    and they should only be altered if you are trying
    to change the overall dimensions of the applet */

    double x1 = 50.0;      //Initial starting positions for
    double y1 = 100.0;     //the two magnets.
    double x2 = 224.0;
    double y2 = 239.0; 
    double bconst = .000;

    double q1 = -1.00;    //Charges and masses for the two
    double q2 = 1.00;     //magnets
    double m1 = 8.00;
    double m2 = 1000.00;

    double dt = 16.0;      //Initial value for delta T

    int r1 = 20;	   //Radius of circles	
    int r2 = 20;

    int dx = 20;		   //Initial value for delta X
    int sig = 1;	   //Initial sign value
    int numline = 17;      //Number of magnetic field lines 

    int ssval1 = numline;  //Initial starting pos. for 	 
    int ssval2 = dx/10;  	   //the scrollbars
    int ssval3 = (int)q2;

    int width = 806;   	   //Defines the dimensions of the 
    int height = 496;	   //main canvas as variables so
    int ixpos = 22;	   //they can be easily changed 
    int iypos = 37;
    int minx = 0;
    int maxx = 750;        //Defines the min and max x and
    int miny = 30;	   //y values of the canvas, after
    int maxy = 470;	   //subtracting the north + south
    			   //borders
    boolean move = false;
    boolean drawline = false;

    /* The next 5 values are used to create and 
    reference the invisible border that exists. */

    int bord = 8;     	   
    int sxpos = 0;
    int lxpos = 450;
    //int sxpos = (ixpos + bord);    	 
    //int lxpos = (ixpos + width) - bord;
    int sypos = (iypos + bord);
    int lypos = (iypos + height) - bord;

    /*  The rest of the variables have no preset values, so
    they are just initialized and then given values later
    on */

    int xcoord, ycoord;

    double dist1;  
    double dist2;
    double compx;
    double compy;

    double arrowlength;
    double arrowlength2 = 17.;
    double squarefunc;
    double angle = 30.;
    double radangle = angle*(Math.PI/180);
    double sinangle = Math.sin(radangle);
    double cosangle = Math.cos(radangle);
    double max = .0003;
    double r;

    long red;
    long green;
    long blue;

    double dx1;
    double dx2;
    double dy1;
    double dy2;

    Line one;		  // Defines a name for the Lines
    Circle cone, ctwo;    // Defines names for the Circles 
	
    /* Adds scrollbars, labels, and buttons, while at the
    same time assigning handles to them */

    Scrollbar dxScroll = new Scrollbar(Scrollbar.HORIZONTAL,ssval2,1,1,5),q2Scroll = new Scrollbar(Scrollbar.HORIZONTAL,1,1,1,10);
    Label dxLabel = new Label("Speed = "+dx),q2Label = new Label("ratio charges =" +q2);
    Button signbutton = new Button("Reverse Sign"),resetbutton = new Button("Reset");

    /* Saves the initial values as backups so they can
    easily be reset to the starting values if neccasery */

    double bx1 = x1;   
    double by1 = y1;  
    double bx2 = x2;
    double by2 = y2; 

    double bq1 = q1;  
    double bq2 = q2; 
    double bm1 = m1;
    double bm2 = m2;

    int bdx = dx;

    int br2 = r2;
    int br1 = r1;
    int bsig = sig;	   
    int bnumline = numline; 

public void init()
    {
    setBackground(Color.white);

    /*Sets up the background and foreground colors for
    both the buttons and the scrollbars */

    signbutton.setForeground(Color.black);
    signbutton.setBackground(Color.lightGray);
    resetbutton.setForeground(Color.black);
    resetbutton.setBackground(Color.lightGray);
    
    dxScroll.setForeground(Color.black);
    dxScroll.setBackground(Color.lightGray);
    q2Scroll.setForeground(Color.black);
    q2Scroll.setBackground(Color.lightGray);

    /*Creates a new layout manager, and groups the buttons
    and scrollbars into panels, which are then placed on
    the North and South sectors of the applet. */

    setLayout(new BorderLayout());
    Panel p = new Panel();
    p.setLayout(new FlowLayout(FlowLayout.CENTER));
    p.add(signbutton);
    p.add(resetbutton);
    add("North",p);

    Panel t = new Panel();
    t.setLayout(new FlowLayout(FlowLayout.CENTER));
    t.add(dxScroll);
    t.add(dxLabel);
    t.add(q2Scroll);
    t.add(q2Label);
    add("South",t);

    /*Draws lines and circles using the syntax defined in
    their respective classes */

    one = new Line(0.0,0.0,0.0,0.0);
    cone = new Circle(0,r1,(int)x1,(int)y1);
    ctwo = new Circle(0,r2,(int)x2,(int)y2);
    }

public void update(Graphics g)
    {
    /*Overrides the update function to only redraw
    specified graphics */

  	if(move == true)
	    {
            paint(g,one,cone, ctwo);
	    move = false;
 	    }
	if(drawline == true)
	    {
            drawline(g,one);
	    }
    }

public void paint(Graphics g)
    {
        paint(g,one,cone,ctwo);
    }

public void paint(Graphics g,Line line,Circle circ, Circle circl) 
    {	

    /*Fills the main drawing canvas with black and then
    draws four white borders around the new drawn area.  
    In order to make this fully customizable, the drawing
    uses variables defined in the beginning. */

    g.setColor(Color.white);    
    g.fillRect(ixpos,iypos,width,height);

    g.setColor(Color.white);     
    g.fillRect(minx,miny,ixpos,(maxy-miny));
    g.fillRect(ixpos,miny,width,(iypos - miny));
    g.fillRect((ixpos + width),miny,(maxx - (ixpos + width)),(maxy - miny));
    g.fillRect(ixpos,(iypos + height),width,(maxy - (iypos + height)));

    /* Does all of the calculations neccasery to make
    the magnets attract and repel eachother, and then
    draws the magnets */

    x1 = circ.cx;
    y1 = circ.cy; 
    circ.cx = (int)x1;
    circ.cy = (int)y1;
    circ.sx = (int)(x1 - r1/2); 
    circ.sy = (int)(y1 - r1/2);

    x2 = circl.cx;
    y2 = circl.cy;
    circl.cx = (int)x2;
    circl.cy = (int)y2;
    circl.sx = (int)(x2 - r2/2); 
    circl.sy = (int)(y2 - r2/2);

    /*Changes the color from black to a light blue, and
    then draws the magnetic field lines originating 
    in the second magnet(m2+q2) using variables defined in 
    the circle and line classes. */

    g.setColor(new Color(26,103,244));

//  draw vector field

    int ix=0;
    int iy=0;
    int numy;
    int numx;
    numx=2+ width/dx;
    numy=2+ height/dx;
    while(ix<numx)
        {
      while(iy<numy)
	{
          line.sx=(ix-1)*dx;
          line.sy=(iy-1)*dx;

                dist1 = Math.sqrt(Math.pow(line.sx-x2, 2) + Math.pow(line.sy-y2, 2));
                dist2 = Math.sqrt(Math.pow(line.sx-x1, 2) + Math.pow(line.sy-y1, 2));
                compx = q2*(line.sx - x2) / Math.pow(dist1,3) + q1*(line.sx - x1) / Math.pow(dist2,3);
                compy = q2*(line.sy - y2) / Math.pow(dist1,3) + q1*(line.sy - y1) / Math.pow(dist2,3)+bconst;
		squarefunc = Math.sqrt(Math.pow(compx,2) + Math.pow(compy,2));
                line.emag = squarefunc;
		r = line.emag/max;

		red = (long)(1020*Math.pow(r-.5,2));
		green = (long)(255*(1.-r));
		blue = (long)(255*(1.-r));

		if(red>255)      {red=255;}
		if(green>255)    {green=255;}
		if(blue>255)     {blue=255;}
	
		if(red<0)      {red=0;}
		if(green<0)    {green=0;}
		if(blue<0)     {blue=0;}
	
		arrowlength = dx/6;

                line.ey = line.sy + (compy/line.emag) * dx/2.;
                line.ex = line.sx + dx*(compx/line.emag)/2.;

                dy1 = 1*(arrowlength*((sinangle*compx-cosangle*compy)/squarefunc));
                dx1 = -1*(arrowlength*((cosangle*compx+sinangle*compy)/squarefunc));
                dy2 = 1*(arrowlength*((-sinangle*compx-cosangle*compy)/squarefunc));
                dx2 = -1*(arrowlength*((cosangle*compx-sinangle*compy)/squarefunc));


		g.setColor(new Color((int)red,(int)green,(int)blue));
                g.drawLine((int)line.sx, (int)line.sy, (int)line.ex, (int)line.ey);
		g.drawLine((int)line.ex, (int)line.ey, (int)(line.ex + dx1),(int)(line.ey + dy1));
		g.drawLine((int)line.ex, (int)line.ey, (int)(line.ex + dx2),(int)(line.ey + dy2));
		
            iy++;
           }
        ix++;
        iy=0;
        }


    g.setColor(Color.red);
    g.fillOval(circl.sx,circl.sy,r2,r2);

    if(q1<0)
	{
    g.setColor(Color.black);
	}
    g.fillOval(circ.sx,circ.sy,r1,r1);

    repaint();
    }

public void drawline(Graphics g,Line line) 
	{
	     line.sx = xcoord;
	     line.sy = ycoord;

	     dist1 = Math.sqrt(Math.pow(line.sx-x2, 2) + Math.pow(line.sy-y2, 2));
	     dist2 = Math.sqrt(Math.pow(line.sx-x1, 2) + Math.pow(line.sy-y1, 2));
             int ilinc = 0;
	     while(dist1 > 5.0 && dist2 > 5. && dist1 < 1000 && dist2 < 1000) 
		{

	     	dist1 = Math.sqrt(Math.pow(line.sx-x2, 2) + Math.pow(line.sy-y2, 2));
		dist2 = Math.sqrt(Math.pow(line.sx-x1, 2) + Math.pow(line.sy-y1, 2));

		compx = q2*(line.sx - x2) / Math.pow(dist1,3) + q1*(line.sx - x1) / Math.pow(dist2,3);
		compy = q2*(line.sy - y2) / Math.pow(dist1,3) + q1*(line.sy - y1) / Math.pow(dist2,3)+bconst;
		line.emag = Math.sqrt(Math.pow(compx,2) + Math.pow(compy,2));

                line.ey = line.sy + (compy/line.emag) * dx/5;
                line.ex = line.sx + dx*(compx/line.emag)/5;


		g.setColor(new Color(0,190,0));
		g.drawLine((int)line.sx, (int)line.sy, (int)line.ex, (int)line.ey);

//   draw arrow head
             if (ilinc>10) {
               double vey,vex;
              vey = line.sy ;
              vex = line.sx ;
               dy1 = 1*(arrowlength2*((sinangle*compx-cosangle*compy)/line.emag));
                dx1 = -1*(arrowlength2*((cosangle*compx+sinangle*compy)/line.emag));
                dy2 = 1*(arrowlength2*((-sinangle*compx-cosangle*compy)/line.emag));
                dx2 = -1*(arrowlength2*((cosangle*compx-sinangle*compy)/line.emag));
               g.drawLine((int)vex, (int)vey, (int)(vex + dx1),(int)(vey + dy1));
                g.drawLine((int)vex, (int)vey, (int)(vex + dx2),(int)(vey + dy2));
               ilinc=0;
                       }

//
		line.sx = line.ex;
		line.sy = line.ey;
                ilinc++;
		}

	    line.sx = xcoord;
	    line.sy = ycoord;
	    dist1 = Math.sqrt(Math.pow(line.sx-x2, 2) + Math.pow(line.sy-y2, 2));
	    dist2 = Math.sqrt(Math.pow(line.sx-x1, 2) + Math.pow(line.sy-y1, 2));
            ilinc=0;
	    while(dist1 > 5.0 && dist2 > 5. && dist1 < 1000 && dist2 < 1000) 
		{
	     	dist1 = Math.sqrt(Math.pow(line.sx-x2, 2) + Math.pow(line.sy-y2, 2));
		dist2 = Math.sqrt(Math.pow(line.sx-x1, 2) + Math.pow(line.sy-y1, 2));

		compx = -1.*(q2*(line.sx - x2) / Math.pow(dist1,3) + q1*(line.sx - x1) / Math.pow(dist2,3));
		compy = -1.*(q2*(line.sy - y2) / Math.pow(dist1,3) + q1*(line.sy - y1) / Math.pow(dist2,3)+bconst);
		line.emag = Math.sqrt(Math.pow(compx,2) + Math.pow(compy,2));
                line.ey = line.sy + (compy/line.emag) * dx/5;
                line.ex = line.sx + dx*(compx/line.emag)/5;
		g.setColor(new Color(0,190,0));
		g.drawLine((int)line.sx, (int)line.sy, (int)line.ex, (int)line.ey);
 
//   draw arrow head
             if (ilinc>10) {
               double vey,vex;
              vey = line.sy ;
              vex = line.sx ;
               dy1 = -1*(arrowlength2*((sinangle*compx-cosangle*compy)/line.emag));
                dx1 = 1*(arrowlength2*((cosangle*compx+sinangle*compy)/line.emag));
                dy2 = -1*(arrowlength2*((-sinangle*compx-cosangle*compy)/line.emag));
                dx2 = 1*(arrowlength2*((cosangle*compx-sinangle*compy)/line.emag));
               g.drawLine((int)vex, (int)vey, (int)(vex + dx1),(int)(vey + dy1));
                g.drawLine((int)vex, (int)vey, (int)(vex + dx2),(int)(vey + dy2));
               ilinc=0;
                    }
//
		line.sx = line.ex;
		line.sy = line.ey;
                ilinc++;
		}

	drawline = false;
	}


public boolean mouseMove(Event e, int x, int y)
    {
    /*Defines the xcoord and ycoord variables in terms
    of the x/y values of the object being moved */

    xcoord = x;
    ycoord = y;
    return true;
    }

public boolean deterHit(Circle circ, int mx, int my)
    {
    /*Tells the program how to decide if an object
    is being selected or not. */

    if (mx > circ.cx - r1 && mx < circ.cx + r1 && my > circ.cy - r1 && my < circ.cy + r1)
	{
	return true;
	}
	return false;
    }

public boolean mouseDown(Event e, int x, int y)
    {
    if (deterHit(cone,x,y))	{cone.hit = 1; }
    if (deterHit(ctwo,x,y))	{ctwo.hit = 1; }
    else
	{
        xcoord = x;
        ycoord = y;
	drawline = true;
	move=false;
	repaint();
	}
    return true;
    }

public boolean mouseUp(Event e, int x, int y)
    {
    cone.hit = 0;
    ctwo.hit = 0;
    move = false;
    return true;
    }

public boolean mouseDrag(Event e, int x, int y)
    {
    xcoord = x;
    ycoord = y;
	
    if (cone.hit == 1) 	{cone.cx = x; cone.cy = y; repaint(); }
    if (ctwo.hit == 1)	{ctwo.cx = x; ctwo.cy = y; repaint(); }
    move = true;
    return true;
    }

public boolean handleEvent(Event e)
    {
    Object target=e.target;

    if(target==dxScroll)
	{
	dx = 10*dxScroll.getValue();
	dxLabel.setText("Speed = " + dx);
	move = true;
	repaint();
   	}
    else if(target==q2Scroll)
	{
	q2 = (double)q2Scroll.getValue();
	q2Label.setText("ratio charges =" + q2);
	move = true;
 	repaint();
	}
    if (e.id==Event.ACTION_EVENT)
	{
	if(target==signbutton)
  	    {
	    sig = (-1*sig);
	    q1  = (-1.0 * q1);
	    move = true;
	    repaint();
	    }
	else if(target==resetbutton)
	    {
	    cone.hit = 0;
	    ctwo.hit = 0;

 	    x1 = bx1;
	    y1 = by1;
	    x2 = bx2;
  	    y2 = by2;

	    cone.cx = (int)bx1;
	    cone.cy = (int)by1;
	    ctwo.cx = (int)bx2;
	    ctwo.cy = (int)by2;

	    q1 = bq1;
	    q2 = bq2;

	    sig = bsig;
	    numline = bnumline;
	    dx = bdx;

	    dxScroll.setValue(ssval2);
	    q2Scroll.setValue(ssval3);

	    dxLabel.setText("Delta X = " + dx);
	    q2Label.setText("ratio charges =" + q2);
	    move = true;
	    repaint();
	    }
	}		
        return super.handleEvent(e); 
    }
}