/* Bouncing Spheres Program */


#include "animation.C"
#include "animation.moc"
#include <math.h>
#include <stdlib.h>

/*  XBOUND  (600),  YBOUND (400)  */

// Some commonly used colors
#define myblack QColor(0,0,0)
#define myblue QColor(0,0,255)
#define myred QColor(255,0,0)
#define mygreen QColor(0,255,0)
#define mywhite QColor(255,255,255)


int distance(int x1, int y1, int x2, int y2)
{
  return (int) sqrt((double)(((x1-x2)*(x1-x2)) + ((y1-y2)*(y1-y2))));
}

int signof(int a) { if (a<0) return -1; else return 1; }

//used to test if a, b have opposite  signs
bool opposite(int a, int b)
{
  return (signof(a) + signof(b)) == 0;
}

class sphere
{
private:
  int x; int y;  int radius;  // center coords and scale
  int dx;  int dy;    // movement vector

  QColor color;
  QPainter *brush;   // ignore
public:

  sphere(int x0, int y0, int r0, QColor c0,  QPainter *b0)
  { x = x0;  y = y0;  radius = r0;
    color = c0;
    brush = b0;  // ignore
    dx = 0;  dy = 0;  // sphere initially stationary
  }

  void setmovement(int newdx, int newdy)
  { dx = newdx;   dy = newdy; }

  void move()   // change coordinates by dx,dy, bounce off walls
  { 
    // xbounce 
    if ( (x <= radius) || (x >= (XBOUND-radius)) )
      dx = dx * -1;   // bounce;
    if ( (y <= radius) || (y >= (YBOUND-radius)) )
      dy = dy * -1;   // bounce;

     x = x + dx;
     y = y + dy;  
  }

  // returns true if "this" sphere collided with sphere b
  bool collided(sphere b)
  {  // have access to x, y and b.x, b.y , radius, b.radius
    int dist;
    bool answer;
    dist = distance(x,y,b.x,b.y);
    answer = (dist <= radius + b.radius);
    return answer;    
  }

  // changes movement after colliding with object moving in direction bdx,bdy
  void collusion(int bdx, int bdy)
  { 
    //  bounce dx:
    if ( opposite(dx,bdx) ) dx = dx * -1;
    else dx = bdx;
    //  bounce dy:
    if ( opposite(dy,bdy) ) dy = dy * -1;
    else dy = bdy;
  }
  
  // the next two functions allows read-only access to dx,dy
  int getdx()  
  { return dx; }

  int getdy()  
  { return dy; }
  
  void draw()                // draws figure to double buffer (not directly on screen)
  {
        brush->setPen(QPen(color,1));  // set to right color
        brush->setBrush(QBrush(color));
        brush->drawEllipse(x-radius,y-radius,2*radius,2*radius);
  }
};   // end class sphere


void mywindow::animate()
{
  int olddx;  int olddy;

  sphere s0(50,100,30,QColor(255,0,0),brush);
  sphere s1(100,200,20,QColor(0,255,0),brush);

  s0.setmovement(3,3);
  s1.setmovement(-2,5);

  while (true)
    {

      s0.draw();
      s1.draw();

      if (s0.collided(s1)) 
     {  olddx = s0.getdx();   // save original values of s0's dx,dy
        olddy = s0.getdy();
        s0.collusion(s1.getdx(), s1.getdy());
        s1.collusion(olddx, olddy);
      }

      s0.move();
      s1.move();

     refresh();        // updates screen (new figure will be shown!)
     delay(50);        // 80 millisecond delay before next frame should be shown
     clear();          // clears screen of old image
    }
}