/* Physics:

  Given two objects with masses M1 and M2, the gravitationl force between
  these objects is F = (G*M1*M2)/(d*d), where d is the distance between the
  center of gravity of the two objects.  Newton also says that F=MA,
  so A1 = G*M2/(d*d) is the accelartion caused by the pull of M2 on M1, and
  A2 = G*M1/(d*d) is that caused by M1 on M2.
 
  The gravitational constant G is 6.673e-11 meters^3/(kg*sec^2) in our
  universe (yours may be different :)

  Acceleration is given in meters/sec^2

  Distances are in meters and mass in kg.
*/


#include "boxworld.h"
#include<pangomm/layout.h>

class darea;
class dwindow;
class body;

// "box" universe dimensions:
#define UW 800
#define UH 600
#define UD 400

// gravitational constant in units of meters^3/(kg*sec^2) 
#define G 6.673e-11
// mass of earth, sun in kg:
#define MEARTH 5.9742e24
#define MSUN 1.99e30

// Simulation Scaling factors, UDIST = distance represented by one pixel,
// UTIME = seconds represented by each animation frame:
#define UDIST 1.0e8
//#define UTIME 1
//#define UTIME 60
//#define UTIME 360
#define UTIME 3600
//#define UTIME 86400
//#define UTIME 2629800
//#define UTIME 31557600
//#define UTIME 31557600.0e3
// time unit between frames - in seconds, minutes, hours, days, etc ...

// Real-time delay between animation frames
#define FDELAY 1.0 
#define GGC Glib::RefPtr<Gdk::GC>


// Main class that contains the simulation:

class darea : public Gtk::DrawingArea
{
 public:
  darea(int x=0, int y=0);
  virtual bool on_expose_event(GdkEventExpose* event);   // inherited method
  Glib::RefPtr<Gdk::GC> makecolorgc(short r, short g, short b);
  void darea::displaytext(const char *c,
		 Glib::RefPtr<Gdk::GC> colorgc,
		 int x, int y
		  );
  int width, height;
  boxworld box;   // 3d boxworld context
  Glib::RefPtr<Gdk::Pixmap> dbuffer;  // offscreen buffer
  Glib::RefPtr<Gdk::Window> win;  // handle on window
  Glib::RefPtr<Gdk::GC> blackgc;  // gcs for drawing different colors
  Glib::RefPtr<Gdk::GC> whitegc;
  Glib::RefPtr<Gdk::GC> rgc, bgc, ggc;
  int i; // some counter
  bool started;  
  void animate();
  void iroutine();
};

// don't touch this class:
class dwindow : public Gtk::Window
{
 public:
  dwindow();
  darea canvas;
};


class body
{
 public:
  double mass; // in kg
  int radius;  // radius in screen pixels
  double xcord, ycord, zcord;    // spacial coordinates
  double xvel, yvel, zvel;       // velocity vector
  // acceleration vector to be calculated dynamically
  body(double m, int r, double x, double y, double z);  // constructor
  void calcforce(body *B);  
  void updateposition();
};