////////////////////////////////////////////////////////////////      
// ballAndTorus.cpp
//
// This program draws a ball that flies around a torus.
//
// Interaction:
// Press space to toggle between animation on and off.
// Press the up/down arrow keys to speed up/slow down animation.
// Press the x, X, y, Y, z, Z keys to rotate the scene.
//
// Sumanta Guha.
////////////////////////////////////////////////////////////////   

#include <iostream>

#ifdef __APPLE__
#  include <GLUT/glut.h>
#else
#  include <GL/glut.h>
#endif

using namespace std;

// Globals.
static float latAngle = 0.0; // Latitudinal angle.
static float longAngle = 0.0; // Longitudinal angle.
static float Xangle = 0.0, Yangle = 0.0, Zangle = 0.0; // Angles to rotate scene.
static int isAnimate = 0; // Animated?
static int animationPeriod = 100; // Time interval between frames.

// Drawing routine.
void drawScene(void)
{
   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -25.0);
       
   // Rotate scene.
   glRotatef(Zangle, 0.0, 0.0, 1.0);
   glRotatef(Yangle, 0.0, 1.0, 0.0);
   glRotatef(Xangle, 1.0, 0.0, 0.0);

   // Fixed torus.
   glColor3f(0.0, 1.0, 0.0);
   glutWireTorus(2.0, 12.0, 20, 20);

   // Begin revolving ball.
   glRotatef(longAngle, 0.0, 0.0, 1.0);
   
   glTranslatef(12.0, 0.0, 0.0);
   glRotatef(latAngle, 0.0, 1.0, 0.0);
   glTranslatef(-12.0, 0.0, 0.0);
   
   glTranslatef(20.0, 0.0, 0.0);

   glColor3f(0.0, 0.0, 1.0);
   glutWireSphere(2.0, 10, 10);
   // End revolving ball.

   // glRotatef(10*latAngle, 0.0, 1.0, 0.0);
   glTranslatef(4.0, 0.0, 0.0);
   
   // Satellite
   glColor3f(1.0, 0.0, 0.0);
   glutWireSphere(0.5, 5, 5);
   
   glutSwapBuffers();
}

// Timer function.
void animate(int value)
{
   if (isAnimate) 
   {
      latAngle += 5.0;
	  if (latAngle > 360.0) latAngle -= 360.0;
      longAngle += 1.0;
	  if (longAngle > 360.0) longAngle -= 360.0;
   }
   glutTimerFunc(animationPeriod, animate, 1);
   glutPostRedisplay();
}

// Initialization routine.
void setup(void) 
{
   glClearColor(1.0, 1.0, 1.0, 0.0); 
   glEnable(GL_DEPTH_TEST); // Enable depth testing.
}

// OpenGL window reshape routine.
void resize(int w, int h)
{
   glViewport(0, 0, (GLsizei)w, (GLsizei)h); 
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-5.0, 5.0, -5.0, 5.0, 5.0, 100.0);

   glMatrixMode(GL_MODELVIEW);
}

// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
{
   switch(key) 
   {
      case 27:
         exit(0);
         break;
	  case ' ': 
         if (isAnimate) isAnimate = 0;
		 else isAnimate = 1;
         glutPostRedisplay();
		 break;
      case 'x':
         Xangle += 5.0;
		 if (Xangle > 360.0) Xangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'X':
         Xangle -= 5.0;
		 if (Xangle < 0.0) Xangle += 360.0;
         glutPostRedisplay();
         break;
      case 'y':
         Yangle += 5.0;
		 if (Yangle > 360.0) Yangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'Y':
         Yangle -= 5.0;
		 if (Yangle < 0.0) Yangle += 360.0;
         glutPostRedisplay();
         break;
      case 'z':
         Zangle += 5.0;
		 if (Zangle > 360.0) Zangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'Z':
         Zangle -= 5.0;
		 if (Zangle < 0.0) Zangle += 360.0;
         glutPostRedisplay();
         break;
      default:
         break;
   }
}

// Callback routine for non-ASCII key entry.
void specialKeyInput(int key, int x, int y)
{
   if (key == GLUT_KEY_DOWN) animationPeriod += 5;
   if( key == GLUT_KEY_UP) if (animationPeriod > 5) animationPeriod -= 5;
   glutPostRedisplay();
}

// Routine to output interaction instructions to the C++ window.
void printInteraction(void)
{
   cout << "Interaction:" << endl;
   cout << "Press space to toggle between animation on and off." << endl
	    << "Press the up/down arrow keys to speed up/slow down animation." << endl
        << "Press the x, X, y, Y, z, Z keys to rotate the scene." << endl;
}

// Main routine.
int main(int argc, char **argv) 
{
   printInteraction();
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); 
   glutInitWindowSize(500, 500);
   glutInitWindowPosition(100, 100); 
   glutCreateWindow("ballAndTorus.cpp"); 
   setup(); 
   glutDisplayFunc(drawScene); 
   glutReshapeFunc(resize);  
   glutKeyboardFunc(keyInput);
   glutSpecialFunc(specialKeyInput);
   glutTimerFunc(5, animate, 1);
   glutMainLoop(); 

   return 0;  
}