/*
	Simple Solar system 
	(C) Bedrich Benes 2003
*/

#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#define R 5

static GLfloat alpha,beta;


void Init(void) 
{
   glClearColor(0,0,0,0);
}


void Display(void)
{
}

void Idle(void)
{
     
   static GLfloat time;

   glClear (GL_COLOR_BUFFER_BIT);
   glPushMatrix();
	   glColor3ub(255, 255, 0.0); //Sun
	   glutWireSphere(0.7,20,20);   

	   glColor3ub(0,255,0);	//Earth
	   glRotatef(time/180, 0, 1, 0);
	   glTranslatef(2,0,0);
	   glRotatef(time/10.f,0.0,1.0,0.0);
	   glutWireSphere(0.2,10,8);  

	   glRotatef(-time/10.f,0.0,1.0,0.0);
	   glRotatef(15,1,0.0,0.0);
	   glRotatef(time/28,0.0,1.0,0.0);
	   glTranslatef(1,0,0);  //Moon
	   glRotatef(time/28,0.0,1.0,0.0);
	   glColor3ub(0,255,255);
	   glutWireTeapot(0.1);  
   glPopMatrix();
   time +=50;
   glutSwapBuffers();
}

void Reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h); 
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective(60.0, (GLfloat)w/(GLfloat)h, 1.0, 20.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(0, 0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}

void Kbd(unsigned char key, int x, int y)
{
    switch (key)
	{
	case 27:  exit(0);break;
    }
}

void Spec(GLint key, int xx, int yy)
{
    switch (key)
	{
		case GLUT_KEY_UP:    beta+=0.1;break;
		case GLUT_KEY_DOWN:  beta-=0.1;break;
		case GLUT_KEY_LEFT:  alpha+=0.1;break;
		case GLUT_KEY_RIGHT: alpha-=0.1;break;
    }
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(R*sin(alpha)*cos(beta), R*sin(beta), R*cos(alpha)*cos(beta), 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
   printf("alpha=%i, beta=%i\n",alpha,beta);
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
   glutInitWindowSize (500, 500); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   Init();
   glutDisplayFunc(Display); 
   glutIdleFunc(Idle); 
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Kbd);
   glutSpecialFunc(Spec);
   glutMainLoop();
   return 0;
}