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

int do_rotate = 1;

// Callback Funktion: Reaktion auf Tastendruck
void keyb(unsigned char keyPressed, int x, int y)
{
   switch (keyPressed) {
   case 'l':
      // Licht aktivieren
      glEnable(GL_LIGHTING);
      glutPostRedisplay();
      break;
   case 'o':
      // Licht deaktivieren
      glDisable(GL_LIGHTING);
      glutPostRedisplay();
      break;
   case 's':
      // Bewegung stoppen
		do_rotate = 0;
      break;
   case 'g':
      // Bewegung starten
		do_rotate = 1;
      break;
   }
}

void DrawScene(void)
{
   static float rtri = 0.0f;
   // Puffer löschen
   glClearColor(0.0, 0.0, 0.0, 0.0);
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   // EINHEITSMATRIX 
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   // Objekt 5.0 nach hinten versetzen
   glTranslatef(0.0f, 0.0f, -5.0f);
   // und drehen
	   glRotatef(rtri, 0.0f, 1.0f, 0.0f);
   	glRotatef(rtri, 0.0f, 0.0f, 1.0f);
	if (do_rotate) {
	   rtri += .1f;
	}

   glBegin(GL_QUADS);
   // VORNE
   glColor3f(1.0f, 0.0f, 0.0f);
   glNormal3f(0.0f, 0.0f, 1.0f);
   glVertex3f(-1.0f, -1.0f, 1.0f);
   glVertex3f(1.0f, -1.0f, 1.0f);
   glVertex3f(1.0f, 1.0f, 1.0f);
   glVertex3f(-1.0f, 1.0f, 1.0f);
   // HINTEN
   glColor3f(0.0f, 1.0f, 0.0f);
   glNormal3f(0.0f, 0.0f, -1.0f);
   glVertex3f(-1.0f, -1.0f, -1.0f);
   glVertex3f(-1.0f, 1.0f, -1.0f);
   glVertex3f(1.0f, 1.0f, -1.0f);
   glVertex3f(1.0f, -1.0f, -1.0f);
   // OBEN
   glColor3f(0.0f, 0.0f, 1.0f);
   glNormal3f(0.0f, 1.0f, 0.0f);
   glVertex3f(-1.0f, 1.0f, -1.0f);
   glVertex3f(-1.0f, 1.0f, 1.0f);
   glVertex3f(1.0f, 1.0f, 1.0f);
   glVertex3f(1.0f, 1.0f, -1.0f);
   // UNTEN
   glColor3f(1.0f, 1.0f, 0.0f);
   glNormal3f(0.0f, -1.0f, 0.0f);
   glVertex3f(-1.0f, -1.0f, -1.0f);
   glVertex3f(1.0f, -1.0f, -1.0f);
   glVertex3f(1.0f, -1.0f, 1.0f);
   glVertex3f(-1.0f, -1.0f, 1.0f);
   // RECHTS
   glColor3f(0.0f, 1.0f, 1.0f);
   glNormal3f(1.0f, 0.0f, 0.0f);
   glVertex3f(1.0f, -1.0f, -1.0f);
   glVertex3f(1.0f, 1.0f, -1.0f);
   glVertex3f(1.0f, 1.0f, 1.0f);
   glVertex3f(1.0f, -1.0f, 1.0f);
   // LINKS
   glColor3f(1.0f, 0.0f, 1.0f);
   glNormal3f(-1.0f, 0.0f, 0.0f);
   glVertex3f(-1.0f, -1.0f, -1.0f);
   glVertex3f(-1.0f, -1.0f, 1.0f);
   glVertex3f(-1.0f, 1.0f, 1.0f);
   glVertex3f(-1.0f, 1.0f, -1.0f);

   glEnd();

   // Vordergrund- und Hintergrundpuffer wechseln
   glutSwapBuffers();
   glutPostRedisplay();
}

// eigene Initialisierungsfunktion
void myinit()
{
   // Lichtposition
   GLfloat LightPosition[] = { 0.0, 0.0, -1.0, 1.0f };
   // Werte für ambienten Lichtanteil
   GLfloat LightAmbient[] = { 0.1f, 0.1f, 0.1f, 1.0f };
   // Werte für diffusen Lichtanteil
   GLfloat LightDiffuse[] = { .6f, .6f, .6f, 1.0f };
   // Werte für specularen Lichtanteil
   GLfloat LightSpecular[] = { .9f, .9f, .9f, 1.0f };

   // Lichtquelle initialisieren
   glLightfv(GL_LIGHT0, GL_AMBIENT, LightAmbient);
   glLightfv(GL_LIGHT0, GL_DIFFUSE, LightDiffuse);
   glLightfv(GL_LIGHT0, GL_SPECULAR, LightSpecular);
   glLightfv(GL_LIGHT0, GL_POSITION, LightPosition);
   // und aktivieren
   glEnable(GL_LIGHT0);
   glEnable(GL_LIGHTING);
   // Material an
   glEnable(GL_COLOR_MATERIAL);
   glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);

   // Z-Puffer aktivieren
   glDepthFunc(GL_LEQUAL);
   glEnable(GL_DEPTH_TEST);

   // Matritzen setzen
   glMatrixMode(GL_PROJECTION);
   // Sichtpyramide erstellen
   gluPerspective(60.0, 1.0, 1.0, 1000.0);
   // glMatrixMode(GL_MODELVIEW);
   // gluLookAt(0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.);

}

int main(int argc, char *argv[])
{
   // GLUT initialisieren, Fenster setzen
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize(500, 500);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);

   // eigene Initialisierungen
   myinit();

   // Callbacks für Tastaturaktivitäten
   glutKeyboardFunc(keyb);

   // Callback zum Zeichnen der GL-Funktion
   glutDisplayFunc(DrawScene);

   glutMainLoop();

   return EXIT_SUCCESS;

}