/* Une animation en OpenGL                      */
/*                                              */
/* Auteur: Nicolas JANEY                        */
/* nicolas.janey@univ-fcomte.fr                 */
/* Mars 2021                                    */

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#include <GL/glut.h>
#include <GL/gl.h>
#include <GL/glu.h>

static void idle1(void);
static void idle2(void);
static void idle3(void);
static void idle4(void);

/* Variables et constantes globales             */
/* pour les angles et les couleurs utilises     */

static float rx = 0.0F;
static float ry = 0.0F;
static float rz = 0.0F;

static float alphaz1 = 0.0F;
static float alphaz2 = 90.0F;
static float alphaz3 = 180.0F;
static float alphaz4 = 270.0F;

static float delta = 0.2F / (2.0F * 3.14159F * 0.75F) * 360.0F;

/* Affichage des informations relatives         */
/* a OpenGL                                     */

static void informationsOpenGL(void) {
  printf("GL_VENDOR     = %s\n",(const char *) glGetString(GL_VENDOR));
  printf("GL_VERSION    = %s\n",(const char *) glGetString(GL_VERSION));
  printf("GL_RENDERER   = %s\n",(const char *) glGetString(GL_RENDERER));
  printf("GL_EXTENSIONS = %s\n",(const char *) glGetString(GL_EXTENSIONS));
}

/* Fonction d'initialisation des parametres     */
/* OpenGL ne changeant pas au cours de la vie   */
/* du programme                                 */

static void init(void) {
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_NORMALIZE);
}

/* Scene dessinee                               */

static void sphere(float angle, const float *couleur) {
  glPushMatrix();
  glRotatef(angle, 0.0F, 0.0F, 1.0F);
  glTranslatef(0.75F, 0.0F, 0.0F);
  glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, couleur);
  glutSolidSphere(0.1, 36, 36);
  glPopMatrix();
}

static void scene(void) {
  glPushMatrix();
  const float gris[4] = { 0.8F, 0.8F, 0.8F, 1.0F };
  glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, gris);
  glutSolidTorus(0.02, 0.75, 72, 180);
  const float rouge[4] = { 1.0F, 0.0F, 0.0F, 1.0F };
  sphere(alphaz1, rouge);
  const float vert[4] = { 0.0F, 1.0F, 0.0F, 1.0F };
  sphere(alphaz2, vert);
  const float bleu[4] = { 0.0F, 0.0F, 1.0F, 1.0F };
  sphere(alphaz3, bleu);
  const float magenta[4] = { 1.0F, 0.0F, 1.0F, 1.0F };
  sphere(alphaz4, magenta);
  glPopMatrix();
}

/* Fonction executee lors d'un rafraichissement */
/* de la fenetre de dessin                      */

static void display(void) {
  glClearColor(0.5F,0.5F,0.5F,0.5F);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glPushMatrix();
  glRotatef(rz,0.0F,0.0F,1.0F);
  glRotatef(ry,0.0F,1.0F,0.0F);
  glRotatef(rx,1.0F,0.0F,0.0F);
  scene();
  glPopMatrix();
  glFlush();
  glutSwapBuffers();
  int error = glGetError();
  if ( error != GL_NO_ERROR )
    printf("Attention erreur %d\n",error);
}

/* Fonction executee lorsqu'aucun evenement     */
/* n'est en file d'attente                      */

static void idle1(void) {
  //printf("I1\n");
  alphaz1 += 0.11F;
  if (alphaz1 + delta >= alphaz2) {
    alphaz1 = alphaz2 - delta + 360.0F;
    glutIdleFunc(idle2);
  }
  glutPostRedisplay();
}

static void idle2(void) {
  //printf("I2\n");
  alphaz2 += 0.13F;
  if (alphaz2 + delta >= alphaz3) {
    alphaz2 = alphaz3 - delta + 360.0F;
    glutIdleFunc(idle3);
  }
  glutPostRedisplay();
}

static void idle3(void) {
  //printf("I3\n");
  alphaz3 += 0.17F;
  if (alphaz3 + delta >= alphaz4) {
    alphaz3 = alphaz4 - delta + 360.0F;
    glutIdleFunc(idle4);
  }
  glutPostRedisplay();
}

static void idle4(void) {
  //printf("I4\n");
  alphaz4 += 0.19F;
  if (alphaz4 + delta >= alphaz1) {
    alphaz4 = alphaz1 - delta + 360.0F;
    glutIdleFunc(idle1);
  }
  glutPostRedisplay();
}

/* Fonction executee lors d'un changement       */
/* de la taille de la fenetre OpenGL            */

static void reshape(int wx, int wy) {
  glViewport(0, 0, wx, wy);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/* Fonction executee lors de l'appui            */
/* d'une touche non alphanumerique du clavier   */

static void special(int key,int x,int y) {
  switch (key) {
    case GLUT_KEY_UP :
      rx += 1.0F;
      glutPostRedisplay();
      break;
    case GLUT_KEY_DOWN :
      rx -= 1.0F;
      glutPostRedisplay();
      break;
    case GLUT_KEY_LEFT :
      ry += 1.0F;
      glutPostRedisplay();
      break;
    case GLUT_KEY_RIGHT :
      ry -= 1.0F;
      glutPostRedisplay();
      break;
    case GLUT_KEY_PAGE_UP :
      rz += 1.0F;
      glutPostRedisplay();
      break;
    case GLUT_KEY_PAGE_DOWN :
      rz -= 1.0F;
      glutPostRedisplay();
      break; }
}

/* Fonction executee lors de l'appui            */
/* d'une touche alphanumerique du clavier       */

static void keyboard(unsigned char key,int x,int y) {
  switch (key) {
    case 'f' :
    case 'F' :
      { static int fullScreen = 0;
        static int tx;
        static int ty;
        static int px;
        static int py;
        fullScreen = !fullScreen;
        if ( fullScreen ) {
          px = glutGet(GLUT_WINDOW_X);
          py = glutGet(GLUT_WINDOW_Y);
          tx = glutGet(GLUT_WINDOW_WIDTH);
          ty = glutGet(GLUT_WINDOW_HEIGHT);
          glutFullScreen(); }
          else
          glutPositionWindow(px,py);
          glutReshapeWindow(tx,ty); }
      break;
    case 0x0D :
      { static int anim = 0;
        anim = !anim;
        glutIdleFunc(( anim ) ? idle1 : NULL); }
      break;
    case ' ' :
      { informationsOpenGL(); }
      break;
    case 0x1B :
      exit(0);
      break; }
}

/* Fonction principale                          */

int main(int argc,char **argv) {
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH|GLUT_DOUBLE);
  glutInitWindowSize(480,480);
  glutInitWindowPosition(50,50);
  glutCreateWindow("Une animation");
  init();
  glutKeyboardFunc(keyboard);
  glutReshapeFunc(reshape);
  glutSpecialFunc(special);
  glutDisplayFunc(display);
  glutMainLoop();
  return(0);
}