#include <iostream>
#include <GL/glut.h>
#include <cmath>
#include <sys/time.h>
using namespace std;

/* return current time (in seconds) */
static int
current_time(void)
{
   struct timeval tv;
#ifdef __VMS
   (void) gettimeofday(&tv, NULL );
#else
   struct timezone tz;
   (void) gettimeofday(&tv, &tz);
#endif
   return (int) tv.tv_sec;
}



#ifndef M_PI
#define M_PI 3.14159265
#endif

int rot = 0;
   

void drawTorus(float r, float R, int nsides, int rings) {
    float ringDelta = 2.0f * M_PI / rings;
    float sideDelta = 2.0f * M_PI / nsides;
    float theta = 0.0f, cosTheta = 1.0f, sinTheta = 0.0f;
    for (int i = rings - 1; i >= 0; i--) {
    float theta1 = theta + ringDelta;
    float cosTheta1 = (float) cos(theta1);
    float sinTheta1 = (float) sin(theta1);
    glBegin(GL_QUAD_STRIP);
    float phi = 0.0f;
    for (int j = nsides; j >= 0; j--) {
        phi += sideDelta;
        float cosPhi = (float) cos(phi);
        float sinPhi = (float) sin(phi);
        float dist = R + r * cosPhi;
        glNormal3f(cosTheta1 * cosPhi, -sinTheta1 * cosPhi, sinPhi);
        glVertex3f(cosTheta1 * dist, -sinTheta1 * dist, r * sinPhi);
        glNormal3f(cosTheta * cosPhi, -sinTheta * cosPhi, sinPhi);
        glVertex3f(cosTheta * dist, -sinTheta * dist, r * sinPhi);
            }
        glEnd();
        theta = theta1;
        cosTheta = cosTheta1;
        sinTheta = sinTheta1;
        }
}

void myInit(char *progname)
{
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(0,0);
    glutCreateWindow(progname);
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    glColor3f(1.0f, 0.0f, 0.0f);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    glClearDepth(1.0);
    glLineWidth(2);
    glEnable(GL_DEPTH_TEST);
}

void myIdle()
{    
    glutPostRedisplay();
                    
    /* calc framerate */
      {
         static int t0 = -1;
         
         static int frames = 0;
         int t = current_time();

         if (t0 < 0)
            t0 = t;

         frames++;

         if (t - t0 >= 5.0) {
            GLfloat seconds = t - t0;
            GLfloat fps = frames / seconds;
            printf("%d frames in %3.1f seconds = %6.3f FPS\n", frames, seconds,
                   fps);
            t0 = t;
            frames = 0;
         }
      }
}

void myDisplay()
{    
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glClearColor(.3f, .5f, .8f, 1.0f);
    glLoadIdentity();
    glTranslatef(0.0f, 0.0f, -10.0f);
    float frot = rot;
    glRotatef(0.15f * rot, 2.0f * frot, 10.0f * frot, 1.0f);
    glRotatef(0.3f * rot, 3.0f * frot, 1.0f * frot, 1.0f);
    rot++;
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glColor3f(0.9f, 0.9f, 0.9f);
    drawTorus(1, 1.9f + ((float) sin((0.004f * frot))), 15, 15);
    glutSwapBuffers();
}

void myReshape(int width, int height)
{
    float fAspect = width / height;
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    gluPerspective(45.0f, fAspect, 0.5f, 400.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    myInit(argv[0]);
    glutReshapeFunc(myReshape);
    glutIdleFunc(myIdle);
    glutDisplayFunc(myDisplay);
    glutMainLoop();
    
    return 0;
}