#include<GL/glut.h>
#include <cstdlib>
#include <iostream>
#include <cmath>

using namespace std;

int n;
int xrot, yrot, zrot;
bool doubleBuffer;

void TeaPot() {
    float color[] = {1.0, 0.0, 0.0, 1.0};

    glColor3f(1.0,0.0,0.0);

      float r, theta, phi;
      float sx, sy,  sz, ex, ey, ez;
      float delta = 2*M_PI/(n);

theta = M_PI /2.0;
      glBegin(GL_LINES);
      for(phi=0; phi<=M_PI*2; phi+= delta) {
        for(theta=0;theta<=M_PI*2;theta+= delta){
            sx = cos(theta)*sin(phi);
            sy = sin(theta)*sin(phi);
            sz  = cos(phi);

            ex = cos(theta+delta)*sin(phi);
            ey = sin(theta+delta)*sin(phi);
            ez  = cos(phi);

            glVertex3f(sx, sy, sz);
            glVertex3f(ex, ey, ez);

            ex = cos(theta)*sin(phi+delta);
            ey = sin(theta)*sin(phi+delta);
            ez  = cos(phi+delta);

            glVertex3f(sx, sy, sz);
            glVertex3f(ex, ey, ez);

       }
      }
      glEnd();

}

void Axis() {
   glColor3f(1.0,0,0); 
   glBegin(GL_LINES);
      glVertex3f(-3,0,0);
      glVertex3f(3,0,0);

      glColor3f(0,1,0); 
      glVertex3f(0,-3,0);
      glVertex3f(0,3,0);
   glEnd();

}

void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();

//    Axis();

    glPushMatrix();
    glRotatef(xrot,1,0,0);
    glRotatef(yrot,0,1,0);
    glRotatef(zrot,0,0,1);
    TeaPot();
    glPopMatrix();
    if(doubleBuffer) { 
        glutSwapBuffers();
    } else {
        glFlush();
    }
}

void myinit() {
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-2.0,2.0,-2.0,2.0,-2.0,2.0);
    glMatrixMode(GL_MODELVIEW);
    glClearColor(1.0,1.0,1.0,1.0);
    glColor3f(0.0,0.0,0.0);
}

void keypress(unsigned char c, int x, int y) {
     switch (c) {
        case 'q': exit(0);
     }
     display();
}

void idle(void){
    xrot += 1;
    yrot += 3;
    zrot -=1;
    xrot=xrot%360;
    yrot=yrot%360;
    zrot=zrot%360;
    display();
}

int main (int argc, char ** argv) {
    int i; 

    doubleBuffer = true;

    for(i=1;i<argc;i++) {
       if (0 == strcmp(argv[i],"-n")) {
           i++;
	   n = atoi(argv[i]);
       } else if (0 == strcmp(argv[i],"-d")) {
           doubleBuffer = !doubleBuffer;
       }
    }

    if (n < 2) {
        n = 20;
    }

    xrot=0; yrot=0; zrot=0;
    glutInit(&argc, argv);

    if (doubleBuffer) {
        glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    } else {
        glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    }

    glutInitWindowSize(500,500);
    glutCreateWindow("Double Buffer Demo");
    glutDisplayFunc(display);
    glutIdleFunc(idle);
    glutKeyboardFunc(keypress);
    myinit();

    glutMainLoop();
}