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

typedef unsigned char uchar;

// number of line segments
static int num_lines = 35;
static int num_circ = 20;
static GLdouble rot_angle = 0;


// callback prototypes
void disp(void);
void keyb(uchar k, int x, int y);
void reshape(int x, int y);
void idle(void);

////////////////////////////////
// main
int main(int argc, char **argv){
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
  glutInitWindowSize(400,400);
  glutInitWindowPosition(100,100);
  glutCreateWindow("spiral.cpp");

  glClearColor(0.0,0.0,0.0,0.0);
  glutDisplayFunc(disp);
  glutKeyboardFunc(keyb);
  glutReshapeFunc(reshape);
  glutIdleFunc(idle);
  glutMainLoop();
  return 0;
}

////////////////
// disp
void disp(void){
  double angle, length;
  glClear(GL_COLOR_BUFFER_BIT);
  glLoadIdentity();
  glRotated(rot_angle, 0.0,0.0,1.0);
  // no GL_LINE_LOOP since it isn't a closed loop
  glBegin(GL_LINE_STRIP);
    for(int i =0;i<num_circ*num_lines;i++){
      angle = i*2*M_PI/num_lines;
      length = 1.0 - i* 1.0 / (num_circ*num_lines);
      glVertex2d(length*cos(angle),length*sin(angle));
    }
  glEnd();

  glutSwapBuffers();
}

////////////////
// idle
void idle(void){

  rot_angle++;

  // avoid rot_angle overflow
  while(rot_angle > 360)
    rot_angle -= 360;

  // redisplay 
  glutPostRedisplay();
}

///////////////////////////////////
// keyb
void keyb(uchar k, int x, int y){

  /*
    Commands:
    -> q: quit
    -> s: start rotate 
    -> S: stop rotate
    -> c: more circles
    -> C: less circles
    -> l: more lines
    -> L: less lines
  */

  switch (k){
  case 'q':
    exit(0);
    break;
  case 'c':
    if(num_lines < 99){
      num_circ++;
      cout << "Spiral consists of " << num_circ << " circles " << endl;
      glutPostRedisplay();
    }
    break;
  case 'C':
    if(num_circ >3){
      num_circ--;
      cout << "Spiral consists of " << num_circ << " circles " << endl;
      glutPostRedisplay();
    }
    break;
  case 'l':
    if(num_lines < 99){
      num_lines++;
      cout << "Circle consists of " << num_lines << " lines " << endl;
      glutPostRedisplay();
    }
    break;
  case 'L':
    if(num_lines >3){
      num_lines--;
      cout << "Circle consists of " << num_lines << " lines " << endl;
      glutPostRedisplay();
    }
    break;
  case 's':
    glutIdleFunc(idle);
    cout << "Rotating " << endl;
    break;
  case 'S':
    glutIdleFunc(NULL);
    cout << "Not rotating" << endl;
    break;
  }
}

//////////////////////////
// reshape
void reshape(int x,int y){
  if(x<y)
    glViewport(0,(y-x)/2,x,x);
  else
    glViewport((x-y)/2,0,y,y);
}