#ifndef SPHERE_H
#define SPHERE_H

#include <GL/gl.h>

void generateSphere(int w, int h, GLuint *VA)
{
  GLuint VB, NB, IB;
  GLfloat vertices[3*w*h + 6];
  GLfloat normals[3*w*h + 6];
  GLuint indices[6*w*h];

  memset(vertices, 0, sizeof(vertices));
  memset(normals, 0, sizeof(normals));
  memset(indices, 0, sizeof(indices));

  for(int i = 0; i < h; i++)
    for(int j = 0; j < w; j++) {
      vertices[3*i*w + 3*j + 0] = normals[3*i*w + 3*j + 0] = sin((float)(i+1.0)/(h+1.0)*M_PI) * cos((float)j/w*2*M_PI);
      vertices[3*i*w + 3*j + 1] = normals[3*i*w + 3*j + 1] = sin((float)(i+1.0)/(h+1.0)*M_PI) * sin((float)j/w*2*M_PI);
      vertices[3*i*w + 3*j + 2] = normals[3*i*w + 3*j + 2] = cos((float)(i+1.0)/(h+1.0)*M_PI);
    }

  vertices[3*w*h + 0] = normals[3*w*h + 0] = 0;
  vertices[3*w*h + 1] = normals[3*w*h + 1] = 0;
  vertices[3*w*h + 2] = normals[3*w*h + 2] = 1;
  vertices[3*w*h + 3] = normals[3*w*h + 3] = 0;
  vertices[3*w*h + 4] = normals[3*w*h + 4] = 0;
  vertices[3*w*h + 5] = normals[3*w*h + 5] = -1;

  for(int i = 0; i < h - 1; i++) {
    for(int j = 0; j < w - 1; j++) {
      indices[6*i*w + 6*j]     = i*w + j;
      indices[6*i*w + 6*j + 1] = i*w + j + 1;
      indices[6*i*w + 6*j + 2] = i*w + j + w;
      indices[6*i*w + 6*j + 3] = i*w + j + 1;
      indices[6*i*w + 6*j + 4] = i*w + j + w + 1;
      indices[6*i*w + 6*j + 5] = i*w + j + w;
    }
    indices[6*i*w + 6*w - 6] = i*w + w - 1;
    indices[6*i*w + 6*w - 5] = i*w;
    indices[6*i*w + 6*w - 4] = i*w + 2*w - 1;
    indices[6*i*w + 6*w - 3] = i*w;
    indices[6*i*w + 6*w - 2] = i*w + w;
    indices[6*i*w + 6*w - 1] = i*w + 2*w - 1;
  }

  for(int i = 0; i < w - 1; i++) {
    indices[6*h*w - 6*w + 6*i + 0] = i;
    indices[6*h*w - 6*w + 6*i + 1] = w*h;
    indices[6*h*w - 6*w + 6*i + 2] = i+1;
    indices[6*h*w - 6*w + 6*i + 3] = w*h - w + i + 1;
    indices[6*h*w - 6*w + 6*i + 4] = w*h + 1;
    indices[6*h*w - 6*w + 6*i + 5] = w*h - w + i;
  }

  indices[6*h*w - 6 + 0] = w - 1;
  indices[6*h*w - 6 + 1] = w*h;
  indices[6*h*w - 6 + 2] = 0;

  glGenVertexArrays(1, VA);
  glBindVertexArray(*VA);

  glGenBuffers(1, &VB);
  glBindBuffer(GL_ARRAY_BUFFER, VB);
  glBufferData(GL_ARRAY_BUFFER, (3*w*h+6)*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);

  glGenBuffers(1, &NB);
  glBindBuffer(GL_ARRAY_BUFFER, NB);
  glBufferData(GL_ARRAY_BUFFER, (3*w*h+6)*sizeof(GLfloat), normals, GL_STATIC_DRAW);
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, 0);

  glGenBuffers(1, &IB);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IB);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6*w*h*sizeof(GLuint), indices, GL_STATIC_DRAW);
}

#endif