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

#define GL_GLEXT_PROTOTYPES

#include <GL/gl.h>
#include <GL/glext.h>
#include <GL/glut.h>
#include <sys/time.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <float.h>


GLfloat points [] =
{
  0.5, -1, 0.5, 0, 0, 1, 0.5, 0, 0.5, 0, 0, 1, -0.5, 0, 0.5, 0, 0, 1, -0.5, -1, 0.5, 0, 0, 1, 0.5, -0.5, 0.5, 0, 0, 1, 0, 0, 0.5, 0, 0, 1, -0.5, -0.5, 0.5, 0, 0, 1, 0, -1, 0.5, 0, 0, 1, 0.5, 1, 0.5, 0, 0, 1, -0.5, 1, 0.5, 0, 0, 1, 0, 1, 0.5, 0, 0, 1, -0.5, 0.5, 0.5, 0, 0, 1, 0.5, 0.5, 0.5, 0, 0, 1
};

GLushort conn [] =
{
  4, 1, 5, 2, 6, 3, 7, 0, 10, 9, 11, 2, 5, 1, 12, 8
};

const GLvoid* offsets [] =
{
  (GLvoid*)0x0, (GLvoid*)0x10
};

const GLsizei counts [] =
{
  8, 8
};

GLuint stride = 24;
GLuint normal_offset = 12;
GLuint vert_buffer, conn_buffer;

static int screen_width, screen_height;

static void draw(void)
{
    glBindBuffer(GL_ARRAY_BUFFER, vert_buffer);
    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3, GL_FLOAT, stride, 0);
    glEnableClientState(GL_NORMAL_ARRAY);
    glNormalPointer(GL_FLOAT, stride, reinterpret_cast<GLvoid*>(normal_offset));
    
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, conn_buffer);
    glMultiDrawElements(GL_POLYGON, counts, GL_UNSIGNED_SHORT, offsets, 2);
    
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}

static void drawfunc(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushMatrix();

    // Render some triangles directly in red
    glColor3f(.5, 0, 0);
    draw();

    glPopMatrix();
    glutSwapBuffers();
}

static void idle_visible()
{
    glutPostRedisplay();
}

/* new window size or exposure */
static void reshape(int width, int height)
{
  float h = (float) height / (float) width;
  float s = 1.0;

  screen_width = width;
  screen_height = height;

  glViewport(0, 0, (GLint) width, (GLint) height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-2, 2, -2, 2, -2, 2);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

static void init()
{
  float ambient[3] = { 1, 1, 1 };

  glClearColor(.5, .5, .9, 1.0);

  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, ambient);

  glGenBuffers(1, &vert_buffer);
  glBindBuffer(GL_ARRAY_BUFFER, vert_buffer);
  glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);
  glBindBuffer(GL_ARRAY_BUFFER, 0);
  
  glGenBuffers(1, &conn_buffer);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, conn_buffer);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(conn), conn, GL_STATIC_DRAW);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    
  draw();
  
  glEnable(GL_COLOR_MATERIAL);
  glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
}

void visible(int vis)
{
    glutIdleFunc(idle_visible);
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB|GLUT_DEPTH|GLUT_DOUBLE);
    glutInitWindowPosition(0, 0);
    glutInitWindowSize(200, 200);
    glutCreateWindow("Test VBO glMultiDrawElements");

    glutDisplayFunc(drawfunc);
    glutReshapeFunc(reshape);
    glutVisibilityFunc(visible);

    printf("Vendor: %s\n", glGetString(GL_VENDOR));
    printf("Renderer: %s\n", glGetString(GL_RENDERER));
    printf("Version: %s\n", glGetString(GL_VERSION));
    printf("Extensions: %s\n", glGetString(GL_EXTENSIONS));
    printf("GLU Version: %s\n", gluGetString(GLU_VERSION));
    printf("GLU Extensions: %s\n", gluGetString(GLU_EXTENSIONS));

    fflush(stdout);

    init();
    glutMainLoop();
    return 0;
}