/* tex_teapot.cpp, based on teatex.c by E. Angel  */
/* An illuminated teapot, with texture mapping that can be turned on/off.
 * The texture mapping can be toggled between replace and modulate modes. 
 *
*/
/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */


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

#define ImageWidth 64
#define ImageHeight 64

GLubyte image[ImageHeight][ImageWidth][3];

static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 2;

int texture = 0; // specifies whether texturing is on or off (default) 
int mode = 0; // specifies texture environment mode (default is replace)


void init_light(void) 
{
  GLfloat mat_diffuse[] = { 1.0, 0.0, 0.0, 1.0 };
  GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
  GLfloat mat_shininess[] = { 60.0 };
  GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };

  glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
  glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
  glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
  glLightfv(GL_LIGHT0, GL_POSITION, light_position);

  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHTING);
  glEnable(GL_DEPTH_TEST);
  glShadeModel(GL_SMOOTH);
}

void init_texture(void)
{
  int i, j, c;

  // create a checker texture pattern
  for(i=0; i<ImageHeight; i++) {
    for(j=0; j<ImageWidth; j++) {
      c = ((((i&0x8)==0)^((j&0x8))==0))*255;
      image[i][j][0]= (GLubyte) c;
      image[i][j][1]= (GLubyte) c;
      image[i][j][2]= (GLubyte) c;
    }
  }

  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, ImageWidth, ImageHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
  glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);
  glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT);
  glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
  glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST); 

  glClearColor(0.4, 0.4, 0.4, 0.0);
}

/* display callback, clear frame buffer and z buffer,
   rotate teapot and draw, swap buffers */
void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  if(texture==1) {
    glEnable(GL_TEXTURE_2D);

    if (mode == 0)
      glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    else
      glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
  }
  else // turn texturing off
      glDisable(GL_TEXTURE_2D);

  glLoadIdentity();
  glRotatef(theta[0], 1.0, 0.0, 0.0);
  glRotatef(theta[1], 0.0, 1.0, 0.0);
  glRotatef(theta[2], 0.0, 0.0, 1.0);

  glutSolidTeapot(1.0);

  glutSwapBuffers();
}

/* Idle callback, spin teapot 2 degrees about selected axis */
void spinTeapot()
{
  theta[axis] += 2.0;
  if( theta[axis] > 360.0 ) theta[axis] -= 360.0;
  glutPostRedisplay();
}

/* mouse callback, selects an axis about which to rotate */
void mouse(int btn, int state, int x, int y)
{
  if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) axis = 0; // X axis
  if(btn==GLUT_MIDDLE_BUTTON && state == GLUT_DOWN) axis = 1; // Y axis
  if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN) axis = 2; // Z axis
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if (w <= h)
    glOrtho(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
            2.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
  else
    glOrtho(-2.0 * (GLfloat) w / (GLfloat) h,
            2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0, -10.0, 10.0);
  glMatrixMode(GL_MODELVIEW);
}

void keyboard(unsigned char key, int x, int y)
{
  if (key == 'q' || key == 'Q')
    exit(0);
  else if(key == '1') 
    glutIdleFunc(spinTeapot);
  else if(key == '2') 
    glutIdleFunc(NULL);
  else if(key == 'p') {
    texture = 0; // plain old shading, turn texturing off
    glutPostRedisplay();
  }
  else if(key == 't') {
    texture = 1; // turn texturing on
    glutPostRedisplay();
  }
  else if(key == 'r') {
    texture = 1; // turn texturing on
    mode = 0; // select Replace mode
    glutPostRedisplay();
  }
  else if(key == 'm') {
    texture = 1; // turn texturing on
    mode = 1; // select Modulate mode
    glutPostRedisplay();
  }
}

int main(int argc, char **argv)
{
  
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(500, 500);
  glutCreateWindow("tex_teapot");

  glutReshapeFunc(myReshape);
  glutDisplayFunc(display);
  glutIdleFunc(NULL);
  glutMouseFunc(mouse);
  glutKeyboardFunc(keyboard);
  init_light();
  init_texture();
  glutMainLoop();

  return 0;
}