//Example program of simple lighting with two different materials on a 3D cube
//by ZJ Wood for CSC471
#include <stdlib.h>
#include <GL/glut.h>
#include <stdio.h>
#include <math.h>
#include <assert.h>

int GW;
int GH;

int light;
//globals for lighting - use a white light and apply materials
//light position
GLfloat light_pos[4] = {1.0, 1.0, 1.5, 1.0};
//light color (ambiant, diffuse and specular)
GLfloat light_amb[4] = {0.6, 0.6, 0.6, 1.0};
GLfloat light_diff[4] = {0.6, 0.6, 0.6, 1.0};
GLfloat light_spec[4] = {0.8, 0.8, 0.8, 1.0};

int mat = 0;
//set up some materials
typedef struct materialStruct {
  GLfloat ambient[4];
  GLfloat diffuse[4];
  GLfloat specular[4];
  GLfloat shininess[1];
} materialStruct;

materialStruct RedFlat = {
  {0.3, 0.0, 0.0, 1.0},
  {0.9, 0.0, 0.0, 1.0},
  {0.0, 0.0, 0.0, 1.0},
  {0.0}
};
materialStruct GreenShiny = {
  {0.0, 0.3, 0.0, 1.0},
  {0.0, 0.9, 0.0, 1.0},
  {0.2, 1.0, 0.2, 1.0},
  {8.0}
};

//sets up a specific material
void materials(materialStruct materials) {
  glMaterialfv(GL_FRONT, GL_AMBIENT, materials.ambient);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, materials.diffuse);
  glMaterialfv(GL_FRONT, GL_SPECULAR, materials.specular);
  glMaterialfv(GL_FRONT, GL_SHININESS, materials.shininess);
}

//initialization calls for opengl for static light
//note that we still need to enable lighting in order for it to work
//see keyboard 'l' event
void init_lighting() {
  //turn on light0
  glEnable(GL_LIGHT0);
  //set up the diffuse, ambient and specular components for the light
  glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diff);
  glLightfv(GL_LIGHT0, GL_AMBIENT, light_amb);
  glLightfv(GL_LIGHT0, GL_SPECULAR, light_spec);
  //specify our lighting model as 1 normal per face
  glShadeModel(GL_FLAT);
}

void pos_light() {
  //set the light's position
  glMatrixMode(GL_MODELVIEW);
  glLightfv(GL_LIGHT0, GL_POSITION, light_pos);
}

//dorky way to draw a cube one face at a time
void drawcube() {
  
  //color of the cube for when lighting is disabled
  glColor3f(1.0, 0.0, 0.0);

  //left face: for lighting you must specify a normal for each face!
  glNormal3f(-1.0, 0.0, 0.0);
  glBegin(GL_POLYGON);
  glVertex3f(-0.5, 0.5, 0.5); //v5
  glVertex3f(-0.5, 0.5, -0.5); //v4
  glVertex3f(-0.5, -0.5, -0.5); //v1
  glVertex3f(-0.5, -0.5, 0.5); //v8
  glEnd();
  
  //right face:  for lighting you must specify a normal for each face!
  glNormal3f(1.0, 0.0, 0.0);
  glBegin(GL_POLYGON);
  glVertex3f(0.5, -0.5, -0.5); //v2
  glVertex3f(0.5, 0.5, -0.5); //v3
  glVertex3f(0.5, 0.5, 0.5); //v6
  glVertex3f(0.5, -0.5, 0.5); 
  glEnd();
  
  //bottom face:  for lighting you must specify a normal for each face!
  glNormal3f(0, -1.0, 0.0);
  glBegin(GL_POLYGON);
  glVertex3f(-0.5, -0.5, 0.5); //v8
  glVertex3f(0.5, -0.5, 0.5); //v7
  glVertex3f(0.5, -0.5, -0.5); //v2
  glVertex3f(-0.5, -0.5, -0.5); //v1
  glEnd();
  
  //top face:  for lighting you must specify a normal for each face!
  glNormal3f(0, 1.0, 0.0);
  glBegin(GL_POLYGON);
  glVertex3f(0.5, 0.5, -0.5); //v3
  glVertex3f(-0.5, 0.5, -0.5); //v4
  glVertex3f(-0.5, 0.5, 0.5); //v5
  glVertex3f(0.5, 0.5, 0.5); //v6
  glEnd();
  
  //front face:  for lighting you must specify a normal for each face!
  glNormal3f(0, 0, 1.0);
  glBegin(GL_POLYGON);
  glVertex3f(-0.5, 0.5, 0.5); //v5
  glVertex3f(0.5, 0.5, 0.5); //v6
  glVertex3f(0.5, -0.5, 0.5); //v7
  glVertex3f(-0.5, -0.5, 0.5); //v8
  glEnd();

  //back face:  for lighting you must specify a normal for each face!
  glNormal3f(0, 0, -1.0);
  glBegin(GL_POLYGON);
  glVertex3f(-0.5, -0.5, -0.5); //v1
  glVertex3f(0.5, -0.5, -0.5); //v2
  glVertex3f(0.5, 0.5, -0.5); //v3
  glVertex3f(-0.5, 0.5, -0.5); //v4
  glEnd();
  
}

void display() {
  
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
  glMatrixMode(GL_MODELVIEW);
  //save current matrix
  glPushMatrix();

  //set up the camera
  gluLookAt(1.0, 1.0, 1.5, //eye position
    0.0, 0.0, 0.0, //point we are looking at
    0.0, 1.0, 0.0);  //up vector

  //position the light in the scene
  pos_light();
  //draw the cube
  drawcube();
  glPopMatrix();
  
  glutSwapBuffers();
  
}

void reshape(int w, int h) {
  GW = w;
  GH = h;
  
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  //notice the change in the near and far planes - they are measure with respect to the
  //camera position
  glOrtho( -2*(float)w/h, (float)2*w/h, -2, 2, 1.0, 15.0);
  glMatrixMode(GL_MODELVIEW);
  glViewport(0, 0, w, h);
  
}


void keyboard(unsigned char key, int x, int y )
{
  switch( key ) {
   case 'l':
    light = !light;
    if (light)
      glEnable(GL_LIGHTING);
    else
      glDisable(GL_LIGHTING);
    break;
    //simple way to toggle the materials
  case 'm':
    mat++;
    if (mat%2 == 0)
      materials(RedFlat);
    else if (mat%2 == 1)
      materials(GreenShiny);
    break;

  case 'q': case 'Q' :
    exit( EXIT_SUCCESS );
    break;
  }
  glutPostRedisplay();
}


int main(int argc, char** argv) {
  //set up glut window
  glutInit(&argc, argv);
  glutInitWindowSize(400, 400);
  glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
  glutCreateWindow("Example 3D cube with lighting");
  glClearColor(0.0, 0.0, 0.0, 1.0);
  
  //set up glut callbacks
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  
  //initialize globals
  GW = 400;
  GH = 400;
  light = 0;
  
  //enable GL features we want
  glEnable(GL_DEPTH_TEST);
  //only do this once
  init_lighting();
  
  glutMainLoop();
  
}