#include <iostream>
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <GL/glext.h>

GLfloat Left, Right, Near, Far, Top, Bottom;
GLfloat MinX, MaxX, MinY, MaxY;
GLfloat TeaX, TeaY, TeaZ;

GLfloat FrustumRotate;
int WindowID[2];

void NewFrustum();

using namespace std;

void DisplayString(void * font, string s) {
    int i;

    for(i=0; i < s.size(); i++) {
        glutStrokeCharacter(font, s[i]);
    }

    return;
}

void DrawFrustum();
void DrawScene();
void DrawAxis();

void display() {

   glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);
   glLoadIdentity();
   
   glScalef(.25, .25, .25);
   glTranslatef(0,0,6);
   glScalef(1,1,-1);
   glRotatef(FrustumRotate, 0,1,0);


   DrawAxis();
   DrawFrustum();

   glScalef(1,1,-1);
   glTranslatef(0,0,-6);
   DrawScene();

   glFlush();

   return;
}

void display1() {
   glClear(GL_COLOR_BUFFER_BIT);
   glLoadIdentity();

   glTranslatef(0,0,-6);
   DrawScene();

   glFlush();

   return;
}

void DrawAxis() {
   glBegin(GL_LINES);
      glColor3f(1,0,0);
      glVertex3f(0,0,0);
      glVertex3f(1,0,0);
      glColor3f(0,0,1);
      glVertex3f(0,0,0);
      glVertex3f(0,1,0);
      glColor3f(0,1,0);
      glVertex3f(0,0,0);
      glVertex3f(0,0,1);
   glEnd();
}

void DrawScene() {

     glPushMatrix();
     glTranslatef(TeaX,TeaY,TeaZ);
     glColor3f(1,0,0);
     glutWireTeapot(0.5);
     glPopMatrix();

     return;
}

void DrawFrustum() {

    glColor3f(0,0,0);
    // draw the eye
    glutWireSphere(0.125,10,10);

    // draw the front and rear clipping planes
    glBegin(GL_POLYGON);
       glVertex3f(Left, Bottom, Near);
       glVertex3f(Left, Top, Near);
       glVertex3f(Right, Top, Near);
       glVertex3f(Right, Bottom, Near);
    glEnd();

    glBegin(GL_POLYGON);
       glVertex3f(MinX, MinY, Far);
       glVertex3f(MaxX, MinY, Far);
       glVertex3f(MaxX, MaxY, Far);
       glVertex3f(MinX, MaxY, Far);
    glEnd();

    // draw the edges of the frustum
    glEnable(GL_LINE_STIPPLE);
    glBegin(GL_LINES);
       glVertex3f(0,0,0);
       glVertex3f(MinX, MinY, Far);
       glVertex3f(0,0,0);
       glVertex3f(MinX, MaxY, Far);
       glVertex3f(0,0,0);
       glVertex3f(MaxX, MaxY, Far);
       glVertex3f(0,0,0);
       glVertex3f(MaxX, MinY, Far);
    glEnd();
    glDisable(GL_LINE_STIPPLE);

    return;
}

void reset() {

   Left = -1.0;
   Right = 1.0;
   Top = 1.0;
   Bottom = -1.0;
   Near = 1.0; 
   Far = 5.0;

   TeaX = 0;
   TeaY = 0;
   TeaZ = 3;

   FrustumRotate = -90;


   return;
}

void setup() {
   glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
   glClearColor(1,1,1,0);
   glEnable(GL_DEPTH_TEST);
   glLineStipple(2,0xAAAA);

   return;
}

void setup1() {
   glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
   glClearColor(1,1,1,0);
   return;
}

void NewFrustum() {
   GLfloat scale = Far/Near;

   MinX = Left * scale; 
   MaxX = Right * scale; 
   MinY = Bottom * scale;
   MaxY = Top * scale;

   glutSetWindow(WindowID[0]);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-2.0, 2.0, -2.0, 2.0, -10, 10);
   glMatrixMode(GL_MODELVIEW);
   glutPostRedisplay();

   glutSetWindow(WindowID[1]);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(Left,Right, Bottom, Top, Near, Far);
   glMatrixMode(GL_MODELVIEW);
   glutPostRedisplay();

   return;
}

void resize(int w, int h) {
   glViewport(0, 0, w, h);
   NewFrustum();
   return;
}

void resize1(int w, int h) {
   glViewport(0, 0, w, h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(Left, Right, Bottom, Top, Near, Far);
   glMatrixMode(GL_MODELVIEW);
   return;
}

void  keypress (unsigned char key, int x, int y) {

   const float MOVE_AMOUNT = 0.25;
   switch(key) {
     case 'H':
         TeaX += MOVE_AMOUNT;
	 break;
     case 'J':
         TeaY += MOVE_AMOUNT;
	 break;
     case 'K':
         TeaZ += MOVE_AMOUNT;
	 break;
     case 'h':
         TeaX -= MOVE_AMOUNT;
	 break;
     case 'j':
         TeaY -= MOVE_AMOUNT;
	 break;
     case 'k':
         TeaZ -= MOVE_AMOUNT;
	 break;
     case 'N': 
          Near *= 1.10;
	  NewFrustum();
	  break;
     case 'F':
          Far *= 1.10;
	  NewFrustum();
	  break;
     case 'T': 
          Top *= 1.10;
	  NewFrustum();
	  break;
     case 'B':
          Bottom *= 1.10;
	  NewFrustum();
          break;
     case 'L':
          Left *= 1.10;
	  NewFrustum();
          break;
     case 'R':
          Right *= 1.10;
	  NewFrustum();
          break;
     case 'n': 
          Near *= .90;
	  NewFrustum();
	  break;
     case 'f':
          Far *= .90;
	  NewFrustum();
	  break;
     case 't': 
          Top *= .90;
	  NewFrustum();
	  break;
     case 'b':
          Bottom *= .90;
	  NewFrustum();
          break;
     case 'l':
          Left *= .90;
	  NewFrustum();
          break;
     case 'r':
          Right *= .90;
	  NewFrustum();
          break;
     case '!':   // shift of the 1
          FrustumRotate -= 5;
	  break;
     case '1': 
          FrustumRotate += 5;
	  break;
     case '2':
          reset();
          NewFrustum();
	  break;
     case 'q':
          exit(0);
   }


   glutSetWindow(WindowID[0]);
   glutPostRedisplay();

   glutSetWindow(WindowID[1]);
   glutPostRedisplay();

   return;
}

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

   glutInitContextVersion(3, 0);
   glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE);

   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA | GLUT_DEPTH);
   glutInitWindowSize(500, 500);

   WindowID[0] = glutCreateWindow("Frustrum");

   glutDisplayFunc(display);
   glutReshapeFunc(resize);
   glutKeyboardFunc(keypress);
   setup();

   WindowID[1] = glutCreateWindow("Frustrum View");
   glutDisplayFunc(display1);
   glutReshapeFunc(resize1);
   glutKeyboardFunc(keypress);
   setup1();


   glewExperimental = GL_TRUE;
   glewInit();


   glutMainLoop();
}