#include <cstdlib>

// for mac osx
#ifdef __APPLE__
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include <GLUT/glut.h>
#else
// only for windows
#ifdef _WIN32
#include <windows.h>
#endif
// for windows and linux
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/freeglut.h>
#include <math.h>
#endif

#include <iostream>
using namespace std;

#define SPEED 0.1      // OpenGL unit
#define ANG_SPEED 0.01 // degrees

double x_cam = 0.0;
double y_cam = 0.0;
double z_cam = 5.0;

double angleX_cam = 0.0;
double angleY_cam = -M_PI / 2;

void display()
{
    /* define the projection transformation */
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60, 1, 1, 10);

    /* define the viewing transformation */
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(
        x_cam, y_cam, z_cam,
        x_cam + cos(angleY_cam), y_cam + sin(angleX_cam), z_cam + sin(angleY_cam) * cos(angleX_cam),
        0, cos(angleX_cam), 0);

    /* clear window */
    glClear(GL_COLOR_BUFFER_BIT);

    // set current matrix as GL_MODELVIEW
    glMatrixMode(GL_MODELVIEW);

    // draw scene

    // add a copy of the curr. matrix to the stack
    glPushMatrix();

    glPushMatrix();
    // translate by -3 on the z
    glTranslatef(0, 0, -3);
    // set drawing color to red
    glColor3f(1.0f, 0.0f, 0.0f);
    // middle red teapot
    glutWireTeapot(1);
    // translate by 2 on the y
    glTranslatef(0, 2, 0);
    // set drawing color to blue
    glColor3f(0.0f, 1.0f, 0.0f);
    // rotate 90 deg around x
    glRotatef(90, 1.0f, 0.0f, 0.0f);
    // top green teapot
    glutWireTeapot(1);
    // pop the current matrix
    glPopMatrix();

    // translate -2 on y and -1 on z
    glTranslatef(0, -2, -1);
    // set drawing color to blue
    glColor3f(0.0f, 0.0f, 1.0f);
    // bottom blue teapot
    glutWireTeapot(1);

    // pop the current matrix
    glPopMatrix();

    /* flush drawing routines to the window */
    glFlush();
}

// Function called everytime a key is pressed
void key(unsigned char key, int x, int y)
{
    switch (key)
    {
    case 'z':
        z_cam -= SPEED;
        break;
    case 's':
        z_cam += SPEED;
        break;
    case 'q':
        x_cam -= SPEED;
        break;
    case 'd':
        x_cam += SPEED;
        break;
    case 'a':
        y_cam -= SPEED;
        break;
    case 'e':
        y_cam += SPEED;
        break;
    case 27:
        exit(EXIT_SUCCESS);
        break;
    default:
        break;
    }
    glutPostRedisplay();
}

void specialkey(int key, int x, int y)
{
    switch (key)
    {
    case GLUT_KEY_LEFT:
        angleY_cam -= ANG_SPEED;
        break;
    case GLUT_KEY_RIGHT:
        angleY_cam += ANG_SPEED;
        break;
    case GLUT_KEY_DOWN:
        angleX_cam -= ANG_SPEED;
        break;
    case GLUT_KEY_UP:
        angleX_cam += ANG_SPEED;
        break;
    default:
        break;
    }
    glutPostRedisplay();
}

void reshape(int width, int height)
{
    /* define the viewport transformation */
    glViewport(0, 0, width, height);
}

int main(int argc, char *argv[])
{
    /* initialize GLUT, using any commandline parameters passed to the
       program */
    glutInit(&argc, argv);

    /* setup the size, position, and display mode for new windows */
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(0, 0);
    glutInitDisplayMode(GLUT_RGB);

    /* create and set up a window */
    glutCreateWindow("hello, navigator!");
    // Set up the callback functions
    // for display
    glutDisplayFunc(display);
    // for the keyboard
    glutKeyboardFunc(key);
    // for special keys
    glutSpecialFunc(specialkey);
    // for reshaping
    glutReshapeFunc(reshape);

    /* tell GLUT to wait for events */
    glutMainLoop();
}