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

float fovy = 45.0f, angle = 0.0f, eyeX = 0.0f, eyeY = 0.0f, eyeZ = 0.0f;
bool keyNormal[256];
bool keySpecial[256];

void drawGround()
{
    glColor3ub(200, 200, 200);
    glPushMatrix();
    glScalef(5, 0, 5);
    glBegin(GL_QUADS);
        glVertex3f(-1, 0,  1);
        glVertex3f( 1, 0,  1);
        glVertex3f( 1, 0, -1);
        glVertex3f(-1, 0, -1);
    glEnd();
    glPopMatrix();
}

void drawTorus()
{
    glColor3ub(255, 0, 0);
    glPushMatrix();
    glTranslatef(0, 1.25, -2);
    glutWireTorus(0.25, 1, 20, 30);
    glPopMatrix();
}

void drawTeapot()
{
    glColor3ub(0, 0, 255);
    glPushMatrix();
    glTranslatef(0, 1, 0);
    glutWireTeapot(1.0);
    glPopMatrix();
}

void checkKeyboard()
{
    if (keySpecial[GLUT_KEY_UP])
    {
        eyeY += 0.5;
        if(eyeY > 20) eyeY = 20;
    }

    if (keySpecial[GLUT_KEY_DOWN])
    {
        eyeY -= 0.5;
        if(eyeY < -20) eyeY = -20;
    }

    if (keySpecial[GLUT_KEY_LEFT])
    {
        angle -= 1;
        if(angle < 0) angle = 359;
    }

    if (keySpecial[GLUT_KEY_RIGHT])
    {
        angle += 1;
        if(angle > 359) angle = 0;
    }
}

void reshapeWindow(int w, int h)
{
    if (h == 0) h = 1;
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0, 0, w, h);
    gluPerspective(fovy, (GLfloat)w / (GLfloat)h, 0.1, 100);
    glMatrixMode(GL_MODELVIEW);
}

void renderGraphics()
{
    glClearColor(1, 1, 1, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    checkKeyboard();
    eyeX = 6 * sin(angle * M_PI  / 180);
    eyeZ = 6 * cos(angle * M_PI / 180);
    //         eyeX  eyeY  eyeZ centerX centerY centerZ upX upY upZ
    gluLookAt( eyeX, eyeY, eyeZ,     0,      0,      0,    0,  1,  0  );
    glColor3ub(0, 0, 255);
    drawTeapot();
    drawTorus();
    drawGround();
    glutSwapBuffers();
}

void timer(int)
{
    glutPostRedisplay();
    glutTimerFunc(1000.0 / 60.0, timer, 0);
}

void normalKeyPressed(unsigned char key, int x, int y){ keyNormal[key] = true; }
void specialKeyPressed(int key, int x, int y){ keySpecial[key] = true; }
void normalKeyReleased(unsigned char key, int x, int y) { keyNormal[key] = false; }
void specialKeyReleased(int key, int x, int y){ keySpecial[key] = false; }

int main(int argc, char** argv)
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
	glutInitWindowPosition(100, 100);
	glutInitWindowSize(640, 480);
	glutCreateWindow("OpenGL 3D | Use arrow keys to move camera");
	glutDisplayFunc(renderGraphics);
	glutReshapeFunc(reshapeWindow);
	glutKeyboardFunc(normalKeyPressed);
	glutKeyboardUpFunc(normalKeyReleased);
	glutSpecialFunc(specialKeyPressed);
	glutSpecialUpFunc(specialKeyReleased);
	glutTimerFunc(1000.0 / 60.0, timer, 0);
        glEnable(GL_DEPTH_TEST);
	glutMainLoop();
	return 0;
}