#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <GL/glut.h>

#define PIXEL_CENTER(x) ((long)(x) + 0.5)

GLint windW, windH;

GLint boxW, boxH;
float color[3];
float angle;

// Initialize OpenGL window - prepare the frame-buffer for z-buffering.
static void glInit ()
{
    // Clear color
    glPushAttrib(GL_COLOR_BUFFER_BIT);
    glColorMask(1, 1, 1, 1);
    glIndexMask(~0);
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glPopAttrib();

   // Enable Depth testing
    glEnable(GL_DEPTH_TEST);
    glClear(GL_DEPTH_BUFFER_BIT);
}

// Function that gets called when the window is resized.
static void Reshape(int width, int height)
{
    // Define window size.
    windW = (GLint)width;
    windH = (GLint)height;

    // Viewport mapping 
    glViewport(0, 0, windW, windH);
    
    // Define a perspective projection with a 45 degree field of view
    // and looking from the the positive z axis at (0,0,10) towards the origin.
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    //glFrustum(-10.0, 10.0, -10.0, 10.0, 1.0, 20.0);	// Alternate method of specifying viewing paramters.
    gluPerspective (45.0, 1.0, 1.0, 20.0);
    
    // Switch matrix stack to modelview stack.
    glMatrixMode(GL_MODELVIEW);
}

// Draw a 1x1x1 box centered about the origin.  The different sides of the box with different colors.
void drawbox (void)
{
   glBegin (GL_POLYGON);
        glColor3f (1.0, 0.0, 0.0);
	glVertex3f (-0.5, -0.5, 0.5);
	glVertex3f (0.5, -0.5, 0.5);
	glVertex3f (0.5, 0.5, 0.5);
	glVertex3f (-0.5, 0.5, 0.5);
   glEnd ();	

   glBegin (GL_POLYGON);
        glColor3f (0.0, 1.0, 0.0);
	glVertex3f (-0.5, -0.5, 0.5);
	glVertex3f (-0.5, 0.5, 0.5);
	glVertex3f (-0.5, 0.5, -0.5);
	glVertex3f (-0.5, -0.5, -0.5);
   glEnd ();	

   glBegin (GL_POLYGON);
        glColor3f (0.0, 0.0, 1.0);
	glVertex3f (0.5, -0.5, 0.5);
	glVertex3f (0.5, 0.5, 0.5);
	glVertex3f (0.5, 0.5, -0.5);
	glVertex3f (0.5, -0.5, -0.5);
   glEnd ();	

   glBegin (GL_POLYGON);
        glColor3f (1.0, 1.0, 0.0);
	glVertex3f (-0.5, 0.5, 0.5);
	glVertex3f (0.5, 0.5, 0.5);
	glVertex3f (0.5, 0.5, -0.5);
	glVertex3f (-0.5, 0.5, -0.5);
   glEnd ();	

   glBegin (GL_POLYGON);
        glColor3f (0.0, 1.0, 1.0);
	glVertex3f (-0.5, -0.5, 0.5);
	glVertex3f (0.5, -0.5, 0.5);
	glVertex3f (0.5, -0.5, -0.5);
	glVertex3f (-0.5, -0.5, -0.5);
   glEnd ();	

   glBegin (GL_POLYGON);
        glColor3f (1.0, 0.0, 1.0);
	glVertex3f (-0.5, -0.5, -0.5);
	glVertex3f (-0.5, 0.5, -0.5);
	glVertex3f (0.5, 0.5, -0.5);
	glVertex3f (0.5, -0.5, -0.5);
   glEnd ();	
}

// Draws the scene at any point in time.
static void Draw(void)
{
    // Clear color and depth buffers
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity ();
    gluLookAt (0.0, 0.0, 10.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

    glPushMatrix ();
      glRotatef (angle, 0.0, 1, 0.0);	// Rotate box
      drawbox ();
    glPopMatrix ();

    glFlush();

    // Increment the rotation angle
    angle += 1.0;
    if (angle == 360.0) angle = 0.0;

	glutSwapBuffers();
}

// Called when a keyboard key is pressed
static void Key(unsigned char key, int x, int y)
{

    switch (key) {
      case 27:
	printf ("exit!\n");
	exit(1);

      default:
	return;
    }

    glutPostRedisplay();
}

// Called when special keys are pressed - arrows and page-up/down
static void SpecialKey(int key, int x, int y)
{

    switch (key) {
    case GLUT_KEY_PAGE_UP: /* PAGE UP key pressed  */
    	printf ("Page Up pressed\n");
	break;
    
    case GLUT_KEY_PAGE_DOWN: /* PAGE DOWN key pressed  */
    	printf ("Page Down pressed\n");
	break;

    case GLUT_KEY_UP: /* Up arrow pressed */
    	printf ("Up Arrow pressed\n");
	break;

    case GLUT_KEY_DOWN: /* Down arrow pressed  */
    	printf ("Down Arrow pressed\n");
	break;

    case GLUT_KEY_LEFT: /* Left arrow pressed  */
    	printf ("Left Arrow pressed\n");
	break;
    
    case GLUT_KEY_RIGHT: /* Right arrow pressed  */
    	printf ("Right Arrow pressed\n");
    	break;

    default:
        return;
    }

    glutPostRedisplay();
}

// Read input.
static GLenum Args(int argc, char **argv)
{
    GLint i, inputfile_count;

    inputfile_count = 0;

    for (i = 1; i < argc; i++) {
    // Add valid input arguments.
	/*if (strcmp(argv[i], "?") == 0) {	
	}
	else {
	    printf("%s (Bad option).\n", argv[i]);
	    return GL_FALSE;
	} */
    }
    return GL_TRUE;
}

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

    if (Args(argc, argv) == GL_FALSE) {
	exit(1);
    }

    // Initialize window size.
    windW = 512;
    windH = 512;
    glutInitWindowPosition(0, 0); glutInitWindowSize( windW, windH);

    // Enable frame buffer for double buffering and z-buffering.
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);

    if (glutCreateWindow("Sample Animation") == GL_FALSE) {
	exit(1);
    }

    angle = 0.0;		// Initialize rotation to 0.0
    glInit ();			
    glutReshapeFunc(Reshape);	// Set reshape function
    glutIdleFunc(Draw);   	// Even if no events, redraw to animate
    glutKeyboardFunc(Key);	// Set keyboard function
    glutSpecialFunc(SpecialKey);   // Set special keyboard function (arrow keys)
    glutDisplayFunc(Draw);	// Set Display function
    glutMainLoop();
    return 0;
}