/* prac8b.c   */

/*
	Purpose: 
		 An example of how to do various model manipulations on
		 mouse clicks.
*/

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include <stdlib.h>
#include <stdio.h>

#define KEY_ESC 27      /* glut doesn't define this one */


/* Global Variables */

static const GLfloat mNearClip = 5.0;  /* near clipping plane */
static const GLfloat mFarClip  = 10.0;  /* far clipping plane */

enum Actions {ROTATE, NONE};
static enum Actions mAction;

static float mRotX;
static float mRotY;

static float mStartX;
static float mStartY;


void printHelp( void )
{
	fprintf(stdout,
		"\nRotate using the mouse\n\n"
		"Escape key - exit the program\n\n");
}


GLvoid keyboard (GLubyte key, GLint x, GLint y)
{ 
	switch(key)
	{
	case KEY_ESC:      /* exit when escape pressed */
		exit (0);
	break;

	default :
	break ;
	}
}


GLvoid specialkeys( GLint key, GLint x, GLint y)
{
    switch (key) 
	{
    	case GLUT_KEY_F1:   /* print Help information */
        	printHelp ( );
	        break;
    }
}


GLvoid checkError( const char* const label )
{
	GLenum error;

	error = glGetError();
	while ( GL_NO_ERROR != error )
	{
		fprintf( stderr,"%s: %s\n", label, gluErrorString(error) );
		error = glGetError();
	}
}

GLvoid reshape (GLint w, GLint h)
{
	/* Note this alternative method of maintaining the aspect ratio of the scene.
		You should try to understand the advantages and disadvantages of this approach.  */

	if (w >= h)
	{
		glViewport(0, 0, h, h);
	}
	else
	{
		glViewport(0, 0, w, w);
	}

	glMatrixMode (GL_PROJECTION);
	glLoadIdentity ();
	gluPerspective (30, 1.0, mNearClip, mFarClip);
	glMatrixMode (GL_MODELVIEW);
	glLoadIdentity ();

}

void rotateXAxis (float incr)
{   
	mRotX += incr;
}



/*	The y value stays constant and the x and z values change 
	The total distance from the y axis stays constant.        */
void rotateYAxis (float incr)
{   
	mRotY += incr;
}


GLvoid mouse (GLint button, GLint state, GLint x, GLint y)
{
	if (state == GLUT_DOWN) 
	{
		switch (button) 
		{
		case (GLUT_LEFT_BUTTON):
			mAction = ROTATE;
			mStartX = x;
			mStartY = y;
		break;

		default:
			mAction = NONE;
		break;
		} 
	}
	else 
	{
		mAction = NONE;
	}

}

GLvoid motion (GLint x, GLint y)
{   
	float rot_Factor = 0.5;
	float xAxisAngle;
	float yAxisAngle;

	switch (mAction) 
	{
	case (ROTATE):
		yAxisAngle = (((float) mStartX - x) * rot_Factor);
		xAxisAngle = (((float) mStartY - y) * rot_Factor);

		mStartY = y;
		mStartX = x;

		rotateXAxis (-xAxisAngle);
		rotateYAxis (-yAxisAngle);

		break;

	case (NONE):
		break;

	default:
		break;
	}

  glutPostRedisplay();
}

/* Displays 6 faces of a cube  */

GLvoid drawModel (GLvoid)
{
	glBegin(GL_QUADS);
		glColor4f(0.0,0.0,1.0,1.0);
		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_QUADS);
		glColor4f(1.0,0.0,0.0,1.0);
		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_QUADS);
		glColor4f(1.0,1.0,0.0,1.0);
		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();

	glBegin(GL_QUADS);
		glColor4f(0.0,1.0,0.0,1.0);
		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();

	glBegin(GL_QUADS);
		glColor4f(1.0,0.0,1.0,1.0);
		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_QUADS);
		glColor4f(0.0,1.0,1.0,1.0);
		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();

}

GLvoid display(GLvoid)
{
	glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glLoadIdentity();
	/* Translate our origin to midway between the near and far clipping plane */
	glTranslatef(0, 0, -(mNearClip+mFarClip)/2);

	glRotatef(mRotX, 1, 0, 0);
	glRotatef(mRotY, 0, 1, 0);

	drawModel ();
	
	glFlush();

}


GLvoid init(GLvoid)
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glShadeModel(GL_FLAT);
	glEnable(GL_DEPTH_TEST);

	glEnable (GL_CULL_FACE);
	glCullFace(GL_BACK);

	mRotX = 0;
	mRotY = 0;
}



int main(int argc, char** argv)
{
	glutInit (&argc, argv) ;
	glutInitDisplayMode ( GLUT_RGB | GLUT_DEPTH ) ;

	glutCreateWindow (argv[0]) ;

	init();

	glutDisplayFunc (display) ;
	glutKeyboardFunc(keyboard) ;
	glutSpecialFunc (specialkeys);
	glutReshapeFunc (reshape);
	glutMouseFunc   (mouse);
	glutMotionFunc  (motion);

	printHelp( );

	glutMainLoop() ;

return 0 ;
}