/* prac4a.c */

/*
	Purpose: This program constructs a barn, and uses function keys
				to control translation, rotation and scaling of the shape.
*/

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

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

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


/* Global Constants */

static const float v0[3] = {0.0,0.0,0.0};
static const float v1[3] = {1.0,0.0,0.0};
static const float v2[3] = {1.0,1.0,0.0};
static const float v3[3] = {0.0,1.0,0.0};
static const float v4[3] = {0.0,0.0,1.0};
static const float v5[3] = {1.0,0.0,1.0};
static const float v6[3] = {1.0,1.0,1.0};
static const float v7[3] = {0.0,1.0,1.0};
static const float v8[3] = {0.5,1.25,0.0};
static const float v9[3] = {0.5,1.25,1.0};

/* Functions */

void printHelp( void )
{
	fprintf(stdout, 
		"\nHouse Transformations\n\n"
                "Escape key - exit the program\n\n"
				"F3  - translate 0.5 in x-axis\n"
				"F4  - translate -0.5 in x-axis\n"
				"F5  - rotate 45deg. around x-axis\n"
				"F6  - rotate 45deg. around y-axis\n"
				"F7  - rotate 45deg. around z-axis\n"
				"F8  - scale 1.25 in all axes\n"
				"F9  - scale 0.75 in all axes\n");
}

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

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

	case GLUT_KEY_F3:   /* translate 0.5 in x-axis */
		glTranslatef(0.5,0.0,0.0);
		break;

	case GLUT_KEY_F4:   /* translate -0.5 in x-axis */
		glTranslatef(-0.5,0.0,0.0);
		break;

	case GLUT_KEY_F5:   /* rotate 45 degrees around x-axis */
		glRotatef(45.0,1.0,0.0,0.0);
		break;

	case GLUT_KEY_F6:   /* rotate 45 degrees around y-axis */
		glRotatef(45.0,0.0,1.0,0.0);
		break;

	case GLUT_KEY_F7:   /* rotate 45 degrees around z-axis */
		glRotatef(45.0,0.0,0.0,1.0);
		break;

	case GLUT_KEY_F8:   /* scale 1.25 in all axes */
		glScalef(1.25,1.25,1.25);
		break;

	case GLUT_KEY_F9:   /* scale 0.75 in all axes */
		glScalef(0.75,0.75,0.75);
		break;
    }
	glutPostRedisplay();
}

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 drawBarn( GLvoid )
{
	/* draw rear of house */
	glBegin(GL_LINE_LOOP);
	  glVertex3fv(v0);
	  glVertex3fv(v1);
	  glVertex3fv(v2);
	  glVertex3fv(v3);
	glEnd();

	/* draw front of house */
	glBegin(GL_LINE_LOOP);
	  glVertex3fv(v4);
	  glVertex3fv(v5);
	  glVertex3fv(v6);
	  glVertex3fv(v7);
	glEnd();

	/* draw roof gable at rear and front of house, and connect the two pieces */
	glBegin(GL_LINES);
	  glVertex3fv(v2);
	  glVertex3fv(v8);
	  glVertex3fv(v8);
	  glVertex3fv(v3);
	  glVertex3fv(v6);
	  glVertex3fv(v9);
	  glVertex3fv(v9);
	  glVertex3fv(v7);
	  glVertex3fv(v8);
	  glVertex3fv(v9);

	  /* join front frame to back frame (the sides of the house) */
	  glVertex3fv(v0);
	  glVertex3fv(v4);
	  glVertex3fv(v1);
	  glVertex3fv(v5);
	  glVertex3fv(v3);
	  glVertex3fv(v7);
	  glVertex3fv(v2);
	  glVertex3fv(v6);
	glEnd();
}

GLvoid display( GLvoid )
{
	glClear( GL_COLOR_BUFFER_BIT );
	/* Do all your OpenGL rendering here */
	drawBarn();
	checkError( "display" );
	glFlush();
}

GLvoid init( GLvoid )
{
        glClearColor( 1.0, 1.0, 1.0, 1.0);

		glColor3f(1.0,0.0,0.0);
		glLineWidth(3.0);

		/* Set a viewing volume for the data we wish to display  */
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		glOrtho(-2.0, 2.0, -2.0, 2.0, -2.0, 2.0);  

		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
}

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

	glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
	glutCreateWindow( argv[0] );

	init();

    glutKeyboardFunc( keyboard );
    glutSpecialFunc( specialkeys );
	glutDisplayFunc( display ); 
	printHelp( );

	glutMainLoop();
	return 0;
}