/* prac2c.c  */

/* 
	This program constructs a hexagonal shape. The space bar
	toggles between flat and smooth shading.
*/

#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  */



void printHelp( void )
{
	fprintf(stdout,
		"prac2c\n\n"
                "SPACE key     - alternate between flat and smooth shading\n"
                "Escape key    - exit the program\n\n");
}

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

	case ' ':
	{
		static GLboolean flat = GL_FALSE;
		/* toggle between flat and smooth shading */
		flat = !flat;
		flat ? glShadeModel(GL_FLAT) : glShadeModel(GL_SMOOTH);
	}
	break;

    }
	glutPostRedisplay();
}

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();
	}
}

void drawHexagon( void )
{
	glBegin(GL_POLYGON);
	  glColor3f(0.0, 0.0, 1.0);
	  glVertex2f(1.0, 0.0);
	  glVertex2f(0.5, 1.0);
      glVertex2f(-0.5, 1.0);
	  glVertex2f(-1.0, 0.0);
	  glVertex2f(-0.5, -1.0);
	  glVertex2f(0.5, -1.0);
	glEnd();
}


void drawTriangle( void )
{
	float sqrt5;
	float sqrt15;

	sqrt5 = sqrt(5.0);
	sqrt15 = sqrt(15.0);

	glBegin(GL_TRIANGLES);
	  glVertex2f(1.0, 0.0);
	  glVertex2f(1.0+sqrt5/4.0, sqrt15/4.0);
	  glColor3f(1.0, 0.0, 0.0);
	  glVertex2f(0.5, 1.0);

	  glVertex2f(0.5, 1.0);
	  glVertex2f(0.0, 1.0+sqrt15/4.0);
	  glColor3f(0.0, 1.0, 0.0);
	  glVertex2f(-0.5, 1.0);

	  glVertex2f(-0.5, 1.0);
	  glVertex2f(-1.0-sqrt5/4.0, sqrt15/4.0);
	  glColor3f(1.0, 1.0, 0.0);
	  glVertex2f(-1.0, 0.0);

	  glVertex2f(-1.0, 0.0);
	  glVertex2f(-1.0-sqrt5/4.0, -sqrt15/4.0);
	  glColor3f(0.0, 1.0, 1.0);
	  glVertex2f(-0.5, -1.0);

	  glVertex2f(-0.5, -1.0);
	  glVertex2f(0.0, -1.0-sqrt15/4.0);
	  glColor3f(1.0, 0.0, 1.0);
	  glVertex2f(0.5, -1.0);

	  glVertex2f(0.5, -1.0);
	  glVertex2f(1.0+sqrt5/4.0, -sqrt15/4.0);
	  glColor3f(0.0, 0.0, 0.0);
	  glVertex2f(1.0, 0.0);

	glEnd();
}

GLvoid display( GLvoid )
{
	/* Do all your OpenGL rendering here */
	glClear( GL_COLOR_BUFFER_BIT );

	drawHexagon();
	
	drawTriangle();

	checkError( "display" );
	glFlush();
}

void init( void )
{
        glClearColor( 1.0, 1.0, 1.0, 1.0);
        glPointSize(3.0);        /* set large point size  */
		glLineWidth(3.0);

		/* Set a viewing volume for the data we wish to display  */
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		glOrtho(-3.0, 3.0, -3.0, 3.0,-3.0, 3.0); 
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
}

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

	glutInit( &argc, argv );
	glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );

	glutCreateWindow( argv[0] );   /* use the default window  */

	printHelp();

	glutDisplayFunc( display );

    glutKeyboardFunc( keyboard );
    glutSpecialFunc( specialkeys );

	init();

	glutMainLoop();

	return 0;
}