/*		Hilbert */

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

int x=0,y=0,linea=4,orden;
char tipo;


void hilbert(char tipo,int orden)
{
  if (orden==1)
  {
	if (tipo=='A')
	{	
		glBegin(GL_LINE_STRIP);
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
		glEnd();
	}
	else if (tipo=='B')
	{	
		glBegin(GL_LINE_STRIP);
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
		glEnd();
	}
	else if (tipo=='C')
	{	
		glBegin(GL_LINE_STRIP);
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
		glEnd();
	}
	else if (tipo == 'D')
	{	
		glBegin(GL_LINE_STRIP);
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
		glEnd();
	}
	else
		printf("Type not understood/n");
  }
  else
  {
	if (tipo=='A')
	{	
		hilbert('B',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('A',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('A',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('C',orden-1);
	}
	else if (tipo=='B')
	{	
		hilbert('A',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('B',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('B',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('D',orden-1);
	}
	else if (tipo=='C')
	{	
		hilbert('D',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('C',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('C',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('A',orden-1);
	}
	else if (tipo == 'D')
	{	 
		hilbert('C',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('D',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			x=x-linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('D',orden-1);
		glBegin(GL_LINES);
			glVertex2f(x,y);
			y=y+linea;
			glVertex2f(x,y);
		glEnd();
		hilbert('B',orden-1);
	}
	else
		printf("Type not understood/n");
  }
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);  /* clear the window */
	hilbert(tipo,orden);
	glFlush(); /* clear buffers */
}


void main(int argc, char** argv)
{
	int i, lado = 1;
	float negsize, possize;

	if (argc != 3) {
		printf("Type and Order required/n");
		exit(0);
	}

	tipo = *argv[1];
	orden = atoi(argv[2]);

	/* Standard GLUT initialization */	

	glutInit(&argc,argv);
	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); /* default, not needed */
	glutInitWindowSize(400,400); /* 400 x 400 pixel window */
	glutInitWindowPosition(120,40); /* place window top left on display */
	glutCreateWindow("Hilbert"); /* window title */
	glutDisplayFunc(display); /* display callback invoked when window opened */

	/* attributes */

	glClearColor(0.0, 0.0, 0.0, 0.0); /* Black background */
	glColor3f(1.0, 0.0, 0.0); /* draw in red */

	/* set up viewing, 250 x 250 window with origin lower left */

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	for (i = 1; i < orden; i++)
		lado = 2*lado + 1;
	if (tipo == 'A' || tipo == 'B')	{
		possize = lado*linea;
		negsize = 0.0;
	}
	else {
		possize = 0.0;
		negsize = -lado*linea;
	}
	gluOrtho2D(negsize,possize,negsize,possize);
	glMatrixMode(GL_MODELVIEW);

	glutMainLoop(); /* enter event loop */
}