/*
 * misc.c - Helper functions for geometry and attributes
 *
 * Written 2016 by Werner Almesberger
 * Copyright 2016 Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


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

#include "misc.h"


static bool eq(int m[6], int xx, int xy, int yx, int yy)
{
	return m[1] == xx && m[2] == xy && m[4] == yx && m[5] == yy;
}


unsigned matrix_to_angle(int m[6])
{
	if (eq(m, 1, 0, 0, -1))
		return 0;
	if (eq(m, 0, -1, -1, 0))
		return 90;
	if (eq(m, -1, 0, 0, 1))
		return 180;
	if (eq(m, 0, 1, 1, 0))
		return 270;
	fprintf(stderr, "unrecognized matrix %d %d %d %d\n",
	    m[1], m[2], m[4], m[5]);
	exit(1);
}


int angle_add(int a, int b)
{
	a += b;
	while (a < 0)
		a += 360;
	return a % 360;
}