#ifndef ISEA_STATIC
#define ISEA_STATIC
#endif

struct hex {
        int iso;
        int x, y, z;
};

/* y *must* be positive down as the xy /iso conversion assumes this */
ISEA_STATIC
int hex_xy(struct hex *h) {
	if (!h->iso) return 1;
	if (h->x >= 0) {
		h->y = -h->y - (h->x+1)/2;
	} else {
		/* need to round toward -inf, not toward zero, so x-1 */
		h->y = -h->y - h->x/2;
	}
	h->iso = 0;

	return 1;
}

ISEA_STATIC
int hex_iso(struct hex *h) {
	if (h->iso) return 1;

	if (h->x >= 0) {
		h->y = (-h->y - (h->x+1)/2);
	} else {
		/* need to round toward -inf, not toward zero, so x-1 */
		h->y = (-h->y - (h->x)/2);
	}

	h->z = -h->x - h->y;
	h->iso = 1;
	return 1;
}

ISEA_STATIC
int hexbin2(int horizontal, double width, double x, double y,
                int *i, int *j) {
	double z, rx, ry, rz;
	double abs_dx, abs_dy, abs_dz;
	int ix, iy, iz, s;
	struct hex h;

	x = x / cos(30 * M_PI / 180.0); /* rotated X coord */
	y = y - x / 2.0; /* adjustment for rotated X */

	/* adjust for actual hexwidth */
	x /= width;
	y /= width;

	z = -x - y;

	ix = rx = floor(x + 0.5);
	iy = ry = floor(y + 0.5);
	iz = rz = floor(z + 0.5);

	s = ix + iy + iz;

	if (s) {
		abs_dx = fabs(rx - x);
		abs_dy = fabs(ry - y);
		abs_dz = fabs(rz - z);

		if (abs_dx >= abs_dy && abs_dx >= abs_dz) {
			ix -= s;
		} else if (abs_dy >= abs_dx && abs_dy >= abs_dz) {
			iy -= s;
		} else {
			iz -= s;
		}
	}
	h.x = ix;
	h.y = iy;
	h.z = iz;
	h.iso = 1;

	hex_xy(&h);
	*i = h.x;
	*j = h.y;
        return ix * 100 + iy;
}