#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/Xlib.h>

/* MAJE_LDLIB=-lX11 */

#define WM_STATE_FORMAT	32

static Bool is_normal(Display *dpy, Window win)
{
	static Atom state = None;
	if (state == None) {
		state = XInternAtom(dpy, "WM_STATE", True);
		if (state == None) {
			return False;
		}
	}

	Atom type = AnyPropertyType;
	int format = WM_STATE_FORMAT;
	unsigned long nitems = 0;
	unsigned long bytes = 0;
	unsigned char *prop = NULL;

	int r = XGetWindowProperty(dpy,
		win,
		state,
		0,
		0,
		False,
		type,
		&type,
		&format,
		&nitems,
		&bytes,
		&prop);

	if (r == Success && prop != NULL) {
		XFree(prop);
		return True;
	}

	return False;
}

static Window find_normal_parent(Display *dpy, Window win)
{
	if (win == PointerRoot || win == None || is_normal(dpy, win)) {
		return win;
	}

	Window root = win, parent = win, *children = NULL;
	unsigned int nchildren = 0;
	if (!XQueryTree(dpy, win, &root, &parent, &children, &nchildren)) {
		return None;
	}

	if (parent == win || is_normal(dpy, parent)) {
		return parent;
	}

	return find_normal_parent(dpy, win);
}

static int xsnap_error(Display *dpy, XErrorEvent *e)
{
	char buf[BUFSIZ];
	XGetErrorText(dpy, e->error_code, buf, sizeof(buf));
	fprintf(stderr, "xsnap: %s\n", buf);
	exit(1);
}

int main(int argc, char *argv[])
{
	enum { NONE, LEFT, RIGHT, UP, DOWN } dir = NONE;

	int c = 0;
	while ((c = getopt(argc, argv, "lrud")) != -1) {
		switch (c) {
		case 'l':
			dir = LEFT;
			break;

		case 'r':
			dir = RIGHT;
			break;

		case 'u':
			dir = UP;
			break;

		case 'd':
			dir = DOWN;
			break;

		default:
			return 1;
		}
	}

	if (dir == NONE) {
		fprintf(stderr, "xsnap: missing direction\n");
		return 1;
	}

	/* TODO: if operand, use that, otherwise find focused */

	Display *dpy = XOpenDisplay(NULL);
	XSetErrorHandler(xsnap_error);

	Window root = XDefaultRootWindow(dpy);

	Window focused = root;
	int revert = RevertToNone;
	XGetInputFocus(dpy, &focused, &revert);
	focused = find_normal_parent(dpy, focused);

	XWindowAttributes rootattr = { 0 };
	XGetWindowAttributes(dpy, root, &rootattr);

	XWindowAttributes attributes = { 0 };
	XGetWindowAttributes(dpy, focused, &attributes);

	if (!attributes.override_redirect) {
		fprintf(stderr, "can't override redirect\n");
		exit(1);
	}

	int x = 0;
	int y = 0;
	unsigned w = 0;
	unsigned h = 0;

	switch (dir) {
	case LEFT:
		x = 0;
		y = 0;
		w = rootattr.width / 2;
		h = rootattr.height;
		break;

	case RIGHT:
		x = rootattr.width / 2;
		y = 0;
		w = rootattr.width / 2;
		h = rootattr.height;
		break;

	case UP:
		x = 0;
		y = 0;
		w = rootattr.width;
		h = rootattr.height / 2;
		break;

	case DOWN:
		x = 0;
		y = rootattr.height / 2;
		w = rootattr.width;
		h = rootattr.height / 2;
		break;

	default:
		fprintf(stderr, "somehow missing direction\n");
		return 1;
		break;
	}

	int r = XMoveResizeWindow(dpy, focused, x, y, w ? w : 1, h ? h : 1);
	if (r != 0) {
		XErrorEvent e = { .error_code = r };
		xsnap_error(dpy, &e);
	}

	return 0;
}