/* [ʞ] safekill.c <c.hale.su/lexi/util>
 *  ~ lexi hale <lexi@hale.su>
 *  $ cc -Ofast safekill.c -lX11 -lc -osafekill
 *  © affero general public license
 * a utility to make it harder to accidentally nuke
 * important windows on i3wm or whatever. */

#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xatom.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
typedef enum { false, true } bool;
char* isvital(char* str) {
	start: // tail calls for dipshits
		if (*str != '{') {
			if (*str == 0) return 0;
			++str; goto start;
		} else {
			if (str[1] == 'V' && str[2] == '}')
				return str;
			else { ++str; goto start; }
		}
}

Display *display;

void killwin(Window w) {
	XEvent ev;
	long mask = SubstructureRedirectMask | SubstructureNotifyMask;
	ev.xclient.type       = ClientMessage;
	ev.xclient.serial     = 0;
	ev.xclient.send_event = True;
	ev.xclient.message_type = XInternAtom(display, "_NET_CLOSE_WINDOW", False);
	ev.xclient.window     = w;
	ev.xclient.format     = 32;
	
	if(!XSendEvent(display, DefaultRootWindow(display), False, mask, &ev)) {
		char* fallback = getenv("k_safekill_fallback");
		bool nofb = (*fallback == '0' && fallback[1] == 0);

		fprintf(stderr,"\x1b[1mwarning:\x1b[m cannot send _NET_CLOSE_WINDOW event to root window; is your window manager okay?");

		if (nofb) {
			fprintf(stderr,"\n");
		} else {
			fprintf(stderr," falling back to XDestroyWindow, but this may wreck your shit - lots of multi-win apps do *not* like it.\n");
			XDestroyWindow(display,w);
		}
	}
}
int main(const int argc, const char** argv) {
	Window focus;
	int revert;

	bool active;
	enum { vitalize, devitalize, hardkill, softkill } op;

	if (argc > 3) goto usage;
	if (argc == 1)
		op = softkill, active = true;
	else {
		if (argc == 2) active = true;
		else           active = false;

		if (argv[1][0] == '-' && argv[1][2] == 0) { // opt is short switch
			switch (argv[1][1]) { // opt char

				// make window mission-critical
				case 'v': op = vitalize; break;

				// make window acceptable loss
				case 'c': op = devitalize; break;

				// liquidate by any means necessary
				case 'q': op = hardkill; break;

				// with all due respect sir what the fuck
				default: goto usage;
			}
		} else goto usage;
	}

	display = XOpenDisplay(NULL);

	if (active) {
		XGetInputFocus(display, &focus, &revert);
	} else {
		unsigned long temp = strtoul(argv[2], NULL, 0);
		if (errno == EINVAL || errno == ERANGE) goto usage;
		if (temp == 0) goto usage;
		focus = (Window)temp;
	}

	if(op == hardkill) {
		killwin(focus);
		XSync(display,false);
		return 0;
	}

	XClassHint xclh;
	if (XGetClassHint(display,focus,&xclh)) {
		char* v;
		if(v = isvital(xclh.res_class)) {

			if (op == vitalize) return 0; // nothing need be done
			else if (op == devitalize) {
				strcpy(v, v+3);
				XSetClassHint(display,focus,&xclh);
				XSync(display,false);
			} else if (op == softkill) {
				fprintf(stderr, "softkill forbidden\n");
				return 1; // ACCESS DENIED
			}
		} else {
			if (op == vitalize) {
				size_t sz=strlen(xclh.res_class); // TODO: remove double-walk
				xclh.res_class=realloc(xclh.res_class, sz+4);
				xclh.res_class[sz]='{';
				xclh.res_class[sz+1]='V';
				xclh.res_class[sz+2]='}';
				xclh.res_class[sz+3]=0;
				XSetClassHint(display,focus,&xclh);
				XSync(display,false);
			} else if (op == devitalize) return 0;
			else if (op == softkill) {
				// ice that motherfucker
				killwin(focus);
				XSync(display,false);
				return 3;
			}
		}
	} else {
		fprintf(stderr,"\x1b[1merror:\x1b[m bad window\n");
		goto usage;
	}

	return 0;

usage:
	#define info  "\x1b[34m-- "
	#define param "\x1b[32m"
	#define eol   "\x1b[m\n"
	#define bold  "\x1b[1m"
	#define nl    "       "
	fprintf(stderr, bold "usage:\x1b[0m %s    "       "     " info "kill active window if non-vital" eol
						 nl "%1$s -v " param "[id] " info "make [id] or active window vital" eol
						 nl "%1$s -c " param "[id] " info "clear vital flag on [id] or active window" eol
						 nl "%1$s -q " param "[id] " info "'emergency' kill w/o reference to vital flag" eol,
				argv[0]);
	return 1;
}
