/*
 * Copyright (C) 2020 Christian Birchinger
 *
 * Version 0.1
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * Build: gcc borderless.c -Wall -o borderless `pkg-config --cflags --libs x11` `pkg-config --cflags --libs xmu`
 *
 * Usage: borderless [window-id] (No argument will use the current active window)
 *
 * This tool should work as a C replacement for the "borderless" python 2 script i found on various forums.
 * Because Python 2 is EOL i first did a Python 3 version but after finding enough C Xlib examples it was trivial
 * to do a plain C version.
 *
 * If something isn't working change DEBUG to 1 below.
 *
 * Frankenstein copy paste code with sources from:
 *
 * toggle-decorations.c: (C) 2017 Alberts Muktupāvels
 *    https://gist.githubusercontent.com/muktupavels/d03bb14ea6042b779df89b4c87df975d/raw/5a0d4ce582c29e9538364ee0eb551cdf2dddb5e5/toggle-decorations.c
 * gistfile1.c (get the active window on X window system): (c) 2015 Keiichiro Ui
 *    https://gist.githubusercontent.com/kui/2622504/raw/6e5378db5c4073ed8a39f527167c150509537e01/gistfile1.c
 *
 */

#include <limits.h>
#include <stdlib.h>
#include <stdio.h>
#include <locale.h>
#include <string.h>

#include <X11/Xlib.h>
#include <X11/Xmu/WinUtil.h>

Bool xerror = False;

#define DEBUG 0
#define debug_print(...) \
	do { if (DEBUG) fprintf(stderr, __VA_ARGS__); } while (0)

typedef struct
{
	unsigned long flags;
	unsigned long functions;
	unsigned long decorations;
	long input_mode;
	unsigned long status;
} MotifWmHints;


static MotifWmHints *get_motif_wm_hints(Display *display, Window window)
{
	Atom property;
	int result;
	Atom actual_type;
	int actual_format;
	unsigned long nitems;
	unsigned long bytes_after;
	unsigned char *data;

	property = XInternAtom (display, "_MOTIF_WM_HINTS", False);
	result = XGetWindowProperty (display, window, property,
			0, LONG_MAX, False, AnyPropertyType,
			&actual_type, &actual_format,
			&nitems, &bytes_after, &data);

	if (result == Success && data != NULL)
	{
		size_t data_size;
		size_t max_size;
		MotifWmHints *hints;

		data_size = nitems * sizeof (long);
		max_size = sizeof (*hints);

		hints = calloc (1, max_size);

		memcpy (hints, data, data_size > max_size ? max_size : data_size);
		XFree (data);

		return hints;
	}

	return NULL;
}

static void toggle_window_decorations(Display *display, Window window)
{
	MotifWmHints *hints;
	Atom property;
	int nelements;

	hints = get_motif_wm_hints (display, window);
	if (hints == NULL)
	{
		hints = calloc (1, sizeof (*hints));
		hints->decorations = (1L << 0);
	}

	hints->flags |= (1L << 1);
	hints->decorations = hints->decorations == 0 ? (1L << 0) : 0;

	property = XInternAtom (display, "_MOTIF_WM_HINTS", False);
	nelements = sizeof (*hints) / sizeof (long);

	XChangeProperty (display, window, property, property, 32, PropModeReplace,
			(unsigned char *) hints, nelements);

	free (hints);
}

Display *open_display(){
	debug_print("connecting X server ... ");
	Display* d = XOpenDisplay(NULL);
	if(d == NULL){
		debug_print("fail\n");
		exit(1);
	}else{
		debug_print("success\n");
	}
	return d;
}

int handle_error(Display *display, XErrorEvent *error){
	debug_print("ERROR: X11 error\n");
	xerror = True;
	return 1;
}

Window get_focus_window(Display *d){
	Window w;
	int revert_to;
	debug_print("getting input focus window ... ");
	XGetInputFocus(d, &w, &revert_to); // see man
	if(xerror){
		debug_print("fail\n");
		exit(1);
	}else if(w == None){
		debug_print("no focus window\n");
		exit(1);
	}else{
		debug_print("success (window: %d)\n", (int)w);
	}

	return w;
}

// get the top window.
// a top window have the following specifications.
//  * the start window is contained the descendent windows.
//  * the parent window is the root window.
Window get_top_window(Display *d, Window start){
	Window w = start;
	Window parent = start;
	Window root = None;
	Window *children;
	unsigned int nchildren;
	Status s;

	debug_print("getting top window ... \n");
	while (parent != root) {
		w = parent;
		s = XQueryTree(d, w, &root, &parent, &children, &nchildren); // see man

		if (s)
			XFree(children);

		if(xerror){
			printf("X error, aborting\n");
			exit(1);
		}

		debug_print("  get parent (window: %d)\n", (int)w);
	}

	debug_print("success (window: %d)\n", (int)w);

	return w;
}

// search a named window (that has a WM_STATE prop)
// on the descendent windows of the argment Window.
Window get_named_window(Display *d, Window start){
	Window w;
	debug_print("getting named window ... ");
	w = XmuClientWindow(d, start); // see man
	if(w == start)
		debug_print("fail\n");
	debug_print("success (window: %d)\n", (int) w);
	return w;
}

// (XFetchName cannot get a name with multi-byte chars)
void print_window_name(Display *d, Window w){
	XTextProperty prop;
	Status s;

	debug_print("window name:\n");

	s = XGetWMName(d, w, &prop); // see man
	if(!xerror && s){
		int count = 0, result;
		char **list = NULL;
		result = XmbTextPropertyToTextList(d, &prop, &list, &count); // see man
		if(result == Success){
			debug_print("\t%s\n", list[0]);
		}else{
			debug_print("ERROR: XmbTextPropertyToTextList\n");
		}
	}else{
		debug_print("ERROR: XGetWMName\n");
	}
}

void print_window_class(Display *d, Window w){
	Status s;
	XClassHint* class;

	debug_print("application: \n");

	class = XAllocClassHint(); // see man
	if(xerror){
		debug_print("ERROR: XAllocClassHint\n");
	}

	s = XGetClassHint(d, w, class); // see man
	if(xerror || s){
		debug_print("\tname: %s\n\tclass: %s\n", class->res_name, class->res_class);
	}else{
		debug_print("ERROR: XGetClassHint\n");
	}
}

void print_window_info(Display *d, Window w){
	debug_print("--\n");
	print_window_name(d, w);
	print_window_class(d, w);
}

int main(int argc, char *argv[]){
	Display* d;
	Window w;
	Window wa = 0;

	// for XmbTextPropertyToTextList
	setlocale(LC_ALL, ""); // see man locale

	if (argc == 2){
		sscanf (argv[1], "0x%lx", &wa);
		if (wa == 0)
			sscanf (argv[1], "%lu", &wa);
		if (wa == 0){
			printf("Error: Invalid Window id\n");
			return 1;
		}
	}

	d = open_display();
	XSetErrorHandler(handle_error);

	if (wa){
		w = wa;
	} else {
		// get active window
		w = get_focus_window(d);
		w = get_top_window(d, w);
		w = get_named_window(d, w);
	}

	print_window_info(d, w);

	toggle_window_decorations (d, w);

	XCloseDisplay(d);

	return 0;
}