/* See LICENSE file for license details. */
#define _XOPEN_SOURCE 500

#include <ctype.h>
#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <X11/keysym.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#define PWD_MAX_LEN 100

#define COLOR1 "#00FF00"
#define COLOR2 "#FF0000"
#define VERSION "42.1337"

typedef struct {
	int screen;
	Window root, win;
	Pixmap pmap;
	unsigned long colors[2];
} Lock;

static Lock **locks;
static int nscreens;
static Bool running = True;

static void
die(const char *errstr, ...) {
	va_list ap;

	va_start(ap, errstr);
	vfprintf(stderr, errstr, ap);
	va_end(ap);
	exit(EXIT_FAILURE);
}

#ifdef __linux__
#include <fcntl.h>
static void
dontkillme(void) {
	int fd;

	fd = open("/proc/self/oom_score_adj", O_WRONLY);
	if (fd < 0 && errno == ENOENT)
		return;
	if (fd < 0 || write(fd, "-1000\n", 6) != 6 || close(fd) != 0)
		die("cannot disable the out-of-memory killer for this process\n");
}
#endif

char *
getpw(void) {
	FILE *pwd_file;
	char *pwd;

	if(!(pwd = malloc(PWD_MAX_LEN * sizeof(*pwd)))) {
		die("could not malloc memory");
	}

#define PWD_FILE "/home/frank/Private/.lock_pwd"
	pwd_file = fopen(PWD_FILE, "r");
	if(!pwd_file) {
		die("Could not open "PWD_FILE" for reading\n");
	}

	fgets(pwd, PWD_MAX_LEN, pwd_file);
	if(pwd[strlen(pwd)-1] == '\n')
		pwd[strlen(pwd)-1] = '\0';
	if(strlen(pwd) <= 1) {
		die("Password seems to short: %s\n", pwd);
	}
	fclose(pwd_file);

	return pwd;

}

static void
readpw(Display *dpy, char *pws)
{
	char buf[32], passwd[256];
	int num, screen;
	unsigned int len, llen;
	KeySym ksym;
	XEvent ev;

	len = llen = 0;
	running = True;

	while(running && !XNextEvent(dpy, &ev)) {
		if(ev.type == KeyPress) {
			buf[0] = 0;
			num = XLookupString(&ev.xkey, buf, sizeof buf, &ksym, 0);
			if(IsKeypadKey(ksym)) {
				if(ksym == XK_KP_Enter)
					ksym = XK_Return;
				else if(ksym >= XK_KP_0 && ksym <= XK_KP_9)
					ksym = (ksym - XK_KP_0) + XK_0;
			}
			if(IsFunctionKey(ksym) || IsKeypadKey(ksym) ||
			   IsMiscFunctionKey(ksym) || IsPFKey(ksym) ||
			   IsPrivateKeypadKey(ksym))
				continue;

			switch(ksym) {
			case XK_Return:
				passwd[len] = '\0';
				running = !!strcmp(passwd, pws);
				if(running)
					XBell(dpy, 100);
				len = 0;
				break;
			case XK_Escape:
				len = 0;
				break;
			case XK_BackSpace:
				if(len)
					--len;
				break;
			default:
				if(num && !iscntrl((int) buf[0]) && 
				   (len + num < sizeof passwd)) { 
					memcpy(passwd + len, buf, num);
					len += num;
				}
				break;
			}
			if(llen == 0 && len != 0) {
				for(screen = 0; screen < nscreens; screen++) {
					XSetWindowBackground(dpy,
					                     locks[screen]->win,
					                     locks[screen]->colors[1]);
					XClearWindow(dpy, locks[screen]->win);
				}
			} else if(llen != 0 && len == 0) {
				for(screen = 0; screen < nscreens; screen++) {
					XSetWindowBackground(dpy,
					                     locks[screen]->win,
					                     locks[screen]->colors[0]);
					XClearWindow(dpy, locks[screen]->win);
				}
			}
			llen = len;
		}
		else for(screen = 0; screen < nscreens; screen++)
			XRaiseWindow(dpy, locks[screen]->win);
	}
}

static void
unlockscreen(Display *dpy, Lock *lock)
{
	if(dpy == NULL || lock == NULL)
		return;

	XUngrabPointer(dpy, CurrentTime);
	XFreeColors(dpy, DefaultColormap(dpy, lock->screen), lock->colors, 2, 0);
	XFreePixmap(dpy, lock->pmap);
	XDestroyWindow(dpy, lock->win);

	free(lock);
}

static Lock *
lockscreen(Display *dpy, int screen)
{
	char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
	unsigned int len;
	Lock *lock;
	XColor color, dummy;
	XSetWindowAttributes wa;
	Cursor invisible;

	if(dpy == NULL || screen < 0)
		return NULL;

	lock = malloc(sizeof(Lock));
	if(lock == NULL)
		return NULL;

	lock->screen = screen;

	lock->root = RootWindow(dpy, lock->screen);

	/* init */
	wa.override_redirect = 1;
	wa.background_pixel = BlackPixel(dpy, lock->screen);
	lock->win = XCreateWindow(dpy, lock->root, 0, 0,
		                  DisplayWidth(dpy, lock->screen),
		                  DisplayHeight(dpy, lock->screen), 0,
		                  DefaultDepth(dpy, lock->screen),
		                  CopyFromParent,
		                  DefaultVisual(dpy, lock->screen),
		                  CWOverrideRedirect | CWBackPixel, &wa);

	XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), COLOR2,
	                 &color, &dummy);
	lock->colors[1] = color.pixel;

	XAllocNamedColor(dpy, DefaultColormap(dpy, lock->screen), COLOR1,
	                 &color, &dummy);
	lock->colors[0] = color.pixel;

	lock->pmap = XCreateBitmapFromData(dpy, lock->win, curs, 8, 8);
	invisible = XCreatePixmapCursor(dpy, lock->pmap, lock->pmap, &color,
	                                &color, 0, 0);
	XDefineCursor(dpy, lock->win, invisible);
	XMapRaised(dpy, lock->win);
	for(len = 1000; len; len--) {
		if(XGrabPointer(dpy, lock->root, False,
		                ButtonPressMask | ButtonReleaseMask | PointerMotionMask,
		                GrabModeAsync, GrabModeAsync, None, invisible,
		                CurrentTime) == GrabSuccess)
			break;
		usleep(1000);
	}
	if(running && (len > 0)) {
		for(len = 1000; len; len--) {
			if(XGrabKeyboard(dpy, lock->root, True, GrabModeAsync,
			                 GrabModeAsync, CurrentTime)
			                 == GrabSuccess)
				break;
			usleep(1000);
		}
	}

	running &= (len > 0);
	if(!running) {
		unlockscreen(dpy, lock);
		lock = NULL;
	}
	else 
		XSelectInput(dpy, lock->root, SubstructureNotifyMask);

	return lock;
}

static void
usage(void) {
	fprintf(stderr, "usage: slock [-v]\n");
	exit(EXIT_FAILURE);
}

int
main(int argc, char **argv) {
	char *pws;
	Display *dpy;
	int screen;

	if((argc == 2) && !strcmp("-v", argv[1]))
		die("slock-%s, © 2006-2012 Anselm R Garbe\n", VERSION);
	else if(argc != 1)
		usage();

#ifdef __linux__
	//dontkillme();
#endif

	pws = getpw();

	if(!(dpy = XOpenDisplay(0)))
		die("slock: cannot open display\n");

	/* Get the number of screens in display "dpy" and blank them all. */
	nscreens = ScreenCount(dpy);
	locks = malloc(sizeof(Lock *) * nscreens);
	if(locks == NULL)
		die("slock: malloc: %s\n", strerror(errno));

	int nlocks = 0;
	for(screen = 0; screen < nscreens; screen++) {
		if((locks[screen] = lockscreen(dpy, screen)) != NULL)
			nlocks++;
	}
	XSync(dpy, False);

	/* Did we actually manage to lock something? */
	if(nlocks == 0) { // nothing to protect
		free(locks);
		XCloseDisplay(dpy);
		return 1;
	}

	/* Everything is now blank. Now wait for the correct password. */
	readpw(dpy, pws);

	/* Password ok, unlock everything and quit. */
	for(screen = 0; screen < nscreens; screen++)
		unlockscreen(dpy, locks[screen]);

	free(locks);
	free(pws);
	XCloseDisplay(dpy);

	return 0;
}