#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <X11/Xmu/WinUtil.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void sendmessage(Window window, Atom type, long data);
Bool can_understand_delete(Window window);

Display *display;
Time current_time;
Atom wm_protocols, wm_delete;

int main(int argc, char **argv)
{
  Window target;

  char buf[4096];
  if (argc == 1 && snprintf(buf, sizeof(buf), "\"%s\" `xselect`", argv[0]) < sizeof(buf))
    execlp("sh", "sh", "-c", buf, NULL);

  if (argc != 2) {
    char *name;
    name = strrchr(argv[0], '/');
    name = name ? name+1 : argv[0];
    fprintf(stderr, "usage: %s window-id\n", name);
    exit(1);
  }

  target = strtol(argv[1], NULL, 10);

  if ((display = XOpenDisplay(NULL)) == NULL) {
    fprintf(stderr, "cannot open display\n");
    exit(1);
  }

  wm_protocols = XInternAtom(display, "WM_PROTOCOLS", False);
  wm_delete = XInternAtom(display, "WM_DELETE_WINDOW", False);

  if (can_understand_delete(target)) {
    sendmessage(target, wm_protocols, wm_delete);
  } else {
    XKillClient(display, target);
  }

  XCloseDisplay(display);
  exit(0);
}

void sendmessage(Window window, Atom type, long data)
{
  XEvent event;

  memset(&event, 0, sizeof(event));
  event.xclient.type = ClientMessage;
  event.xclient.window = window;
  event.xclient.message_type = type;
  event.xclient.format = 32;
  event.xclient.data.l[0] = data;
  event.xclient.data.l[1] = current_time;

  if (XSendEvent(display, window, False, 0L, &event) == 0) {
    fprintf(stderr, "sendmessage failed\n");
  }
}

Bool can_understand_delete(Window window)
{
  unsigned long n, extra;
  Atom *properties;
  Bool result = False;
  Atom real_type;
  int format;
  int i;

  if (XGetWindowProperty(
        display, window, wm_protocols, 0L, 20L, False, XA_ATOM,
        &real_type, &format, &n, &extra, (unsigned char **)&properties)
      != Success) {
    return False;
  }

  for (i=0; i<n; ++i)
    if (properties[i] == wm_delete)
      result = True;

  XFree((char *)properties);
  return result;
}