/* Send the close-button protocol to one PID-checked X11 window. */
#include <X11/Xatom.h>
#include <X11/Xlib.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

static unsigned long parse_id(const char *text) {
    char *end;
    errno = 0;
    unsigned long value = strtoul(text, &end, 0);
    if (errno || *end || end == text || !value || *text == '-') {
        fprintf(stderr, "Invalid positive window ID or PID: %s\n", text);
        exit(2);
    }
    return value;
}

int main(int argc, char **argv) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s WINDOW_ID EXPECTED_PID\n", argv[0]);
        return 2;
    }
    Window window = parse_id(argv[1]);
    unsigned long expected_pid = parse_id(argv[2]);
    Display *display = XOpenDisplay(NULL);
    if (!display) {
        fprintf(stderr, "Cannot open DISPLAY\n");
        return 1;
    }

    Atom type;
    int format;
    unsigned long count, remaining;
    unsigned char *data = NULL;
    int result = XGetWindowProperty(display, window,
        XInternAtom(display, "_NET_WM_PID", False), 0, 1, False, XA_CARDINAL,
        &type, &format, &count, &remaining, &data);
    int matches = result == Success && type == XA_CARDINAL && format == 32 &&
        count == 1 && data && *(unsigned long *)data == expected_pid;
    if (data) XFree(data);
    if (!matches) {
        fprintf(stderr, "Window does not belong to expected PID %lu\n", expected_pid);
        XCloseDisplay(display);
        return 1;
    }

    Atom protocol = XInternAtom(display, "WM_DELETE_WINDOW", False);
    Atom *protocols = NULL;
    int protocol_count = 0, supports_close = 0;
    if (XGetWMProtocols(display, window, &protocols, &protocol_count)) {
        for (int i = 0; i < protocol_count; i++)
            supports_close |= protocols[i] == protocol;
        XFree(protocols);
    }
    if (!supports_close) {
        fprintf(stderr, "Window does not advertise WM_DELETE_WINDOW\n");
        XCloseDisplay(display);
        return 1;
    }

    XEvent event = {0};
    event.xclient.type = ClientMessage;
    event.xclient.window = window;
    event.xclient.message_type = XInternAtom(display, "WM_PROTOCOLS", False);
    event.xclient.format = 32;
    event.xclient.data.l[0] = protocol;
    event.xclient.data.l[1] = CurrentTime;
    int sent = XSendEvent(display, window, False, NoEventMask, &event);
    XSync(display, False);
    XCloseDisplay(display);
    printf("WM_DELETE_WINDOW sent=%d window=%lu pid=%lu\n", sent, window, expected_pid);
    return sent ? 0 : 1;
}