// SPDX-License-Identifier: WTFPL
// based on https://wayland.freedesktop.org/libinput/doc/latest/api/
// cc -Wall -O2 key_event_unix.c `pkg-config --cflags --libs libinput libudev` -o key_event_unix
// On OpenBSD, this program must be run as root without X.org

#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <inttypes.h>
#include <fcntl.h>
#include <unistd.h>
#include <poll.h>
#include <errno.h>
#include <libudev.h>
#include <libinput.h>

static int open_restricted(const char *path, int flags, void *user_data)
{
	int fd = open(path, flags);
	return fd < 0 ? -errno : fd;
}
 
static void close_restricted(int fd, void *user_data)
{
	close(fd);
}
 
const static struct libinput_interface interface = {
	.open_restricted = open_restricted,
	.close_restricted = close_restricted,
};

int main(void)
{
	struct udev *udev;
	struct libinput *li;
	struct libinput_event *ev;
	struct pollfd pfd;
	struct libinput_event_keyboard *kev;
	struct libinput_event_pointer *pev;
	enum libinput_event_type type;
	enum libinput_key_state ks;
	enum libinput_button_state bs;
	uint32_t key;
	uint64_t us, last_us = 0;
	bool quit = false, first = true;

	if ((udev = udev_new()) == NULL)
		goto fin0;
	if ((li = libinput_udev_create_context(&interface, NULL, udev)) == NULL)
		goto fin1;

	libinput_udev_assign_seat(li, "seat0");
	pfd.fd = libinput_get_fd(li);
	pfd.events = POLLIN;

	while (!quit) {
		poll(&pfd, 1, -1);
		libinput_dispatch(li);

		while ((ev = libinput_get_event(li)) != NULL) {
			type = libinput_event_get_type(ev);

			switch (type) {
			default:
				break;

			case LIBINPUT_EVENT_POINTER_BUTTON:
				pev = libinput_event_get_pointer_event(ev);
				key = libinput_event_pointer_get_button(pev);
				bs = libinput_event_pointer_get_button_state(pev);
				us = libinput_event_pointer_get_time_usec(pev);
				printf("Button %s: VK: 0x%-3X | Interval: ",
				       bs ? "Pressed " : "Released", key);
				if (first) {
					printf("---- ms (First)\n");
					first = false;
				} else {
					printf("%.3f ms\n",
					       (double)(us - last_us) / 1000);
				}
				last_us = us;

				break;

			case LIBINPUT_EVENT_KEYBOARD_KEY:
				kev = libinput_event_get_keyboard_event(ev);
				key = libinput_event_keyboard_get_key(kev);
				ks = libinput_event_keyboard_get_key_state(kev);
				us = libinput_event_keyboard_get_time_usec(kev);
				quit = (key == 1);

				printf("Key %s: VK: 0x%-3X | Interval: ",
				       ks ? "Pressed " : "Released", key);
				if (first) {
					printf("---- ms (First)\n");
					first = false;
				} else {
					printf("%.3f ms\n",
					       (double)(us - last_us) / 1000);
				}
				last_us = us;

				break;
			}
		}

		libinput_event_destroy(ev);
	}

	libinput_unref(li);
fin1:
	udev_unref(udev);
fin0:
	return 0;
}