// SPDX-License-Identifier: GPL-2.0-only
/*
 * Userspace replacement for mac_hid.c from Linux.
 *
 * Copyright (C) 2022 Thomas Weißschuh
 */

/* cc $(pkg-config --cflags libevdev) $(pkg-config --libs libevdev) mac_hid_userspace.c -o mac_hid_userspace */

#define _GNU_SOURCE

#include <stdio.h>
#include <fcntl.h>
#include <assert.h>
#include <stdlib.h>

#include <libevdev/libevdev.h>
#include <libevdev/libevdev-uinput.h>
#include <linux/input-event-codes.h>

static void update_name(struct libevdev *dev)
{
	char *name;
	int rc = asprintf(&name, "%s (mac_hid)", libevdev_get_name(dev));
	assert(rc > 0);
	libevdev_set_name(dev, name);
	free(name);
}

int main(int argc, char **argv)
{
	int button2 = KEY_RIGHTCTRL;
	int button3 = KEY_RIGHTALT;

	if (argc != 2 && argc != 4) {
		fprintf(stderr, "usage: %s DEVICE [BUTTON2 BUTTON3]\n",
				argv[0]);
		return 1;
	}
	if (argc == 4) {
		char *endptr;
		button2 = strtol(argv[2], &endptr, 0);
		assert(!*endptr);
		button3 = strtol(argv[3], &endptr, 0);
		assert(!*endptr);
	}

	struct libevdev *dev;
	int fd = open(argv[1], O_RDONLY);
	assert(fd != -1);
	int rc = libevdev_new_from_fd(fd, &dev);
	assert(rc == 0);

	libevdev_enable_event_type(dev, EV_KEY);
	libevdev_enable_event_code(dev, EV_KEY, BTN_MIDDLE, NULL);
	libevdev_enable_event_code(dev, EV_KEY, BTN_RIGHT, NULL);

	update_name(dev);

	struct libevdev_uinput *uinput_dev;
	rc = libevdev_uinput_create_from_device(
			dev,
			LIBEVDEV_UINPUT_OPEN_MANAGED,
			&uinput_dev);
	assert(rc == 0);

	rc = libevdev_grab(dev, LIBEVDEV_GRAB);
	assert(rc == 0);

	while (1) {
		struct input_event ev;
		rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
		assert(rc == 0);
		if (ev.type == EV_KEY) {
			if (ev.code == button2)
				ev.code = BTN_MIDDLE;
			else if (ev.code == button3)
				ev.code = BTN_RIGHT;
		}
		rc = libevdev_uinput_write_event(uinput_dev, ev.type, ev.code, ev.value);
		assert(rc == 0);
	}

	libevdev_uinput_destroy(uinput_dev);
	libevdev_free(dev);
}