#include <math.h>
#include <stdio.h>

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/input.h>

static void screenlight(int up)
{
	static const char *path = "/sys/class/backlight/gmux_backlight/brightness";
	static int    prev, next, tmp;
	static double val;
	static FILE  *fd;

	// Open brightness file
	if (fd == NULL)
		fd = fopen(path, "r+");
	if (fd == NULL) {
		printf("error opening file\n");
		return;
	}

	// Reset if someone else changed the value
	fseek(fd, 0, SEEK_SET);
	fscanf(fd, "%d", &tmp);
	if (tmp != prev)
		val = pow(tmp/1024.0, 1/10.0);
	//if (tmp != prev)
	//	printf("convert: %d -> %d -> %f\n",
	//			prev, tmp, val);

	// Update the current value
	val += 0.01 * (up?1:-1);
	if (val < 0) val = 0;
	if (val > 1) val = 1;

	// Write it back to the file
	next = pow(val, 10) * 1024;
	if (next == prev)
		next += (up?1:-1);
	else
		prev = next;

	//printf("saving:  %d\n", next);
	fprintf(fd, "%d", next);
	fflush(fd);
}

static void keylight(int up)
{
	//static const char *path = "/sys/class/leds/smc::kbd_backlight/brightness";
}

int main(int argc, char **argv)
{
	struct input_event ev;
	int fd, len, debug=0;

	//if ((fd = open("/dev/input/event4", O_RDONLY)) < 0) {
	//if ((fd = open("/dev/input/event6", O_RDONLY)) < 0) {
	if ((fd = open("/dev/input/event10", O_RDONLY)) < 0) {
		printf("Error\n");
		return 0;
	}

	while ((len = read(fd, &ev, sizeof(ev)))) {
		if (len != sizeof(ev)) {
			printf("Error\n");
			sleep(1);
			continue;
		}

		if (debug) {
			printf("%ld.%06lu: type=%04hx code=%04hx val=%08x\n",
					ev.time.tv_sec,
					ev.time.tv_usec,
					ev.type, ev.code, ev.value);
			fflush(stdout);
		}

		if (ev.type != EV_KEY)
			continue;
		if (ev.value == 0) // key up
			continue;

		switch (ev.code) {
			case KEY_BRIGHTNESSDOWN:
				screenlight(0);
				break;
			case KEY_BRIGHTNESSUP:
				screenlight(1);
				break;
			case KEY_KBDILLUMDOWN:
				keylight(0);
				break;
			case KEY_KBDILLUMUP:
				keylight(1);
				break;
		}
		fflush(stdout);
	}
	return 0;
}