#!/usr/bin/env bash

current=$(cat /sys/class/backlight/radeon_bl0/brightness)
max=$(cat /sys/class/backlight/radeon_bl0/max_brightness)
step=$2

function setbrightness() {
	sudo tee /sys/class/backlight/radeon_bl0/brightness <<< $1
}

function getpercentage() {
	echo $(awk "BEGIN { pc=100*${current}/${max}; i=int(pc); print (pc-i<0.5)?i:i+1 }")
}

if [ "$1" == "up" ]; then
	current=$((current + step))
	if [ "$current" -gt "$max" ]; then
		current=$max
	fi
	setbrightness $current >> /dev/null
	getpercentage >> /tmp/.brightness
elif [ "$1" == "down" ]; then
	current=$((current - step))
	if [ "$current" -lt "0" ]; then
		current=0
	fi
	setbrightness $current >> /dev/null
	getpercentage >> /tmp/.brightness
elif [ "$1" == "pc" ]; then
	getpercentage
elif [ "$1" == "listen" ]; then
	if [ ! -f /tmp/.brightness ]; then
		getpercentage > /tmp/.brightness
	fi
	tail -f /tmp/.brightness
fi