#!/usr/bin/env sh
set -e

path="/sys/class/backlight/intel_backlight"

current_abs=$(cat "$path/actual_brightness")
max_abs=$(cat "$path/max_brightness")

percent=$(( max_abs / 100 ))
current=$(( current_abs / percent ))
new="$current"

change=$2

if [ "$1" = "-get" ]
then
    echo "$current"
    exit 0
fi

if [ "$1" = "-inc" ]
then
    new=$(( current + change ))
fi
if [ "$1" = "-dec" ]
then
    new=$(( current - change ))
fi
if [ "$1" = "-set" ]
then
    new=$2
fi

if [ "$new" -lt 10 ]
then
    new=10
fi
if [ "$new" -gt 100 ]
then
    new=100
fi

echo "$(( new * percent ))" | tee "$path/brightness"