#!/bin/sh

brightness=$(cat /sys/class/backlight/intel_backlight/brightness)
max_brightness=$(cat /sys/class/backlight/intel_backlight/max_brightness)
step=$((max_brightness/20))

case "$1" in
	'-u')
		case "$brightness" in
			0) echo 1;;
			1) echo "$step";;
			"$max_brightness") exit 0;;
			*)
				if [ "$brightness" -gt "$((max_brightness-step))" ]; then
					echo "$max_brightness"
				else
					echo "$((brightness+step))"
				fi
				;;
		esac
	;;
	'-d')
		case "$brightness" in
			0) exit 0;;
			1) echo 0;;
			"$step") echo 1;;
			*)
				if [ "$brightness" -le "$step" ]; then
					echo 1
				else
					echo "$((brightness-step))"
				fi
				;;
		esac
	;;
	*) exit 1;;
esac > /sys/class/backlight/intel_backlight/brightness