#!/bin/sh

help() {
cat << EOF
${0}: Wrapper script to change backlight

options:
 -i [Brg]	Increase backlight by Brg
 -d [Brg]	Decrease backlight by Brg
 -s [Brg] 	Set backlight to Brg
 -p		Show the current backlight
 -h 		Print this message and exit

NOTE: Script interprets values as percentages
EOF
}

err() {
	for line in "${@}"; do
		echo "${line}" >&2
	done

	exit 1
}

run() {
	if ! ${1} > /dev/null 2>&1; then
		err "${2}"
	fi
}

if ! command -v brightnessctl > /dev/null 2>&1; then
	err "${0}: brightnessctl must be installed"
fi

if [ ${#} != 1 ] && [ ${#} != 2 ]; then
	err "${0}: Invalid usage" \
	    "Try '${0} -h' for help."
fi

while getopts "i:d:s:ph" option; do
	case "${option}" in
	i)
		run "brightnessctl set +${OPTARG}%" \
		"${0}: Failed to increase brightness"
		exit 0
	;;
	d)
		run "brightnessctl set ${OPTARG}-%" \
		"${0}: Failed to decrease brightness"
		exit 0
	;;
	s)
		run "brightnessctl set ${OPTARG}%" \
		"${0}: Failed to set brightness"
		exit 0
	;;
	p)
		if ! brightnessctl 2>/dev/null; then
			err "Failed to get current brightness"
		else
			exit 0
		fi
	;;
	h) help; exit 0 ;;

	*) err "Try '${0} -h' for help.";;

	esac
done

err "${0}: Invalid usage" \
    "Try '${0} -h' for help."