#!/usr/bin/env bash
# Keep brightness changes on the backlight; keyboard LEDs are separate devices.
set -euo pipefail
export LC_ALL=C

case "${1:-}" in
    up|down|show) ;;
    *) echo "Usage: notify-brightness {up|down|show}" >&2; exit 2 ;;
esac

# Brightness keys have no target on hosts without a laptop backlight.
compgen -G '/sys/class/backlight/*' >/dev/null || exit 0

case "$1" in
    up) brightnessctl --class=backlight set +5% >/dev/null ;;
    down) brightnessctl --class=backlight --min-value=1 set 5%- >/dev/null ;;
    show) ;;
esac

level=$(brightnessctl --class=backlight --machine-readable info)
IFS=, read -r _ _ _ percent _ <<< "$level"
percent=${percent%%%}
if [[ ! $percent =~ ^[0-9]+$ ]] || (( percent > 100 )); then
    echo "notify-brightness: cannot read backlight percentage" >&2
    exit 1
fi

notify-send --app-name=desktop-feedback --urgency=low --expire-time=1500 \
    --icon=display-brightness-symbolic \
    --hint=string:x-canonical-private-synchronous:brightness \
    --hint="int:value:$percent" --hint=boolean:transient:true \
    --hint=boolean:suppress-sound:true "Brightness: $percent%"