#!/bin/bash
# Usage: night-light [increase|decrease|day|night]
set -e

TMPFILE=/tmp/.night-light-index

# https://askubuntu.com/a/1061304
STEPS=(
    "1:0.18172716:0.00000001"
    "1:0.42322816:0.00000001"
    "1:0.54360078:0.08679949"
    "1:0.64373109:0.28819679"
    "1:0.71976951:0.42860152"
    "1:0.77987699:0.54642268"
    "1:0.82854786:0.64816570"
    "1:0.86860704:0.73688797"
    "1:0.90198230:0.81465502"
    "1:0.93853986:0.88130458"
    "1:0.97107439:0.94305985"
	"1:1:1"
)

CUR=$((${#STEPS[@]}-1))
if [ -f $TMPFILE ]; then
	CUR=$(cat $TMPFILE)
fi

case "$1" in
	increase) NEW=$(($CUR >= ${#STEPS[@]} ? $CUR : $CUR+1)) ;;
	decrease) NEW=$(($CUR <= 0 ? $CUR : $CUR-1)) ;;
	day) NEW=$((${#STEPS[@]}-1)) ;;
	night) NEW=0 ;;
	*)
		echo "Invalid argument '$1'"
		exit 1
		;;
esac

echo $NEW > $TMPFILE

for MONITOR in $(xrandr --listactivemonitors | tail -n +2 | cut -d'+' -f2 | cut -d' ' -f1 | sed 's/^\*//'); do
	BRIGHTNESS=$(xrandr --verbose | grep "^$MONITOR" -A5 | grep Brightness | cut -d':' -f2 | sed 's/\s*//')
	xrandr --output $MONITOR --gamma ${STEPS[$NEW]} --brightness $BRIGHTNESS || true
done