#! /bin/sh

# 2023 may
# уто 09 10:22 < Fruit> joostvb: https://www.fruit.je/m/brightness
# уто 09 10:26 < Fruit> mijn advies is om het aan een toetscombo te hangen,
#                      bijvoorbeeld met xbindkeys
# jуто 09 10:26 < Fruit> met xev kun je zien wat voor key event je Fn-knopjes
#                      uitspugen


set -e

sys=/sys/class/backlight/intel_backlight

case $* in *help*)
	echo "Usage: $0 {cur|max|inc|dec}"
	exit
esac

read cur <$sys/actual_brightness

case $# in 0)
	echo $cur
	exit
esac

case $1 in cur*)
	echo $cur
	exit
esac

read max <$sys/max_brightness

case $1 in max*)
	echo $max
	exit
esac

log=$max
inc=$max
dec=$max

while :
do
	log=$((log * 4 / 5))
	case $((log > cur)) in 1) inc=$log; esac
	case $((log < cur)) in 1) dec=$log; break; esac
	case $log in 0) dec=0; break; esac
done

case $1 in inc*)
	new=$inc
;; dec*)
	new=$dec
;; *)
	echo "Usage: $0 {cur|max|inc|dec}" >&2
	exit 2
esac

log=$max
step=0
steps=0

while :
do
	log=$((log * 4 / 5))
	steps=$((steps + 1))
	case $((log < new)) in 0) step=$((step + 1)); esac
	case $log in 0) break; esac
done

case $new in $max)
	redshift -m randr -x
;; *)
	mintemp=-1000
	maxtemp=6500

	newtemp=$((maxtemp - (maxtemp - mintemp) * step / steps))
	case $((newtemp < 1000)) in 1)
		newtemp=1000
	esac
	redshift -m randr -O $newtemp -P
	#echo ${newtemp}K >&2
esac

sudo tee $sys/brightness >/dev/null <<EOT
$new
EOT