#!/bin/sh
# A small script manually writing into the /sys/class/backlight/* files
# If multiple go through all and apply changes/printout status
# if no first argument is given prints out current status
# else: apply changes (+/- -> relative, only number: -> absolute)
# numbers in percentages

for backlight in "/sys/class/backlight/"*; do
	max_brightness=$(cat $backlight/max_brightness)
	current_brightness_abs=$(cat $backlight/brightness)
	current_brightness_rel="$(echo "$current_brightness_abs * 100 / $max_brightness" | bc -l | xargs printf '%.0f')"

	# For statusbar
	if [ -z  $1 ]; then
		echo "☀️$current_brightness_rel%"
		# continue as relative changes can result in differing brightness for multiple backlights
		continue
	fi

	max(){
		echo $(( $1 > $2 ? $1 : $2 ))
	}
	min(){
		echo $(( $1 < $2 ? $1 : $2 ))
	}
	limit(){
		echo $(min $(max $1 0) 100)
	}

	if echo $1 | grep -q '^[+-]'; then
		new_brightness_rel=$(limit $(echo $current_brightness_rel $1 | bc))
	else
		new_brightness_rel=$(limit $1)
	fi
	new_brightness_abs=$(echo "($new_brightness_rel * $max_brightness)/ 100" | bc)
	echo "$new_brightness_abs" | sudo tee $backlight/brightness > /dev/null
done
[ -z $1 ] ||
	pkill -RTMIN+2 dwmblocks