Vbrightness

#!/bin/zsh

. Vlib.sh
. Vglobals

if [ "$#" -ne 1 ]; then 
	echo "no argument";
	exit 1;
fi

# Constants
path_to_brightness="/sys/class/backlight/intel_backlight";
path_to_toggle="$(REQUIRE_CACHE vbrightness 0)";
new_brightness=111;
min_brightness=1;

current_brightness=$(cat $path_to_brightness/brightness);
max_brightness=$(cat $path_to_brightness/max_brightness);

if [ $1 = "+" ]; then
	new_brightness=$((current_brightness + BRIGHTNESS_DERIVATIVE_SLOPE));	
	if ((new_brightness > max_brightness)); then new_brightness=$((max_brightness - 10)); fi
elif [ $1 = "-" ]; then
	new_brightness=$((current_brightness - BRIGHTNESS_DERIVATIVE_SLOPE));
	if ((new_brightness < min_brightness)); then new_brightness=$min_brightness; fi
elif [ $1 = "0" ]; then
	if [[ $current_brightness -ne $min_brightness ]]; then
		echo $current_brightness > $path_to_toggle;
		new_brightness=$min_brightness;
	else
		new_brightness=$(cat $path_to_toggle);
		
		# wrong brightness written to file
		if ((new_brightness < min_brightness || new_brightness > max_brightness)); then
			echo "wrong brightness in $path_to_toggle file";
			new_brightness=$((min_brightness + 77));
		fi
	fi
elif [ $1 = "%" ]; then
	echo $((current_brightness * 100 / max_brightness + 1));
	exit 0;
else
	echo "argument must be +, -, % or 0";
	exit 2;
fi
echo $new_brightness > $path_to_brightness/brightness;