#!/bin/sh
psupath=/sys/class/power_supply
warning_level=0  # 0 = not warned, 1 = warned, 2 = warned critical

sum_props() {
	for prop in $(cat $psupath/*/$1); do sum=$(( $sum + $prop )); done
	echo $sum
}
is_discharging() { cat $psupath/*/status | grep "Discharging" > /dev/null ; }

while true; do
	capacity=$(( $(sum_props energy_now) * 100 / $(sum_props energy_full) ))

	if is_discharging; then
		if   [ $capacity -le  5 ] && [ $warning_level -lt 2 ]; then
			notify_send "Critical Low Battery Warning" "${capacity}% remains"
		elif [ $capacity -le 20 ] && [ $warning_level -lt 1 ]; then
			notify_send "Low Battery Warning" "${capacity}% remains"
		fi
	else
		warning_level=0
	fi

	printf "\r%d%%" $capacity
	sleep 3
done