#!/bin/sh

battery_path='/sys/class/power_supply/BAT0'

percentage=$(head -n1 "${battery_path}/capacity")
state=$(head -n1 "${battery_path}/status")
rate=$([ -f "${battery_path}/current_now" ] &&
           head -n1 "${battery_path}/current_now" ||
               head -n1 "${battery_path}/power_now")
volt=$(head -n1 "${battery_path}/voltage_now")
now=$([ -f "${battery_path}/charge_now" ] &&
          head -n1 "${battery_path}/charge_now" ||
              head -n1 "${battery_path}/energy_now")
max=$([ -f "${battery_path}/current_full" ] &&
          head -n1 "${battery_path}/current_full" ||
              head -n1 "${battery_path}/energy_full")
cap=$([ "$state" = "Charging" ] &&
          echo "$max $now" | awk '{printf "%d", $1 - $2}' ||
              echo "$now")

remaining=$( echo "$cap $volt" | awk '{printf "%f", $1/$2}' )
current_rate=$( echo "$rate $volt" | awk '{printf "%f", $1/$2}' )
seconds_remaining=$( [ "${current_rate#0.00}" = "$current_rate" ] &&
                         echo "$remaining $current_rate" |
                             awk '{printf "%d", 3600*$1/$2}' ||
                 echo "0" )
time_remaining=$( date -ud "@${seconds_remaining}" "+%H:%M:%S" )

# TODO: more variable output with flags?
echo "$state $percentage $time_remaining"