#!/usr/bin/env nix-shell
#!nix-shell -i bash

full=$(cat /sys/class/power_supply/axp20x-battery/charge_full_design)
rate=$(cat /sys/class/power_supply/axp20x-battery/current_now)
perc=$(cat /sys/class/power_supply/axp20x-battery/capacity)
perc_left=$((100 - $perc))
# these icons come from sxmo; they only render in nerdfonts
bat_dis="󱊢"
bat_chg="󱊥"

fmt_minutes() {
  # args: <battery symbol> <text if ludicrous estimate> <estimated minutes to full/empty>
  if [[ $3 -gt 1440 ]]; then
    printf "%s %s" "$1" "$2"  # more than 1d
  else
    hr=$(($3 / 60))
    hr_in_min=$(($hr * 60))
    min=$(($3 - $hr_in_min))
    printf "%s %dh%02dm" "$1" "$hr" "$min"
  fi
}

if [[ $rate -lt 0 ]]; then
  # discharging
  fmt_minutes "$bat_dis" '∞' "$(($full * 60 * $perc / (-100 * $rate)))"
elif [[ $rate -gt 0 ]]; then
  # charging
  fmt_minutes "$bat_chg" '100%' "$(($full * 60 * $perc_left / (100 * $rate)))"
else
  echo "$bat_dis $perc%"
fi