#!/bin/bash

### VARIABLES

POLL_INTERVAL=120 # seconds at which to check battery level
LAST_NOTIFIED=-1  # track last notified battery percentage to avoid repeated notifications

# If BAT0 doesn't work for you, check available devices with:
#   $ ls -1 /sys/class/power_supply/
BAT_PATH=/sys/class/power_supply/BAT0
BAT_STAT=$BAT_PATH/status

if [[ -f $BAT_PATH/charge_full ]]; then
  BAT_FULL=$BAT_PATH/charge_full
  BAT_NOW=$BAT_PATH/charge_now
elif [[ -f $BAT_PATH/energy_full ]]; then
  BAT_FULL=$BAT_PATH/energy_full
  BAT_NOW=$BAT_PATH/energy_now
else
  exit
fi

kill_running() {
  local mypid=$$
  local pids
  mapfile -t pids < <(pgrep -f "${0##*/}")

  for pid in "${pids[@]}"; do
    if [[ $pid -ne $mypid ]]; then
      kill "$pid"
      sleep 1
    fi
  done
}

get_battery_icon() {
  local percent=$1
  if ((percent > 80)); then
    echo "🔋" # Full battery
  elif ((percent > 60)); then
    echo "🔋" # High battery
  elif ((percent > 40)); then
    echo "🔋" # Medium battery
  elif ((percent > 20)); then
    echo "🪫" # Low battery
  else
    echo "⚠️" # Critical battery
  fi
}

# Run only if battery is detected
if ls -1qA /sys/class/power_supply/ | grep -q BAT; then

  kill_running

  while true; do
    bf=$(cat "$BAT_FULL")
    bn=$(cat "$BAT_NOW")
    bs=$(cat "$BAT_STAT")

    bat_percent=$((100 * $bn / $bf))
    bat_icon=$(get_battery_icon "$bat_percent")

    # Notify only at exact levels: 20%, 15%, and 10%
    if [[ ($bat_percent -eq 20 || $bat_percent -eq 15 || $bat_percent -eq 10) && "$bs" = "Discharging" && $bat_percent -ne $LAST_NOTIFIED ]]; then
      notify-send --urgency=critical "$bat_icon $bat_percent% : $([[ $bat_percent -eq 10 ]] && echo 'Critical Battery! Shutting down in 1 minute...' || echo 'Low Battery!')"
      LAST_NOTIFIED=$bat_percent

      if [[ $bat_percent -eq 10 ]]; then
        sleep 60
        shutdown now
      fi
    elif [[ "$bs" = "Charging" ]]; then
      LAST_NOTIFIED=-1
    fi

    sleep "$POLL_INTERVAL"
  done
fi