#!/usr/bin/env zsh

local system_uname="$(uname)"

if [[ "${system_uname}" = 'Linux' ]]; then
    let charge_full="$(cat '/sys/class/power_supply/BAT0/charge_full')."
    function get_battery_percent {
        let charge_now="$(cat '/sys/class/power_supply/BAT0/charge_now')."
        printf '%.0f' "$((charge_now / charge_full * 100))"
    }

    function is_adapted_connected {
        let connected="$(cat /sys/class/power_supply/ADP1/online)"
        ((${connected} == 1))
    }
# Linux ends here
else
    echo "${0}: error: unknown os: \"${system_uname}\"" >&2
    exit 1
fi

function send_battery_warning {
    dunstify -p -t 0 "Low Battery" "Battery is at ${1}%!"
}

local did_notify=false
let notify_id=-1

while true; do
    let battery_percent="$(get_battery_percent)"
    if ((${battery_percent} > 10)) || is_adapted_connected; then
        did_notify=false
        if ((${notify_id} > 0)); then
            dunstify -C ${notify_id}
            notify_id=-1
        fi
    elif ! ${did_notify}; then
        did_notify=true
        notify_id="$(send_battery_warning ${battery_percent})"
    fi
    sleep 10
done