#/bin/bash

# battery-monitor.sh
# This program lets the user know when the battery needs to be charged.
# Copyright (c) 2024, Scott C. MacCallum (scm@sdf.org).
# All rights reserved.

# Redistribution and use of this software in source and binary forms, with or
# without modification, are permitted provided that the following conditions
# are met:

# * Redistributions of source code must retain the above copyright notice,
#      this list of conditions and the following disclaimer.

# * Neither the name of Scott C. MacCallum nor the names of its
#      contributors may be used to endorse or promote products derived from
#      this software without specific prior written permission of Scott C.
#      MacCallum.

# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

# Change this variable to your batteries identification e.g. BAT0

battery=""
charge=$(cat /sys/class/power_supply/$battery/charge_now)
discharge=$(cat /sys/class/power_supply/$battery/current_now)
hours=$(echo "scale=2; $charge / $discharge" | bc -l)
minutes=$(echo "scale=2; $hours * 60" | bc -l)
minimum=0.33

# If the battery has 15 minutes left of charge, let all users know

if (( $(echo "$minutes < $minimum" | bc -l) )); then
    echo "Recharge battery!" | wall
fi

exit 0