#!/bin/bash

# on-ac-power-state-change
# Copyright 2019 Mike Peralta
# Released under the MIT license (https://opensource.org/licenses/MIT)
# Check out my music https://www.MikePeralta.com
# This script will execute a command each time the power state is changed (ie: laptop power unplugged or plugged back in)
# Pass your desired command to execute as arguments to this script
# Example:
# $ on-ac-power-state-change echo "My power state has changed!"
# Written and tested with acpi version 1.7
# Enjoy!
# (Note: Use with caution; It will execute any parameters received verbatim)

#
COMMANDS_FOR_STATE_CHANGE="$@"
CHECKED_AT_LEAST_ONCE="0"
LAST_KNOWN_PLUGGED_IN_STATE=""
CURRENT_PLUGGED_IN_STATE=""

#
do_log()
{
	logger "[on-ac-power-state-change] $1"
	echo "[on-ac-power-state-change] $1"
}
do_complaint()
{
	logger -s "[on-ac-power-state-change] $1"
}
do_die()
{
	do_complaint "Fatal: $1"
	exit 1
}

#
demand_acpi()
{
	which acpi > /dev/null
	if [ $? -ne 0 ];then
		do_die "acpi doesn't seem to be installed"
	fi
}

#
is_ac_connected()
{
	#	Grab output of acpi
	demand_acpi
	ACPI=$(acpi -a)
	
	#
	echo "$ACPI" | grep "on-line" > /dev/null
	if [ $? -eq 0 ];then
		#echo "Power seems to be plugged in"
		echo "1"
	fi
	echo "$ACPI" | grep "off-line" > /dev/null
	if [ $? -eq 0 ];then
		#echo "Power seems to be unplugged"
		echo "0"
	fi
}

#
handle_acpi_state_change()
{
	#
	CURRENT_PLUGGED_IN_STATE=$(is_ac_connected)
	
	#
	if [ "$CHECKED_AT_LEAST_ONCE" = "1" ];then
		if [ "$CURRENT_PLUGGED_IN_STATE" != "$LAST_KNOWN_PLUGGED_IN_STATE" ];then
			do_log "Power state has changed!"
			do_log "Executing commands: $COMMANDS_FOR_STATE_CHANGE"
			eval "$COMMANDS_FOR_STATE_CHANGE"
		fi
	else
		CHECKED_AT_LEAST_ONCE="1"
	fi
	
	#
	LAST_KNOWN_PLUGGED_IN_STATE="$CURRENT_PLUGGED_IN_STATE"
}

#
main_loop()
{
	#
	do_log "Begin main loop"
	while [ true ];do
		handle_acpi_state_change
		sleep 1
	done
	do_log "Done with main loop"
}


do_log "Begin"
main_loop


do_log "Exiting"