#!/bin/bash

mywget="/usr/bin/wget -q --tries=1 --spider"

online_time_max=86400	# nach ~24h wird die Verbindung unzuverlaessig 
online_time_sleep=1000  # alle ~17 Minuten Verbindung prüfen
online_delay=145	# ~2½ Minuten auf Router warten

online_fail="maxtime"	# Grund des beendens (>24h oder keine Verbindung)
online_err_count=0
online_err_max=1
online_try_count=0

declare -a check_online_urls=(	'http://www.google.com'
				'https://debianforum.de/forum'
				'https://www.heise.de'
				'https://www.debian.org'
				'https://www.drei.at'
				'https://www.tugraz.at/home')


function log ()
{
	echo "${1}" | systemd-cat -p ${2} -t switchrouter
}

function switch ()
{
	case "${1}" in
		on)
			echo -n -e '\xA0\x01\x01\xA2' > /dev/ttyUSB0
			;;
		*)
			echo -n -e '\xA0\x01\x00\xA1' > /dev/ttyUSB0
			;;
	esac
}

function onsignal ()
{
	log "Received signal. Trying to switch off and exit" 6
	switch off
	exit ${?}
}

trap onsignal SIGTERM SIGKILL

# Router einschalten
if switch on ; then
	log "Switched on router." 6
else
	log "Switching on router failed, trying to switch off nevertheless." 3
	switch off
	exit 75
fi

# Auf Router warten
sleep ${online_delay}
systemd-notify --ready	#gefaehrlich!

# Internetverbindung ueberwachen
while [ ${SECONDS} -lt ${online_time_max} ]
do
	for i in "${check_online_urls[@]}" ; do
		${mywget} "${i}" && break
		(( online_try_count++ ))
		sleep 10s
	done || (( online_err_count++ ))
	if [ ${online_err_count} -gt ${online_err_max} ] ; then
		online_fail="connection"
		log "No internet connection (${online_try_count} tries)." 4
		break
	else
		log "Internet connection ok (${online_try_count} fails)." 7
		online_err_count=0
		online_try_count=0
		sleep ${online_time_sleep}
	fi
done

# Grund für das Beenden
case "${online_fail}" in
	maxtime)
		log "Maximum connection time reached, exiting." 6
	;;
	connection)
		log "Exiting." 4
	;;
esac

# Router ausschalten
if switch off ; then
	log "Switched off router." 6
else
	log "Switching off router failed." 2
	exit 75
fi