#!/bin/sh 

interface="${1:?}"
timeout="${2:?}"
pinghosts="${3:?}"
pinginterval="${4:?}"
hookname="${5:?}"

run_hooks () {
	reason="$1"
	interface="$2"
	last_hooks_run="$reason"
	for hook in /etc/watchping/$interface-$reason.d/* ; do
		[ -x "$hook" ] && $hook
	done
}

watchping_ping() {
	local ifname="$1"; local timeout="$2"; local pinghosts="$3"; local pinginterval="$4"; local hookname="$5"
	local last_hooks_run="undefined"

	if [ ! -r "/sys/class/net/$ifname/ifindex" ] ; then
		echo "Interface $ifname unsupported or not found!"
		exit 1
	fi

	[ -z "$hookname" ] && hookname="$ifname"
	time_now="$(cat /proc/uptime)"
	time_now="${time_now%%.*}"
	time_lastcheck="$time_now"
	time_lastcheck_withinternet="$time_now"

	while true ; do
		# account for the time ping took to return. With a ping interval of 5s, ping might take more than that, so it is important to avoid even more delay.
		time_now="$(cat /proc/uptime)"
		time_now="${time_now%%.*}"
		time_diff="$((time_now-time_lastcheck))"

		[ "$time_diff" -lt "$pinginterval" ] && {
			sleep_time="$((pinginterval-time_diff))"
			sleep "$sleep_time"
		}

		time_now="$(cat /proc/uptime)"
		time_now="${time_now%%.*}"
		time_lastcheck="$time_now"

		for host in "$pinghosts" ; do
			if ping -I "$ifname" -c 1 "$host" &> /dev/null ; then
				time_lastcheck_withinternet="$time_now"
			else
				time_diff="$((time_now-time_lastcheck_withinternet))"
			fi
		done
		
		if [ "$time_diff" -ge "$timeout" ] && [ "$last_hooks_run" != "fail" ] ; then
			logger -p daemon.info -t "watchping[$$]" "no ping reply for $time_diff seconds. Running $hookname-fail.d hooks..."
			run_hooks fail "$hookname"
		elif [ "$time_lastcheck_withinternet" == "$time_now" ] && [ "$last_hooks_run" != "ok" ] ; then 
			logger -p daemon.info -t "watchping[$$]" "ping reply. Running $hookname-ok.d hooks..."
			run_hooks ok "$hookname"
		fi
	done
}

watchping_ping "$interface" "$timeout" "$pinghosts" "$pinginterval" "$hookname"