#!/bin/bash

logfile=
watchfile=

while true; do
	case $1 in
		--log) logfile=$2; shift ;;
		--watchfile) watchfile=$2; shift ;;
		-h|--help)
			echo "$0 [--log logfile] [--watchfile /tmp/\${host}.ip] zonefile host"
			exit 0
			;;
		*) break ;;
	esac
	shift
done


zonefile=$1
host=$2
[ -z "${watchfile}" ] && watchfile=/tmp/${host}.ip
[ -z "${logfile}" ] && logfile="/var/log/nsd-dynipwatch-${host}.log"


echo "Watch ${watchfile} for host ${host} and update ${zonefile}. Logfile: ${logfile}"


function getAddrFromZonefile # <host> <zonefile>
{
	egrep "^$1\\s.*\\sA\\s.*" $2 | egrep -o "([0-9]+\\.)+[0-9]+"
}

function setAddrInZonefile # <host> <zonefile> <addr>
{
	sed -i -e "s_^\\($1\\s.*A\\s.*\\s\\)\\([0-9]\\+\\.\\)\\+[0-9]\\+_\\1$3_g" "$2"
}


function run()
{
	touch ${watchfile}
	while true; do
		inotifywait -q -t 30 -e close_write "${watchfile}"  > /dev/null
		ret=$?
		[ "$ret" = "0" ] || continue

		oldip=`getAddrFromZonefile "${host}" "${zonefile}"`
		newip=`cat ${watchfile}`
		echo "`date '+%a %F %T'` :: ${oldip} => ${newip}."

		if ! echo "${newip}" | egrep -q "^([0-9]+\\.)+[0-9]+$"  ; then
			echo "Wrong format of new IP address."
			continue
		fi

		if ! [ "${oldip}" = "${newip}" ]; then
			echo " Update IP address. Increment serial."
			setAddrInZonefile "${host}" "${zonefile}" "${newip}"
            nsd-incrserial "${zonefile}"

			/etc/nsd3/signzone.sh sthu.org
			nsdc rebuild && nsdc reload && nsdc notify
		fi
	done
}


run >> $logfile