#! /bin/bash
### BEGIN INIT INFO
# Provides:          dns-sync
# Required-Start:
# Required-Stop:
# Default-Start:     S
# Default-Stop:
# Short-Description: Synchronizes /etc/resolv.conf in WLS with Windows DNS
### END INIT INFO

PATH=/sbin:/bin
PS=/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe

. /lib/init/vars.sh
. /lib/lsb/init-functions

do_start () {
        #Retrieve nameservers from via Powershell
        IFS=$'\r\n' GLOBIGNORE='*' command eval  'NAMESERVERS=($($PS -Command "Get-DnsClientServerAddress -AddressFamily IPv4 | Select-Object -ExpandPropert ServerAddresses"))'

        #Retrive search domains via powershell
        IFS=$'\r\n' GLOBIGNORE='*' command eval  'SEARCH_DOMAIN=($($PS -Command "Get-DnsClientGlobalSetting | Select-Object -ExpandProperty SuffixSearchList"))'

        #Uniqify
        UNIQUE_NAMESERVERS=($(/usr/bin/tr ' ' '\n' <<< "${NAMESERVERS[@]}" | /usr/bin/sort -u | /usr/bin/tr '\n' ' '))
        UNIQUE_SEARCH_DOMAIN=($(/usr/bin/tr ' ' '\n' <<< "${SEARCH_DOMAIN[@]}" | /usr/bin/sort -u | /usr/bin/tr '\n' ' '))

        #Modify /etc/resolv.conf
        touch /etc/resolv.conf
        sed -i '/nameserver/d' /etc/resolv.conf > /dev/null  2>&1 || true
        sed -i '/search/d' /etc/resolv.conf > /dev/null  2>&1 || true

        for i in "${UNIQUE_NAMESERVERS[@]}"
        do
        	echo "nameserver ${i}" >> /etc/resolv.conf
        done

        echo "search ${UNIQUE_SEARCH_DOMAIN[@]}" >> /etc/resolv.conf
}

do_status () {
        HOSTNAME=$(hostname)
        if [ "$HOSTNAME" ] ; then
                return 0
        else
                return 4
        fi
}

case "$1" in
  start|"")
        do_start
        ;;
  restart|reload|force-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        ;;
  stop)
        # No-op
        ;;
  status)
        do_status
        exit $?
        ;;
  *)
        echo "Usage: dns-sync.sh [start|stop]" >&2
        exit 3
        ;;
esac