#!/bin/bash

set -e

stty &> /dev/null || \
  sleep $[$RANDOM%60]

if ! ipCmd="$(which ip 2> /dev/null)"
then
  for p1 in / /usr/
  do
    for p2 in bin/ sbin/
    do
      ipCmd="${p1}${p2}ip"
      [ -x "${ipCmd}" ] && break
    done
    [ -x "${ipCmd}" ] && break
  done
fi

while read -r ipVer updateUrl dev dnsName
do

  if [[ "${ipVer}" = '#'* ]] || [ -z "${ipVer}" ]
  then
    continue
  fi

  if [ "${ipVer}" == '4' ]
  then
    dnsVer='A'
    inetVer='inet'
    ipCmdVer='-4'
  elif [ "${ipVer}" == '6' ]
  then
    dnsVer='AAAA'
    inetVer='inet6'
    ipCmdVer='-6'
  else
    >&2 echo 'Error: First column in "#ETCDIR#/update-ddns.conf" needs to be "4" or "6"!'
    exit 1
  fi

  if [ -z "${dnsName}" ]
  then
    dnsIps="$(
      curl -${ipVer} "${dev}" 2> /dev/null
    )"
    ips="1"
    unset updateIp
  else
    dnsIps="$(
      dig $1 "${dnsName}" ${dnsVer} | \
        grep -v '^\s*\(;\|$\)' | \
        grep "\s${dnsVer}\s" | \
        awk '{print $5}' | \
        sort -u
    )"

    if [ "${dev}" == "-" ]
    then
      unset dev
    else
      dev="dev ${dev}"
    fi

    ips="$(
      "${ipCmd}" -o "${ipCmdVer}" addr show ${dev} scope global | \
        awk '{print $4}' | \
        cut -d/ -f1 | \
        sort -u
    )"

    if [ $(echo "${ips}" | wc -l) -eq 0 ]
    then
      unset updateIp
    else
      updateIp='address='"$(echo -n "${ips}" | tr '\n' ',')"
      if [[ "${updateUrl}" = *'?'* ]]
      then
        updateIp='&'"${updateIp}"
      else
        updateIp='?'"${updateIp}"
      fi
    fi
  fi

  if [ -z "$(
    (
      echo "${dnsIps}"
      echo "${ips}"
    ) | \
      sort | \
      uniq -d
  )" ]
  then
    curl -${ipVer} -sS "${updateUrl}${updateIp}" 2> /dev/null
  fi

done < #ETCDIR#/update-ddns.conf