pre_upgrade() {
  local _myip='/etc/update-dnsomatic/myip'
  if [ -s "${_myip}" ]; then
    mv "${_myip}" "${_myip}.pacsave"
  fi
}

post_upgrade() {
  local _myip='/etc/update-dnsomatic/myip'
  if [ -s "${_myip}.pacsave" ] && [ ! -s "${_myip}" ]; then
    mv "${_myip}.pacsave" "${_myip}"
  fi
  rm -f "${_myip}.pacsave"
  chmod 664 "${_myip}"
  systemctl daemon-reload
  local _config='/etc/update-dnsomatic/config'
  # It would be safer to create our own user but it's easier just to use nobody
  chown -R 'root:nobody' "$(dirname "${_config}")" '/usr/bin/update-dnsomatic'
  chmod 640 "${_config}"
  echo
  if [ ! -s "${_config}" ] || grep -q '^user = userid$\|^npass = password$' "${_config}"; then
    echo "Add your OpenDNS username and password to ${_config}"
  fi
  if ! crontab -l 2>/dev/null | grep -q '/usr/bin/update-dnsomatic' && ! systemctl -q is-enabled 'update-dnsomatic.timer'; then
    echo 'crontab example to update every 10 minutes:'
    echo '  */10 * * * * /usr/bin/update-dnsomatic > /dev/null 2>&1'
    echo
    echo 'systemd timer example:'
    echo 'If desired, change time in usr/lib/systemd/system/update-dnsomatic.timer'
    echo "  systemctl enable 'update-dnsomatic.timer'"
    echo "  systemctl start 'update-dnsomatic.timer'"
  fi
  if systemctl -q is-enabled 'update-dnsomatic.timer'; then
    systemctl start 'update-dnsomatic.timer'
  fi
}

post_install() {
  post_upgrade
}

pre_remove() {
  if systemctl -q is-enabled 'update-dnsomatic.timer'; then
    systemctl stop 'update-dnsomatic.timer'
  fi
}

post_remove() {
  systemctl daemon-reload
}