#!/usr/bin/env bash

set -e;

usage() {
USAGE=$(cat <<EOF
Usage: dynv6 [CONFIG_FILE (absolute path)]

If no CONFIG_FILE is given, HOME/.dynv6.conf is used. This fallback option
has to exist or the script will exit.

Configuration can be done in any file and any pre-defined variable can be overwritten.

The following are at least required for the script to work:
- DYNV6_MAIL_ENABLED= // if notify via mail
- DYNV6_MAIL_ADDRESS="" // (optional) mail.rc has to be configured
- DYNV6_TOKEN="" // the dynv6 token
- DYNV6_HOSTNAME="" // the dynv6 hostname
- DYNV6_DEVICE="" // the (optional) dynv6 device
- DYNV6_NETMASK="" // the (optional) netmask

You can copy this script to '/usr/local/bin' and use create a custom CONFIG_FILE as user. Examples can be found in '/usr/share/doc/<scriptname>'.
EOF
)
  echo "$USAGE";
}

# check for config file
source_config() {
  local config=$1;
  local configFallback=$2;

  if [[ ! -f "$config" ]]; then
    if [[ ! -f "$configFallback" ]]; then
      echo "No config file specified and could not find default in '$configFallback'!";
      echo "";
      usage;
      exit 1;
    else
      config=$configFallback;
    fi
  fi

  set -a;
  source "$config";
  set +a;
}

apply_defaults() {
    [[ -z ${DYNV6_MAIL_ENABLED} ]] && DYNV6_MAIL_ENABLED=false;
}
check_required() {
    if [[ -z ${DYNV6_TOKEN} ]]; then
      echo "DYNV6_TOKEN is required"
        exit 1;
    fi
    if [[ -z ${DYNV6_HOSTNAME} ]]; then
      echo "DYNV6_HOSTNAME is required"
        exit 1;
    fi

    if [ -e /usr/bin/curl ]; then
      bin="curl -fsS"
    elif [ -e /usr/bin/wget ]; then
      bin="wget -O-"
    else
      echo "neither curl nor wget found"
      exit 1
    fi
    }

# check requirements
CONFIG_FILE="$1";
FALLBACK_CONFIG_FILE="${HOME}/.dynv6.conf";
source_config "${CONFIG_FILE}" "${FALLBACK_CONFIG_FILE}";
apply_defaults;
check_required;

# DO NOT CHANGE
token=${DYNV6_TOKEN}
hostname=${DYNV6_HOSTNAME}
device=${DYNV6_DEVICE}
netmask=${DYNV6_NETMASK}

file=$HOME/.dynv6.addr6
[ -e $file ] && old=`cat $file`

if [ -z "$netmask" ]; then
  netmask=128
fi

if [ -n "$device" ]; then
  device="dev $device"
fi
address=$(ip -6 addr list scope global $device | grep -v " fd" | sed -n 's/.*inet6 \([0-9a-f:]\+\).*/\1/p' | head -n 1)

if [ -z "$address" ]; then
  echo "no IPv6 address found"
  exit 1
fi

# address with netmask
current=$address/$netmask

if [ "$old" = "$current" ]; then
  echo "IPv6 address unchanged"
  exit
fi

# send addresses to dynv6
$bin "http://dynv6.com/api/update?hostname=$hostname&ipv6=$current&token=$token"
$bin "http://ipv4.dynv6.com/api/update?hostname=$hostname&ipv4=auto&token=$token"

# save current address
echo $current > $file

# sent mail that IP changed
if [ "${DYNV6_MAIL_ENABLED}" = true ]; then
  HOSTMACHINE=$(hostname)
  echo -e "IP for ${hostname} changed from '${old}' to '${address}' on host ${HOSTMACHINE}" | mailx -s "[dynv6 ${HOSTMACHINE}] IP changed for ${hostname}" "${DYNV6_MAIL_ADDRESS}"
fi