#!/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_IPV4_ENABLED=true // if should update ipv4
- DYNV6_IPV6_ENABLED=true // if should update ipv6

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() {
  if [ -z ${DYNV6_MAIL_ENABLED} ]; then
    DYNV6_MAIL_ENABLED=false;
  fi
  if [ -z ${DYNV6_MAIL_ADDRESS} ]; then
    DYNV6_MAIL_ADDRESS="";
  fi
  if [ -z ${DYNV6_TOKEN} ]; then
    DYNV6_TOKEN="";
  fi
  if [ -z ${DYNV6_HOSTNAME} ]; then
    DYNV6_HOSTNAME="";
  fi
  if [ -z ${DYNV6_IPV4_ENABLED} ]; then
    DYNV6_IPV4_ENABLED=true;
  fi
  if [ -z ${DYNV6_IPV6_ENABLED} ]; then
    DYNV6_IPV6_ENABLED=true;
  fi
}

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
}

# 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}

echo "Checking ${hostname}"

# check via service
# ipv6
if [ "${DYNV6_IPV6_ENABLED}" = "true" ]; then
  echo "Testing IPv6";
  ipv6Address=$(curl -s "https://v6.ident.me/")
  ipv6Res=$(curl -fsS "http://ipv6.dynv6.com/api/update?hostname=${hostname}&ipv6=${ipv6Address}&token=${token}")
  ipv6Changed=true;

  if [ "${ipv6Res}" = "addresses unchanged" ]; then
    ipv6Changed=false;
  fi
  if [ "${ipv6Changed}" = "true" ]; then
    echo "IPv6 changed"

    if [ "${DYNV6_MAIL_ENABLED}" = "true" ]; then
      HOSTMACHINE=$(hostname)
      echo -e "IPv6 for ${hostname} on host ${HOSTMACHINE} changed to ${ipv6Address}" | mailx -s "[dynv6 IPv6 ${HOSTMACHINE}] IPv6 changed for ${hostname}" "${DYNV6_MAIL_ADDRESS}"
    fi
  fi
fi

# ipv4
if [ "${DYNV6_IPV4_ENABLED}" = "true" ]; then
  echo "Testing IPv4";
  ipv4Address=$(curl -s "https://v4.ident.me/")
  ipv4Res=$(curl -fsS "http://ipv4.dynv6.com/api/update?hostname=${hostname}&ipv4=${ipv4Address}&token=${token}")
  ipv4Changed=true;
  if [ "$ipv4Res" = "addresses unchanged" ]; then
    ipv4Changed=false;
  fi
  if [ "${ipv4Changed}" = "true" ]; then
    echo "IPv4 changed"

    if [ "${DYNV6_MAIL_ENABLED}" = "true" ]; then
      HOSTMACHINE=$(hostname)
      echo -e "IPv4 for ${hostname} on host ${HOSTMACHINE} changed changed to ${ipv4Address}" | mailx -s "[dynv6 IPv4 ${HOSTMACHINE}] IPv4 changed for ${hostname}" "${DYNV6_MAIL_ADDRESS}"
    fi
  fi
fi