#!/usr/bin/env bash

set -e;

usage() {
USAGE=$(cat <<EOF
Usage: dynv6 [CONFIG_FILE (absolute path)]
updates dynv6 (an external service) and notifies about changes of IP addresses. Please see man dynv6.
EOF
)
  echo "$USAGE";
}

# check for config file
apply_config() {
  local config=$1;

  if [[ ! -f "$config" ]]; then
      echo "No config file specified";
      echo "";
      usage;
      exit 1;
  fi

  set -a;
  # shellcheck disable=SC1090
  source "$config";
  set +a;
}

source_config() {
  local config=$1;
  local configFallback=$2;
  local configGlobalFallback=$3;

  if [[ -f "$config" ]]; then
    apply_config "$config";
    return;
  fi

  if [[ -f "$configFallback" ]]; then
    apply_config "$configFallback";
    return;
  fi

  if [[ -f "$configGlobalFallback" ]]; then
    apply_config "$configGlobalFallback";
    return;
  fi
}

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
  if [ -z "${DYNV6_IPV6_INTERFACE}" ]; then
    DYNV6_IPV6_INTERFACE="eth0";
  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

    type hostname &> /dev/null || { echo "Requiring 'hostname' but it's not installed"; exit 1; }
    type mailx &> /dev/null || { echo "Requiring 'mailx' but it's not installed"; exit 1; }
    type ip &> /dev/null || { echo "Requiring 'ip' but it's not installed"; exit 1; }
    type grep &> /dev/null || { echo "Requiring 'grep' but it's not installed"; exit 1; }
    type curl &> /dev/null || { echo "Requiring 'curl' but it's not installed"; exit 1; }
}

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

# DO NOT CHANGE
token=${DYNV6_TOKEN}
hostname=${DYNV6_HOSTNAME}

echo "Checking ${hostname}"

# check via service
# ipv6
if [ "${DYNV6_IPV6_ENABLED}" = "true" ]; then
  echo "Testing IPv6";
  ipv6Address=$(LC_ALL=C /usr/bin/ip -c=never -6 -o a s dev ${DYNV6_IPV6_INTERFACE} | grep --color=never -Po '(?<=inet6 )(2.*?)(?=\/64 scope global dynamic mngtmpaddr)')
  
  ipv6AddressLocalFile="/tmp/dynv6_ip6";

  if [ ! -f "${ipv6AddressLocalFile}" ]; then
    touch "${ipv6AddressLocalFile}";
  fi

  if grep --color=never -Fxq "${ipv6Address}" "${ipv6AddressLocalFile}"; then
    echo "IPv6 is still ${ipv6Address}";
  else
      echo "IPv6 changed"
      echo "${ipv6Address}" > "${ipv6AddressLocalFile}";

      ipv6Res=$(curl -s -v "https://ipv6.dynv6.com/api/update?hostname=${hostname}&ipv6=${ipv6Address}&token=${token}")
      ipv6Changed=true;

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

# ipv4
if [ "${DYNV6_IPV4_ENABLED}" = "true" ]; then
  echo "Testing IPv4";
  ipv4Address=$(curl -s "https://api.ipify.org/?format=text")
  ipv4Res=$(curl -fsS "https://ipv4.dynv6.com/api/update?hostname=${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 to ${ipv4Address}" | mailx -s "[dynv6 IPv4 ${HOSTMACHINE}] IPv4 changed for ${hostname}" "${DYNV6_MAIL_ADDRESS}"
    fi
  fi
fi