#!/usr/bin/env bash

# there are a few different ways to resolve public-ip,
# keep trying until we get a result

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

# dig
if [[ -z "${address}" ]] && [[ -n $(command -v 'dig') ]]; then
    # via opendns
    address=$(dig '@resolver1.opendns.com' -6 'myip.opendns.com' AAAA '+short')
    if [[ "$?" -ne '0' ]]; then
        # dig was unsuccessful
        echo "${address}" 1>&2
        address=''
    fi
fi

# curl
if [[ -z "${address}" ]] && [[ -n $(command -v 'curl') ]]; then
    # via ipinfo.io
    address=$(curl -6 --fail --silent --show-error 'https://v6.ipinfo.io/ip')

    if [[ -z "${address}" ]]; then
        # via google
        address=$(curl -6 --fail --silent --show-error 'https://domains.google.com/checkip')
    fi
fi

# wget
if [[ -z "${address}" ]] && [[ -n $(command -v 'wget') ]]; then
    # via ipinfo.io
    address=$(wget -6 --quiet --output-document - 'https://v6.ipinfo.io/ip')

    if [[ -z "${address}" ]]; then
        # via google
        address=$(wget -6 --quiet --output-document - 'https://domains.google.com/checkip')
    fi
fi

if [[ -n "${address}" ]]; then
    echo "${address}"
else
    echo 'Tried everything, unable to resolve IP address.' 1>&2
fi