#!/bin/bash

# Script to invoke resolvconf (if installed) to add/remove lokinet into/from the resolvconf DNS
# server list.  This script does not add if any of these are true:
#
# - /sbin/resolvconf does not exist
# - the systemd-resolved service is active
# - a `no-resolvconf=1` item is present in the [dns] section of lokinet.ini
#
# It always attempts to remove if resolvconf is installed (so that commenting out while running,
# then stopping still removes the added entry).
#
# Usage: lokinet-resolvconf {add|remove} /etc/loki/lokinet.ini

set -e

action="$1"
conf="$2"

if [[ ! ("$action" == "add" || "$action" == "remove") || ! -f "$conf" ]]; then
    echo "Usage: $0 {add|remove} /path/to/lokinet.ini" >&2
    exit 1
fi

if ! [ -x /sbin/resolvconf ]; then
    exit 0
fi

if [ -x /bin/systemctl ] && /bin/systemctl --quiet is-active systemd-resolved.service; then
    exit 0
fi

if [ "$action" == "add" ]; then
    if ! [ -x /sbin/resolvconf ]; then exit 0; fi

    lokinet_ns=$(perl -e '
    $ns = "127.3.2.1"; # default if none found in .ini
    while (<>) {
        if ((/^\[dns\]/ ... /^\[/)) {
            if (/^bind\s*=\s*([\d.]+)(?::53)?\s*$/) {
                $ns=$1;
            } elsif (/^no-resolvconf\s*=\s*1\s*/) {
                exit;
            }
        }
    }
    print $ns' "$conf")

    if [ -n "$lokinet_ns" ]; then
        echo "nameserver $lokinet_ns" | /sbin/resolvconf -a lo.000lokinet
    fi
else
    /sbin/resolvconf -d lo.000lokinet
fi