#!/bin/sh
# shellcheck shell=dash
# -*- sh -*-

: << =cut

=head1 NAME

whois - Plugin to monitor expiry dates of domains in the WHOIS database

Though the plugin will be called every 5 minutes, it will keep a cache, and
only query the WHOIS database C<cache_expiry_mins> minutes.

=head1 CONFIGURATION

First, create a section in your munin-node configuration files. The domain
envvar is mandatory, others are optional. Optionally, a specific WHOIS server
to query for a given domain can be specified with the @WHOIS_SERVER suffix

	[whois]
	env.domains example.com example.org@whois.example.net
	env.extract_re s/PATTERN/REPL/
	env.warning_days <default: 7 days>
	env.critical_days <default: 3 days>
	env.cache_expiry_mins <default: 60 minutes>


C<domains> is a space-separated list of domains to be checked.
The C<extract_re> will be used in C<sed> to extract the relevant expiry date. It
default to C<s/^.*[Ee]xpir.*: //>. Only lines for which a replacement has
happened will be considered, and the pattern should take care to only output
one line. While the default RegExp just finds a leader pattern and removes it,
it is possible to write more complex logic to format the date. The extracted
date needs to be in a format supported by C<date(1)>'s C<--date> parameter.

Then create a symlink to enable this plugin:

	ln -s /path/to/whois /etc/munin/plugins/


=head1 AUTHOR

Olivier Mehani

Copyright (C) 2020,2021 Olivier Mehani <shtrom+munin@ssji.net>

=head1 LICENSE

SPDX-License-Identifier: GPL-3.0-or-later

=head1 MAGIC MARKERS

 #%# family=manual

=cut

set -eu

# shellcheck disable=SC1091
. "${MUNIN_LIBDIR}/plugins/plugin.sh"

if [ "${MUNIN_DEBUG:-0}" = 1 ]; then
	set -x
fi

DOMAINS=${domains:-""}
EXTRACT_RE=${extract_re:-'s/^.*[Ee]xpir.*: //'}
WARNING=${warning_days:-7}
CRITICAL=${critical_days:-3}
CACHE_EXPIRY=${cache_expiry_mins:-60}

# Args: domain name (optional, for title)
graph_config() {
	cat << EOF
graph_title Domain registration expiry
graph_category network
graph_vlabel days
graph_args --units-exponent 0
EOF
}

# Args: domain name
# Separated from graph_config so we can easily extend the plugin to support multiple domains.
config() {
	local NAME
	local FIELDNAME
	for NAME in $DOMAINS
	do
		NAME="$(echo "${NAME}" | cut -d @ -f 1)"

		FIELDNAME="$(clean_fieldname "${NAME}")"

		cat << EOF
${FIELDNAME}.label ${NAME}
${FIELDNAME}.cdef ${FIELDNAME},86400,/
${FIELDNAME}.warning ${WARNING}:
${FIELDNAME}.critical ${CRITICAL}:
EOF
	done
}

# Args: domain name
fetch() {
	local NAME
	local SERVER
	local FIELDNAME
	local CACHEFILE

	for NAME in $DOMAINS
	do
		SERVER=''
		if echo "${NAME}" | grep -q '@'; then
			SERVER="$(echo "${NAME}" | cut -d @ -f 2)"
			NAME="$(echo "${NAME}" | cut -d @ -f 1)"
		fi

		FIELDNAME="$(clean_fieldname "${NAME}")"

		CACHEFILE="${MUNIN_PLUGSTATE}/$(basename "${0}").${FIELDNAME}.cache"

		if [ -z "$(find "${CACHEFILE}" -mmin -"${CACHE_EXPIRY}" 2>/dev/null)" ]; then
			EXPIRY="$(whois "${NAME}" "${SERVER:+-h${SERVER}}" 2>/dev/null | sed -n "${EXTRACT_RE}p;T;q")" # T;q exits after printing the first match
			DELTA_TS=U
			if [ -n "${EXPIRY}" ]; then
				EXPIRY_TS="$(date +%s -d "${EXPIRY}")"

				NOW_TS="$(date +%s)"
				DELTA_TS=$((EXPIRY_TS-NOW_TS))
			fi

			echo "${FIELDNAME}.value ${DELTA_TS}" > "${CACHEFILE}"
		fi

		cat "${CACHEFILE}"
	done
}

main() {
	local MODE="${1:-}"

	case "${MODE}" in
		'config')
			graph_config
			config
			;;
		*)
			fetch
			;;
	esac
}

main "$@"