#!/bin/bash

# Little monitoring script to check that the version of a
# Forgejo instance is up to date.
#
# Licence: WTFPL
# Copyright: chl-dev@bugness.org 2023

PROGPATH=$( echo $0 | sed -e 's,[\\/][^\\/][^\\/]*$,,' )
REVISION="0.1"

# Default values
DNS_RECORD_RELEASES="release.forgejo.org"
RELEASE_MEDIUM="dns"
URL_RSS_RELEASES="https://codeberg.org/forgejo/forgejo/releases.rss"
URL_LOCAL_HOSTNAME="localhost:3000"
URL_LOCAL_VERSION_TEMPLATE="%s://%s/api/v1/version"
URL_LOCAL_PROTOCOL="http"

# Include check_range()
# Not needed at the moment
#. $PROGPATH/utils.sh
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3
STATE_DEPENDENT=4

# Stop at first uncaught error
set -e

# Wrapper to use whatever is available to make HTTP queries
fetch_with_curl_wget_or_whatever () {
	if which "wget" >/dev/null 2>&1; then
		wget -q -O - "$1"
	elif which "curl" >/dev/null 2>&1 ; then
		curl -s "$1"
	else
		echo "UNKNOWN: no wget/curl/whatever available to make HTTP queries."
		exit $STATE_UNKNOWN
	fi
}

# Wrapper to use whatever is available to make DNS queries
fetch_with_dig_or_whatever () {
	if which "dig" >/dev/null 2>&1; then
		dig +short "$1" "$2"
	elif which "nslookup" >/dev/null 2>&1; then
		nslookup -query="$2" "$1" | sed -n "/$1/p"
	else
		echo "UNKNOWN: no dig/nslookup/whatever available to make DNS queries."
		exit $STATE_UNKNOWN
	fi
}

# Sort the multiple <title> contents and print the last one.
# ex: 1.21.1-5
# Note: Gitea has some spurious v1.22-dev/-rc releases, we ignore them.
get_latest_version_number_from_rss () {
	fetch_with_curl_wget_or_whatever "$1" | while rdom; do
		# In RSS streams, we only want the <title> in <item>
		# In Atom streams, it's <entry> -> <title>
		case "$E" in
			"item"|"entry") INSIDE_ITEM=1;;
			"/item"|"/entry") INSIDE_ITEM="";;
		esac

		if [ -n "$INSIDE_ITEM" ] && [ "$E" == "title" ]; then
			printf "%s\n" "$C"
		fi
	done | sed -e 's/^v//' -e '/-dev/d' -e '/-rc/d' | sort --version-sort | tail -n 1
}

# Sort the multiple "forgejo_versions=x,y,z" and print the last one.
# ex: 1.21.1-5
get_latest_version_number_from_dns () {
	fetch_with_dig_or_whatever "$1" "TXT" | \
	sed -e 's/.*=\(.*\)".*/\1/' -e 's/,/\n/g' | \
	sort --version-sort | \
	tail -n 1
}

print_url_local_version () {
	printf "$URL_LOCAL_VERSION_TEMPLATE" "$URL_LOCAL_PROTOCOL" "$URL_LOCAL_HOSTNAME"
}

# Quick 'n dirty function to parse XML without having to install
# a real parser (not necessary at the moment here, but may be
# needed in the future)
# The tag will be stored in $E and the content in $C
# note: this function is not POSIX-compliant (needs bash)
rdom () {
	local IFS=\>
	read -d \< E C
}

# Help function
usage() {
	cat <<EOF
Usage :
  $0 [-H hostname] [-u local_URL] [-sS] [-D] [-d release_dns_record] [-R] [-r release_rss_URL]

	-D Use the DNS to determine the last release available (default)
	-R Use the RSS to determine the last release available
	-s Use HTTP to query the hostname (default)
	-S Use HTTPS to query the hostname

Example :
	./check_forgejo_version.sh -H forge.example.net
	(seems to somewhat work for Gitea too :)
	./check_forgejo_version.sh -R -r https://github.com/go-gitea/gitea/releases.atom

Default values:
	local_URL: $( print_url_local_version )
	release_dns_record: $DNS_RECORD_RELEASES
	release_rss_URL: $URL_RSS_RELEASES
EOF
}

# Loop on parameters
while getopts hDH:r:RsSu: f; do
	case "$f" in
		'h')
			usage
			exit
			;;

		'D')
			RELEASE_MEDIUM="dns"
			;;

		'H')
			URL_LOCAL_HOSTNAME="$OPTARG"
			;;

		'r')
			URL_RSS_RELEASES="$OPTARG"
			;;

		'R')
			RELEASE_MEDIUM="rss"
			;;

		's')
			URL_LOCAL_PROTOCOL="http"
			;;

		'S')
			URL_LOCAL_PROTOCOL="https"
			;;

		'u')
			URL_LOCAL_VERSION="$OPTARG"
			;;

		?)
			usage
			exit 1
			;;
	esac
done

# If the local URL hasn't been overridden, let's compute it.
if [ -z "$URL_LOCAL_VERSION" ]; then
	URL_LOCAL_VERSION="$( print_url_local_version )"
fi

# Query the upstream and local versions...
case "$RELEASE_MEDIUM" in
	'rss') UPSTREAM_VERSION="$( get_latest_version_number_from_rss "$URL_RSS_RELEASES" )" ;;
	'dns') UPSTREAM_VERSION="$( get_latest_version_number_from_dns "$DNS_RECORD_RELEASES" )" ;;
esac
# note : the API seems to switch 1.21.1-0 to 1.21.1+0. We dumbly switch back ?
LOCAL_VERSION="$( fetch_with_curl_wget_or_whatever "$URL_LOCAL_VERSION" | sed -n 's/{"version":"\([^"]\+\)"}/\1/p' | sed 's/+/-/' )"

# ...and check if they match.
if [ "$UPSTREAM_VERSION" = "$LOCAL_VERSION" ]; then
	echo "OK ($LOCAL_VERSION / $UPSTREAM_VERSION)"
	exit $STATE_OK
else
	# we are not yet able to distinguish security releases from simple upgrades
	# so, to avoid alert fatigue, we chose to stay at "warning".
	echo "WARNING ($LOCAL_VERSION / $UPSTREAM_VERSION)"
	exit $STATE_WARNING
fi