#!/usr/bin/perl

use warnings;
use strict;
use Mail::SpamAssassin;
use Net::DNS;

# variables
my ( $sa_version, $rev_sa_version, $SA, $update_dir, $version_on_disk,
    $LOCAL_STATE_DIR, $resolver, $query, $version_dns, $sa_channel );

# get the SpamAssassin version from the Perl module
$sa_version =  Mail::SpamAssassin::Version();

# reverse this number. We will need it for a txt forware query later
$rev_sa_version = join(".", reverse split(/\./, $sa_version) ) ;

# sa channel we want to monitor
$sa_channel = "updates.spamassassin.org";

# get the local state dir update path
$LOCAL_STATE_DIR = '/var/lib/spamassassin';

$SA = Mail::SpamAssassin->new( {
        LOCAL_STATE_DIR => $LOCAL_STATE_DIR,
    }
);

$update_dir = $SA->sed_path('__local_state_dir__/__version__');

# inside $update_dir, get the line starting with "# UPDATE "
# save the version in $version_on_disk

if ( -e "$update_dir/updates_spamassassin_org.cf" ) {
    open (CF, "$update_dir/updates_spamassassin_org.cf" ) or die "$!\n";
    while (<CF> ) {
        last unless /^# UPDATE\s+[A-Za-z]+\s+(\S+)/;
        $version_on_disk = $1;
    }
}

print "$sa_channel channel version on disk is:  $version_on_disk\n";

$resolver = Net::DNS::Resolver->new;

$query = $resolver->query("$rev_sa_version.$sa_channel", 'txt');

if ( $query ) {
    for my $rr ( $query->answer ) {
        $version_dns = $rr->rdata;
    }
}

print "$sa_channel channel dns txt query version is $version_dns\n";

print "[$version_on_disk]\t version on disk\n";
print "[$version_dns]\t version dns\n";

if ( "$version_on_disk" >= "$version_dns" ) {
    print "OK: the $sa_channel version on disk is up to date: $version_on_disk\n";
    exit 0;
}
else {
    print "WARNING: there is a newer version available for SpamAssassin $sa_channel rules (on disk version is $version_on_disk, new version is $version_dns. Run sa-update -D as root to upgrade your SpamAssassin channel version.\n";
    exit 1;
}