#!/usr/bin/env perl

use strict;
use warnings;

use Net::LDAP;
use Net::LDAP::Util qw(ldap_explode_dn escape_filter_value);
use Authen::SASL;

open my $fh, '<', '/usr/local/etc/openldap/ldap.conf' or die($!);
my %config;
while (<$fh>) {
  chomp;
  next if /^#/;
  my @pair = split(' ', $_, 2);
  next unless (@pair == 2);
  $config{$pair[0]} = $pair[1];
}
close($fh);

my $mech         = $config{SASL_MECH}   // 'GSSAPI';
my $uri          = $config{URI}         // die("URI not specified\n");
my $user_basedn  = $config{USERS_BASE}  // die("USERS_BASE not specified\n");
my $group_basedn = $config{GROUPS_BASE} // die("GROUPS_BASE not specified\n");

@ARGV == 1 or die "usage: $0 USERNAME\n";
my $username = $ARGV[0];

my $conn = Net::LDAP->new($uri, version => '3') or die "$0: $@";
my $sasl = Authen::SASL->new($mech);
my $status = $conn->bind(sasl => $sasl);
$status->code and die "$0: ".$status->error;

my $search = $conn->search(
  scope  => 'sub',
  base   => $user_basedn,
  filter => '(uid='.escape_filter_value($username).')',
  attrs  => ['memberOf']);
$search->code and die "$0: ".$search->error;

$search->entries == 0 and die "no such user: $username\n";
$search->entries  > 1 and die "multiple results returned for user: $username\n";

foreach my $group_dn (($search->entries)[0]->get_value('memberOf')) {
  next unless $group_dn =~ /,\Q$group_basedn\E$/;

  my $parts = ldap_explode_dn($group_dn);
  next unless exists $parts->[0]{'CN'};

  print $parts->[0]{'CN'} =~ s/\s/_/gr . "\n";
}