package Vulcan::Sudo;

=head1 NAME

Vulcan::Sudo - Become a user by setting uid or invoking sudo

=cut
use warnings;
use strict;

use Carp;
use POSIX;

=head1 SYNOPSIS

 use Vulcan::Sudo;

 Vulcan::Sudo->sudo( 'joe' );

=head1 Methods

=head3 sudo( $user )

Become $user ( default root ). 

=cut
sub sudo
{
    my ( $class, $user ) = splice @_;
    my $me = ( getpwuid $< )[0];

    return $user if $me eq ( $user ||= 'root' );
    confess "invalid user $user\n" unless my @pw = getpwnam $user;
    @pw = map { 0 + sprintf '%d', $_ } @pw[2,3];
    POSIX::setgid( $pw[1] );
    return $user if POSIX::setuid( $pw[0] );

    warn "$me: need '$user' privilege, invoking sudo.\n";
    confess "exec $0: $!" unless exec 'sudo', '-u', $user, $0, @ARGV;
}

1;