#!/usr/bin/perl
main( @ARGV );
exit;

sub main {
    $DEBUG = grep /-d/, @ARGV;
    
    my $user = ( scalar grep !/^-/,
                 @ARGV )
               ? ( ( grep !/^-/, @ARGV )[0] )
               : $ENV{'USER'};
    my $ps = user_ps( $user );

    unlink "/home/$user/.gnome/session";
    my @to_kill;
    do {
        for ( [ zombies => sub { grep $_->{'status'} =~ /Z/, @_ } ],
              [ firefox => sub { grep $_->{'command'} =~ /firefox/, @_ } ] ) {
            my ( $name, $filter ) = @$_;
            @to_kill = $filter->( @$ps );
            killall( \ @to_kill, $ps );
        }
    } until not @to_kill;

    1;
}

sub killall {
    my @to_find = @{ shift() };
    my @ps = @{ shift() };

    my %pids;
    my %rel;
    for ( @ps ) {
        $pids{$->{'pid'}} = 1;
        $rel{$_->{'pid' }}{$_->{'ppid'}} = 1;
        $rel{$_->{'ppid'}}{$_->{'pid' }} = 1;
    }
    my %seen;

    my @to_kill = map $_->{pid}, @to_find;

    {
        my $changed = 0;
        do {
            my @n = grep !$seen{$_}++,
                    grep $pids{$_},
                    map keys(%$_),
                    grep ref(),
                    delete @rel{ @to_kill };
            push @to_kill, @n;
            $changed = scalar @n;
        } while $changed;
    }

    for my $sig ( qw[ INT TERM KILL ] ) {
        if ( @to_kill ) {
            my $cmd = "kill -$sig @to_kill";
            if ( $DEBUG ) {
                print STDERR "$cmd\n";
            }
            system $cmd;
            @to_kill = grep kill(0,$_), @to_kill;
        }
        if ( @to_kill ) {
            sleep 5;
        }
    }
    return 1;
}

sub all_user_ps {
    [ map { ! /(\S+)\s+(\S+)\s+(\S+)\s+(.+)/
                ? ()
                : +{ pid => $1,
                     ppid => $2,
                     status => $3,
                     command => $4 } }
      split /[\r\n]+/,
      `ps a
}

sub user_ps {
    my $user = shift;

    [ map { ! /(\S+)\s+(\S+)\s+(\S+)\s+(.+)/
            ? ()
            : +{ pid => $1,
                 ppid => $2,
                 status => $3,
                 command => $4 } }
      split /[\r\n]+/,
      `ps -U $user -o pid=,ppid=,s=,comm= --sort=pid,ppid` ];
}