#!perl -w

=head1 NAME

file - Simple log-to-file logging for qpsmtpd

=head1 DESCRIPTION

The 'file' logging plugin for qpsmtpd records qpsmtpd log messages into a
file (or a named pipe, if you prefer.)

=head1 CONFIGURATION

To enable the logging plugin, add a line of this form to the qpsmtpd plugins
configuration file:

=over

logging/file [loglevel I<level>] [reopen] [nosplit] [tsformat I<format>] I<path>

For example:

 logging/file loglevel LOGINFO /var/log/qpsmtpd.log
 logging/file /var/log/qpsmtpd.log.%Y-%m-%d
 logging/file loglevel LOGCRIT reopen |/usr/local/sbin/page-sysadmin
 logging/file loglevel LOGDEBUG tsformat %FT%T /var/log/qpsmtpd.log

=back

Multiple instances of the plugin can be configured by appending :I<N> for any
integer(s) I<N>, to log to multiple files simultaneously, e.g. to log critical
errors and normally verbose logs elsewhere.

The filename or command given can include strftime conversion specifiers,
which can be used to substitute time and date information into the logfile.
The file will be reopened whenever this output changes (for example, with a
format of qpsmtpd.log.%Y-%m-%d-%h, the log would be reopened once per hour).

The list of supported conversion specifiers depends on the strftime()
implementation of your C library. See strftime(3) for details.  Additionally,
%i will be expanded to a (hopefully) unique session-id; if %i is used, a new
logfile will be started for each SMTP connection.

The following optional configuration setting can be supplied:

=over

=item nosplit

If specified, the output file or pipe will be reopened at once once per
connection, and only prior to the first log output.  This prevents logs for
sessions that span log intervals being split across multiple logfiles.
Without this option, the log will be reopened only when its output filename
changes; if strftime specifiers are not used, the log will not be reopened
at all.

=item reopen

Forces the log output to be reopened once per connection, as soon as something
is available to be logged.  This can be combined with a high log severity (see
I<loglevel> below) to facilitate SMTP service alarms with Nagios or a similar
monitoring agent.

=item loglevel I<loglevel>

The internal log level below which messages will be logged.  The I<loglevel>
given should be chosen from the list below.  Priorities count downward (for
example, if LOGWARN were selected, LOGERROR, LOGCRIT and LOGEMERG messages
would be logged as well).

=item tsformat I<format>

By default qpsmtpd will prepend log items with the date and time as given in
the format by perl's C<localtime()> function. If you prefer another format then
you can specify a tsformat parameter.

=over

=item B<LOGDEBUG>

=item B<LOGINFO>

=item B<LOGNOTICE>

=item B<LOGWARN>

=item B<LOGERROR>

=item B<LOGCRIT>

=item B<LOGALERT>

=item B<LOGEMERG>

=back

=back


The chosen I<path> should be writable by the user running qpsmtpd; it will be
created it did not already exist, and appended to otherwise.

=head1 AUTHORS

Devin Carraway <qpsmtpd@devin.com>, with contributions by Peter J.
Holzer <hjp@hjp.at>.

=head1 LICENSE

Copyright (c) 2005-2006, Devin Carraway
Copyright (c) 2006, Peter J. Holzer.

This plugin is licensed under the same terms as the qpsmtpd package itself.
Please see the LICENSE file included with qpsmtpd for details.

=cut

use strict;
use warnings;

use IO::File;
use Sys::Hostname;
use POSIX qw(strftime);
use Qpsmtpd::Constants;

sub register {
    my ($self, $qp, @args) = @_;
    my %args;

    $self->{_loglevel} = LOGWARN;
    $self->{_tsformat} = '%a %b %d %T %Y';    # same as scalar localtime

    while (1) {
        last if !@args;
        if (lc $args[0] eq 'loglevel') {
            shift @args;
            my $ll = shift @args;
            if (!defined $ll) {
                warn "Malformed arguments to logging/file plugin";
                return;
            }
            if ($ll =~ /^(\d+)$/) {
                $self->{_loglevel} = $1;
            }
            elsif ($ll =~ /^(LOG\w+)$/) {
                $self->{_loglevel} = log_level($1);
                defined $self->{_loglevel} or $self->{_loglevel} = LOGWARN;
            }
        }
        elsif (lc $args[0] eq 'nosplit') {
            shift @args;
            $self->{_nosplit} = 1;
        }
        elsif (lc $args[0] eq 'reopen') {
            shift @args;
            $self->{_reopen} = 1;
        }
        elsif (lc $args[0] eq 'tsformat') {
            shift @args;
            my $format = shift @args;
            $self->{_tsformat} = $format;
        }
        else { last }
    }

    unless (@args && $args[0]) {
        warn "Malformed arguments to syslog plugin";
        return;
    }

    my $output = join(' ', @args);

    if ($output =~ /^\s*\|(.*)/) {
        $self->{_log_pipe}   = 1;
        $self->{_log_format} = $1;
    }
    else {
        $output =~ /^(.*)/;    # detaint
        $self->{_log_format} = $1;
    }
    $self->{_current_output}  = '';
    $self->{_session_counter} = 0;
    1;
}

sub log_output {
    my ($self, $transaction) = @_;
    my $output = $self->{_log_format};
    $output =~ s/%i/($transaction->notes('logging-session-id') || 'parent')/ge;
    $output = strftime $output, localtime;
    $output;
}

sub open_log {
    my ($self, $output, $qp) = @_;

    if ($self->{_log_pipe}) {
        unless ($self->{_f} = new IO::File "|$output") {
            warn "Error opening log output to command $output: $!";
            return undef;
        }
    }
    else {
        unless ($self->{_f} = new IO::File ">>$output") {
            warn "Error opening log output to path $output: $!";
            return undef;
        }
    }
    $self->{_current_output} = $output;
    $self->{_f}->autoflush(1);
    1;
}

# Reopen the output iff the interpolated output filename has changed
# from the one currently open, or if reopening was selected and we haven't
# yet done so during this session.
#
# Returns true if the file was reopened, zero if not, undef on error.
sub maybe_reopen {
    my ($self, $transaction) = @_;

    my $new_output = $self->log_output($transaction);
    if (
          !$self->{_current_output}
        || $self->{_current_output} ne $new_output
        || ($self->{_reopen}
            && !$transaction->notes('file-reopened-this-session'))
       )
    {
        unless ($self->open_log($new_output, $transaction)) {
            return undef;
        }
        $transaction->notes('file-reopened-this-session', 1);
        return 1;
    }
    return 0;
}

sub hook_connect {
    my ($self, $transaction) = @_;

    $transaction->notes('file-logged-this-session',   0);
    $transaction->notes('file-reopened-this-session', 0);
    $transaction->notes(
                        'logging-session-id',
                        sprintf("%08d-%04d-%d",
                                scalar time, $$,
                                ++$self->{_session_counter})
                       );
    return DECLINED;
}

sub hook_disconnect {
    my ($self) = @_;

    if ($self->{reopen_} && $self->{_f}) {
        $self->{_f} = undef;
    }
    return DECLINED;
}

sub hook_logging {
    my ($self, $transaction, $trace, $hook, $plugin, @log) = @_;

    return DECLINED
      if !defined $self->{_loglevel}
      or $trace > $self->{_loglevel};
    return DECLINED if defined $plugin and $plugin eq $self->plugin_name;

    # Possibly reopen the log iff:
    # - It's not already open
    # - We're allowed to split sessions across logfiles
    # - We haven't logged anything yet this session
    # - We aren't in a session
    if (   !$self->{_f}
        || !$self->{_nosplit}
        || !$transaction
        || !$transaction->notes('file-logged-this-session'))
    {
        unless (defined $self->maybe_reopen($transaction)) {
            return DECLINED;
        }
        $transaction->notes('file-logged-this-session', 1) if $transaction;
    }

    my $f = $self->{_f};
    print $f strftime($self->{_tsformat}, localtime), ' ',
      hostname(), '[', $$, ']: ', @log, "\n";
    return DECLINED;
}