# -*- perl -*-
#
#  Net::Server::Multiplex - Net::Server personality
#
#  $Id$
#
#  Copyright (C) 2001-2022
#
#    Rob Brown <bbb@cpan,org>
#
#    Paul Seamons <paul@seamons.com>
#
#  This package may be distributed under the terms of either the
#  GNU General Public License
#    or the
#  Perl Artistic License
#
################################################################

package Net::Server::Multiplex;

use strict;
use base qw(Net::Server);
use Net::Server::SIG qw(register_sig check_sigs);
use Carp qw(confess);
eval { require IO::Multiplex; import IO::Multiplex 1.05; };
$@ && warn "Module IO::Multiplex is required for Multiplex.";

our $VERSION = $Net::Server::VERSION;

sub net_server_type { __PACKAGE__ }

sub loop {
    my $self = shift;
    my $prop = $self->{server};

    my $mux = IO::Multiplex->new;
    $self->{mux} = $mux;

    foreach my $sock ( @{ $prop->{sock} } ) {
        if (Net::Server::SOCK_DGRAM == $sock->getsockopt(Socket::SOL_SOCKET(),Socket::SO_TYPE())) {
            $mux->add($sock);
        } else {
            $mux->listen($sock);
        }
    }
    $mux->set_callback_object(Net::Server::Multiplex::MUX->init($self));

    ###
    ### Use Net::Server::SIG for safe signal handling.
    ###

    ### register some of the signals for safe handling
    register_sig(PIPE => sub { $self->log(4, "SIG$_[0] received") },
                 INT  => sub { $self->server_close() },
                 TERM => sub { $self->server_close() },
                 QUIT => sub { $self->server_close() },
                 HUP  => sub { $self->sig_hup() },
                 CHLD => sub { $self->sig_chld() },
                );

    if ( defined $prop->{check_for_dequeue} ) {
        # It does not matter which socket the timeout is associated with.
        $mux->set_timeout( $prop->{sock}->[0], $prop->{check_for_dequeue} );
    }

    $mux->loop(sub {
        my ($rdready, $wrready) = @_;
        check_sigs();
        $mux->endloop if $prop->{_HUP};
    });

    ### fall back to the main run routine
}

### make sure that we properly disconnect from the mux if we are HUPing
sub sig_hup {
    my $self = shift;
    my $prop = $self->{server};

    if (my $mux  = $self->{mux}) {
        foreach my $sock ( @{ $prop->{sock} } ){
            $mux->remove($sock);
        }
    }

    return $self->SUPER::sig_hup(@_);
}

# This method instead of run_client_connection
# because STDOUT should be tied correctly,
# not just globbed onto the socket.  This
# tie is taken care of in the mux_connection
# routine instead of within post_accept.
# Also, the process_request stuff should never be
# used since the request should be really processed
# via mux_* methods.

sub setup_client_connection {
    my ($self, $mux) = @_;
    my $prop = $self->{server};

    ### Copied from Net::Server::post_accept...
    $prop->{requests} ++;
    if (! $prop->{no_client_stdout}) {
        *STDIN  = \*{ $prop->{client} };
        #  *STDOUT = \*{ $prop->{client} };
        #  STDIN->autoflush(1);
    }

    ### Copied from Net::Server::run_client_connection...
    $self->get_client_info;     # determines information about peer and local
    $self->post_accept_hook;    # user customizable hook
    unless($self->allow_deny &&       # do allow/deny check on client info
    $self->allow_deny_hook ){  # user customizable hook
        $self->request_denied_hook;     # user customizable hook
        # Flush output buffer and close connection since it should be denied.
        if (! $prop->{no_client_stdout}) {
            close (STDOUT);
        }
        return 0;
    }
    return 1;
}

# Compatibility interface for Net::Server
sub run_dequeue {
    confess "&$Net::Server::Multiplex::MUX::ISA[0]\::run_dequeue never defined";
}

sub mux_connection {}
sub mux_input {
    confess "&$Net::Server::Multiplex::MUX::ISA[0]\::mux_input never defined";
}
sub mux_eof {}
sub mux_close {}
sub mux_timeout {
    confess "&$Net::Server::Multiplex::MUX::ISA[0]\::mux_timeout never defined";
}

package Net::Server::Multiplex::MUX;

# Just a dumb module to be used for the
# Multiplex callback_object hooks

use strict;

our $VERSION = $Net::Server::Multiplex::VERSION;
# This temporary @ISA should always be overridden
# at runtime when init() is called.  This module should
# really ISA whatever module ISA Net::Server::Multiplex.
our @ISA = qw(Net::Server::Multiplex);

# This subroutine is meant to create the main callback
# object to be used for all listen file descriptors.
# It just needs to make sure the {net_server} property
# is set.
sub init {
    my $package  = shift;
    my $net_server= shift;
    # On-the-fly runtime polymorphism hack
    # to ISA the same type of thing passed.
    @ISA = (ref $net_server);
    my $self     = bless {
        net_server => $net_server,
    } => $package;
    return $self;
}

# The new() routine is passed the Net::Server object.  It
# is meant to create the client specific callback object.
# Note that the $net_server->{server} property hash may be
# modified by future connections through Net::Server.
# Any values within it that this object may need to use
# later must be copied within itself.
sub new {
    my $package    = shift;
    my $net_server = shift;
    my $self       = bless {
        # Some nice values to remember for this client
        net_server => $net_server,
        peeraddr   => $net_server->{server}->{peeraddr},
        connected  => time,
    }, $package;
    return $self;
}

sub log { shift->{net_server}->log(@_) }

# This subroutine is only used by the listen callback object.
sub mux_connection {
    my ($self, $mux, $fh) = @_;
    my $net_server = $self->{net_server};
    $net_server->{server}->{client} = $fh;

    $self->_link_stdout($mux, $fh);

    if ($net_server->setup_client_connection($mux)) {
        # Create client specific callback object
        my $client_object = Net::Server::Multiplex::MUX->new($net_server, $fh);

        # Set this as the callback object for this client
        $mux->set_callback_object($client_object, $fh);

        # Finally call the clients real mux_connection routine,
        # if any.  This allows all the mux_* routines to be
        # called from the same type of object.
        $client_object->SUPER::mux_connection($mux, $fh);
        #$client_object->mux_connection($mux, $fh);
    }

    $self->_unlink_stdout();

    return;
}

sub mux_input {
    my ($self, $mux, $fh, $in_ref) = @_;
    $self->_link_stdout($mux, $fh);
    $self->SUPER::mux_input($mux, $fh, $in_ref);
    $self->_unlink_stdout();
    return;
}

sub mux_eof {
    my ($self, $mux, $fh, $in_ref) = @_;
    $self->_link_stdout($mux, $fh);
    $self->SUPER::mux_eof($mux, $fh, $in_ref);
    $self->_unlink_stdout();
    $mux->shutdown($fh, 1);
    return;
}

sub mux_close {
    my ($self, $mux, $fh) = @_;
    $self->{net_server}->post_process_request_hook;
    $self->SUPER::mux_close($mux, $fh);
    return;
}

sub mux_timeout {
    my ($self, $mux, $fh) = @_;

    if ( my $check = $self->{net_server}->{server}->{check_for_dequeue} ) {
        $self->{net_server}->run_dequeue();
        $mux->set_timeout( $fh, $check );
    } else {
        $self->_link_stdout($mux, $fh);
        $self->SUPER::mux_timeout($mux, $fh);
        $self->_unlink_stdout();
    }
    return;
}

sub _link_stdout {
    my ($self, $mux, $fh) = @_;
    return if $self->{net_server}->{server}->{no_client_stdout};

    # Hook up STDOUT to the correct socket
    if (tied *$fh) {
        # Make sure STDOUT is tied however $fh is
        tie (*STDOUT, (ref tied *$fh), $mux, $fh);
    } else {
        *STDOUT = *$fh;
    }
}

sub _unlink_stdout {
    my $self = shift;
    return if $self->{net_server}->{server}->{no_client_stdout};
    my $x = tied *STDOUT;
    if ($x) {
        undef $x;
        untie *STDOUT;
    }
}

1;

__END__

=head1 NAME

Net::Server::Multiplex - Multiplex several connections within one process

=head1 SYNOPSIS

    package MyPlexer;

    use base qw(Net::Server::Multiplex);

    sub mux_input {
        #...code...
    }

    __PACKAGE__->run();

=head1 DESCRIPTION

This personality is designed to handle multiple connections all within
one process.  It should only be used with protocols that are
guaranteed to be able to respond quickly on a packet by packet basis.
If determining a response could take a while or an unknown period of
time, all other connections established will block until the response
completes.  If this condition might ever occur, this personality
should probably not be used.

This takes some nice features of Net::Server (like the server listen
socket setup, configuration file processing, safe signal handling,
convenient inet style STDIN/STDOUT handling, logging features,
deamonization and pid tracking, and restartability -SIGHUP) and some
nice features of IO::Multiplex (automatic buffered IO and
per-file-handle objects) and combines them for an easy-to-use
interface.

See examples/samplechat.pl distributed with Net::Server for a simple
chat server that uses several of these features.

=head1 PROCESS FLOW

The process flow is written in an open, easy to override, easy to
hook, fashion.  The basic flow is shown below.

    $self->configure_hook;

    $self->configure(@_);

    $self->post_configure;

    $self->post_configure_hook;

    $self->pre_bind;

    $self->bind;

    if (Restarting server) {
        $self->restart_open_hook();
    }

    $self->post_bind_hook;

    $self->post_bind;

    $self->pre_loop_hook;

    $self->loop; # This basically just runs IO::Multiplex::loop
    # For routines inside a $self->loop
    # See CLIENT PROCESSING below

    $self->pre_server_close_hook;

    $self->post_child_cleanup_hook;

    $self->server_close;

    if (Restarting server) {
        $self->restart_close_hook();
        $self->hup_server;
        # Redo process again starting with configure_hook
  }

The server then exits.

=head1 CLIENT PROCESSING

The following represents the client processing program flow:

    $self->{server}->{client} = Net::Server::Proto::TCP->accept();  # NOTE: Multiplexed with mux_input() below

    if (check_for_dequeue seconds have passed) {
        $self->run_dequeue();
    }

    $self->get_client_info;

    $self->post_accept_hook; # Net::Server style

    if ($self->allow_deny
        && $self->allow_deny_hook) {

      # (Net::Server style $self->process_request() is never called.)

      # A unique client specific object is created
      # for all mux_* methods from this point on.
      $self = __PACKAGE__->new($self, client);

      $self->mux_connection; # IO::Multiplex style

      for (every packet received) {
        $self->mux_input;  # NOTE: Multiplexed with accept() above
      }

    } else {

      $self->request_denied_hook;

      # Notice that if either allow_deny or allow_deny_hook fails, then
      # new(), mux_connection(), and mux_input() will never be called.
      # mux_eof() and mux_close() will still be called, but using a
      # common listen socket callback object instead of a unique client
      # specific object.

    }

    $self->mux_eof;

    $self->post_process_request_hook;

    $self->mux_close;


This process then loops multiplexing between the accept() for the next
connection and mux_input() when input arrives to avoid blocking either
one.

=head1 HOOKS

The *_hook methods mentioned above are meant to be overridden with
your own subroutines if you desire to provide additional
functionality.

The loop() method of Net::Server has been overridden to run the loop
routine of IO::Multiplex instead.  The Net::Server methods may access
the IO::Multiplex object at C<$self-E<gt>{mux}> if desired.  The
IO::Multiplex methods may access the Net::Server object at
C<$self-E<gt>{net_server}> if desired.

The process_request() method is never used with this personality.

The other Net::Server hooks and methods should work the same.

=over 4

=item C<$self-E<gt>run_dequeue()>

This hook only gets called in conjunction with the check_for_dequeue
setting.  It will run every check_for_dequeue seconds.  Since no
forking is done, this hook should run fast in order to prevent
blocking the rest of the processing.

=back

=head1 TIMEOUTS

=head2 set_timeout

To utilize the optional timeout feature of IO::Multiplex, you need to
specify a timeout by using the set_timeout method.

$self->{net_server}->{mux}->set_timeout($fh, $seconds_from_now);

$fh may be either a client socket or a listen socket file descriptor
within the mux.  $seconds_from_now may be fractional to achieve more
precise timeouts.  This is used in conjunction with mux_timeout, which
you should define yourself.

=head2 mux_timeout

The main loop() routine will call $obj->mux_timeout($mux, $fh) when
the timeout specified in set_timeout is reached where $fh is the same
as the one specified in set_timeout() and $obj is its corresponding
object (either the unique client specific object or the main listen
callback object) and $mux is the main IO::Multiplex object itself.

=head1 CALLBACK INTERFACE

Callback objects should support the following interface.  You do not
have to provide all of these methods, just provide the ones you are
interested in.  These are just like the IO::Multiplex hooks except
that STDOUT is tied to the corresponding client socket handle for your
convenience and to more closely emulate the Net::Server model.
However, unlike some other Net::Server personalities, you should never
read directly from STDIN yourself.  You should define one or more of
the following methods:

=head2 mux_connection ($mux,$fh)

(OPTIONAL) Run once when the client first connects if the allow_deny
passes.  Note that the C<$self-E<gt>{net_server}-E<gt>{server}>
property hash may be modified by future connections through
Net::Server.  Any values within it that this object may need to use
later should be copied within its own object at this point.

  Example:
  $self->{peerport} = $self->{net_server}->{server}->{peerport};

=head2 mux_input ($mux,$fh,\$data)

(REQUIRED) Run each time a packet is read.  It should consume $data
starting at the left and leave unconsumed data in the scalar for
future calls to mux_input.

=head2 mux_eof ($mux,$fh,\$data)

(OPTIONAL) Run once when the client is done writing.  It should
consume the rest of $data since mux_input() will never be run again.

=head2 mux_close ($mux,$fh)

(OPTIONAL) Run after the entire client socket has been closed.  No
more attempts should be made to read or write to the client or to
STDOUT.

=head2 mux_timeout ($mux,$fh)

(OPTIONAL) Run once when the set_timeout setting expires as explained
above.

=head1 BUGS

This is only known to work with TCP servers.

If you need to use the IO::Multiplex style set_timeout / mux_timeout
interface, you cannot use the Net::Server style check_for_dequeue /
run_dequeue interface.  It will not work if the check_for_dequeue
option is specified.  The run_dequeue method is just a compatibility
interface to comply with the Net::Server::Fork style run_dequeue but
is implemented in terms of the IO::Multiplex style set_timeout and
mux_timeout methods.

=head1 AUTHOR

Rob Brown <bbb@cpan.org>

=head1 MAINTAINER

Paul Seamons <paul@seamons.com>

=head1 LICENSE

  This package may be distributed under the terms of either the
  GNU General Public License
     or the
  Perl Artistic License

  All rights reserved.

=head1 SEE ALSO

L<Net::Server> by Paul Seamons <paul@seamons.com>,

L<IO::Multiplex> by Bruce Keeler <bruce@gridpoint.com>.

=cut