=head1 NAME

AnyEvent::MP::Global - some network-global services

=head1 SYNOPSIS

   use AnyEvent::MP::Global;

=head1 DESCRIPTION

This module maintains a fully-meshed network between global nodes and
tries to have connections with all nodes in the network.

It also manages named port groups - ports can register themselves in any
number of groups that will be available network-wide, which is great for
discovering services.

Running it on one node will automatically run it on all nodes, although,
at the moment, the global service is started by default anyways.

=head1 GLOBALS AND FUNCTIONS

=over 4

=cut

package AnyEvent::MP::Global;

use common::sense;
use Carp ();

use AnyEvent ();
use AnyEvent::Util ();

use AnyEvent::MP;
use AnyEvent::MP::Kernel;
use AnyEvent::MP::Transport ();

use base "Exporter";

our @EXPORT = qw(
   grp_reg
   grp_get
   grp_mon
);

$AnyEvent::MP::Kernel::WARN->(7, "starting global service.");

#############################################################################
# node protocol parts for global nodes

{
   package AnyEvent::MP::Kernel;

   # TODO: this is ugly, maybe this should go into MP::Kernel or a separate module #d#

   our $GLOBAL;
   our $NODE_ADDR;
   our $GLOBAL_ADDR;
   our $NODE;
   our %GLOBAL_SLAVE;
   our $GLOBAL_MON;
   our $LISTENER;

   # switch to global mode
   $GLOBAL = 1;
   $MASTER = $NODE;
   undef $GLOBAL_MON;

   $GLOBAL_ADDR->{$NODE} = $LISTENER;

   $GLOBAL_MON = mon_nodes sub {
      return if $_[1];

      delete $NODE_ADDR->{$_[0]};

      if (delete $GLOBAL_ADDR->{$_[0]}) {
         # if the node is global, tell our slaves

         our %GLOBAL_SLAVE; # ugh, will be in AnyEvent::MP::Global
         snd $_, g_del => $_[0]
            for keys %GLOBAL_SLAVE;
      }
   };

   # tell everybody who connects that we are a global node
   push @AnyEvent::MP::Transport::HOOK_GREET, sub {
      $_[0]{local_greeting}{global} = 1;
   };

   # tell every global node that connects that we are global too
   push @AnyEvent::MP::Transport::HOOK_CONNECT, sub {
      snd $_[0], g_add => $NODE, $LISTENER
         if $_[0]{remote_greeting}{global};
   };

   # tell everybody else that we are global now
   snd $_ => g_add => $NODE, $LISTENER
      for up_nodes;
}

=item $guard = grp_reg $group, $port

Register the given (local!) port in the named global group C<$group>.

The port will be unregistered automatically when the port is destroyed.

When not called in void context, then a guard object will be returned that
will also cause the name to be unregistered when destroyed.

=cut

# register local port
sub grp_reg($$) {
   my ($group, $port) = @_;

   port_is_local $port
      or Carp::croak "AnyEvent::MP::Global::grp_reg can only be called for local ports, caught";

   defined wantarray && AnyEvent::Util::guard { unregister ($port, $group) }
}

=item $ports = grp_get $group

Returns all the ports currently registered to the given group (as
read-only(!) array reference). When the group has no registered members,
return C<undef>.

=cut

sub grp_get($) {
}

=item $guard = grp_mon $group, $callback->($ports, $add, $del)

Installs a monitor on the given group. Each time there is a change it
will be called with the current group members as an arrayref as the
first argument. The second argument only contains ports added, the third
argument only ports removed.

Unlike C<grp_get>, all three arguments will always be array-refs, even if
the array is empty. None of the arrays must be modified in any way.

The first invocation will be with the first two arguments set to the
current members, as if all of them were just added, but only when the
group is actually non-empty.

Optionally returns a guard object that uninstalls the watcher when it is
destroyed.

=cut

sub grp_mon($$) {
   my ($grp, $cb) = @_;
}

=back

=head1 SEE ALSO

L<AnyEvent::MP>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

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