=head1 NAME

AnyEvent::STOMP::Client - An event-based non-blocking STOMP 1.2 client based on
AnyEvent and Object::Event.

=head1 SYNOPSIS

  use AnyEvent::STOMP::Client;

  my $stomp_client = new AnyEvent::STOMP::Client()

  $stomp_client->connect();

  $stomp_client->on_connected(
      sub {
          my $self = shift;

          $self->subscribe('/queue/test-destination');

          $self->send(
              '/queue/test-destination',
              {'content-type' => 'text/plain',},
              "Hello World!"
          );
      }
  );

  $stomp_client->on_message(
      sub {
          my ($self, $header, $body) = @_;
          print "$body\n";
      }
  );

  AnyEvent->condvar->recv;


=head1 DESCRIPTION

AnyEvent::STOMP::Client provides a STOMP (Simple Text Oriented Messaging
Protocol) client. Thanks to AnyEvent, AnyEvent::STOMP::Client is completely
non-blocking, by making extensive use of the AnyEvent::Handle and timers (and,
under the hood, AnyEvent::Socket). Building on Object::Event,
AnyEvent::STOMP::Client implements various events (e.g. the MESSAGE event, when
a STOMP MESSAGE frame is received) and offers callbacks for these (e.g.
on_message($callback)).

=head1 METHODS

=head2 $client = new $host, $port, $connect_headers, $tls_context

Create an instance of C<AnyEvent::STOMP::Client>.

=over

=item C<$host>

String, optional, defaults to C<localhost>. The host, where a STOMP-compatible
message broker is running.

=item C<$port>

Integer, optional, defaults to C<61613>. The TCP port we connect to. I.e. the
port where the message broker instance is listening.

=item C<$connect_headers>

Hash, optional, empty by default. May be used to add arbitrary headers to the
STOMP C<CONNECT> frame. STOMP login headers would, for example, be supplied
using this parameter.

=item C<$tls_context>

Hash, optional, undef by default. May be used to supply a SSL/TLS context
directly to C<AnyEvent::Handle>. See L<AnyEvent::TLS> for documentation.

=back

=head3 Example

C<< my $client = AnyEvent::STOMP::Client->new(
    '127.0.0.1',
    61614,
    {'login' => 'guest', 'passcode' => 'guest', 'virtual-host' => 'foo'}
); >>

=head2 $client = connect

Connect to the specified  STOMP message broker. Croaks if you already
established a connection.

=head2 $client->disconnect

Sends a C<DISCONNECT> STOMP frame to the message broker (if we are still
connected). Croaks, if you are trying to disconnect without actually being
connected.

=over

=item C<$ungraceful>

Boolean, defaults to 0. If the ungraceful option is set, then simply a
C<DISCONNECT> STOMP frame is sent and the connection state is considered to be
disconnected without awaiting any response from the server.
If, however, the option is not set, then a receipt is asked for and the
connection is only considered to be no longer established upon receiving a
receipt for the C<DISCONNECT> frame.

=back

=head2 bool $client->is_connected

Check whether we are still connected to the broker. May only be accurate if
STOMP heart-beats are used.

=head2 $subscription_id = $client->subscribe $destination, $ack_mode, $additional_headers

Subscribe to a destination by sending a C<SUBSCRIBE> STOMP frame to the message
broker. Returns the subscription identifier.

=over

=item C<$destination>

String, mandatory. The destination to which we want to subscribe to.

=item C<$ack_mode>

C<auto> | C<client> | C<client-individual>, optional, defaults to C<auto>.
See the STOMP documentation for further information on acknowledgement modes.

=item C<$additional_headers>

Used to pass arbitrary headers to the C<SUBSCRIBE> STOMP frame. Broker specific
flow control parameters for example is what would want to supply here.

=back

=head2 $client->unsubscribe $destination, $additional_headers

Unsubscribe from a destination by sending an C<UNSUBSCRIBE> STOMP frame to the
message broker.

=over

=item C<$destination>

String, mandatory. The destination from which we want to unsubscribe.

=item C<$additional_headers>

Used to pass arbitrary headers to the C<UNSUBSCRIBE> STOMP frame.

=back

=head2 $client->send $destination, $headers, $body

Send a STOMP C<SEND> frame to the message broker.

=over

=item C<$destination>

String, mandatory. The destination to which to send the message to.

=item C<$header>

Hash, optional, empty by default. Arbitrary headers included in the C<SEND>
frame. See the STOMP documentation for supported headers.

=item C<$body>

String, optional, empty by default. The body of the message, according to the
content-type specified in the header.

=back

=head2 $client->ack $ack_id, $transaction_id

Send an C<ACK> frame to acknowledge a received message.

=over

=item C<$ack_id>

String, mandatory. Has to match the C<ack> header of the message that is to be
acknowledged.

=item C<$transaction_id>

String, optional. A transaction identifier, if the C<ACK> is part of a transaction.

=back

=head2 $client->nack $ack_id, $transaction_id

Send an C<NACK> frame to NOT acknowledge a received message.

=over

=item C<$ack_id>

String, mandatory. Has to match the C<ack> header of the message that is to be
nacked.

=item C<$transaction_id>

String, optional. A transaction identifier, if the C<NACK> is part of a
transaction.

=back

=head2 $client->begin_transaction $transaction_id, $additional_headers

Begin a STOMP transaction.

=over

=item C<$transaction_id>

String, mandatory. A unique identifier for the transaction.

=item C<$additional_headers>

Hash, optional, empty by default. Used to pass arbitrary headers to the STOMP
frame.

=back

=head2 $client->commit_transaction $transaction_id, $additional_headers

Commit a STOMP transaction.

=over

=item C<$transaction_id>

String, mandatory. A unique identifier for the transaction.

=item C<$additional_headers>

Hash, optional, empty by default. Used to pass arbitrary headers to the STOMP
frame.

=back

=head2 $client->abort_transaction $transaction_id, $additional_headers

Abort a STOMP transaction.

=over

=item C<$transaction_id>

String, mandatory. A unique identifier for the transaction.

=item C<$additional_headers>

Hash, optional, empty by default. Used to pass arbitrary headers to the STOMP
frame.

=back

=head2 $client->destroy

Disconnects and cleans up all callbacks. To be called when the client object
is not used any more and should be cleaned up.

=head2 Callbacks

In order for the C<AnyEvent::STOMP::Client> to be useful, callback subroutines
can be registered for the following events:

=head3 $guard = $client->on_connected $callback

Invoked when a CONNECTED frame is received. Parameters passed to the callback:
C<$self>, C<$header_hashref>.

=head3 $guard = $client->on_disconnected $callback

Invoked after having successfully disconnected from a broker. I.e. when a
callback is registered for this event and the C<disconnect> subroutine is
called, then a receipt header is included in the DISCONNECT frame and the
disconnected event is fired upon receiving the receipt for the DISCONNECT frame.
Parameters passed to the callback: C<$self>, C<$host>, C<$port>.

=head3 $guard = $client->on_connection_lost $callback

Invoked when either the C<on_error> callback specified in the
C<AnyEvent::Handle> constructor is called, or when no more
heartbeats arrive from the server.
Parameters passed to the callback: C<$self>, C<$host>, C<$port>, C<$error_message>.

=head3 $guard = $client->on_connect_error $callback

Invoked when the C<on_connect_error> callback specified in the
C<AnyEvent::Handle> constructor is called.
Parameters passed to the callback: C<$self>, C<$host>, C<$port>.

=head3 $guard = $client->on_send_frame $callback

Invoked when a STOMP frame is sent. Parameters passed to the callback:
C<$self>, C<$frame> (the sent frame as string).

=head3 $guard = $client->on_send $callback

Invoked when a STOMP SEND command is sent. Parameters passed to the callback:
C<$self>, C<$frame> (the sent frame as string).

=head3 $guard = $client->on_ack $callback

Invoked when a STOMP ACK command is sent. Parameters passed to the callback:
C<$self>, C<$frame> (the sent frame as string).

=head3 $guard = $client->on_nack $callback

Invoked when a STOMP NACK command is sent. Parameters passed to the callback:
C<$self>, C<$frame> (the sent frame as string).

=head3 $guard = $client->on_read_frame $callback

Invoked when a STOMP frame is received (irrespective of the STOMP command).
Parameters passed to the callback: C<$self>, C<$command>, C<$header_hashref>,
C<$body> (may be C<undef>, if the frame is not specified to contain a body).

=head3 $guard = $client->on_message $callback $destination

Invoked when a MESSAGE frame is received. Optionally, a C<$destination>
parameter may be specified, resulting in the callback only being invoked,
when a MESSAGE is received from that specific destination.
Parameters passed to the callback: C<$self>, C<$header_hashref>, C<$body>.

=head3 $guard = $client->on_receipt $callback

Invoked when a RECEIPT frame is received. Parameters passed to the callback:
C<$self>, C<$header_hashref>.

=head3 $guard = $client->on_error $callback

Invoked when an ERROR frame is received. Parameters passed to the callback: C<$self>, C<$host>, C<$port>, C<$error_message>.

=head3 $guard = $client->on_subscribed $callback

Invoked after having successfully subscribed to a destination. Works behind the
scenes like the C<on_disconnected> described above. Parameters passed to the
callback: C<$self>, C<$destination>.

=head3 $guard = $client->on_unsubscribed $callback

Invoked after having successfully unsubscribed to a destination. Works behind
the scenes like the C<on_disconnected> described above. Parameters passed to the
callback: C<$self>, C<$destination>.

=head3 $client->unregister_callback $guard

To unregister a previously registered callback.

=over

=item C<$guard>

The return value of one of the above on_<xyz> subroutines, identifying the
registered callback.

=back

=head1 BUGS / LIMITATIONS

=over

=item

Currently only the most recent version of STOMP, i.e. 1.2, is supported.

=back


=head1 SEE ALSO

L<AnyEvent>, L<AnyEvent::Handle>, L<AnyEvent::TLS>, L<Object::Event>,
L<STOMP 1.2 Documentation|http://stomp.github.io/stomp-specification-1.2.html>

=head1 AUTHOR

Raphael Seebacher, E<lt>raphael@seebachers.chE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2013 by L<Open Systems AG|http://www.open.ch>. All rights reserved.

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.