/*
* Copyright (c) 2013 Mike Heath. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package cloudeventbus.client;
/**
* Holds the attributes associated with a subscription. Instances of this class are also {@link Iterable} so they can
* be used in a {@code for} loop.
*
* <p>If the subscription has multiple {@link MessageHandler}s associated with it, each will be invoked when a message
* is received. Additionally, each iterator created with this subscription will get each message received by this
* subscription. If an iterator stops being used, its {@link MessageIterator#close()} method should be invoked to keep
* messages from being queued unnecessarily and wasting memory.
*
* @see EventBus#subscribe(String, MessageHandler...)
* @see EventBus#subscribe(String, Integer, MessageHandler...)
* @author Mike Heath <elcapo@gmail.com>
*/
public interface Subscription extends Iterable<Message>, AutoCloseable {
/**
* Closes this subscription. Any {@link MessageHandler} objects associated with this request will no longer receive
* messages for this subscription after this method is invoked. All {@link MessageIterator} objects created by
* this subscription will also be closed.
*/
@Override
void close();
/**
* Returns the subscription's subject.
*
* @return the subscription's subject.
*/
String getSubject();
/**
* Returns the number of messages this subscriptions has received.
*
* @return the number of messages this subscriptions has received.
*/
int getReceivedMessages();
/**
* Returns the maximum number of messages this subscription will receive before being closed automatically.
*
* @return the maximum number of messages this subscription will receive or {@code null} if no maximum was specified.
*/
Integer getMaxMessages();
/**
* Creates a {@link MessageIterator} to iterate over messages received on this subscription. Because
* {@code Subscription} implements the {@link Iterable} interface, a subscription can be* used in a Java for loop.
* For example:
* <p/>
* <pre>
* for (Message message : nats.subscribe("foo.>") {
* System.out.println(message);
* }
* </pre>
* <p/>
* The for loop may terminate with an exception when the subscription is closed.
*
* @return an iterator.
*/
@Override
MessageIterator iterator();
/**
* Registers a {@link MessageHandler} instance with this subscription that will be invoked every time the
* subscription receives a message.
*
* @param messageHandler the message handler to be invoked
* @return a {@code HandlerRegistration} for removing the {@code MessageHandler}.
*/
HandlerRegistration addMessageHandler(MessageHandler messageHandler);
}