/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.qpid.server.queue;

import java.util.List;
import java.util.concurrent.Executor;

import org.apache.qpid.AMQException;
import org.apache.qpid.framing.AMQShortString;
import org.apache.qpid.server.AMQChannel;
import org.apache.qpid.server.protocol.AMQProtocolSession;
import org.apache.qpid.server.store.StoreContext;

interface DeliveryManager
{
    /**
     * Determines whether there are queued messages. Sets _queueing to false if there are no queued messages. This needs
     * to be atomic.
     *
     * @return true if there are queued messages
     */
    boolean hasQueuedMessages();

    /**
     * This method should not be used to determin if there are messages in the queue.
     *
     * @return int The number of messages in the queue
     *
     * @use hasQueuedMessages() for all controls relating to having messages on the queue.
     */
    int getQueueMessageCount();

    /**
     * Requests that the delivery manager start processing the queue asynchronously if there is work that can be done
     * (i.e. there are messages queued up and subscribers that can receive them. <p/> This should be called when
     * subscribers are added, but only after the consume-ok message has been returned as message delivery may start
     * immediately. It should also be called after unsuspending a client. <p/>
     *
     * @param executor the executor on which the delivery should take place
     */
    void processAsync(Executor executor);

    /**
     * Handles message delivery. The delivery manager is always in one of two modes; it is either queueing messages for
     * asynchronous delivery or delivering directly.
     *
     * @param storeContext
     * @param name         the name of the entity on whose behalf we are delivering the message
     * @param msg          the message to deliver
     * @param deliverFirst
     *
     * @throws org.apache.qpid.server.queue.FailedDequeueException
     *          if the message could not be dequeued
     */
    void deliver(StoreContext storeContext, AMQShortString name, AMQMessage msg, boolean deliverFirst) throws FailedDequeueException, AMQException;

    void removeAMessageFromTop(StoreContext storeContext) throws AMQException;

    long clearAllMessages(StoreContext storeContext) throws AMQException;

    void startMovingMessages();

    void enqueueMovedMessages(StoreContext context, List<AMQMessage> messageList);

    void stopMovingMessages();

    void removeMovedMessages(List<AMQMessage> messageListToRemove);

    List<AMQMessage> getMessages();

    List<AMQMessage> getMessages(long fromMessageId, long toMessageId);

    void populatePreDeliveryQueue(Subscription subscription);

    boolean performGet(AMQProtocolSession session, AMQChannel channel, boolean acks) throws AMQException;

    long getTotalMessageSize();

    long getOldestMessageArrival();

    void subscriberHasPendingResend(boolean hasContent, Subscription subscription, AMQMessage msg);
}
