001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.broker.region.cursors;
018
019import java.util.Collection;
020import java.util.Iterator;
021
022import org.apache.activemq.broker.region.MessageReference;
023import org.apache.activemq.command.MessageId;
024
025public interface PendingList extends Iterable<MessageReference> {
026
027    /**
028     * Returns true if there are no Messages in the PendingList currently.
029     * @return true if the PendingList is currently empty.
030     */
031    public boolean isEmpty();
032
033    /**
034     * Discards all Messages currently held in the PendingList.
035     */
036    public void clear();
037
038    /**
039     * Adds the given message to the head of the list.
040     *
041     * @param message
042     *      The MessageReference that is to be added to this list.
043     *
044     * @return the PendingNode that contains the newly added message.
045     */
046    public PendingNode addMessageFirst(MessageReference message);
047
048    /**
049     * Adds the given message to the tail of the list.
050     *
051     * @param message
052     *      The MessageReference that is to be added to this list.
053     *
054     * @return the PendingNode that contains the newly added message.
055     */
056    public PendingNode addMessageLast(MessageReference message);
057
058    /**
059     * Removes the given MessageReference from the PendingList if it is
060     * contained within.
061     *
062     * @param message
063     *      The MessageReference that is to be removed to this list.
064     *
065     * @return the PendingNode that contains the removed message or null if the
066     *         message was not present in this list.
067     */
068    public PendingNode remove(MessageReference message);
069
070    /**
071     * Returns the number of MessageReferences that are awaiting dispatch.
072     * @return current count of the pending messages.
073     */
074    public int size();
075
076    public long messageSize();
077
078    /**
079     * Returns an iterator over the pending Messages.  The subclass controls how
080     * the returned iterator actually traverses the list of pending messages allowing
081     * for the order to vary based on factors like Message priority or some other
082     * mechanism.
083     *
084     * @return an Iterator that returns MessageReferences contained in this list.
085     */
086    @Override
087    public Iterator<MessageReference> iterator();
088
089    /**
090     * Query the PendingList to determine if the given message is contained within.
091     *
092     * @param message
093     *      The Message that is the target of this query.
094     *
095     * @return true if the MessageReference is contained in this list.
096     */
097    public boolean contains(MessageReference message);
098
099    /**
100     * Returns a new Collection that contains all the MessageReferences currently
101     * held in this PendingList.  The elements of the list are ordered using the
102     * same rules as the subclass uses for iteration.
103     *
104     * @return a new Collection containing this lists MessageReferences.
105     */
106    public Collection<MessageReference> values();
107
108    /**
109     * Adds all the elements of the given PendingList to this PendingList.
110     *
111     * @param pendingList
112     *      The PendingList that is to be added to this collection.
113     */
114    public void addAll(PendingList pendingList);
115
116    public MessageReference get(MessageId messageId);
117}