content: /**
   * 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.activemq.broker.region.cursors;
  
  import static org.apache.activemq.broker.region.cursors.OrderedPendingList.getValues;
  
  import java.util.ArrayDeque;
  import java.util.Collection;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.activemq.broker.region.MessageReference;
  import org.apache.activemq.command.MessageId;
  import org.apache.activemq.management.SizeStatisticImpl;
  
  public class PrioritizedPendingList implements PendingList {
  
      private static final Integer MAX_PRIORITY = 10;
      private final OrderedPendingList[] lists = new OrderedPendingList[MAX_PRIORITY];
      private final Map<MessageId, PendingNode> map = new HashMap<MessageId, PendingNode>();
      private final SizeStatisticImpl messageSize;
      private final PendingMessageHelper pendingMessageHelper;
  
  
      public PrioritizedPendingList() {
          for (int i = 0; i < MAX_PRIORITY; i++) {
              this.lists[i] = new OrderedPendingList();
          }
          messageSize = new SizeStatisticImpl("messageSize", "The size in bytes of the pending messages");
          messageSize.setEnabled(true);
          pendingMessageHelper = new PendingMessageHelper(map, messageSize);
      }
  
      @Override
      public PendingNode addMessageFirst(MessageReference message) {
          PendingNode node = getList(message).addMessageFirst(message);
          this.pendingMessageHelper.addToMap(message, node);
          return node;
      }
  
      @Override
      public PendingNode addMessageLast(MessageReference message) {
          PendingNode node = getList(message).addMessageLast(message);
          this.pendingMessageHelper.addToMap(message, node);
          return node;
      }
  
      @Override
      public void clear() {
          for (int i = 0; i < MAX_PRIORITY; i++) {
              this.lists[i].clear();
          }
          this.map.clear();
          this.messageSize.reset();
      }
  
      @Override
      public boolean isEmpty() {
          return this.map.isEmpty();
      }
  
      @Override
      public Iterator<MessageReference> iterator() {
          return new PrioritizedPendingListIterator();
      }
  
      @Override
      public PendingNode remove(MessageReference message) {
          PendingNode node = null;
          if (message != null) {
              node = this.pendingMessageHelper.removeFromMap(message);
              if (node != null) {
                  node.getList().removeNode(node);
              }
          }
          return node;
      }
  
      @Override
      public int size() {
          return this.map.size();
      }
  
      @Override
      public long messageSize() {
          return this.messageSize.getTotalSize();
      }
  
      @Override
      public String toString() {
          return "PrioritizedPendingList(" + System.identityHashCode(this) + ")";
      }
  
      protected int getPriority(MessageReference message) {
          int priority = jakarta.jms.Message.DEFAULT_PRIORITY;
          if (message.getMessageId() != null) {
              priority = Math.max(message.getMessage().getPriority(), 0);
              priority = Math.min(priority, 9);
          }
          return priority;
      }
  
      protected OrderedPendingList getList(MessageReference msg) {
          return lists[getPriority(msg)];
      }
  
      private final class PrioritizedPendingListIterator implements Iterator<MessageReference> {
  
          private final Deque<Iterator<MessageReference>> iterators = new ArrayDeque<Iterator<MessageReference>>();
  
          private Iterator<MessageReference> current;
          private MessageReference currentMessage;
  
          PrioritizedPendingListIterator() {
              for (OrderedPendingList list : lists) {
                  if (!list.isEmpty()) {
                      iterators.push(list.iterator());
                  }
              }
  
              current = iterators.poll();
          }
  
          @Override
          public boolean hasNext() {
              while (current != null) {
                  if (current.hasNext()) {
                      return true;
                  } else {
                      current = iterators.poll();
                  }
              }
  
              return false;
          }
  
          @Override
          public MessageReference next() {
              MessageReference result = null;
  
              while (current != null) {
                  if (current.hasNext()) {
                      result = currentMessage = current.next();
                      break;
                  } else {
                      current = iterators.poll();
                  }
              }
  
              return result;
          }
  
          @Override
          public void remove() {
              if (currentMessage != null) {
                  pendingMessageHelper.removeFromMap(currentMessage);
                  current.remove();
                  currentMessage = null;
              }
          }
      }
  
      @Override
      public boolean contains(MessageReference message) {
          if (message != null) {
              return this.map.containsKey(message.getMessageId());
          }
          return false;
      }
  
      @Override
      public Collection<MessageReference> values() {
          return getValues(this);
      }
  
      @Override
      public void addAll(PendingList pendingList) {
          for(MessageReference messageReference : pendingList) {
              addMessageLast(messageReference);
          }
      }
  
      @Override
      public MessageReference get(MessageId messageId) {
          PendingNode node = map.get(messageId);
          if (node != null) {
              return node.getMessage();
          }
          return null;
      }
  
  }
  