#ifndef QPID_BROKER_PRIORITYQUEUE_H
#define QPID_BROKER_PRIORITYQUEUE_H

/*
 *
 * 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.
 *
 */
#include "qpid/broker/MessageDeque.h"
#include "qpid/sys/IntegerTypes.h"
#include <deque>
#include <vector>

namespace qpid {
namespace broker {

/**
 * Basic priority queue with a configurable number of recognised
 * priority levels. This is implemented as a separate deque per
 * priority level.
 *
 * Browsing is FIFO not priority order. There is a MessageDeque
 * for fast browsing.
 */
class PriorityQueue : public Messages
{
  public:
    PriorityQueue(int levels);
    virtual ~PriorityQueue() {}
    size_t size();

    bool deleted(const QueuedMessage&);
    void release(const QueuedMessage&);
    bool acquire(const framing::SequenceNumber&, QueuedMessage&);
    bool find(const framing::SequenceNumber&, QueuedMessage&);
    bool browse(const framing::SequenceNumber&, QueuedMessage&, bool);
    bool consume(QueuedMessage&);
    bool push(const QueuedMessage& added, QueuedMessage& removed);
    void updateAcquired(const QueuedMessage& acquired);
    void foreach(Functor);
    void removeIf(Predicate);

    static uint getPriority(const QueuedMessage&);

  protected:
    typedef std::deque<QueuedMessage*> Deque;
    typedef std::vector<Deque> PriorityLevels;
    virtual bool findFrontLevel(uint& p, PriorityLevels&);

    const int levels;

  private:
    /** Available messages separated by priority and sorted in priority order.
     *  Holds pointers to the QueuedMessages in fifo
     */
    PriorityLevels messages;
    /** FIFO index of all messsagse (including acquired messages)  for fast browsing and indexing */
    MessageDeque fifo;
    uint frontLevel;
    bool haveFront;
    bool cached;

    void erase(const QueuedMessage&);
    uint getPriorityLevel(const QueuedMessage&) const;
    void clearCache();
    bool checkFront();
};

}} // namespace qpid::broker

#endif  /*!QPID_BROKER_PRIORITYQUEUE_H*/
