/*

 * Copyright (C) 2008 Apple Inc. All rights reserved.

 * Copyright (C) 2009 Google Inc. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1.  Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 * 2.  Redistributions in binary form must reproduce the above copyright

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     its contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#ifndef MessageQueue_h

#define MessageQueue_h

#include <limits>

#include <wtf/Assertions.h>

#include <wtf/Deque.h>

#include <wtf/Noncopyable.h>

#include <wtf/Threading.h>

namespace WTF {

    enum MessageQueueWaitResult {

        MessageQueueTerminated,       // Queue was destroyed while waiting for message.

        MessageQueueTimeout,          // Timeout was specified and it expired.

        MessageQueueMessageReceived,  // A message was successfully received and returned.

    };

    // The queue takes ownership of messages and transfer it to the new owner

    // when messages are fetched from the queue.

    // Essentially, MessageQueue acts as a queue of OwnPtr<DataType>.

    template<typename DataType>

    class MessageQueue : public Noncopyable {

    public:

        MessageQueue() : m_killed(false) { }

        ~MessageQueue();

        void append(PassOwnPtr<DataType>);

        bool appendAndCheckEmpty(PassOwnPtr<DataType>);

        void prepend(PassOwnPtr<DataType>);

        PassOwnPtr<DataType> waitForMessage();

        PassOwnPtr<DataType> tryGetMessage();

        template<typename Predicate>

        PassOwnPtr<DataType> waitForMessageFilteredWithTimeout(MessageQueueWaitResult&, Predicate&, double absoluteTime);

        template<typename Predicate>

        void removeIf(Predicate&);

        void kill();

        bool killed() const;

        // The result of isEmpty() is only valid if no other thread is manipulating the queue at the same time.

        bool isEmpty();

        static double infiniteTime() { return std::numeric_limits<double>::max(); }

    private:

        static bool alwaysTruePredicate(DataType*) { return true; }

        mutable Mutex m_mutex;

        ThreadCondition m_condition;

        Deque<DataType*> m_queue;

        bool m_killed;

    };

    template<typename DataType>

    MessageQueue<DataType>::~MessageQueue()

    {

        deleteAllValues(m_queue);

    }

    template<typename DataType>

    inline void MessageQueue<DataType>::append(PassOwnPtr<DataType> message)

    {

        MutexLocker lock(m_mutex);

        m_queue.append(message.leakPtr());

        m_condition.signal();

    }

    // Returns true if the queue was empty before the item was added.

    template<typename DataType>

    inline bool MessageQueue<DataType>::appendAndCheckEmpty(PassOwnPtr<DataType> message)

    {

        MutexLocker lock(m_mutex);

        bool wasEmpty = m_queue.isEmpty();

        m_queue.append(message.leakPtr());

        m_condition.signal();

        return wasEmpty;

    }

    template<typename DataType>

    inline void MessageQueue<DataType>::prepend(PassOwnPtr<DataType> message)

    {

        MutexLocker lock(m_mutex);

        m_queue.prepend(message.leakPtr());

        m_condition.signal();

    }

    template<typename DataType>

    inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessage()

    {

        MessageQueueWaitResult exitReason; 

        PassOwnPtr<DataType> result = waitForMessageFilteredWithTimeout(exitReason, MessageQueue<DataType>::alwaysTruePredicate, infiniteTime());

        ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);

        return result;

    }

    template<typename DataType>

    template<typename Predicate>

    inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessageFilteredWithTimeout(MessageQueueWaitResult& result, Predicate& predicate, double absoluteTime)

    {

        MutexLocker lock(m_mutex);

        bool timedOut = false;

        DequeConstIterator<DataType*> found = m_queue.end();

        while (!m_killed && !timedOut && (found = m_queue.findIf(predicate)) == m_queue.end())

            timedOut = !m_condition.timedWait(m_mutex, absoluteTime);

        ASSERT(!timedOut || absoluteTime != infiniteTime());

        if (m_killed) {

            result = MessageQueueTerminated;

            return 0;

        }

        if (timedOut) {

            result = MessageQueueTimeout;

            return 0;

        }

        ASSERT(found != m_queue.end());

        DataType* message = *found;

        m_queue.remove(found);

        result = MessageQueueMessageReceived;

        return message;

    }

    template<typename DataType>

    inline PassOwnPtr<DataType> MessageQueue<DataType>::tryGetMessage()

    {

        MutexLocker lock(m_mutex);

        if (m_killed)

            return 0;

        if (m_queue.isEmpty())

            return 0;

        return m_queue.takeFirst();

    }

    template<typename DataType>

    template<typename Predicate>

    inline void MessageQueue<DataType>::removeIf(Predicate& predicate)

    {

        MutexLocker lock(m_mutex);

        // See bug 31657 for why this loop looks so weird

        while (true) {

            DequeConstIterator<DataType*> found = m_queue.findIf(predicate);

            if (found == m_queue.end())

                break;

            DataType* message = *found;

            m_queue.remove(found);

            delete message;

       }

    }

    template<typename DataType>

    inline bool MessageQueue<DataType>::isEmpty()

    {

        MutexLocker lock(m_mutex);

        if (m_killed)

            return true;

        return m_queue.isEmpty();

    }

    template<typename DataType>

    inline void MessageQueue<DataType>::kill()

    {

        MutexLocker lock(m_mutex);

        m_killed = true;

        m_condition.broadcast();

    }

    template<typename DataType>

    inline bool MessageQueue<DataType>::killed() const

    {

        MutexLocker lock(m_mutex);

        return m_killed;

    }

} // namespace WTF

using WTF::MessageQueue;

// MessageQueueWaitResult enum and all its values.

using WTF::MessageQueueWaitResult;

using WTF::MessageQueueTerminated;

using WTF::MessageQueueTimeout;

using WTF::MessageQueueMessageReceived;

#endif // MessageQueue_h