/*

* Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:

*

*/

#ifndef HGSCROLLBUFFERMANAGER_H_

#define HGSCROLLBUFFERMANAGER_H_

#include <qobject>

#include <QTimer>

class UpdatePair

{

public:

    UpdatePair(int start, int count);

    int start() const;

    int end() const;

    bool adjacent(int start, int count) const;

    bool contains(const UpdatePair &other) const;

    void extend(int start, int count);

    void subtract(int start, int count);

    void shiftRight(int count);

    void shiftLeft(int count);

    bool operator== (const UpdatePair &other) const;

    bool operator< (const UpdatePair &other) const;

private:

    int mStart;

    int mCount;

};

class UpdateBuffer : public QList<UpdatePair>

{

public:

    UpdateBuffer();

    void add(int start, int count);

    void remove(int start, int count);

    void shiftRight(int startingFrom, int amount);

    void shiftLeft(int startingFrom, int amount);

};

class HgScrollBufferManager: public QObject

    {

    Q_OBJECT

public:

    HgScrollBufferManager(

            int bufferSize,

            int bufferTreshold,

            int initialPosition,

            int totalCount);

    virtual ~HgScrollBufferManager();

    void resetBuffer(int aPosition, int aTotalCount);

    void scrollPositionChanged(int newPosition);

    bool positionInsideBuffer(int position);

    void addItems(int start, int count);

    void removeItems(int start, int end);

    void moveItems(int start, int end, int target);

    void flushRequestBuffers();

    void currentBuffer(int& bufferStart, int& bufferEnd);

signals:

    void releaseItems(int releaseStart, int releaseEnd);

    void requestItems(int requestStart, int requestEnd);

protected slots:

    void timeout();

protected:

    void init();

    void asyncUpdate();

    int changeBufferPosition(int newPos);

    void simpleAddItems(int start, int end);

    void simpleRemoveItems(int start, int end);

    void appendRequestBuffer(int start, int end);

    void appendReleaseBuffer(int start, int end);

private:

    int mBufferSize;

    int mBufferTreshold;

    int mBufferPosition;

    int mDiff;

    int mTotalCount;

    bool mResetOrdered;

    int mRequestStart;

    int mRequestCount;

    int mReleaseStart;

    int mReleaseCount;

    QTimer mTimer;

    UpdateBuffer mRequestBuffer;

    UpdateBuffer mReleaseBuffer;

private:

    Q_DISABLE_COPY(HgScrollBufferManager)

    };

#endif /*HGSCROLLBUFFERMANAGER_H_*/