/*

* 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:

*

*  Version     : %version: 1 %

*/

#include "hgbuffermanager.h"

#include <hgwidgets/hgcacheproxymodel.h>

HgBufferManager::HgBufferManager(

    HgBufferManagerObserver* aObserver,

	int aBufferSize,

	int aBufferTreshold,

	int aInitialPosition,

	int aTotalCount )

:

mObserver(aObserver),

mBufferSize( aBufferSize ),

mBufferTreshold( aBufferTreshold ),

mBufferPosition( aInitialPosition ),

mTotalCount( aTotalCount )

{

    ASSERT( mObserver != 0 );

    mBufferPosition -= (mBufferSize / 2);

    if( mBufferPosition + mBufferSize > mTotalCount - 1 ){

        mBufferPosition = (mTotalCount - 1) - mBufferSize;

    }

    if(mBufferPosition < 0 ){

        mBufferPosition = 0;

    }

    mDiff = 0;

	//request Initial Buffer

	mRequestStart = mBufferPosition;

	mRequestCount = mBufferSize;

	calculate();

}

HgBufferManager::~HgBufferManager()

{

}

void HgBufferManager::resizeCache(int newSize, int newTreshold)

{

    if (newTreshold != mBufferTreshold){

        mBufferTreshold = newTreshold;

    }

    if (newSize!=mBufferSize){

//        int pos = mBufferPosition + (mBufferSize / 2);

        int a = Max(0, mBufferPosition + mBufferSize/2 - newSize/2);

        int b = Min(a + newSize, mTotalCount);

        if ( b == mTotalCount){

            a = mTotalCount - newSize;

        }

        int c = Max(0, mBufferPosition);

        int d = Min(c + mBufferSize, mTotalCount);

        if ( d == mTotalCount){

            c = mTotalCount - mBufferSize;

        }

        if ( newSize>mBufferSize){

            mObserver->request(a, c-1, HgCacheProxyModel::HgRequestOrderAscending);

            mObserver->request(d, b-1, HgCacheProxyModel::HgRequestOrderAscending);

        }else if ( newSize<mBufferSize){

            mObserver->release(c, a-1);

            mObserver->release(b, d);

        }

        mBufferPosition = a;

        mBufferSize = newSize;

    }

}

void HgBufferManager::calculate()

{  

    HgCacheProxyModel::HgRequestOrder direction = HgCacheProxyModel::HgRequestOrderAscending;

    if(mResetOrdered){

        mResetOrdered = false;

    } else {

        if(mDiff < 0){

            mReleaseStart = mBufferPosition;

            mRequestStart = mBufferPosition + mBufferSize;

            direction = HgCacheProxyModel::HgRequestOrderAscending; 

        } else if( mDiff > 0) {

            mReleaseStart = mBufferPosition + mBufferSize - mDiff;

            mRequestStart = mBufferPosition - mDiff;

            direction = HgCacheProxyModel::HgRequestOrderDescending;

        }

    }

    // Release 

    int end = mReleaseStart + mReleaseCount < mTotalCount ?

        mReleaseStart + mReleaseCount: mTotalCount; 

    end--;

    if(end >= mReleaseStart ){

        mObserver->release(mReleaseStart, end);

    }

    mReleaseCount = 0;

    // Request

    end = mRequestStart + mRequestCount < mTotalCount ? 

        mRequestStart + mRequestCount : mTotalCount;

    end--;

    if(end >= mRequestStart ){

        mObserver->request(mRequestStart, end, direction);

	}

    mRequestCount = 0;

    // Move Buffer

    mBufferPosition -= mDiff;

    // Reset Diff

    mDiff = 0;

}

// -----------------------------------------------------------------------------

// BufferManager::SetPosition()

// -----------------------------------------------------------------------------

//

void HgBufferManager::setPosition( int aIndex )

{

    // If all the items fit in the buffer no need to move the buffer

    if(mTotalCount <= mBufferSize)

        return;

	bool forceUpdate = false;

    aIndex -= mBufferSize / 2; // normalize index to Buffer start

    if(aIndex < 0){

        aIndex = 0;

        forceUpdate = true;

    }else if( aIndex > mTotalCount - mBufferSize ){

        aIndex = mTotalCount - mBufferSize;

        forceUpdate = true;

    }

    mDiff = mBufferPosition - aIndex; 

    // Too large change reset whole buffer

    if( mDiff >= mBufferSize || -mDiff >= mBufferSize || mResetOrdered ) {

        resetBuffer(aIndex + (mBufferSize/2), mTotalCount);

    } else if( mDiff >= mBufferTreshold ) { // Move Up

        mRequestCount = mDiff;

        mReleaseCount = mDiff;

        calculate();

    } else if ( -mDiff >= mBufferTreshold ) {// Move Down

        mRequestCount = -mDiff;

        mReleaseCount = -mDiff;

        calculate();

    } else if( forceUpdate && mDiff ) { // Top or bottom has been reached

        int diff = mDiff < 0 ? -mDiff : mDiff;

        mRequestCount = diff;

        mReleaseCount = diff;

        calculate();

    }

}

// -----------------------------------------------------------------------------

// BufferManager::ResetBuffer()

// -----------------------------------------------------------------------------

//

void HgBufferManager::resetBuffer( int aPosition, int aTotalCount)

{

    if( !mResetOrdered ){

        // release Old buffer

        mReleaseStart = mBufferPosition;

        mReleaseCount = mBufferSize;

    }

    // set position and count

    mBufferPosition = aPosition - (mBufferSize / 2);

    mTotalCount = aTotalCount;

    mDiff = 0;

    if( mBufferPosition + mBufferSize > mTotalCount - 1 ){

        mBufferPosition = mTotalCount - mBufferSize;

    }

    if(mBufferPosition < 0 ){

        mBufferPosition = 0;

    }

    //request new Buffer

    mRequestStart = mBufferPosition;

    mRequestCount = mBufferSize;

    mResetOrdered = true;

    calculate();

}

void HgBufferManager::itemCountChanged( int aIndex, 

                                      bool aRemoved,

                                      int aNewTotalCount )

{    

    Q_UNUSED(aIndex);    

    Q_UNUSED(aRemoved);

    //release all, to make sure that no old items are skipped

    mObserver->release(0, aNewTotalCount);

    resetBuffer(mBufferPosition + (mBufferSize / 2), aNewTotalCount);

}

//eof