/*

* Copyright (c) 2010 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: This file implements class CMessageIterator.

*

*/

#include "emailmessage.h"

#include "messageiterator.h"

#include "emailapiutils.h"

#include "CFSMailPlugin.h"

#include "emailapiutils.h"

#include "emailclientapi.hrh"

#include "MFSMailIterator.h"

// number of messages in chunk to retrive from protocol plugin. Actual chunk

// size is one less because last element is used for reference to next chunk

// retrieval. See ReadNextChunkL() for details.

const TInt KMessageChunkSize = 5;

const TInt KUndefined = -1;

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

// 

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

CMessageIterator* CMessageIterator::NewL( 

    MFSMailIterator* aIterator,

    CPluginData& aPluginData,

    TUint aCount )

    {

    CMessageIterator* iter = new ( ELeave ) 

        CMessageIterator( aIterator, aPluginData, aCount );

    return iter;

    }

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

// 

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

CMessageIterator::~CMessageIterator()

    {

    iPluginData.ReleaseInstance();

    TInt count = iMessageArray.Count();

    iMessageArray.ResetAndDestroy();

    for ( TInt i = count; i < iFsMessageArray.Count(); i++ )

        {

        delete iFsMessageArray[i];

        }

    iFsMessageArray.Reset();

    delete iIterator;

    }

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

// 

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

TEmailTypeId CMessageIterator::InterfaceId() const

    {

    return KEmailIFUidMessageIterator;

    }

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

// 

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

void CMessageIterator::Release()

    {

    delete this;

    }

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

// Returns next message

// Messages are retrieved from protocol plugin in chunks of x messages and

// when NextL has be called for x times, next chunk is retrieved. This

// is trade-off between RAM consumption and speed.

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

MEmailMessage* CMessageIterator::NextL()

    {

    if ( iCursor == KUndefined )

        {

        // Buffer empty, read the first chunk

        if ( !ReadNextChunkL() )

            {

            // No messages found, 

            // Reset the cursor and return NULL

            iCursor = KUndefined;

            iStartMsgId = TFSMailMsgId();

            return NULL;

            }

        // Items found, return the first item in the buffer

        iCursor = 0;

        }

    else

        {

        // Iterate to the next item

        iCursor++;

        }

    return ReadFromChunkL();

    }

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

// 

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

MEmailMessage* CMessageIterator::PreviousL()

    {

    if ( iCursor == KUndefined )

        {

        iStartMsgId = TFSMailMsgId();

        // Buffer empty, client should first call NextL

        return NULL;

        }

    // Iterate to the previous item

    iCursor--;

    return ReadFromChunkL();

    }

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

// 

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

TBool CMessageIterator::ReadNextChunkL()

    {

    User::LeaveIfNull( iIterator );

    TBool chunkFound = EFalse;

    // Delete previous items if exist

    CleanCache();

    iHasMoreNextItems = iIterator->NextL(

            iStartMsgId,

            KMessageChunkSize,

            iFsMessageArray );

    if ( iFsMessageArray.Count() > 0 )

        {

        chunkFound = ETrue;

        // Set the cursor to the first item 

        iCursor = 0;

        iHasMorePrevItems = ETrue;

        }

    return chunkFound;

    }

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

// 

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

TBool CMessageIterator::ReadPreviousChunkL()

    {

    User::LeaveIfNull( iIterator );

    TBool chunkFound = EFalse;

    // Delete previous items if exist

    CleanCache();

    RPointerArray<CFSMailMessage> tmp;

    iHasMorePrevItems = iIterator->PreviousL(

            iStartMsgId,

            KMessageChunkSize, 

            tmp );

    TInt count = tmp.Count();

    if ( count > 0 )

        {

        // It seems that items have been found

        // Set the cursor to the end of array

        iCursor = count - 1;

        iHasMoreNextItems = ETrue;

        chunkFound = ETrue;

        // Revise the order of the buffer.

        // Create complete cache, so it is easier to iterate, 

        // as now we have to start from the end of cache

        for ( TInt i = count; i > 0; i-- )

            {

            CFSMailMessage* msg = tmp[i-1];

            iFsMessageArray.AppendL( msg );

            AddToCacheL( msg );

            }

        }

    return chunkFound;

    }

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

// 

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

MEmailMessage* CMessageIterator::ReadFromChunkL()

    {

    if ( iCursor >= KMessageChunkSize )

        {

        if ( iHasMoreNextItems )

            {

            iStartMsgId = iFsMessageArray[iCursor-1]->GetMessageId();

            if ( !ReadNextChunkL() )

                {

                // No more items found, 

                // set the cursor to the previous item,

                // and return NULL.

                iCursor--;

                return NULL;

                }

            }

        else

            {

            // No more items found, 

            // set the cursor to the previous item,

            // and return NULL.

            iCursor--;

            return NULL;

            }

        }

    else if ( iCursor < 0 )

        {

        iStartMsgId = iFsMessageArray[0]->GetMessageId();

        if ( iHasMorePrevItems )

            {

            if ( !ReadPreviousChunkL() )

                {

                // Buffer is empty now, client should call nextL,

                // and start reading from the start of the buffer

                iCursor = KUndefined;

                return NULL;

                }

            }

        else

            {

            // Buffer is empty now, client should call nextL,

            // and start reading from the start of the buffer

            iCursor = KUndefined;   

            return NULL;

            }

        }

    if ( iCursor < iFsMessageArray.Count() )

        {

        /* There are items to read in the cache */

        if ( iCursor >= iMessageArray.Count() )

            {

            AddToCacheL( iFsMessageArray[iCursor] );

            }

        return iMessageArray[iCursor];

        }

    else

        {

        // No more items found,

        // set the cursor to the previous item,

        // and return NULL.

        iCursor--;

        return NULL;

        }

    }

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

// 

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

void CMessageIterator::AddToCacheL( CFSMailMessage* aFsMsg )

    {

    CEmailMessage* message = CEmailMessage::NewL( iPluginData, aFsMsg, EAPIOwns );

    iMessageArray.AppendL( message );

    }

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

// 

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

void CMessageIterator::CleanCache()

    {

    // This is strange loop indeed

    // Both arrays has items that are deleted, iMessageArray has objects that point to iFsMessageArray

    // Index in both arrays goes syncronously

    // To prevent double destruction, first delete iMessageArray onjects and then the rest of the iFsMessageArray

    TInt count = iMessageArray.Count();

    iMessageArray.ResetAndDestroy();

    for ( TInt i = count; i < iFsMessageArray.Count(); i++ )

        {

        iFsMessageArray.Remove( count );

        }

    iFsMessageArray.Reset();    

    }

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

// 

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

TUint CMessageIterator::Count() const

    {

    return iCount;

    }

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

// 

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

void CMessageIterator::ConstructL()

    {

    iPlugin = iPluginData.ClaimInstanceL();

    }

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

// 

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

CMessageIterator::CMessageIterator( 

    MFSMailIterator* aIterator,

    CPluginData& aPluginData,

    TUint aCount ) :

    iIterator( aIterator ),

    iPluginData( aPluginData ),

    iStartMsgId( TFSMailMsgId() ),

    iState( EReadNextMessageChunk ),

    iFsMessageArray( KMessageChunkSize ),

    iCount( aCount ),

    iCursor ( KUndefined ),

    iFirstMsgId( TFSMailMsgId() ),

    iHasMoreNextItems( ETrue ),

    iHasMorePrevItems( ETrue )

    {

    }

// End of file