/****************************************************************************

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** This file is part of the QtXmlPatterns module of the Qt Toolkit.

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****************************************************************************/

#include "qcachingiterator_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

CachingIterator::CachingIterator(ItemSequenceCacheCell::Vector &cacheCells,

                                 const VariableSlotID slot,

                                 const DynamicContext::Ptr &context) : m_position(0),

                                                                       m_varSlot(slot),

                                                                       m_context(context),

                                                                       m_cacheCells(cacheCells),

                                                                       m_usingCache(true)

{

    Q_ASSERT(m_varSlot > -1);

    Q_ASSERT(m_context);

    Q_ASSERT(m_cacheCells.at(m_varSlot).sourceIterator);

    Q_ASSERT_X((m_cacheCells.at(m_varSlot).cachedItems.isEmpty() && m_cacheCells.at(m_varSlot).cacheState == ItemSequenceCacheCell::Empty) ||

               m_cacheCells.at(m_varSlot).cacheState == ItemSequenceCacheCell::PartiallyPopulated,

               Q_FUNC_INFO,

               "It makes no sense to construct a CachingIterator for a cache that is ItemSequenceCacheCell::Full.");

}

Item CachingIterator::next()

{

    ItemSequenceCacheCell &cell = m_cacheCells[m_varSlot];

    if(m_position == -1)

        return Item();

    if(m_usingCache)

    {

        ++m_position;

        /* QAbstractXmlForwardIterator::position() starts at 1, while Qt's container classes

         * starts at 0. */

        if(m_position - 1 < cell.cachedItems.count())

        {

            m_current = cell.cachedItems.at(m_position - 1);

            return m_current;

        }

        else

        {

            cell.cacheState = ItemSequenceCacheCell::PartiallyPopulated;

            m_usingCache = false;

            /* We decrement here so we don't have to add a branch for this

             * when using the source QAbstractXmlForwardIterator below. */

            --m_position;

        }

    }

    m_current = cell.sourceIterator->next();

    if(m_current)

    {

        cell.cachedItems.append(m_current);

        Q_ASSERT(cell.cacheState == ItemSequenceCacheCell::PartiallyPopulated);

        ++m_position;

        return m_current;

    }

    else

    {

        m_position = -1;

        cell.cacheState = ItemSequenceCacheCell::Full;

        return Item();

    }

}

Item CachingIterator::current() const

{

    return m_current;

}

xsInteger CachingIterator::position() const

{

    return m_position;

}

Item::Iterator::Ptr CachingIterator::copy() const

{

    const ItemSequenceCacheCell &cell = m_cacheCells.at(m_varSlot);

    if(cell.cacheState == ItemSequenceCacheCell::Full)

        return makeListIterator(cell.cachedItems);

    else

        return Item::Iterator::Ptr(new CachingIterator(m_cacheCells, m_varSlot, m_context));

}

QT_END_NAMESPACE