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#include "qcommonsequencetypes_p.h"

#include "qdeduplicateiterator_p.h"

#include "qnodesort_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

NodeSortExpression::NodeSortExpression(const Expression::Ptr &op) : SingleContainer(op)

{

}

bool NodeSortExpression::lessThanUsingNodeModel(const Item &n1,

                                                const Item &n2)

{

    Q_ASSERT(n1.isNode());

    Q_ASSERT(n2.isNode());

    if(n1.asNode().model() == n2.asNode().model())

        return n1.asNode().compareOrder(n2.asNode()) == QXmlNodeModelIndex::Precedes;

    else

    {

        /* The two nodes are from different trees. The sort order is implementation

         * defined, but it must be stable.

         *

         * We do this by looking at the pointer difference. The value means nothing,

         * but it is stable, and that's what we're looking for. */

        return n1.asNode().model() - n2.asNode().model() < 0;

    }

}

Item::Iterator::Ptr NodeSortExpression::evaluateSequence(const DynamicContext::Ptr &context) const

{

    Q_ASSERT_X(m_operand->staticType()->cardinality().allowsMany(), Q_FUNC_INFO,

               "It makes no sense to sort a single node.");

    Item::List nodes(m_operand->evaluateSequence(context)->toList());

    if(nodes.isEmpty())

        return CommonValues::emptyIterator;

    else if(nodes.first().isAtomicValue())

        return makeListIterator(nodes);

    else

    {

        qSort(nodes.begin(), nodes.end(), lessThanUsingNodeModel);

        return Item::Iterator::Ptr(new DeduplicateIterator(nodes));

    }

}

Expression::Ptr NodeSortExpression::wrapAround(const Expression::Ptr &operand,

                                               const StaticContext::Ptr &context)

{

    Q_ASSERT(operand);

    Q_ASSERT(context);

    const Expression::Ptr sort(new NodeSortExpression(operand));

    context->wrapExpressionWith(operand.data(), sort);

    return sort;

}

Expression::Ptr NodeSortExpression::compress(const StaticContext::Ptr &context)

{

    const Expression::Ptr me(SingleContainer::compress(context));

    /* It make no sense to sort & deduplicate a single node. */

    if(m_operand->staticType()->cardinality().allowsMany())

        return me;

    else

        return m_operand;

}

SequenceType::Ptr NodeSortExpression::staticType() const

{

    return m_operand->staticType();

}

SequenceType::List NodeSortExpression::expectedOperandTypes() const

{

    SequenceType::List result;

    result.append(CommonSequenceTypes::ZeroOrMoreItems);

    return result;

}

ExpressionVisitorResult::Ptr

NodeSortExpression::accept(const ExpressionVisitor::Ptr &visitor) const

{

    return visitor->visit(this);

}

Expression::Properties NodeSortExpression::properties() const

{

    /* The reason we disable elimination is that the assert for sorting a

     * single node in evaluateSequence() triggers unless our compress() routine

     * has been run. Anyhow, it's not that we would manage to write away anyway,

     * since the node source in most(all?) cases prevents it.

     */

    return AffectsOrderOnly | DisableElimination;

}

QT_END_NAMESPACE