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#include <QtAlgorithms>

#include "qcommonsequencetypes_p.h"

#include "qnodebuilder_p.h"

#include "qschemanumeric_p.h"

#include "qpatternistlocale_p.h"

#include "qreturnorderby_p.h"

#include "qsorttuple_p.h"

#include "qsequencemappingiterator_p.h"

#include "qorderby_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

OrderBy::OrderBy(const Stability stability,

                 const OrderSpec::Vector &aOrderSpecs,

                 const Expression::Ptr &op,

                 ReturnOrderBy *const returnOrderBy) : SingleContainer(op)

                                                     , m_stability(stability)

                                                     , m_orderSpecs(aOrderSpecs)

                                                     , m_returnOrderBy(returnOrderBy)

{

    Q_ASSERT(m_returnOrderBy);

}

void OrderBy::OrderSpec::prepare(const Expression::Ptr &source,

                                 const StaticContext::Ptr &context)

{

    m_expr = source;

    const ItemType::Ptr t(source->staticType()->itemType());

    prepareComparison(fetchComparator(t, t, context));

}

/**

 * @short Functor used by Qt's qSort() and qStableSort(). Used for FLWOR's

 * <tt>order by</tt> expression.

 *

 * This must be in the global namespace, since it is specializing qLess(), which

 * is in the global namespace. Hence it can't be in QPatternist.

 */

template<>

class qLess<Item::List>

{

private:

    static inline bool isNaN(const Item &i)

    {

        return BuiltinTypes::xsDouble->xdtTypeMatches(i.type()) &&

               i.as<Numeric>()->isNaN();

    }

public:

    inline qLess(const OrderBy::OrderSpec::Vector &orderspecs,

                 const DynamicContext::Ptr &context) : m_orderSpecs(orderspecs)

                                                     , m_context(context)

    {

        Q_ASSERT(!m_orderSpecs.isEmpty());

        Q_ASSERT(context);

    }

    inline bool operator()(const Item &item1, const Item &item2) const

    {

        const SortTuple *const s1 = item1.as<SortTuple>();

        const SortTuple *const s2 = item2.as<SortTuple>();

        const Item::Vector &sortKeys1 = s1->sortKeys();

        const Item::Vector &sortKeys2 = s2->sortKeys();

        const int len = sortKeys1.count();

        Q_ASSERT(sortKeys1.count() == sortKeys2.count());

        for(int i = 0; i < len; ++i)

        {

            const Item &i1 = sortKeys1.at(i);

            const Item &i2 = sortKeys2.at(i);

            const OrderBy::OrderSpec &orderSpec = m_orderSpecs.at(i);

            if(!i1)

            {

                if(i2 && !isNaN(i2))

                {

                    /* We got ((), item()). */

                    return orderSpec.orderingEmptySequence == StaticContext::Least ? orderSpec.direction == OrderBy::OrderSpec::Ascending

                                                                                   : orderSpec.direction != OrderBy::OrderSpec::Ascending;

                }

                else

                    return false;

            }

            if(!i2)

            {

                if(i1 && !isNaN(i1))

                    /* We got (item(), ()). */

                    return orderSpec.orderingEmptySequence == StaticContext::Greatest ? orderSpec.direction == OrderBy::OrderSpec::Ascending

                                                                                      : orderSpec.direction != OrderBy::OrderSpec::Ascending;

                else

                    return false;

            }

            Q_ASSERT(orderSpec.direction == OrderBy::OrderSpec::Ascending ||

                     orderSpec.direction == OrderBy::OrderSpec::Descending);

            const AtomicComparator::ComparisonResult result = orderSpec.detailedFlexibleCompare(i1, i2, m_context);

            switch(result)

            {

                case AtomicComparator::LessThan:

                    return orderSpec.direction == OrderBy::OrderSpec::Ascending;

                case AtomicComparator::GreaterThan:

                    return orderSpec.direction != OrderBy::OrderSpec::Ascending;

                case AtomicComparator::Equal:

                    continue;

                case AtomicComparator::Incomparable:

                    Q_ASSERT_X(false, Q_FUNC_INFO, "This code path assume values are always comparable.");

            }

        }

        return false;

    }

private:

    /* Yes, we store references here. */

    const OrderBy::OrderSpec::Vector & m_orderSpecs;

    const DynamicContext::Ptr & m_context;

};

Item::Iterator::Ptr OrderBy::mapToSequence(const Item &i,

                                           const DynamicContext::Ptr &) const

{

    return i.as<SortTuple>()->value();

}

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

{

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

    const qLess<Item::List> sorter(m_orderSpecs, context);

    Q_ASSERT(m_stability == StableOrder || m_stability == UnstableOrder);

    /* On one hand we could just disregard stability and always use qStableSort(), but maybe qSort()

     * is a bit faster? */

    if(m_stability == StableOrder)

        qStableSort(tuples.begin(), tuples.end(), sorter);

    else

    {

        Q_ASSERT(m_stability == UnstableOrder);

        qSort(tuples.begin(), tuples.end(), sorter);

    }

    return makeSequenceMappingIterator<Item>(ConstPtr(this),

                                             makeListIterator(tuples),

                                             context);

}

Expression::Ptr OrderBy::typeCheck(const StaticContext::Ptr &context,

                                   const SequenceType::Ptr &reqType)

{

    m_returnOrderBy->setStay(true);

    /* It's important we do the typeCheck() before calling OrderSpec::prepare(), since

     * atomizers must first be inserted. */

    const Expression::Ptr me(SingleContainer::typeCheck(context, reqType));

    const Expression::List ops(m_returnOrderBy->operands());

    const int len = ops.count();

    Q_ASSERT(ops.count() > 1);

    Q_ASSERT(m_orderSpecs.count() == ops.count() - 1);

    for(int i = 1; i < len; ++i)

        m_orderSpecs[i - 1].prepare(ops.at(i), context);

    return me;

    /* It's not meaningful to sort a single item or less, so rewrite ourselves

     * away if that is the case. This is an optimization. */

    /* TODO: How do we remove ReturnOrderBy?

    if(Cardinality::zeroOrOne().isMatch(m_operand->staticType()->cardinality()))

        return m_operand->typeCheck(context, reqType);

    else

        return SingleContainer::typeCheck(context, reqType);

     */

}

Expression::Properties OrderBy::properties() const

{

    return m_operand->properties() & DisableElimination;

}

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

{

    /* If we only will produce one item, there's no point in sorting. */

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

        return SingleContainer::compress(context);

    else

    {

        m_returnOrderBy->setStay(false);

        return m_operand->compress(context);

    }

}

SequenceType::Ptr OrderBy::staticType() const

{

    return m_operand->staticType();

}

SequenceType::List OrderBy::expectedOperandTypes() const

{

    SequenceType::List result;

    result.append(CommonSequenceTypes::ZeroOrMoreItems);

    return result;

}

ExpressionVisitorResult::Ptr

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

{

    return visitor->visit(this);

}

QT_END_NAMESPACE