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//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.

#ifndef Patternist_ReturnOrderBy_H
#define Patternist_ReturnOrderBy_H

#include "qorderby_p.h"
#include "qunlimitedcontainer_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist
{
    /**
     * @short Together with OrderBy, it implements XQuery 1.0's <tt>order by</tt> expression.
     *
     * ReturnOrderBy evaluates the sort keys and values, and hands it over to
     * OrderBy, which is an AST ancestor, using SortTuples.
     *
     * @author Frans Englich <frans.englich@nokia.com>
     * @ingroup Patternist_expressions
     */
    class ReturnOrderBy : public UnlimitedContainer
    {
    public:
        /**
         * In @p operands the first item is the return expression, and the
         * rest, which is at least one, are the sort keys.
         */
        ReturnOrderBy(const OrderBy::Stability stability,
                      const OrderBy::OrderSpec::Vector &oSpecs,
                      const Expression::List &operands);

        virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const;
        virtual bool evaluateEBV(const DynamicContext::Ptr &context) const;
        virtual SequenceType::Ptr staticType() const;
        virtual SequenceType::List expectedOperandTypes() const;
        virtual Expression::Ptr compress(const StaticContext::Ptr &context);
        virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;
        virtual ID id() const;

        inline OrderBy::OrderSpec::Vector orderSpecs() const
        {
            return m_orderSpecs;
        }

        inline OrderBy::Stability stability() const
        {
            return m_stability;
        }

        /**
         * In the case of that we don't have a for-expression beloning us, but
         * only a let clause, this ReturnOrderBy breaks if it stays in the AST.
         * So, by default we assume that we should write ourselves away, unless
         * this function is called. The associated ForClause will call it
         * during typeCheck(), if it exists.
         */
        inline void setStay(const bool a)
        {
            m_flyAway = !a;
        }

        virtual Properties properties() const;
    private:
        /**
         * This variable is unfortunately only used at compile time. However,
         * it's tricky to get rid of it due to how QueryTransformParser would
         * have to be adapted.
         */
        const OrderBy::Stability    m_stability;

        OrderBy::OrderSpec::Vector  m_orderSpecs;

        /**
         * @see stay()
         */
        bool                        m_flyAway;
    };
}

QT_END_NAMESPACE

QT_END_HEADER

#endif