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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_GenericPredicate_H

#define Patternist_GenericPredicate_H

#include "qpaircontainer_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short A predicate that can handle all kinds of predicates and

     * is therefore not very efficient, but can cope with all the tricky scenarios.

     *

     * @see FirstItemPredicate

     * @see TruthPredicate

     * @author Frans Englich <frans.englich@nokia.com>

     * @ingroup Patternist_expressions

     */

    class GenericPredicate : public PairContainer

    {

    public:

        /**

         * Creates a predicate expression that filters the items gained

         * from evaluating @p sourceExpression through the filter @p predicateExpression.

         *

         * This function performs type analyzis on the passed expressions, and may

         * return more specialized expressions depending on the analyzis.

         *

         * If @p predicateExpression is an invalid predicate, an error is issued

         * via the @p context.

         */

        static Expression::Ptr create(const Expression::Ptr &sourceExpression,

                                      const Expression::Ptr &predicateExpression,

                                      const StaticContext::Ptr &context,

                                      const QSourceLocation &location);

        static Expression::Ptr createFirstItem(const Expression::Ptr &sourceExpression);

        /**

         * Creates a source iterator which is passed to the ItemMappingIterator

         * and the Focus. The ItemMappingIterator modifies it with

         * its QAbstractXmlForwardIterator::next() calls, and since the Focus references the same QAbstractXmlForwardIterator,

         * the focus is automatically moved.

         */

        virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &context) const;

        /**

         * Doesn't return the first item from calling evaluateSequence(), but does the mapping

         * manually. This avoid allocating an ItemMappingIterator.

         */

        virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const;

        inline Item mapToItem(const Item &subject,

                                   const DynamicContext::Ptr &) const;

        virtual SequenceType::List expectedOperandTypes() const;

        virtual SequenceType::Ptr staticType() const;

        virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const;

        virtual ID id() const;

        /**

         * @returns always CreatesFocusForLast.

         */

        virtual Properties properties() const;

        virtual QString description() const;

    protected:

        /**

         * Creates a GenericPredicate which filters the items from the @p sourceExpression

         * through @p predicate.

         *

         * This constructor is protected. The proper way to create predicates is via the static

         * create() function.

         */

        GenericPredicate(const Expression::Ptr &sourceExpression,

                         const Expression::Ptr &predicate);

        /**

         * @returns the ItemType of the first operand's staticType().

         */

        virtual ItemType::Ptr newFocusType() const;

    private:

        typedef QExplicitlySharedDataPointer<const GenericPredicate> ConstPtr;

    };

}

QT_END_NAMESPACE

QT_END_HEADER

#endif