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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_DistinctIterator_H
#define Patternist_DistinctIterator_H

#include <QList>

#include <private/qexpression_p.h>
#include <private/qitem_p.h>
#include <private/qatomiccomparator_p.h>
#include <private/qcomparisonplatform_p.h>
#include <private/qsourcelocationreflection_p.h>

QT_BEGIN_NAMESPACE

namespace QPatternist
{

    /**
     * @short Filters another sequence by removing duplicates such that the items are unique.
     *
     * DistinctIterator takes an input sequence, and returns a sequence where each
     * item is unique. Thus, DistinctIterator removes the duplicates of items
     * in a sequence. DistinctIterator is central in the implementation of the
     * <tt>fn:distinct-values()</tt> function.
     *
     * @see <a href="http://www.w3.org/TR/xpath-functions/#func-distinct-values">XQuery 1.0
     * and XPath 2.0 Functions and Operators, 15.1.6 fn:distinct-values</a>
     * @author Frans Englich <frans.englich@nokia.com>
     * @ingroup Patternist_iterators
     */
    class DistinctIterator : public Item::Iterator
                           , public ComparisonPlatform<DistinctIterator, false>
                           , public SourceLocationReflection
    {
    public:
        /**
         * Creates a DistinctIterator.
         * @param comp the AtomicComparator to be used for comparing values. This may be @c null,
         * meaning the IndexOfIterator iterator will dynamically determine what comparator to use
         * @param seq the sequence whose duplicates should be filtered out
         * @param context the usual context, used for error reporting and by AtomicComparators.
         * @param expression the Expression that this DistinctIterator is
         * evaluating for. It is used for error reporting, via
         * actualReflection().
         */
        DistinctIterator(const Item::Iterator::Ptr &seq,
                         const AtomicComparator::Ptr &comp,
                         const Expression::ConstPtr &expression,
                         const DynamicContext::Ptr &context);

        virtual Item next();
        virtual Item current() const;
        virtual xsInteger position() const;
        virtual Item::Iterator::Ptr copy() const;
        virtual const SourceLocationReflection *actualReflection() const;

        inline AtomicComparator::Operator operatorID() const
        {
            return AtomicComparator::OperatorEqual;
        }

    private:
        const Item::Iterator::Ptr   m_seq;
        const DynamicContext::Ptr   m_context;
        const Expression::ConstPtr  m_expr;
        Item                        m_current;
        xsInteger                   m_position;
        Item::List                  m_processed;
    };
}

QT_END_NAMESPACE

#endif
