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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_RangeIterator_H
#define Patternist_RangeIterator_H

#include <private/qitem_p.h>

QT_BEGIN_NAMESPACE

namespace QPatternist
{
    /**
     * @short RangeIterator represents a sequence of integers between a
     * start and end value.
     *
     * The RangeIterator contains the evaluation logic for the range expression, <tt>N to M</tt>,
     * and its behavior is therefore consistent with the definition of that XPath expression.
     * Hence, the detailed behavior of the RangeIterator can be found in the XPath 2.0
     * specification.
     *
     * @see <a href="http://www.w3.org/TR/xpath20/\#doc-xpath-RangeExpr">XML Path Language
     * (XPath) 2.0, 3.3 Sequence Expressions, RangeExpr</a>
     * @see RangeExpression
     * @author Frans Englich <frans.englich@nokia.com>
     * @ingroup Patternist_iterators
     * @todo Documentation is missing
     */
    class Q_AUTOTEST_EXPORT RangeIterator : public Item::Iterator
    {
    public:

        /**
         * RangeIterator can iterate in both directions.
         * This enumerator exist for identifying different directions.
         */
        enum Direction
        {
            /**
             * Signifies that the QAbstractXmlForwardIterator operates in a reverse direction, where the
             * first item returned by the next() function is from the beginning of the
             * source sequence.
             */
            Backward = 0,

            /**
             * Signifies the forward direction. Iterators do conceptually operate
             * in the forward direction by default.
             */
            Forward = 1
        };

        /**
         * Creates an QAbstractXmlForwardIterator that returns integer values from consecutive sequence
         * of integers between @p start and @p end, where the step taken
         * between each integer is 1 with polarity as specified in @p direction.
         *
         * @note @p start must be smaller than @p end, not larger
         * or equal. This is not checked.
         */
        RangeIterator(const xsInteger start,
                      const Direction direction,
                      const xsInteger end);

        Item next() override;
        Item current() const override;
        xsInteger position() const override;
        xsInteger count() override;
        Item::Iterator::Ptr toReversed() override;
        Item::Iterator::Ptr copy() const override;

    private:
        xsInteger m_start;
        xsInteger m_end;
        Item m_current;
        xsInteger m_position;
        xsInteger m_count;
        const Direction m_direction;

        /**
         * We only need to store -1 or 1, so save memory with a bit field.
         */
        const qint8 m_increment : 2;
    };
}

QT_END_NAMESPACE

#endif