/****************************************************************************

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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_SingletonIterator_H

#define Patternist_SingletonIterator_H

#include <QtXmlPatterns/private/qabstractxmlforwarditerator_p.h>

#include <QtXmlPatterns/private/qprimitives_p.h>

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short An QAbstractXmlForwardIterator over exactly one item.

     *

     * SingletonIterator's constructor takes one value which is

     * the item it forms an QAbstractXmlForwardIterator over. Other QAbstractXmlForwardIterator instances can

     * also form an QAbstractXmlForwardIterator with one in length, but by that SingletonIterator

     * has this as it only task, it means it is efficient at it.

     *

     * Having to represent single items in Iterators is relatively common.

     *

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

     * @ingroup Patternist_iterators

     */

    template<typename T>

    class SingletonIterator : public QAbstractXmlForwardIterator<T>

    {

    public:

        /**

         * Creates an iterator over @p item.

         *

         * @note item may not be @c null. Use the EmptyIterator for

         * the empty sequence

         */

        SingletonIterator(const T &item) : m_item(item),

                                           m_position(0)

        {

            Q_ASSERT(!qIsForwardIteratorEnd(item));

        }

        virtual T next()

        {

            switch(m_position)

            {

                case 0:

                {

                    ++m_position;

                    return m_item;

                }

                case 1:

                {

                    m_position = -1;

                    return T();

                }

                default:

                {

                    Q_ASSERT(m_position == -1);

                    return T();

                }

            }

        }

        virtual T current() const

        {

            if(m_position == 1)

                return m_item;

            else

                return T();

        }

        virtual xsInteger position() const

        {

            return m_position;

        }

        /**

         * @returns a copy of this instance, rewinded to the beginning.

         */

        virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed()

        {

            return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator<T>(m_item));

        }

        /**

         * @returns always 1

         */

        virtual xsInteger count()

        {

            return 1;

        }

        virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const

        {

            return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator(m_item));

        }

    private:

        const T m_item;

        qint8 m_position;

    };

    /**

     * @short An object generator for SingletonIterator.

     *

     * makeSingletonIterator() is a convenience function for avoiding specifying

     * the full template instantiation for SingletonIterator. Conceptually, it

     * is identical to Qt's qMakePair().

     *

     * @relates SingletonIterator

     */

    template<typename T>

    inline

    typename SingletonIterator<T>::Ptr

    makeSingletonIterator(const T &item)

    {

        return typename SingletonIterator<T>::Ptr(new SingletonIterator<T>(item));

    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif