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

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** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

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** This file is part of the QtXmlPatterns module of the Qt Toolkit.

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** Foundation and appearing in the file LICENSE.LGPL included in the

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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_ItemMappingIterator_H

#define Patternist_ItemMappingIterator_H

#include "qabstractxmlforwarditerator_p.h"

#include "qdynamiccontext_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the

     * Item returned from a mapping function.

     *

     * ItemMappingIterator is practical when the items in an QAbstractXmlForwardIterator needs to

     * be translated to another sequence, while still doing it in a pipe-lined

     * fashion.

     *

     * This is achieved by that ItemMappingIterator's constructor takes

     * an instance of a class, that must have the following member:

     *

     * @code

     * TResult::Ptr mapToItem(const TSource &item,

     *                        const Context &context) const

     * @endcode

     *

     * For each item in the QAbstractXmlForwardIterator ItemMappingIterator proxies, this function is

     * called and its return value becomes the return value of the ItemMappingIterator. If the

     * mapping function returns null, ItemMappingIterator maps the next item in the source sequence

     * such that a contiguous sequence of items is returned.

     *

     * Declaring the mapToItem() function as inline, can be a good way to improve performance.

     *

     * @see SequenceMappingIterator

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

     * @ingroup Patternist_iterators

     */

    template<typename TResult, typename TSource, typename TMapper, typename Context = DynamicContext::Ptr>

    class ItemMappingIterator : public QAbstractXmlForwardIterator<TResult>

    {

    public:

        /**

         * Constructs an ItemMappingIterator.

         *

         * @param mapper the object that has the mapToItem() sequence.

         * @param iterator the QAbstractXmlForwardIterator whose items should be mapped.

         * @param context the context that will be passed to the map function.

         * May be null.

         */

        ItemMappingIterator(const TMapper &mapper,

                            const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator,

                            const Context &context) : m_mapper(mapper)

                                                    , m_it(iterator)

                                                    , m_context(context)

                                                    , m_position(0)

        {

            Q_ASSERT(mapper);

            Q_ASSERT(iterator);

        }

        /**

         * @returns the next item in the sequence, or

         * @c null if the end have been reached.

         */

        virtual TResult next()

        {

            const TSource sourceItem(m_it->next());

            if(qIsForwardIteratorEnd(sourceItem))

            {

                m_current = TResult();

                m_position = -1;

                return TResult();

            }

            else

            {

                m_current = m_mapper->mapToItem(sourceItem, m_context);

                if(qIsForwardIteratorEnd(m_current))

                    return next(); /* The mapper returned null, so continue with the next in the source. */

                else

                {

                    ++m_position;

                    return m_current;

                }

            }

        }

        virtual TResult current() const

        {

            return m_current;

        }

        virtual xsInteger position() const

        {

            return m_position;

        }

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

        {

            return typename QAbstractXmlForwardIterator<TResult>::Ptr

                (new ItemMappingIterator<TResult, TSource, TMapper, Context>(m_mapper, m_it->copy(), m_context));

        }

    private:

        const TMapper                                               m_mapper;

        const typename QAbstractXmlForwardIterator<TSource>::Ptr    m_it;

        const Context                                               m_context;

        TResult                                                     m_current;

        xsInteger                                                   m_position;

    };

    /**

     * @short An object generator for ItemMappingIterator.

     *

     * makeItemMappingIterator() is a convenience function for avoiding specifying

     * the full template instantiation for ItemMappingIterator. Conceptually, it

     * is identical to Qt's qMakePair().

     *

     * @relates ItemMappingIterator

     */

    template<typename TResult, typename TSource, typename TMapper, typename Context>

    static inline

    typename QAbstractXmlForwardIterator<TResult>::Ptr

    makeItemMappingIterator(const TMapper &mapper,

                            const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source,

                            const Context &context)

    {

        return typename QAbstractXmlForwardIterator<TResult>::Ptr

            (new ItemMappingIterator<TResult, TSource, TMapper, Context>(mapper, source, context));

    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif