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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_SequenceMappingIterator_H

#define Patternist_SequenceMappingIterator_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

     * Sequence 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. In contrast to ItemMappingIterator, SequenceMappingIterator maps

     * each item into another QAbstractXmlForwardIterator, and where the SequenceMappingIterator's own

     * result is the concatenation of all those Iterators. Hence, while ItemMappingIterator

     * is better tailored for one-to-one or one-to-zero conversion, SequenceMappingIterator

     * is more suitable for one-to-many conversion.

     *

     * This is achieved by that SequenceMappingIterator's constructor takes

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

     *

     * @code

     * QAbstractXmlForwardIterator<TResult>::Ptr mapToSequence(const TSource::Ptr &item,

     *                                                      const DynamicContext::Ptr &context) const;

     * @endcode

     *

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

     * @see ItemMappingIterator

     * @ingroup Patternist_iterators

     */

    template<typename TResult, typename TSource, typename TMapper>

    class SequenceMappingIterator : public QAbstractXmlForwardIterator<TResult>

    {

    public:

        /**

         * Constructs a SequenceMappingIterator.

         *

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

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

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

         * May be null.

         */

        SequenceMappingIterator(const TMapper &mapper,

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

                                const DynamicContext::Ptr &context);

        virtual TResult next();

        virtual xsInteger count();

        virtual TResult current() const;

        virtual xsInteger position() const;

        /**

         * The reason the implementation is placed in line here, is due to a bug

         * in MSVC-2005 version 14.00.50727.762. Note that it works with version 14.00.50727.42.

         */

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

        {

            return typename QAbstractXmlForwardIterator<TResult>::Ptr

                    (new SequenceMappingIterator<TResult, TSource, TMapper>(m_mapper,

                                                                            m_mainIterator->copy(),

                                                                            m_context));

        }

    private:

        xsInteger                                           m_position;

        TResult                                             m_current;

        typename QAbstractXmlForwardIterator<TSource>::Ptr  m_mainIterator;

        typename QAbstractXmlForwardIterator<TResult>::Ptr  m_currentIterator;

        const typename DynamicContext::Ptr                  m_context;

        const TMapper                                       m_mapper;

    };

    template<typename TResult, typename TSource, typename TMapper>

    SequenceMappingIterator<TResult, TSource, TMapper>::SequenceMappingIterator(

                                        const TMapper &mapper,

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

                                        const DynamicContext::Ptr &context)

                                        : m_position(0),

                                          m_mainIterator(iterator),

                                          m_context(context),

                                          m_mapper(mapper)

    {

        Q_ASSERT(mapper);

        Q_ASSERT(iterator);

    }

    template<typename TResult, typename TSource, typename TMapper>

    TResult SequenceMappingIterator<TResult, TSource, TMapper>::next()

    {

        /* This was once implemented with a recursive function, but the stack

         * got blown for some inputs by that approach. */

        while(true)

        {

            while(!m_currentIterator)

            {

                const TSource mainItem(m_mainIterator->next());

                if(qIsForwardIteratorEnd(mainItem)) /* We've reached the very end. */

                {

                    m_position = -1;

                    m_current = TResult();

                    return TResult();

                }

                else

                    m_currentIterator = m_mapper->mapToSequence(mainItem, m_context);

            }

            m_current = m_currentIterator->next();

            if(qIsForwardIteratorEnd(m_current))

            {

                m_currentIterator.reset();

                continue;

            }

            else

            {

                ++m_position;

                return m_current;

            }

        }

    }

    template<typename TResult, typename TSource, typename TMapper>

    xsInteger SequenceMappingIterator<TResult, TSource, TMapper>::count()

    {

        TSource unit(m_mainIterator->next());

        xsInteger c = 0;

        while(!qIsForwardIteratorEnd(unit))

        {

            const typename QAbstractXmlForwardIterator<TResult>::Ptr sit(m_mapper->mapToSequence(unit, m_context));

            c += sit->count();

            unit = m_mainIterator->next();

        }

        return c;

    }

    template<typename TResult, typename TSource, typename TMapper>

    TResult SequenceMappingIterator<TResult, TSource, TMapper>::current() const

    {

        return m_current;

    }

    template<typename TResult, typename TSource, typename TMapper>

    xsInteger SequenceMappingIterator<TResult, TSource, TMapper>::position() const

    {

        return m_position;

    }

    /**

     * @short An object generator for SequenceMappingIterator.

     *

     * makeSequenceMappingIterator() is a convenience function for avoiding specifying

     * the full template instantiation for SequenceMappingIterator. Conceptually, it

     * is identical to Qt's qMakePair().

     *

     * @returns a SequenceMappingIterator wrapped in a smart pointer, that has been

     * passed the constructor arguments @p mapper, @p source, and @p context.

     * @see makeMappingCallbackPtr()

     * @relates QAbstractXmlForwardIterator

     */

    template<typename TResult, typename TSource, typename TMapper>

    static inline

    typename QAbstractXmlForwardIterator<TResult>::Ptr

    makeSequenceMappingIterator(const TMapper &mapper,

                                const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source,

                                const DynamicContext::Ptr &context)

    {

        return typename QAbstractXmlForwardIterator<TResult>::Ptr

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

    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif