/****************************************************************************
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** This file is part of the QtXmlPatterns module of the Qt Toolkit.
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#include "qcommonsequencetypes_p.h"
#include "qcommonvalues_p.h"
#include "qitemmappingiterator_p.h"
#include "qpatternistlocale_p.h"

#include "qtracefn_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

namespace QPatternist
{
    /**
     * @short TraceCallback is a MappingCallback and takes care of
     * the tracing of each individual item.
     *
     * Because Patternist must be thread safe, TraceFN creates a TraceCallback
     * each time the function is evaluated. In other words, TraceFN, which is
     * an Expression sub class, can't modify its members, but MappingCallback
     * does not have this limitation since it's created on a per evaluation basis.
     *
     * @author Frans Englich <fenglich@trolltech.com>
     */
    class TraceCallback : public QSharedData
    {
    public:
        typedef QExplicitlySharedDataPointer<TraceCallback> Ptr;

        inline TraceCallback(const QString &msg) : m_position(0),
                                                   m_msg(msg)
        {
        }

        /**
         * Performs the actual tracing.
         */
        Item mapToItem(const Item &item,
                            const DynamicContext::Ptr &context)
        {
            QTextStream out(stderr);
            ++m_position;
            if(m_position == 1)
            {
                if(item)
                {
                    out << qPrintable(m_msg)
                        << " : "
                        << qPrintable(item.stringValue());
                }
                else
                {
                    out << qPrintable(m_msg)
                        << " : ("
                        << qPrintable(formatType(context->namePool(), CommonSequenceTypes::Empty))
                        << ")\n";
                    return Item();
                }
            }
            else
            {
                out << qPrintable(item.stringValue())
                    << '['
                    << m_position
                    << "]\n";
            }

            return item;
        }

    private:
        xsInteger m_position;
        const QString m_msg;
    };
}

Item::Iterator::Ptr TraceFN::evaluateSequence(const DynamicContext::Ptr &context) const
{
    const QString msg(m_operands.last()->evaluateSingleton(context).stringValue());

    return makeItemMappingIterator<Item>(TraceCallback::Ptr(new TraceCallback(msg)),
                                              m_operands.first()->evaluateSequence(context),
                                              context);
}

Item TraceFN::evaluateSingleton(const DynamicContext::Ptr &context) const
{
    const QString msg(m_operands.last()->evaluateSingleton(context).stringValue());
    const Item item(m_operands.first()->evaluateSingleton(context));

    return TraceCallback::Ptr(new TraceCallback(msg))->mapToItem(item, context);
}

SequenceType::Ptr TraceFN::staticType() const
{
    return m_operands.first()->staticType();
}

QT_END_NAMESPACE