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#include "qcommonsequencetypes_p.h"

#include "qemptysequence_p.h"

#include "qgenericsequencetype_p.h"

#include "qitemmappingiterator_p.h"

#include "qoptimizationpasses_p.h"

#include "qsequencemappingiterator_p.h"

#include "qforclause_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

ForClause::ForClause(const VariableSlotID varSlot,

                     const Expression::Ptr &bindingSequence,

                     const Expression::Ptr &returnExpression,

                     const VariableSlotID positionSlot) : PairContainer(bindingSequence, returnExpression),

                                                          m_varSlot(varSlot),

                                                          m_positionSlot(positionSlot),

                                                          m_allowsMany(true)

{

    Q_ASSERT(m_positionSlot > -2);

}

Item ForClause::mapToItem(const Item &item,

                          const DynamicContext::Ptr &context) const

{

    context->setRangeVariable(m_varSlot, item);

    return m_operand2->evaluateSingleton(context);

}

Item::Iterator::Ptr ForClause::mapToSequence(const Item &item,

                                             const DynamicContext::Ptr &context) const

{

    context->setRangeVariable(m_varSlot, item);

    return m_operand2->evaluateSequence(context);

}

void ForClause::riggPositionalVariable(const DynamicContext::Ptr &context,

                                       const Item::Iterator::Ptr &source) const

{

    if(m_positionSlot > -1)

        context->setPositionIterator(m_positionSlot, source);

}

Item::Iterator::Ptr ForClause::evaluateSequence(const DynamicContext::Ptr &context) const

{

    const Item::Iterator::Ptr source(m_operand1->evaluateSequence(context));

    riggPositionalVariable(context, source);

    if(m_allowsMany)

    {

        return makeSequenceMappingIterator<Item>(ConstPtr(this),

                                                 source,

                                                 context);

    }

    else

    {

        return makeItemMappingIterator<Item>(ConstPtr(this),

                                             source,

                                             context);

    }

}

Item ForClause::evaluateSingleton(const DynamicContext::Ptr &context) const

{

    return evaluateSequence(context)->next();

}

void ForClause::evaluateToSequenceReceiver(const DynamicContext::Ptr &context) const

{

    Item::Iterator::Ptr it;

    const Item::Iterator::Ptr source(m_operand1->evaluateSequence(context));

    riggPositionalVariable(context, source);

    Item next(source->next());

    while(next)

    {

        context->setRangeVariable(m_varSlot, next);

        m_operand2->evaluateToSequenceReceiver(context);

        next = source->next();

    }

}

Expression::Ptr ForClause::typeCheck(const StaticContext::Ptr &context,

                                     const SequenceType::Ptr &reqType)

{

    const Expression::Ptr me(PairContainer::typeCheck(context, reqType));

    const Cardinality card(m_operand1->staticType()->cardinality());

    /* If our source is empty we will always evaluate to the empty sequence, so rewrite. */

    if(card.isEmpty())

        return EmptySequence::create(this, context);

    else

        return me;

    /* This breaks because  the variable references haven't rewritten themselves, so

     * they dangle. When this is fixed, evaluateSingleton can be removed. */

    /*

    else if(card->allowsMany())

        return me;

    else

        return m_operand2;

        */

}

Expression::Ptr ForClause::compress(const StaticContext::Ptr &context)

{

    const Expression::Ptr me(PairContainer::compress(context));

    if(me != this)

        return me;

    /* This is done after calling PairContainer::typeCheck(). The advantage of this is that

     * m_allowsMany is updated according to what the operand says after it has compressed. However,

     * if it was initialized to false(as it once was..), ForClause::evaluateSequence()

     * would potentially have been called by PairContainer::compress(), and it would have

     * used an unsafe branch. */

    m_allowsMany = m_operand2->staticType()->cardinality().allowsMany();

    return me;

}

SequenceType::Ptr ForClause::staticType() const

{

    const SequenceType::Ptr returnType(m_operand2->staticType());

    return makeGenericSequenceType(returnType->itemType(),

                                   m_operand1->staticType()->cardinality()

                                        * /* multiply operator */

                                   returnType->cardinality());

}

SequenceType::List ForClause::expectedOperandTypes() const

{

    SequenceType::List result;

    result.append(CommonSequenceTypes::ZeroOrMoreItems);

    result.append(CommonSequenceTypes::ZeroOrMoreItems);

    return result;

}

ExpressionVisitorResult::Ptr ForClause::accept(const ExpressionVisitor::Ptr &visitor) const

{

    return visitor->visit(this);

}

OptimizationPass::List ForClause::optimizationPasses() const

{

    return OptimizationPasses::forPasses;

}

Expression::ID ForClause::id() const

{

    return IDForClause;

}

QT_END_NAMESPACE