QVariant_impl.h

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#pragma once

#include <QtCore/qvariant.h>
#include <QtCore/qstack.h>

#include "QBind.h"

// //////////////////////////////////////////////////////////////////////////
// QBind<T,QVariant*> support for the fixed set of QVariantBuilder's BindNative types

class QVariantBuilder : public QAbstractValueWriter
{
    Q_DISABLE_COPY(QVariantBuilder)
public:
    QVariantBuilder(QVariant* v) : variant(v) { Q_ASSERT(v); }
   ~QVariantBuilder() { while (!levels.isEmpty()) tryOut(); }
    void reset(QVariant* v) { variant=v; Q_ASSERT(v); levels.resize(0); }

    // Shortcuts
    /**/             QValue value   (                  ) { return QValueStatus(this).value(); }
    /**/             QSeq<QValueStatus> sequence(quint32* s=nullptr) { return QValueStatus(this).value().sequence            ( s); }
    template<typename T> QValueStatus  bind    (             T&& t) { return QValueStatus(this).value().bind(std::forward<T>(t)); }
protected:
    // TODO Support _meta to be able to cache and restitute all metadata as well as data+datatype

    bool tryBind(QUtf8DataView u) {
        return tryBind(QUtf8Data(u));
    }
    bool tryBind(  QStringView u) { return tryBind(u.toString()); }

    bool tryBind(  QUtf8Data&& t) {
        set(QVariant::fromValue(t));
        return true;
    }
    bool tryBind(    QString&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(       bool&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(      qint8&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(     quint8&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(     qint16&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(    quint16&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(     qint32&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(    quint32&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(     qint64&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(    quint64&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(      float&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(     double&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind( QByteArray&& t) { set(QVariant::fromValue(t)); return true; }
    bool tryBind(   QVariant&& v) { set(                    v ); return true; }

    bool tryNull(               ) { set(QVariant           ( )); return true; }

    bool trySequence(quint32* =nullptr) { levels.push(Level(                 )); return true; }
    bool tryRecord  (quint32* =nullptr) { levels.push(Level(qBindExpectedItem)); return true; }

    bool tryItem(QIdentifier& n) { levels.last().key=n            ; return true; }
    bool tryItem(              ) { levels.last().key=QIdentifier(); return true; }
    bool tryOut (              ) { auto level = levels.pop(); set(!level.key.isNull() ? QVariant(level.object) : QVariant(level.array)); return true; }
private:
    void set(const QVariant& v) {
        if (levels.isEmpty()) {
            *variant = v;
        }
        else {
            if (!levels.last().key.isNull())
                levels.last().object[levels.last().key.latin1()]=v;
            else
                levels.last().array.append(v);
        }
    }

    QVariant* variant;
    struct Level { QIdentifier key; /* TODO union */ QVariantMap object; QVariantList array; Level(QIdentifier k=QIdentifier()) : key(k) {} };
    QStack<Level> levels = QStack<Level>(); //!< minimal dynamic context to implement out() and ensure actual building in case QVariantBuilder is abandoned
};

// --------------------------------------------------------------------------

class QVariantVisitor : public QAbstractValueReader
{
    Q_DISABLE_COPY(QVariantVisitor)
public:
    Q_ENABLE_MOVE_DEFAULT(QVariantVisitor)
    QVariantVisitor(const QVariant* v) : value(v) { Q_ASSERT(v); }
    void reset(const QVariant* v) { value=v; Q_ASSERT(v); levels.resize(0); errors.resize(0); }

    struct Error { QIdentifierLiteral error; QAsciiData path; template<class T> T bind(QVal<T>&& value) { return value.bind(QUtf8Data(error.utf8()+' '+path.utf8())); } };
    QVector<Error> errors;

    QAsciiData currentPath() {
        QByteArray path;
        Q_FOREACH(Level l, levels) {
            if (l.key.isNull()) { path.append('{').append(                   l.key.utf8() ); }
            else                { path.append('[').append(QByteArray::number(l.idx       )); }
        }
        return QAsciiData(path);
    }
protected:
    // TODO Support _meta to be able to cache and restitute all metadata as well as data+datatype

    template<typename T>
    bool tryBind(T& t) { if (current()->type()==qMetaTypeId<T>()) { t = current()->value<T>(); return true; } _reportError(QIdentifierLiteral("ExpectedDeclaredMetatypeT")); return false; }

    bool tryBind( QUtf8Data& t) { if (current()->userType() // TODO ->type() if QUtf8Data lands into Qt
                                                     ==qMetaTypeId< QUtf8Data>()) { t = current()->value< QUtf8Data>(); return true; } _reportError(qBindExpectedText          ); return false; }
    bool tryBind(   QString& t) { if (current()->type()==qMetaTypeId<   QString>()) { t = current()->value<   QString>(); return true; } _reportError(qBindExpectedText          ); return false; }
    bool tryBind(      bool& t) { if (current()->type()==qMetaTypeId<      bool>()) { t = current()->value<      bool>(); return true; } _reportError(qBindExpectedBoolean       ); return false; }
    bool tryBind(QByteArray& t) { if (current()->type()==qMetaTypeId<QByteArray>()) { t = current()->value<QByteArray>(); return true; } _reportError(qBindExpectedBytes         ); return false; }
    // Convert numerical types to strictly larger ones // TODO convert all compatible values
    bool tryBind(     qint8& t) { if (current()->type()==qMetaTypeId<     qint8>()) { t = current()->value<     qint8>(); return true; } _reportError(qBindExpectedInteger       ); return false; }
    bool tryBind(    qint16& t) { if (current()->type()==qMetaTypeId<     qint8>()||
                                    current()->type()==qMetaTypeId<    qint16>()) { t = current()->value<    qint16>(); return true; } _reportError(qBindExpectedInteger       ); return false; }
    bool tryBind(    qint32& t) { if (current()->type()==qMetaTypeId<     qint8>()||
                                    current()->type()==qMetaTypeId<    qint16>()||
                                    current()->type()==qMetaTypeId<    qint32>()) { t = current()->value<    qint32>(); return true; } _reportError(qBindExpectedInteger       ); return false; }
    bool tryBind(    qint64& t) { if (current()->type()==qMetaTypeId<     qint8>()||
                                    current()->type()==qMetaTypeId<    qint16>()||
                                    current()->type()==qMetaTypeId<    qint32>()||
                                    current()->type()==qMetaTypeId<    qint64>()) { t = current()->value<    qint64>(); return true; } _reportError(qBindExpectedInteger       ); return false; }
    bool tryBind(    quint8& t) { if (current()->type()==qMetaTypeId<    quint8>()) { t = current()->value<    quint8>(); return true; } _reportError(qBindExpectedPositiveInteger); return false; }
    bool tryBind(   quint16& t) { if (current()->type()==qMetaTypeId<    quint8>()||
                                    current()->type()==qMetaTypeId<   quint16>()) { t = current()->value<   quint16>(); return true; } _reportError(qBindExpectedPositiveInteger); return false; }
    bool tryBind(   quint32& t) { if (current()->type()==qMetaTypeId<    quint8>()||
                                    current()->type()==qMetaTypeId<   quint16>()||
                                    current()->type()==qMetaTypeId<   quint32>()) { t = current()->value<   quint32>(); return true; } _reportError(qBindExpectedPositiveInteger); return false; }
    bool tryBind(   quint64& t) { if (current()->type()==qMetaTypeId<    quint8>()||
                                    current()->type()==qMetaTypeId<   quint16>()||
                                    current()->type()==qMetaTypeId<   quint32>()||
                                    current()->type()==qMetaTypeId<   quint64>()) { t = current()->value<   quint64>(); return true; } _reportError(qBindExpectedPositiveInteger); return false; }
    bool tryBind(     float& t) { if (current()->type()==qMetaTypeId<     float>()) { t = current()->value<     float>(); return true; } _reportError(qBindExpectedDecimal       ); return false; }
    bool tryBind(    double& t) { if (current()->type()==qMetaTypeId<     float>()||
                                    current()->type()==qMetaTypeId<    double>()) { t = current()->value<    double>(); return true; } _reportError(qBindExpectedDecimal       ); return false; }

    bool trySequence(quint32* =nullptr) { if (current()->type()==QVariant::List  ) { levels.push(Level()); return true; } _reportError(qBindExpectedSequence); return false; }
    bool tryRecord  (quint32* =nullptr) { if (current()->type()==QVariant::Map   ) { levels.push(Level()); return true; } _reportError(qBindExpectedRecord  ); return false; }
    bool tryNull    (                 ) { if (current()->isNull()                ) {                       return true; } _reportError(qBindExpectedNull    ); return false; }

    bool tryItem(QIdentifier& k) { levels.last().key=k; return (levels.last().item = current(1)->toMap ().value(QString(levels.last().key.latin1()), QVariant())).isValid(); }
    bool tryItem(              ) { levels.last().idx++; return (levels.last().item = current(1)->toList().value(        levels.last().idx          , QVariant())).isValid(); }
    bool tryOut (              ) { levels.pop()       ; return true; }

    bool _isOk() const noexcept { return value; }
    void _setChoice(bool v) { isChoice=v; }
    void _reportError(QIdentifierLiteral error) { if (!isChoice) errors.append(Error{ error, currentPath() }); }
private:
    const QVariant* current(unsigned outer=0) const { return unsigned(levels.size())-outer <= 0 ? value : &(levels[unsigned(levels.size())-outer-1].item); }

    const QVariant* value;
    struct Level { QIdentifier key=QIdentifier(); int idx=-1; QVariant item; Level() = default; };
    QStack<Level> levels;
    bool isChoice = false;
};