ContainerBuilder.h

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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
 
/*
    Dataquay
 
    A C++/Qt library for simple RDF datastore management.
    Copyright 2009-2012 Chris Cannam.
  
    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
    files (the "Software"), to deal in the Software without
    restriction, including without limitation the rights to use, copy,
    modify, merge, publish, distribute, sublicense, and/or sell copies
    of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
 
    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.
 
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
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    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
    Except as contained in this notice, the name of Chris Cannam
    shall not be used in advertising or otherwise to promote the sale,
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    authorization.
*/
 
#ifndef DATAQUAY_CONTAINER_BUILDER_H
#define DATAQUAY_CONTAINER_BUILDER_H
 
#include <QHash>
#include <QString>
#include <QStringList>
#include <QVariant>
 
namespace Dataquay {
 
class ContainerBuilder
{
public:
    static ContainerBuilder *getInstance();
 
    enum ContainerKind {
        UnknownKind = 0,
        SequenceKind,   // e.g. list
        SetKind         // e.g. set
        // perhaps also something for maps
    };
 
    template <typename T, typename Container>
    void registerContainer(QString typeName, QString containerName,
                           ContainerKind kind) {
        registerContainerExtractor<T, Container>
            (typeName, containerName, kind);
    }
 
    bool canExtractContainer(QString containerName) {
        return m_containerExtractors.contains(containerName);
    }
 
    bool canInjectContainer(QString containerName) {
        return m_containerExtractors.contains(containerName);
    }
 
    QString getTypeNameForContainer(QString containerName) {
        if (!canExtractContainer(containerName)) return QString();
        return m_containerExtractors[containerName]->getTypeName();
    }
 
    ContainerKind getContainerKind(QString containerName) {
        if (!canExtractContainer(containerName)) return UnknownKind;
        return m_containerExtractors[containerName]->getKind();
    }
 
    QVariantList extractContainer(QString containerName, const QVariant &v) {
        if (!canExtractContainer(containerName)) return QVariantList();
        return m_containerExtractors[containerName]->extract(v);
    }
 
    QVariant injectContainer(QString containerName, const QVariantList &vl) {
        if (!canInjectContainer(containerName)) return QVariant();
        return m_containerExtractors[containerName]->inject(vl);
    }
 
private:
    ContainerBuilder() {
        registerContainer<QString, QStringList>
            ("QString", "QStringList", SequenceKind);
    }
    ~ContainerBuilder() {
        for (ContainerExtractorMap::iterator i = m_containerExtractors.begin();
             i != m_containerExtractors.end(); ++i) {
            delete *i;
        }
    }
 
    template <typename T, typename Container>
    void
    registerContainerExtractor(QString typeName, QString containerName,
                               ContainerKind kind) {
        m_containerExtractors[containerName] =
            new ContainerExtractor<T, Container>(typeName, kind);
    }
 
    struct ContainerExtractorBase {
        virtual ~ContainerExtractorBase() { }
        virtual QVariantList extract(const QVariant &v) = 0;
        virtual QVariant inject(const QVariantList &) = 0;
        virtual QString getTypeName() const = 0;
        virtual ContainerKind getKind() const = 0;
    };
 
    template <typename T, typename Container>
    struct ContainerExtractor : public ContainerExtractorBase
    {
        ContainerExtractor(QString typeName, ContainerKind kind) :
            m_typeName(typeName), m_kind(kind) { }
 
        virtual QVariantList extract(const QVariant &v) {
            Container tl = v.value<Container>();
            QVariantList vl;
            foreach (const T &t, tl) vl << QVariant::fromValue<T>(t);
            return vl;
        }
        virtual QVariant inject(const QVariantList &vl) {
            Container tl;
            foreach (const QVariant &v, vl) tl << v.value<T>();
            return QVariant::fromValue<Container>(tl);
        }
        virtual QString getTypeName() const {
            return m_typeName;
        }
        virtual ContainerKind getKind() const {
            return m_kind;
        }
 
        QString m_typeName;
        ContainerKind m_kind;
    };
 
    typedef QHash<QString, ContainerExtractorBase *> ContainerExtractorMap;
    ContainerExtractorMap m_containerExtractors;
};
 
}
 
#endif