/****************************************************************************

**

** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtXmlPatterns module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file.  Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

**

**

**

**

**

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

//

//  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_CastingPlatform_H

#define Patternist_CastingPlatform_H

#include "qatomiccasterlocator_p.h"

#include "qatomiccaster_p.h"

#include "qatomicstring_p.h"

#include "qatomictype_p.h"

#include "qbuiltintypes_p.h"

#include "qcommonsequencetypes_p.h"

#include "qpatternistlocale_p.h"

#include "qqnamevalue_p.h"

#include "qschematypefactory_p.h"

#include "qstaticcontext_p.h"

#include "qvalidationerror_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist

{

    /**

     * @short Provides casting functionality for classes, such as CastAs or NumberFN, which

     * needs to perform casting.

     *

     * Classes which need to perform casting can simply from this class and gain

     * access to casting functinality wrapped in a convenient way. At the center of this

     * class is the cast() function, which is used at runtime to perform the actual cast.

     *

     * The actual circumstances where casting is used, such as in the 'castable as'

     * expression or the <tt>fn:number()</tt> function, often have other things to handle as well,

     * error handling and cardinality checks for example. This class handles only casting

     * and leaves the other case-specific details to the sub-class such that this class only

     * do one thing well.

     *

     * This template class takes two parameters:

     * - TSubClass This should be the class inheriting from CastingPlatform.

     * - issueError if true, errors are issued via ReportContext, otherwise

     *   ValidationError instances are returned appropriately.

     *

     * The class inheriting CastingPlatform must implement the following function:

     * @code

     * ItemType::Ptr targetType() const

     * @endcode

     *

     * that returns the type that should be cast to. The type must be an AtomicType.

     * Typically, it is appropriate to declare this function @c inline.

     *

     * A sub-class calls prepareCasting() at compile time(such that CastingPlatform can attempt

     * to lookup the proper AtomicCaster) and then it simply uses the cast() function at runtime. The

     * function targetType() must be implemented such that CastingPlatform knows

     * what type it shall cast to.

     *

     * @see ValueFactory

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

     * @ingroup Patternist_expressions

     */

    template<typename TSubClass, const bool issueError>

    class CastingPlatform

    {

    protected:

        /**

         * @note issueCastError() depends on the default value.

         */

        inline CastingPlatform(const ReportContext::ErrorCode code = ReportContext::FORG0001) : m_errorCode(code)

        {

        }

        /**

         * Attempts to cast @p sourceValue to targetType(), and returns

         * the created value. Remember that prepareCasting() should have been

         * called at compile time, otherwise this function will be slow.

         *

         * Error reporting is done in two ways. If a cast fails because

         * of an error in lexical representation a ValidationError is returned.

         * If the cause of failure is that the casting combination is invalid(such as

         * when attempting to cast @c xs:date to @c xs:integer), a ValidationError

         * is returned if @c false was passed in the template instantiation,

         * an error is issued via @p context.

         *

         * @param sourceValue the value to cast. Must be non @c null.

         * @param context the usual ReportContext, used for error reporting.

         * @returns the new value which was the result of the cast. If the

         * cast failed, an ValidationError is returned.

         */

        Item cast(const Item &sourceValue,

                  const ReportContext::Ptr &context) const;

        /**

         * This function should be called at compiled time, it attempts to determine

         * what AtomicCaster that should be used when casting from @p sourceType to

         * targetType(). If that is not possible, because the @p sourceType is

         * @c xs:anyAtomicType for instance, the AtomicCaster lookup will done at

         * runtime on a case-per-case basis.

         *

         * @returns @c true if the requested casting combination is valid or might be valid.

         * If it is guranteed to be invalid, @c false is returned.

         */

        bool prepareCasting(const ReportContext::Ptr &context,

                            const ItemType::Ptr &sourceType);

        /**

         * Checks that the targetType() is a valid target type for <tt>castable as</tt>

         * and <tt>cast as</tt>. For example, that it is not abstract. If the type is

         * invalid, an error is raised via the @p context. Note that it is assumed the type

         * is atomic.

         */

        void checkTargetType(const ReportContext::Ptr &context) const;

    private:

        inline Item castWithCaster(const Item &sourceValue,

                                   const AtomicCaster::Ptr &caster,

                                   const ReportContext::Ptr &context) const;

        /**

         * Locates the caster for casting values of type @p sourceType to targetType(), if

         * possible.

         *

         * @p castImpossible is not initialized. Initialize it to @c false.

         */

        static AtomicCaster::Ptr locateCaster(const ItemType::Ptr &sourceType,

                                              const ReportContext::Ptr &context,

                                              bool &castImpossible,

                                              const SourceLocationReflection *const location,

                                              const ItemType::Ptr &targetType);

    private:

        inline Item castWithCaster(const Item &sourceValue,

                                   const AtomicCaster::Ptr &caster,

                                   const DynamicContext::Ptr &context) const;

        inline ItemType::Ptr targetType() const

        {

            Q_ASSERT(static_cast<const TSubClass *>(this)->targetType());

            return static_cast<const TSubClass *>(this)->targetType();

        }

        void issueCastError(const Item &validationError,

                            const Item &sourceValue,

                            const ReportContext::Ptr &context) const;

        Q_DISABLE_COPY(CastingPlatform)

        AtomicCaster::Ptr m_caster;

        const ReportContext::ErrorCode m_errorCode;

    };

#include "qcastingplatform.cpp"

}

QT_END_NAMESPACE

QT_END_HEADER

#endif