/*

* Copyright (c) 2004-2008 Nokia Corporation and/or its subsidiary(-ies). 

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:  CCFContextChanged class declaration.

*

*/

#ifndef C_CFCONTEXTCHANGED_H

#define C_CFCONTEXTCHANGED_H

// INCLUDES

#include "cfcontextoperation.h"

#include <e32base.h>

// FORWARD DECLARATIONS

class CCFContextObject;

// CLASS DECLARATION

/**

*  This class implements ContextChanged context object event.

*

*  @lib CFScriptEngine

*  @since Series 60 2.6

*/

NONSHARABLE_CLASS( CCFContextChanged ): public CCFContextOperation

    {

public: // Constructors and destructor

    /**

    * Two-phased constructor.

    * @param aServices is the operation services interface for nodes.

    * @param aParent is parent node for this node.

    * @param aName is name of the context object this operation operates on.

    * @param aSource is the source of the context object this operation

    *   operates on.

    * @param aValue is the expected value of the context object this operation

    *   operates on. Use KNullDesC if no particular value is expected.

    */

    static CCFContextChanged* NewL( MCFOperationServices& aServices,

            CCFOperationNode* aParent,

            const TDesC& aName,

            const TDesC& aSource,

            const TDesC& aValue );

    /**

    * Two-phased constructor that leaves the class into CleanupStack.

    * @param aServices is the operation services interface for nodes.

    * @param aParent is parent node for this node.

    * @param aName is name of the context object this operation operates on.

    * @param aSource is the source of the context object this operation

    *   operates on.

    * @param aValue is the expected value of the context object this operation

    *   operates on. Use KNullDesC if no particular value is expected.

    */

    static CCFContextChanged* NewLC( MCFOperationServices& aServices,

            CCFOperationNode* aParent,

            const TDesC& aName,

            const TDesC& aSource,

            const TDesC& aValue );

    /**

    * Creates and parses a CCFContextChanged instance from an xml node.

    * @param aServices is the operation services interface for nodes.

    * @param aParent is the parent of this node or NULL if this is a root.

    *   The ownership of the parent is not transferred.

    * @param aNode is the node to be parsed.

    * @return a pointer to the created instance of CCFContextChanged, or NULL if

    *   the node is not this context changed node. May leave with any system

    *   wide error code.

    */

    static CCFContextChanged* ParseL( MCFOperationServices& aServices,

            CCFOperationNode* aParent,

            CMDXMLNode& aNode );

    /**

    * Destructor.

    */

    ~CCFContextChanged();

private:

    /**

    * C++ default constructor.

    */

    CCFContextChanged( MCFOperationServices& aServices,

            CCFOperationNode* aParent,

            HBufC* aName,

            HBufC* aSource );

    /**

    * By default Symbian 2nd phase constructor is private.

    * @param aValue is the expected value of the context object this operation

    *   operates on. Use KNullDesC if no particular value is expected.

    */

    void ConstructL( const TDesC& aValue );

protected: // From CFContextOperation

    /**

    * Tests if this listener requires notification of all contexts.

    * @returns ETrue if this listener is interested in all contexts,

    *   EFalse otherwise.

    */

    TBool IsAllRequired() const;

    /**

    * Evaluates a node with a context.

    * @param aContext is the context for evaluation.

    * @param aContextLevelDelay contains the context level delay defined by

    *  contextRef after the call.

    * @return ETrue if the operation was evaluated, EFalse otherwise.

    */

    virtual TBool Evaluate( const CCFContextObject& aContext,

            TInt& aContextLevelDelay );

    /**

    * Method that returns whether or not this this operation is true.

    * @returns ETrue if this operation is true, EFalse otherwise

    */

    TBool IsTrueL( const CCFContextObject& aContextObject );

private: // Data

    // Flag for context used with previous truth check (call to isTrueL),

    // tells whether it was the referenced context or not.

    TBool iPreviousTruthCheckWithReferencedContext;

    // When set, the required context value for making the operation true.

    HBufC* iCmpValue;

    };

#endif // C_CFCONTEXTCHANGED_H