/*

* 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:  CCFContextOperation class declaration.

*

*/

#ifndef C_CFCONTEXTOPERATION_H

#define C_CFCONTEXTOPERATION_H

// INCLUDES

#include <e32base.h>

#include <cfcontextobject.h>

#include "cfoperationnode.h"

#include "cfscriptlistener.h"

// FORWARD DECLARATIONS

// CLASS DECLARATION

/**

*  CCFContextOperation class is the base class for all Context Framework script

*  operations that operate on contexts.

*  All instances of this class are leaf nodes in operation tree.

*

*  @lib CFScriptEngine

*  @since Series 60 2.6

*/

NONSHARABLE_CLASS( CCFContextOperation ): public CCFOperationNode,

    public MCFScriptListener

    {

public: // Constructors and destructor

    /**

    * Destructor.

    */

    virtual ~CCFContextOperation();

public: // Enumerations

    enum TCmpType

        {

        EInvalidCmpType = -1,

        EIntCmp,

        EFloatCmp,

        EPositionCmp,

        ETimeCmp,

        EStringCmp

        };

public: // From MCFScriptListener

    /**

    * Performs evaluation based on a context.

    * @param aContext is the context for evaluation.

    * @param aContextLevelDelay is storage for context level delay required by

    *   the evaluation.

    * @return ETrue if evaluation was performed and firing actions should be

    *   considered based on clause conditions, EFalse otherwise.

    */

    TBool Evaluate( const CCFContextObject& aContext,

            TInt& aContextLevelDelay );

    /**

    * Returns a context source this listener is interested in.

    * @returns the source of the context.

    */

    TPtrC Source() const;

    /**

    * Returns a context type this listener is interested in.

    * @returns the type of the context.

    */

    TPtrC Type() const;

    /**

    * Tests if this listener requires notification of all contexts.

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

    *   EFalse otherwise.

    */

    TBool IsAllRequired() const;

protected:

    /**

    * C++ default constructor.

    */

    CCFContextOperation( MCFOperationServices& aServices,

            CCFOperationNode* aParent,

            HBufC* aType,

            HBufC* aSource );

protected: // New functions

    /**

    * All concrete classes must implement this method.

    * @param aContext is context that has changed.

    * @return the result of the comparison.

    */

    virtual TBool IsTrueL( const CCFContextObject& aContext ) = 0;

    /**

    * Updates the previous value the operation was evaluated with.

    * @param aNewValue is the new previous value.

    * @return KErrNone when update was successful, KErrNoMemory if update failed

    *   due to low memory.

    */

    TInt UpdatePreviousValue( const TDesC& aNewValue );

    /**

    * Gets the previous value the operation was evaluated with.

    * @return the previous value the operation was evaluated with.

    */

    const TDesC& PreviousValue();

protected: // From CCFOperationNode

    /**

    * Activates this node by subscribing to a context.

    * @return None.

    */

    void ActivateL();

    /**

    * Deactivates this node by removing context subscription.

    * @return None.

    */

    void Deactivate();

    /**

    * Asks this node to check its security (via services interface). For

    * example, the security of contexts to be subscribed.

    * @return KErrNone if security check passed, otherwise any of the system

    *   wide error codes.

    */

    TInt CheckSecurity();

private: // From CCFOperationNode

    /**

    * Called by child node, to ask the parent to re-evaluate its value,

    * since the child's value has changed.

    */

    void Evaluate();

protected: // Data

    /**

    * Context level delay for firing actions after evaluation

    * (defined by contextRef).

    */

    TInt iContextLevelDelay;

private: // Data

    /**

    * Context source and type as defined by contextRef for the operation.

    */

    HBufC* iSource;

    HBufC* iType;

    /** Previous context value. */

    HBufC* iPreviousValue;

    };

#endif // C_CFCONTEXTOPERATION_H