// Copyright (c) 2005-2009 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:

// Extension function interface

//

/**

 @file

 @publishedAll

 @released

*/

#ifndef XMLENGXPATHFUNCTION_H

#define XMLENGXPATHFUNCTION_H

#include <xml/dom/xmlengxpathresult.h>

class MXmlEngXPathEvaluationContext;

/**

Provides an interface for an object to participate in the evaluation of XPath

expression via a XPath function call.

Objects that implement the MXmlEngXPathExtensionFunction interface can be

registered in a XmlEngXPathConfiguration object for global action (across

all evaluations globally). 

@see XmlEngXPathConfiguration::AddExtensionFunctionL()

When the extension function is no longer required, it must be deregistered

by calling XmlEngXPathConfiguration::RemoveExtensionFunction().

*/ 

class MXmlEngXPathExtensionFunction

    {

public:

    /** Evaluation status */

    enum TXmlEngEvaluationStatus

        {

		/** Evaluation was accomplished successfully */

        ESucceeded,

		/** An exceptional condition occurs */

        EError,

		/** Type of argument does not match function specification */

        EInvalidArgumentType,

		/** Number of arguments do not match function specification */

        EInvalidArgumentNumber

        };

public:

    /** 

    Gets the minimum number of arguments the function can take.

    @return Minimum number of arguments

    */

    virtual TInt MinArity() {return 0;}

    /** 

    Gets the maximum number of arguments the function can take.

	@return The maximum number of arguments or -1 if unbounded

    */

    virtual TInt MaxArity() {return MinArity();}

    /**

	Called to evaluate the extension function.

	This function is called only if simple arity constraints (min/max number of

	arguments) are satisfied. The implementation of this function may need to

	check further that the types of arguments and their positions in the

	function call match function-specific requirements.

	@param aEvalCtxt Evaluation context, which contains data about arguments

	and provides a number of methods for setting the result of the extension

	function.

    @return ESucceeded if evaluation success, otherwise one of the errors 

	defined in TXmlEngEvaluationStatus.

    */

    virtual TXmlEngEvaluationStatus Evaluate(MXmlEngXPathEvaluationContext* aEvalCtxt) = 0; 

    };

#endif /* XMLENGXPATHFUNCTION_H */