/*
 * This file is part of the syndication library
 *
 * Copyright (C) 2006 Frank Osterfeld <osterfeld@kde.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */
#ifndef SYNDICATION_RDF_NODE_H
#define SYNDICATION_RDF_NODE_H

#include <syndication/ksyndication_export.h>
#include <boost/shared_ptr.hpp>

namespace Syndication {
namespace RDF {

class Model;
class Node;
class NodeVisitor;
//@cond PRIVATE
typedef boost::shared_ptr<Node> NodePtr;
//@endcond

/**
 * an RDF node, abstract baseclass for all RDF node types, like resources and
 * literals
 */
class SYNDICATION_EXPORT Node
{
    public:

        /**
         * destructor
         */
        virtual ~Node();

        /**
         * Used by visitors for double dispatch. See NodeVisitor
         * for more information.
         * @param visitor the visitor calling the method
         * @param ptr a shared pointer object for this node
         */
        virtual void accept(NodeVisitor* visitor, NodePtr ptr);

        /**
         * checks whether two nodes are equal. The meaning of equality
         * is defined per subclass (e.g. equality of URIs, IDs etc.)
         * 
         * @param other the node to compare to
         */
        virtual bool operator==(const Node& other) const = 0;

        /**
         * returns a copy of the object. Must be implemented
         * by subclasses to return a copy using the concrete
         * type
         */
        virtual Node* clone() const = 0;

        /**
         * returns whether this node is a null node
         */
        virtual bool isNull() const = 0;

        /**
         * returns whether this node is a resource
         */
        virtual bool isResource() const = 0;

        /**
         * returns whether this node is a property
         */
        virtual bool isProperty() const = 0;

        /**
         * returns whether this node is a literal
         */
        virtual bool isLiteral() const = 0;

        /**
         * returns whether this node is an RDF sequence
         */
        virtual bool isSequence() const = 0;

        /**
         * returns whether this node is an anonymous resource
         */
        virtual bool isAnon() const = 0;

        /**
         * the identifier of this node. the ID is unique per model
         * and set by the associated model at creation time.
         */
        virtual unsigned int id() const = 0;

        /**
         * returns a textual representation of the node.
         * This is the literal string for literals, and a null string for other
         * node types.
         */
        virtual QString text() const = 0;
        
        /**
         * used in Model
         * @internal
         */
        virtual void setModel(const Model& model) = 0;

        /**
         *  used in Model
         * @internal
         */
        virtual void setId(unsigned int id) = 0;

    protected:

        /**
         * used to generate unique IDs for node objects
         */
        static unsigned int idCounter;
};

} // namespace RDF
} // namespace Syndication

#endif // SYNDICATION_RDF_NODE_H
