/**
 * OpenSpotLight - Open Source IT Governance Platform
 *
 * Copyright (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA
 * or third-party contributors as indicated by the @author tags or express
 * copyright attribution statements applied by the authors.  All third-party
 * contributions are distributed under license by CARAVELATECH CONSULTORIA E
 * TECNOLOGIA EM INFORMATICA LTDA.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program 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 Lesser General Public License  for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 ***********************************************************************
 * OpenSpotLight - Plataforma de Governança de TI de Código Aberto
 *
 * Direitos Autorais Reservados (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA
 * EM INFORMATICA LTDA ou como contribuidores terceiros indicados pela etiqueta
 * @author ou por expressa atribuição de direito autoral declarada e atribuída pelo autor.
 * Todas as contribuições de terceiros estão distribuídas sob licença da
 * CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA.
 *
 * Este programa é software livre; você pode redistribuí-lo e/ou modificá-lo sob os
 * termos da Licença Pública Geral Menor do GNU conforme publicada pela Free Software
 * Foundation.
 *
 * Este programa é distribuído na expectativa de que seja útil, porém, SEM NENHUMA
 * GARANTIA; nem mesmo a garantia implícita de COMERCIABILIDADE OU ADEQUAÇÃO A UMA
 * FINALIDADE ESPECÍFICA. Consulte a Licença Pública Geral Menor do GNU para mais detalhes.
 *
 * Você deve ter recebido uma cópia da Licença Pública Geral Menor do GNU junto com este
 * programa; se não, escreva para:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */

package org.openspotlight.graph;

import java.math.BigInteger;

import org.openspotlight.graph.annotation.DefineHierarchy;
import org.openspotlight.log.LogableObject;

/**
 * The Node is the base data structure that enables represent any information into graph. Any information can be modeled as a Node
 * using its unique identifiers or properties. <br>
 * A Node is uniquely identified by three properties: Type, Name and ParentNode, and based on these data an algorithm is used to
 * generate an unique id.
 * <p>
 * To secure the data consistency its not possible change the unique identifiers of a Node. If you need so, you'll have to delete
 * it and create a new one.
 * </p>
 * <p>
 * A Node defines a information, to relate this data with other you'll have to create {@link Link} to connect those nodes.
 * </p>
 * <p>
 * The graph node typing system is very similar to object-oriented languages, where its possible to create a node hierarchy, as
 * higher in heirarchy more abstract the node type is, and the oposite is true, as lowest the type is in hierarchy is its more
 * specific. <br>
 * Its necessary to use the {@link org.openspotlight.graph.annotation.DefineHierarchy} annotation to mark a node as the higher
 * element in a hierarchy, all node types that extends this node type are in the same hierarchy and are considered more specific.
 * <br>
 * The graph has a mechanism that automatically promotes types, if users creates a node that can be considered the same (based on
 * type hierarchy, parent node and name) the graph system will always keep the node with the more specific node type. <br>
 * <b>Note</b> that these promotion are automatically handled by graph engine.
 * </p>
 * <p>
 * Nodes can be created as transients by
 * {@link org.openspotlight.graph.manipulation.GraphTransientWriter#addTransientNode(Context, Class, String)} or
 * {@link org.openspotlight.graph.manipulation.GraphTransientWriter#addTransientChildNode(Node, Class, String)} methods or as
 * permanent by {@link org.openspotlight.graph.manipulation.GraphWriter#addNode(Context, Class, String)},
 * {@link org.openspotlight.graph.manipulation.GraphWriter#addNode(Context, Class, String, java.util.Collection, java.util.Collection)}, {@link org.openspotlight.graph.manipulation.GraphWriter#addChildNode(Node, Class, String)} or
 * {@link org.openspotlight.graph.manipulation.GraphWriter#addChildNode(Node, Class, String, java.util.Collection, java.util.Collection)}
 * methods wich are the most common use.
 * </p>
 * <p>
 * Along with {@link org.openspotlight.graph.Link}, nodes are are the core of graph data model.
 * </p>
 * <p>
 * <b>Important Notes:</b><br>
 *  1. Its a abstract class to avoid more than one type of element for a node.<br>
 *  2. The same node (uniquely identified by Type, Name and Parent) can be stored in more than one
 * {@link org.openspotlight.graph.Context}.
 * </p>
 * 
 * @author feuteston
 * @author porcelli
 */
public abstract class Node implements Element, Comparable<Node>, LogableObject {

    /**
     * Returns the caption.
     * 
     * @return the caption
     */
    public abstract String getCaption();

    /**
     * Returns the name. <br>
     * The name is one of the three properties ({@link Node#getName}, {@link Node#getParentId} and {@link Node#getTypeName}) that
     * defines uniquely the node.
     * 
     * @return the name
     */
    public abstract String getName();

    /**
     * The numeric type is used to find node types inherited from some type. To understand its use, first it' necessary to
     * understand how it is created: Each node should extend {@link Node} class, but it is possible to have an hierarchy of node
     * inheritance. One of this nodes needs to define a hierarchy. For example, a JavaType node defines an hierarchy wich should
     * have JavaTypeClass, JavaTypeInterface, JavaTypeClassEnum and so on. So, this node JavaType is special and needs to be
     * annotated with {@link DefineHierarchy}. To create this numeric type index, first the node associated with the annotation
     * {@link DefineHierarchy} will be used to create a hash key. After this, for each inherited type this numeric type will be
     * incremented. So, it is possible to look for a range of types with this numeric types. Example: find the types inherited for
     * this one for at least two leves.
     * 
     * @return the numeric type associated with this node class
     */
    public abstract BigInteger getNumericType();

    /**
     * Returns the parent's node id. <br>
     * The parentId is one of the three properties ({@link Node#getName}, {@link Node#getParentId} and {@link Node#getTypeName})
     * that defines uniquely the node.
     * <p>
     * <b>Note</b> the parent node is not directly exposed due performance issues.
     * 
     * @return the parent id
     */
    public abstract String getParentId();

    /**
     * Sets the caption. Caption is just a simple form to identify (not uniquely) the node.
     * 
     * @param caption the caption
     * @throws IllegalArgumentException if the input param is null
     */
    public abstract void setCaption(String caption)
        throws IllegalArgumentException;
}