/**

  * Copyright (c) 2008-2011, http://www.snakeyaml.org

  *

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.yaml.snakeyaml.nodes;

 import org.yaml.snakeyaml.error.Mark;

 /**

  * Base class for all nodes.

  * <p>

  * The nodes form the node-graph described in the <a

  * href="http://yaml.org/spec/1.1/">YAML Specification</a>.

  * </p>

  * <p>

  * While loading, the node graph is usually created by the

  * {@link org.yaml.snakeyaml.composer.Composer}, and later transformed into

  * application specific Java classes by the classes from the

  * {@link org.yaml.snakeyaml.constructor} package.

  * </p>

  */

 public abstract class Node {

     private Tag tag;

     private Mark startMark;

     protected Mark endMark;

     private Class<? extends Object> type;

     private boolean twoStepsConstruction;

     /**

      * true when the tag is assigned by the resolver

      */

     protected boolean resolved;

     protected Boolean useClassConstructor;

     public Node(Tag tag, Mark startMark, Mark endMark) {

         setTag(tag);

         this.startMark = startMark;

         this.endMark = endMark;

         this.type = Object.class;

         this.twoStepsConstruction = false;

         this.resolved = true;

         this.useClassConstructor = null;

     }

     /**

      * Tag of this node.

      * <p>

      * Every node has a tag assigned. The tag is either local or global.

      * 

      * @return Tag of this node.

      */

     public Tag getTag() {

         return this.tag;

     }

     public Mark getEndMark() {

         return endMark;

     }

     /**

      * For error reporting.

      * 

      * @see class variable 'id' in PyYAML

      * @return scalar, sequence, mapping

      */

     public abstract NodeId getNodeId();

     public Mark getStartMark() {

         return startMark;

     }

     public void setTag(Tag tag) {

         if (tag == null) {

             throw new NullPointerException("tag in a Node is required.");

         }

         this.tag = tag;

     }

     /**

      * Two Nodes are never equal.

      */

     @Override

     public final boolean equals(Object obj) {

         return super.equals(obj);

     }

     public Class<? extends Object> getType() {

         return type;

     }

     public void setType(Class<? extends Object> type) {

         if (!type.isAssignableFrom(this.type)) {

             this.type = type;

         }

     }

     public void setTwoStepsConstruction(boolean twoStepsConstruction) {

         this.twoStepsConstruction = twoStepsConstruction;

     }

     /**

      * Indicates if this node must be constructed in two steps.

      * <p>

      * Two-step construction is required whenever a node is a child (direct or

      * indirect) of it self. That is, if a recursive structure is build using

      * anchors and aliases.

      * </p>

      * <p>

      * Set by {@link org.yaml.snakeyaml.composer.Composer}, used during the

      * construction process.

      * </p>

      * <p>

      * Only relevant during loading.

      * </p>

      * 

      * @return <code>true</code> if the node is self referenced.

      */

     public boolean isTwoStepsConstruction() {

         return twoStepsConstruction;

     }

     @Override

     public final int hashCode() {

         return super.hashCode();

     }

     public boolean useClassConstructor() {

         if (useClassConstructor == null) {

             if (isResolved() && !Object.class.equals(type) && !tag.equals(Tag.NULL)) {

                 return true;

             } else if (tag.isCompatible(getType())) {

                 // the tag is compatible with the runtime class

                 // the tag will be ignored

                 return true;

             } else {

                 return false;

             }

         }

         return useClassConstructor.booleanValue();

     }

     public void setUseClassConstructor(Boolean useClassConstructor) {

         this.useClassConstructor = useClassConstructor;

     }

     /**

      * Indicates if the tag was added by

      * {@link org.yaml.snakeyaml.resolver.Resolver}.

      * 

      * @return <code>true</code> if the tag of this node was resolved</code>

      */

     public boolean isResolved() {

         return resolved;

     }

 }