001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.configuration2.tree;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.Collections;
022import java.util.List;
023
024/**
025 * <p>
026 * A simple data class used by {@link ExpressionEngine} to store
027 * the results of the {@code prepareAdd()} operation.
028 * </p>
029 * <p>
030 * If a new property is to be added to a configuration, the affected
031 * {@code Configuration} object must know, where in its hierarchy of
032 * configuration nodes new elements have to be added. This information is
033 * obtained by an {@code ExpressionEngine} object that interprets the key
034 * of the new property. This expression engine will pack all information
035 * necessary for the configuration to perform the add operation in an instance
036 * of this class.
037 * </p>
038 * <p>
039 * Information managed by this class contains:
040 * </p>
041 * <ul>
042 * <li>the configuration node, to which new elements must be added</li>
043 * <li>the name of the new node</li>
044 * <li>whether the new node is a child node or an attribute node</li>
045 * <li>if a whole branch is to be added at once, the names of all nodes between
046 * the parent node (the target of the add operation) and the new node</li>
047 * </ul>
048 *
049 * @since 1.3
050 * @param <T> the type of nodes this class can handle
051 */
052public class NodeAddData<T>
053{
054    /** Stores the parent node of the add operation. */
055    private final T parent;
056
057    /**
058     * Stores a list with the names of nodes that are on the path between the
059     * parent node and the new node.
060     */
061    private final List<String> pathNodes;
062
063    /** Stores the name of the new node. */
064    private final String newNodeName;
065
066    /** Stores the attribute flag. */
067    private final boolean attribute;
068
069    /**
070     * Creates a new instance of {@code NodeAddData} and initializes it.
071     *
072     * @param parentNode the parent node of the add operation
073     * @param newName the name of the new node
074     * @param isAttr flag whether the new node is an attribute
075     * @param intermediateNodes an optional collection with path nodes
076     */
077    public NodeAddData(final T parentNode, final String newName, final boolean isAttr,
078            final Collection<String> intermediateNodes)
079    {
080        parent = parentNode;
081        newNodeName = newName;
082        attribute = isAttr;
083        pathNodes = createPathNodes(intermediateNodes);
084    }
085
086    /**
087     * Returns a flag if the new node to be added is an attribute.
088     *
089     * @return <b>true</b> for an attribute node, <b>false</b> for a child
090     * node
091     */
092    public boolean isAttribute()
093    {
094        return attribute;
095    }
096
097    /**
098     * Returns the name of the new node.
099     *
100     * @return the new node's name
101     */
102    public String getNewNodeName()
103    {
104        return newNodeName;
105    }
106
107    /**
108     * Returns the parent node.
109     *
110     * @return the parent node
111     */
112    public T getParent()
113    {
114        return parent;
115    }
116
117    /**
118     * Returns a list with further nodes that must be added. This is needed if a
119     * complete branch is to be added at once. For instance, imagine that there
120     * exists only a node {@code database}. Now the key
121     * {@code database.connection.settings.username} (assuming the syntax
122     * of the default expression engine) is to be added. Then
123     * {@code username} is the name of the new node, but the nodes
124     * {@code connection} and {@code settings} must be added to
125     * the parent node first. In this example these names would be returned by
126     * this method.
127     *
128     * @return a list with the names of nodes that must be added as parents of
129     * the new node (never <b>null</b>)
130     */
131    public List<String> getPathNodes()
132    {
133        return pathNodes;
134    }
135
136    /**
137     * Creates the list with path nodes. Handles null input.
138     *
139     * @param intermediateNodes the nodes passed to the constructor
140     * @return an unmodifiable list of path nodes
141     */
142    private static List<String> createPathNodes(
143            final Collection<String> intermediateNodes)
144    {
145        if (intermediateNodes == null)
146        {
147            return Collections.emptyList();
148        }
149        return Collections.unmodifiableList(new ArrayList<>(
150                intermediateNodes));
151    }
152}