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.HashMap;
023import java.util.Map;
024
025/**
026 * <p>
027 * A simple data class used by node models to store parameters of an update operation.
028 * </p>
029 * <p>
030 * The {@code Configuration} interface provides a method for setting the value of a given key. The passed in value can
031 * be a single object or a collection of values. This makes an update operation rather complicated because a collection
032 * of query results selected by the passed in key has to be matched to another collection of values - and both
033 * collections can have different sizes. Therefore, an update operation may involve changing of existing nodes, adding
034 * new nodes (if there are more values than currently existing nodes), and removing nodes (if there are more existing
035 * nodes than provided values). This class collects all this information making it possible to actually perform the
036 * update based on a passed in instance.
037 * </p>
038 *
039 * @since 2.0
040 * @param <T> the type of nodes involved in this update operation
041 */
042public class NodeUpdateData<T> {
043    /**
044     * Creates an unmodifiable defensive copy of the passed in collection with may be null.
045     *
046     * @param col the collection to be copied
047     * @param <T> the element type of the collection
048     * @return the unmodifiable copy
049     */
050    private static <T> Collection<T> copyCollection(final Collection<? extends T> col) {
051        if (col == null) {
052            return Collections.emptySet();
053        }
054        return Collections.unmodifiableCollection(new ArrayList<>(col));
055    }
056
057    /**
058     * Creates an unmodifiable defensive copy of the passed in map which may be null.
059     *
060     * @param map the map to be copied
061     * @param <K> the type of the keys involved
062     * @param <V> the type of the values involved
063     * @return the unmodifiable copy
064     */
065    private static <K, V> Map<K, V> copyMap(final Map<? extends K, ? extends V> map) {
066        if (map == null) {
067            return Collections.emptyMap();
068        }
069        return Collections.unmodifiableMap(new HashMap<>(map));
070    }
071
072    /** The map with the query results whose value has to be changed. */
073    private final Map<QueryResult<T>, Object> changedValues;
074
075    /** The collection with the new values to be added. */
076    private final Collection<Object> newValues;
077
078    /** The collection with query results about the nodes to be removed. */
079    private final Collection<QueryResult<T>> removedNodes;
080
081    /** The key of the current update operation. */
082    private final String key;
083
084    /**
085     * Creates a new instance of {@code NodeUpdateData} and initializes all its properties. All passed in collections are
086     * optional and can be <b>null</b>.
087     *
088     * @param changedValues the map defining the changed values
089     * @param newValues the collection with the new values
090     * @param removedNodes the collection with the nodes to be removed
091     * @param key the key of the update operation
092     */
093    public NodeUpdateData(final Map<QueryResult<T>, Object> changedValues, final Collection<Object> newValues, final Collection<QueryResult<T>> removedNodes,
094        final String key) {
095        this.changedValues = copyMap(changedValues);
096        this.newValues = copyCollection(newValues);
097        this.removedNodes = copyCollection(removedNodes);
098        this.key = key;
099    }
100
101    /**
102     * Gets an unmodifiable map with the values to be changed. The keys of the map are the query results for the nodes
103     * affected, the values are the new values to be assigned to these nodes.
104     *
105     * @return the map with values to be changed
106     */
107    public Map<QueryResult<T>, Object> getChangedValues() {
108        return changedValues;
109    }
110
111    /**
112     * Gets the key for this update operation.
113     *
114     * @return the key for this operation
115     */
116    public String getKey() {
117        return key;
118    }
119
120    /**
121     * Gets a collection with the values to be newly added. For these values new nodes have to be created and added under
122     * the key stored in this object.
123     *
124     * @return the collection with new values
125     */
126    public Collection<Object> getNewValues() {
127        return newValues;
128    }
129
130    /**
131     * Adds a collection with the nodes to be removed. These nodes are no longer needed and have to be removed from the node
132     * model processing this request.
133     *
134     * @return the collection with nodes to be removed
135     */
136    public Collection<QueryResult<T>> getRemovedNodes() {
137        return removedNodes;
138    }
139}