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 *      https://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.lang3.builder;
018
019import java.util.Collections;
020import java.util.Iterator;
021import java.util.List;
022import java.util.Objects;
023
024import org.apache.commons.lang3.StringUtils;
025
026/**
027 * A {@link DiffResult} contains a collection of the differences between two
028 * {@link Diffable} objects. Typically these differences are displayed using
029 * {@link #toString()} method, which returns a string describing the fields that
030 * differ between the objects.
031 *
032 * <p>
033 * Use a {@link DiffBuilder} to build a {@link DiffResult} comparing two objects.
034 * </p>
035 * @param <T> type of the left and right object.
036 * @since 3.3
037 */
038public class DiffResult<T> implements Iterable<Diff<?>> {
039
040    /**
041     * The {@link String} returned when the objects have no differences:
042     * {@value}
043     */
044    public static final String OBJECTS_SAME_STRING = StringUtils.EMPTY;
045
046    private final List<Diff<?>> diffList;
047    private final T lhs;
048    private final T rhs;
049    private final ToStringStyle style;
050    private final String toStringFormat;
051
052    /**
053     * Creates a {@link DiffResult} containing the differences between two
054     * objects.
055     *
056     * @param lhs
057     *            the left-hand side object
058     * @param rhs
059     *            the right-hand side object
060     * @param diffList
061     *            the list of differences, may be empty
062     * @param style
063     *            the style to use for the {@link #toString()} method. May be
064     *            {@code null}, in which case
065     *            {@link ToStringStyle#DEFAULT_STYLE} is used
066     * @param toStringFormat
067     *            Two-argument format string for {@link String#format(String, Object...)}, for example {@code "%s differs from %s"}.
068     * @throws NullPointerException if {@code lhs}, {@code rhs} or {@code diffs} are {@code null}.
069     */
070    DiffResult(final T lhs, final T rhs, final List<Diff<?>> diffList, final ToStringStyle style, final String toStringFormat) {
071        this.diffList = Objects.requireNonNull(diffList, "diffList");
072        this.lhs = Objects.requireNonNull(lhs, "lhs");
073        this.rhs = Objects.requireNonNull(rhs, "rhs");
074        this.style = Objects.requireNonNull(style, "style");
075        this.toStringFormat = Objects.requireNonNull(toStringFormat, "toStringFormat");
076    }
077
078    /**
079     * Gets an unmodifiable list of {@link Diff}s. The list may be empty if
080     * there were no differences between the objects.
081     *
082     * @return an unmodifiable list of {@link Diff}s
083     */
084    public List<Diff<?>> getDiffs() {
085        return Collections.unmodifiableList(diffList);
086    }
087
088    /**
089     * Gets the object the right object has been compared to.
090     *
091     * @return the left object of the diff
092     * @since 3.10
093     */
094    public T getLeft() {
095        return this.lhs;
096    }
097
098    /**
099     * Gets the number of differences between the two objects.
100     *
101     * @return the number of differences
102     */
103    public int getNumberOfDiffs() {
104        return diffList.size();
105    }
106
107    /**
108     * Gets the object the left object has been compared to.
109     *
110     * @return the right object of the diff
111     * @since 3.10
112     */
113    public T getRight() {
114        return this.rhs;
115    }
116
117    /**
118     * Gets the style used by the {@link #toString()} method.
119     *
120     * @return the style
121     */
122    public ToStringStyle getToStringStyle() {
123        return style;
124    }
125
126    /**
127     * Returns an iterator over the {@link Diff} objects contained in this list.
128     *
129     * @return the iterator
130     */
131    @Override
132    public Iterator<Diff<?>> iterator() {
133        return diffList.iterator();
134    }
135
136    /**
137     * Builds a {@link String} description of the differences contained within
138     * this {@link DiffResult}. A {@link ToStringBuilder} is used for each object
139     * and the style of the output is governed by the {@link ToStringStyle}
140     * passed to the constructor.
141     *
142     * <p>
143     * If there are no differences stored in this list, the method will return
144     * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
145     * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
146     * might be:
147     * </p>
148     *
149     * <pre>
150     * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
151     * </pre>
152     *
153     * <p>
154     * This indicates that the objects differ in name and age, but not in
155     * smoking status.
156     * </p>
157     *
158     * <p>
159     * To use a different {@link ToStringStyle} for an instance of this class,
160     * use {@link #toString(ToStringStyle)}.
161     * </p>
162     *
163     * @return a {@link String} description of the differences.
164     */
165    @Override
166    public String toString() {
167        return toString(style);
168    }
169
170    /**
171     * Builds a {@link String} description of the differences contained within
172     * this {@link DiffResult}, using the supplied {@link ToStringStyle}.
173     *
174     * @param style
175     *            the {@link ToStringStyle} to use when outputting the objects
176     *
177     * @return a {@link String} description of the differences.
178     */
179    public String toString(final ToStringStyle style) {
180        if (diffList.isEmpty()) {
181            return OBJECTS_SAME_STRING;
182        }
183
184        final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
185        final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);
186
187        diffList.forEach(diff -> {
188            lhsBuilder.append(diff.getFieldName(), diff.getLeft());
189            rhsBuilder.append(diff.getFieldName(), diff.getRight());
190        });
191
192        return String.format(toStringFormat, lhsBuilder.build(), rhsBuilder.build());
193    }
194}