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.collections4.sequence;
018
019import java.util.ArrayList;
020import java.util.List;
021
022/**
023 * This class gathers all the {@link EditCommand commands} needed to transform
024 * one objects sequence into another objects sequence.
025 * <p>
026 * An edit script is the most general view of the differences between two
027 * sequences. It is built as the result of the comparison between two sequences
028 * by the {@link SequencesComparator SequencesComparator} class. The user can
029 * walk through it using the <em>visitor</em> design pattern.
030 * <p>
031 * It is guaranteed that the objects embedded in the {@link InsertCommand insert
032 * commands} come from the second sequence and that the objects embedded in
033 * either the {@link DeleteCommand delete commands} or {@link KeepCommand keep
034 * commands} come from the first sequence. This can be important if subclassing
035 * is used for some elements in the first sequence and the <code>equals</code>
036 * method is specialized.
037 *
038 * @see SequencesComparator
039 * @see EditCommand
040 * @see CommandVisitor
041 * @see ReplacementsHandler
042 *
043 * @since 4.0
044 */
045public class EditScript<T> {
046
047    /** Container for the commands. */
048    private final List<EditCommand<T>> commands;
049
050    /** Length of the longest common subsequence. */
051    private int lcsLength;
052
053    /** Number of modifications. */
054    private int modifications;
055
056    /**
057     * Simple constructor. Creates a new empty script.
058     */
059    public EditScript() {
060        commands = new ArrayList<>();
061        lcsLength = 0;
062        modifications = 0;
063    }
064
065    /**
066     * Add a keep command to the script.
067     *
068     * @param command  command to add
069     */
070    public void append(final KeepCommand<T> command) {
071        commands.add(command);
072        ++lcsLength;
073    }
074
075    /**
076     * Add an insert command to the script.
077     *
078     * @param command  command to add
079     */
080    public void append(final InsertCommand<T> command) {
081        commands.add(command);
082        ++modifications;
083    }
084
085    /**
086     * Add a delete command to the script.
087     *
088     * @param command  command to add
089     */
090    public void append(final DeleteCommand<T> command) {
091        commands.add(command);
092        ++modifications;
093    }
094
095    /**
096     * Visit the script. The script implements the <em>visitor</em> design
097     * pattern, this method is the entry point to which the user supplies its
098     * own visitor, the script will be responsible to drive it through the
099     * commands in order and call the appropriate method as each command is
100     * encountered.
101     *
102     * @param visitor  the visitor that will visit all commands in turn
103     */
104    public void visit(final CommandVisitor<T> visitor) {
105        for (final EditCommand<T> command : commands) {
106            command.accept(visitor);
107        }
108    }
109
110    /**
111     * Get the length of the Longest Common Subsequence (LCS). The length of the
112     * longest common subsequence is the number of {@link KeepCommand keep
113     * commands} in the script.
114     *
115     * @return length of the Longest Common Subsequence
116     */
117    public int getLCSLength() {
118        return lcsLength;
119    }
120
121    /**
122     * Get the number of effective modifications. The number of effective
123     * modification is the number of {@link DeleteCommand delete} and
124     * {@link InsertCommand insert} commands in the script.
125     *
126     * @return number of effective modifications
127     */
128    public int getModifications() {
129        return modifications;
130    }
131
132}