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.text.diff;
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 StringsComparator StringsComparator} 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 StringsComparator
039 * @see EditCommand
040 * @see CommandVisitor
041 * @see ReplacementsHandler
042 *
043 * @param <T> object type
044 * @since 1.0
045 */
046public class EditScript<T> {
047
048    /** Container for the commands. */
049    private final List<EditCommand<T>> commands;
050
051    /** Length of the longest common subsequence. */
052    private int lcsLength;
053
054    /** Number of modifications. */
055    private int modifications;
056
057    /**
058     * Simple constructor. Creates a new empty script.
059     */
060    public EditScript() {
061        commands = new ArrayList<>();
062        lcsLength = 0;
063        modifications = 0;
064    }
065
066    /**
067     * Add a keep command to the script.
068     *
069     * @param command  command to add
070     */
071    public void append(final KeepCommand<T> command) {
072        commands.add(command);
073        ++lcsLength;
074    }
075
076    /**
077     * Add an insert command to the script.
078     *
079     * @param command  command to add
080     */
081    public void append(final InsertCommand<T> command) {
082        commands.add(command);
083        ++modifications;
084    }
085
086    /**
087     * Add a delete command to the script.
088     *
089     * @param command  command to add
090     */
091    public void append(final DeleteCommand<T> command) {
092        commands.add(command);
093        ++modifications;
094    }
095
096    /**
097     * Visit the script. The script implements the <em>visitor</em> design
098     * pattern, this method is the entry point to which the user supplies its
099     * own visitor, the script will be responsible to drive it through the
100     * commands in order and call the appropriate method as each command is
101     * encountered.
102     *
103     * @param visitor  the visitor that will visit all commands in turn
104     */
105    public void visit(final CommandVisitor<T> visitor) {
106        for (final EditCommand<T> command : commands) {
107            command.accept(visitor);
108        }
109    }
110
111    /**
112     * Get the length of the Longest Common Subsequence (LCS). The length of the
113     * longest common subsequence is the number of {@link KeepCommand keep
114     * commands} in the script.
115     *
116     * @return length of the Longest Common Subsequence
117     */
118    public int getLCSLength() {
119        return lcsLength;
120    }
121
122    /**
123     * Get the number of effective modifications. The number of effective
124     * modification is the number of {@link DeleteCommand delete} and
125     * {@link InsertCommand insert} commands in the script.
126     *
127     * @return number of effective modifications
128     */
129    public int getModifications() {
130        return modifications;
131    }
132
133}