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 * <p>
032 * It is guaranteed that the objects embedded in the {@link InsertCommand insert
033 * commands} come from the second sequence and that the objects embedded in
034 * either the {@link DeleteCommand delete commands} or {@link KeepCommand keep
035 * commands} come from the first sequence. This can be important if subclassing
036 * is used for some elements in the first sequence and the <code>equals</code>
037 * method is specialized.
038 * </p>
039 *
040 * @see SequencesComparator
041 * @see EditCommand
042 * @see CommandVisitor
043 * @see ReplacementsHandler
044 *
045 * @since 4.0
046 */
047public class EditScript<T> {
048
049    /** Container for the commands. */
050    private final List<EditCommand<T>> commands;
051
052    /** Length of the longest common subsequence. */
053    private int lcsLength;
054
055    /** Number of modifications. */
056    private int modifications;
057
058    /**
059     * Simple constructor. Creates a new empty script.
060     */
061    public EditScript() {
062        commands = new ArrayList<>();
063        lcsLength = 0;
064        modifications = 0;
065    }
066
067    /**
068     * Add a keep command to the script.
069     *
070     * @param command  command to add
071     */
072    public void append(final KeepCommand<T> command) {
073        commands.add(command);
074        ++lcsLength;
075    }
076
077    /**
078     * Add an insert command to the script.
079     *
080     * @param command  command to add
081     */
082    public void append(final InsertCommand<T> command) {
083        commands.add(command);
084        ++modifications;
085    }
086
087    /**
088     * Add a delete command to the script.
089     *
090     * @param command  command to add
091     */
092    public void append(final DeleteCommand<T> command) {
093        commands.add(command);
094        ++modifications;
095    }
096
097    /**
098     * Visit the script. The script implements the <em>visitor</em> design
099     * pattern, this method is the entry point to which the user supplies its
100     * own visitor, the script will be responsible to drive it through the
101     * commands in order and call the appropriate method as each command is
102     * encountered.
103     *
104     * @param visitor  the visitor that will visit all commands in turn
105     */
106    public void visit(final CommandVisitor<T> visitor) {
107        for (final EditCommand<T> command : commands) {
108            command.accept(visitor);
109        }
110    }
111
112    /**
113     * Get the length of the Longest Common Subsequence (LCS). The length of the
114     * longest common subsequence is the number of {@link KeepCommand keep
115     * commands} in the script.
116     *
117     * @return length of the Longest Common Subsequence
118     */
119    public int getLCSLength() {
120        return lcsLength;
121    }
122
123    /**
124     * Get the number of effective modifications. The number of effective
125     * modification is the number of {@link DeleteCommand delete} and
126     * {@link InsertCommand insert} commands in the script.
127     *
128     * @return number of effective modifications
129     */
130    public int getModifications() {
131        return modifications;
132    }
133
134}