    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}