    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}