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