    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 *      https://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.codec.language;
    018
    019import java.util.ArrayList;
    020import java.util.Arrays;
    021import java.util.Collections;
    022import java.util.HashMap;
    023import java.util.LinkedHashSet;
    024import java.util.List;
    025import java.util.Map;
    026import java.util.Scanner;
    027import java.util.Set;
    028
    029import org.apache.commons.codec.CharEncoding;
    030import org.apache.commons.codec.EncoderException;
    031import org.apache.commons.codec.Resources;
    032import org.apache.commons.codec.StringEncoder;
    033
    034/**
    035 * Encodes a string into a Daitch-Mokotoff Soundex value.
    036 * <p>
    037 * The Daitch-Mokotoff Soundex algorithm is a refinement of the Russel and American Soundex algorithms, yielding greater
    038 * accuracy in matching especially Slavish and Yiddish surnames with similar pronunciation but differences in spelling.
    039 * </p>
    040 * <p>
    041 * The main differences compared to the other soundex variants are:
    042 * </p>
    043 * <ul>
    044 * <li>coded names are 6 digits long
    045 * <li>the initial character of the name is coded
    046 * <li>rules to encoded multi-character n-grams
    047 * <li>multiple possible encodings for the same name (branching)
    048 * </ul>
    049 * <p>
    050 * This implementation supports branching, depending on the used method:
    051 * <ul>
    052 * <li>{@link #encode(String)} - branching disabled, only the first code will be returned
    053 * <li>{@link #soundex(String)} - branching enabled, all codes will be returned, separated by '|'
    054 * </ul>
    055 * <p>
    056 * Note: This implementation has additional branching rules compared to the original description of the algorithm. The
    057 * rules can be customized by overriding the default rules contained in the resource file
    058 * {@code org/apache/commons/codec/language/dmrules.txt}.
    059 * </p>
    060 * <p>
    061 * This class is thread-safe.
    062 * </p>
    063 *
    064 * @see Soundex
    065 * @see <a href="https://en.wikipedia.org/wiki/Daitch%E2%80%93Mokotoff_Soundex"> Wikipedia - Daitch-Mokotoff Soundex</a>
    066 * @see <a href="http://www.avotaynu.com/soundex.htm">Avotaynu - Soundexing and Genealogy</a>
    067 * @since 1.10
    068 */
    069public class DaitchMokotoffSoundex implements StringEncoder {
    070
    071    /**
    072     * Inner class representing a branch during DM soundex encoding.
    073     */
    074    private static final class Branch {
    075        private final StringBuilder builder;
    076        private String cachedString;
    077        private String lastReplacement;
    078
    079        private Branch() {
    080            builder = new StringBuilder();
    081            lastReplacement = null;
    082            cachedString = null;
    083        }
    084
    085        /**
    086         * Creates a new branch, identical to this branch.
    087         *
    088         * @return a new, identical branch
    089         */
    090        public Branch createBranch() {
    091            final Branch branch = new Branch();
    092            branch.builder.append(toString());
    093            branch.lastReplacement = this.lastReplacement;
    094            return branch;
    095        }
    096
    097        @Override
    098        public boolean equals(final Object other) {
    099            if (this == other) {
    100                return true;
    101            }
    102            if (!(other instanceof Branch)) {
    103                return false;
    104            }
    105
    106            return toString().equals(((Branch) other).toString());
    107        }
    108
    109        /**
    110         * Finish this branch by appending '0's until the maximum code length has been reached.
    111         */
    112        public void finish() {
    113            while (builder.length() < MAX_LENGTH) {
    114                builder.append('0');
    115                cachedString = null;
    116            }
    117        }
    118
    119        @Override
    120        public int hashCode() {
    121            return toString().hashCode();
    122        }
    123
    124        /**
    125         * Process the next replacement to be added to this branch.
    126         *
    127         * @param replacement
    128         *            the next replacement to append
    129         * @param forceAppend
    130         *            indicates if the default processing shall be overridden
    131         */
    132        public void processNextReplacement(final String replacement, final boolean forceAppend) {
    133            final boolean append = lastReplacement == null || !lastReplacement.endsWith(replacement) || forceAppend;
    134
    135            if (append && builder.length() < MAX_LENGTH) {
    136                builder.append(replacement);
    137                // remove all characters after the maximum length
    138                if (builder.length() > MAX_LENGTH) {
    139                    builder.delete(MAX_LENGTH, builder.length());
    140                }
    141                cachedString = null;
    142            }
    143
    144            lastReplacement = replacement;
    145        }
    146
    147        @Override
    148        public String toString() {
    149            if (cachedString == null) {
    150                cachedString = builder.toString();
    151            }
    152            return cachedString;
    153        }
    154    }
    155
    156    /**
    157     * Inner class for storing rules.
    158     */
    159    private static final class Rule {
    160        private final String pattern;
    161        private final String[] replacementAtStart;
    162        private final String[] replacementBeforeVowel;
    163        private final String[] replacementDefault;
    164
    165        protected Rule(final String pattern, final String replacementAtStart, final String replacementBeforeVowel,
    166                final String replacementDefault) {
    167            this.pattern = pattern;
    168            this.replacementAtStart = replacementAtStart.split("\\|");
    169            this.replacementBeforeVowel = replacementBeforeVowel.split("\\|");
    170            this.replacementDefault = replacementDefault.split("\\|");
    171        }
    172
    173        public int getPatternLength() {
    174            return pattern.length();
    175        }
    176
    177        public String[] getReplacements(final String context, final boolean atStart) {
    178            if (atStart) {
    179                return replacementAtStart;
    180            }
    181
    182            final int nextIndex = getPatternLength();
    183            final boolean nextCharIsVowel = nextIndex < context.length() && isVowel(context.charAt(nextIndex));
    184            if (nextCharIsVowel) {
    185                return replacementBeforeVowel;
    186            }
    187
    188            return replacementDefault;
    189        }
    190
    191        private boolean isVowel(final char ch) {
    192            return ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u';
    193        }
    194
    195        public boolean matches(final String context) {
    196            return context.startsWith(pattern);
    197        }
    198
    199        @Override
    200        public String toString() {
    201            return String.format("%s=(%s,%s,%s)", pattern, Arrays.asList(replacementAtStart),
    202                    Arrays.asList(replacementBeforeVowel), Arrays.asList(replacementDefault));
    203        }
    204    }
    205
    206    private static final String COMMENT = "//";
    207
    208    private static final String DOUBLE_QUOTE = "\"";
    209
    210    private static final String MULTILINE_COMMENT_END = "*/";
    211
    212    private static final String MULTILINE_COMMENT_START = "/*";
    213
    214    /** The resource file containing the replacement and folding rules */
    215    private static final String RESOURCE_FILE = "/org/apache/commons/codec/language/dmrules.txt";
    216
    217    /** The code length of a DM soundex value. */
    218    private static final int MAX_LENGTH = 6;
    219
    220    /** Transformation rules indexed by the first character of their pattern. */
    221    private static final Map<Character, List<Rule>> RULES = new HashMap<>();
    222
    223    /** Folding rules. */
    224    private static final Map<Character, Character> FOLDINGS = new HashMap<>();
    225
    226    static {
    227        try (Scanner scanner = new Scanner(Resources.getInputStream(RESOURCE_FILE), CharEncoding.UTF_8)) {
    228            parseRules(scanner, RESOURCE_FILE, RULES, FOLDINGS);
    229        }
    230
    231        // sort RULES by pattern length in descending order
    232        RULES.forEach((k, v) -> v.sort((rule1, rule2) -> rule2.getPatternLength() - rule1.getPatternLength()));
    233    }
    234
    235    private static void parseRules(final Scanner scanner, final String location,
    236            final Map<Character, List<Rule>> ruleMapping, final Map<Character, Character> asciiFoldings) {
    237        int currentLine = 0;
    238        boolean inMultilineComment = false;
    239
    240        while (scanner.hasNextLine()) {
    241            currentLine++;
    242            final String rawLine = scanner.nextLine();
    243            String line = rawLine;
    244
    245            if (inMultilineComment) {
    246                if (line.endsWith(MULTILINE_COMMENT_END)) {
    247                    inMultilineComment = false;
    248                }
    249                continue;
    250            }
    251
    252            if (line.startsWith(MULTILINE_COMMENT_START)) {
    253                inMultilineComment = true;
    254            } else {
    255                // discard comments
    256                final int cmtI = line.indexOf(COMMENT);
    257                if (cmtI >= 0) {
    258                    line = line.substring(0, cmtI);
    259                }
    260
    261                // trim leading-trailing whitespace
    262                line = line.trim();
    263
    264                if (line.isEmpty()) {
    265                    continue; // empty lines can be safely skipped
    266                }
    267
    268                if (line.contains("=")) {
    269                    // folding
    270                    final String[] parts = line.split("=");
    271                    if (parts.length != 2) {
    272                        throw new IllegalArgumentException("Malformed folding statement split into " + parts.length +
    273                                " parts: " + rawLine + " in " + location);
    274                    }
    275                    final String leftCharacter = parts[0];
    276                    final String rightCharacter = parts[1];
    277
    278                    if (leftCharacter.length() != 1 || rightCharacter.length() != 1) {
    279                        throw new IllegalArgumentException("Malformed folding statement - " +
    280                                "patterns are not single characters: " + rawLine + " in " + location);
    281                    }
    282
    283                    asciiFoldings.put(leftCharacter.charAt(0), rightCharacter.charAt(0));
    284                } else {
    285                    // rule
    286                    final String[] parts = line.split("\\s+");
    287                    if (parts.length != 4) {
    288                        throw new IllegalArgumentException("Malformed rule statement split into " + parts.length +
    289                                " parts: " + rawLine + " in " + location);
    290                    }
    291                    try {
    292                        final String pattern = stripQuotes(parts[0]);
    293                        final String replacement1 = stripQuotes(parts[1]);
    294                        final String replacement2 = stripQuotes(parts[2]);
    295                        final String replacement3 = stripQuotes(parts[3]);
    296
    297                        final Rule r = new Rule(pattern, replacement1, replacement2, replacement3);
    298                        final char patternKey = r.pattern.charAt(0);
    299                        final List<Rule> rules = ruleMapping.computeIfAbsent(patternKey, k -> new ArrayList<>());
    300                        rules.add(r);
    301                    } catch (final IllegalArgumentException e) {
    302                        throw new IllegalStateException(
    303                                "Problem parsing line '" + currentLine + "' in " + location, e);
    304                    }
    305                }
    306            }
    307        }
    308    }
    309
    310    private static String stripQuotes(String str) {
    311        if (str.startsWith(DOUBLE_QUOTE)) {
    312            str = str.substring(1);
    313        }
    314
    315        if (str.endsWith(DOUBLE_QUOTE)) {
    316            str = str.substring(0, str.length() - 1);
    317        }
    318
    319        return str;
    320    }
    321
    322    /** Whether to use ASCII folding prior to encoding. */
    323    private final boolean folding;
    324
    325    /**
    326     * Creates a new instance with ASCII-folding enabled.
    327     */
    328    public DaitchMokotoffSoundex() {
    329        this(true);
    330    }
    331
    332    /**
    333     * Creates a new instance.
    334     * <p>
    335     * With ASCII-folding enabled, certain accented characters will be transformed to equivalent ASCII characters, e.g.
    336     * è -&gt; e.
    337     * </p>
    338     *
    339     * @param folding
    340     *            if ASCII-folding shall be performed before encoding
    341     */
    342    public DaitchMokotoffSoundex(final boolean folding) {
    343        this.folding = folding;
    344    }
    345
    346    /**
    347     * Performs a cleanup of the input string before the actual soundex transformation.
    348     * <p>
    349     * Removes all whitespace characters and performs ASCII folding if enabled.
    350     * </p>
    351     *
    352     * @param input
    353     *            the input string to clean up
    354     * @return a cleaned up string
    355     */
    356    private String cleanup(final String input) {
    357        final StringBuilder sb = new StringBuilder();
    358        for (char ch : input.toCharArray()) {
    359            if (Character.isWhitespace(ch)) {
    360                continue;
    361            }
    362
    363            ch = Character.toLowerCase(ch);
    364            final Character character = FOLDINGS.get(ch);
    365            if (folding && character != null) {
    366                ch = character;
    367            }
    368            sb.append(ch);
    369        }
    370        return sb.toString();
    371    }
    372
    373    /**
    374     * Encodes an Object using the Daitch-Mokotoff soundex algorithm without branching.
    375     * <p>
    376     * This method is provided in order to satisfy the requirements of the Encoder interface, and will throw an
    377     * EncoderException if the supplied object is not of type {@link String}.
    378     * </p>
    379     *
    380     * @see #soundex(String)
    381     * @param obj
    382     *            Object to encode
    383     * @return An object (of type {@link String}) containing the DM soundex code, which corresponds to the String
    384     *         supplied.
    385     * @throws EncoderException
    386     *             if the parameter supplied is not of type {@link String}
    387     * @throws IllegalArgumentException
    388     *             if a character is not mapped
    389     */
    390    @Override
    391    public Object encode(final Object obj) throws EncoderException {
    392        if (!(obj instanceof String)) {
    393            throw new EncoderException(
    394                    "Parameter supplied to DaitchMokotoffSoundex encode is not of type java.lang.String");
    395        }
    396        return encode((String) obj);
    397    }
    398
    399    /**
    400     * Encodes a String using the Daitch-Mokotoff soundex algorithm without branching.
    401     *
    402     * @see #soundex(String)
    403     * @param source
    404     *            A String object to encode
    405     * @return A DM Soundex code corresponding to the String supplied
    406     * @throws IllegalArgumentException
    407     *             if a character is not mapped
    408     */
    409    @Override
    410    public String encode(final String source) {
    411        if (source == null) {
    412            return null;
    413        }
    414        return soundex(source, false)[0];
    415    }
    416
    417    /**
    418     * Encodes a String using the Daitch-Mokotoff soundex algorithm with branching.
    419     * <p>
    420     * In case a string is encoded into multiple codes (see branching rules), the result will contain all codes,
    421     * separated by '|'.
    422     * </p>
    423     * <p>
    424     * Example: the name "AUERBACH" is encoded as both
    425     * </p>
    426     * <ul>
    427     * <li>097400</li>
    428     * <li>097500</li>
    429     * </ul>
    430     * <p>
    431     * Thus the result will be "097400|097500".
    432     * </p>
    433     *
    434     * @param source
    435     *            A String object to encode
    436     * @return A string containing a set of DM Soundex codes corresponding to the String supplied
    437     * @throws IllegalArgumentException
    438     *             if a character is not mapped
    439     */
    440    public String soundex(final String source) {
    441        return String.join("|", soundex(source, true));
    442    }
    443
    444    /**
    445     * Perform the actual DM Soundex algorithm on the input string.
    446     *
    447     * @param source
    448     *            A String object to encode
    449     * @param branching
    450     *            If branching shall be performed
    451     * @return A string array containing all DM Soundex codes corresponding to the String supplied depending on the
    452     *         selected branching mode
    453     */
    454    private String[] soundex(final String source, final boolean branching) {
    455        if (source == null) {
    456            return null;
    457        }
    458
    459        final String input = cleanup(source);
    460
    461        final Set<Branch> currentBranches = new LinkedHashSet<>();
    462        currentBranches.add(new Branch());
    463
    464        char lastChar = '\0';
    465        for (int index = 0; index < input.length(); index++) {
    466            final char ch = input.charAt(index);
    467
    468            // ignore whitespace inside a name
    469            if (Character.isWhitespace(ch)) {
    470                continue;
    471            }
    472
    473            final String inputContext = input.substring(index);
    474            final List<Rule> rules = RULES.get(ch);
    475            if (rules == null) {
    476                continue;
    477            }
    478
    479            // use an EMPTY_LIST to avoid false positive warnings wrt potential null pointer access
    480            final List<Branch> nextBranches = branching ? new ArrayList<>() : Collections.emptyList();
    481
    482            for (final Rule rule : rules) {
    483                if (rule.matches(inputContext)) {
    484                    if (branching) {
    485                        nextBranches.clear();
    486                    }
    487                    final String[] replacements = rule.getReplacements(inputContext, lastChar == '\0');
    488                    final boolean branchingRequired = replacements.length > 1 && branching;
    489
    490                    for (final Branch branch : currentBranches) {
    491                        for (final String nextReplacement : replacements) {
    492                            // if we have multiple replacements, always create a new branch
    493                            final Branch nextBranch = branchingRequired ? branch.createBranch() : branch;
    494
    495                            // special rule: occurrences of mn or nm are treated differently
    496                            final boolean force = lastChar == 'm' && ch == 'n' || lastChar == 'n' && ch == 'm';
    497
    498                            nextBranch.processNextReplacement(nextReplacement, force);
    499
    500                            if (!branching) {
    501                                break;
    502                            }
    503                            nextBranches.add(nextBranch);
    504                        }
    505                    }
    506
    507                    if (branching) {
    508                        currentBranches.clear();
    509                        currentBranches.addAll(nextBranches);
    510                    }
    511                    index += rule.getPatternLength() - 1;
    512                    break;
    513                }
    514            }
    515
    516            lastChar = ch;
    517        }
    518
    519        final String[] result = new String[currentBranches.size()];
    520        int index = 0;
    521        for (final Branch branch : currentBranches) {
    522            branch.finish();
    523            result[index++] = branch.toString();
    524        }
    525
    526        return result;
    527    }
    528}