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 */
017
018package org.apache.commons.codec.language;
019
020import org.apache.commons.codec.EncoderException;
021import org.apache.commons.codec.StringEncoder;
022
023/**
024 * Encodes a string into a Refined Soundex value. A refined Soundex code is
025 * optimized for spell checking words. Soundex method originally developed by
026 * <CITE>Margaret Odell</CITE> and <CITE>Robert Russell</CITE>.
027 *
028 * <p>
029 * This class is immutable and thread-safe.
030 * </p>
031 */
032public class RefinedSoundex implements StringEncoder {
033
034    /**
035     * Mapping:
036     * <pre>
037     * 0: A E I O U Y H W
038     * 1: B P
039     * 2: F V
040     * 3: C K S
041     * 4: G J
042     * 5: Q X Z
043     * 6: D T
044     * 7: L
045     * 8: M N
046     * 9: R
047     * </pre>
048     * @since 1.4
049     */
050    //                                                      ABCDEFGHIJKLMNOPQRSTUVWXYZ
051    public static final String US_ENGLISH_MAPPING_STRING = "01360240043788015936020505";
052
053   /**
054     * RefinedSoundex is *refined* for a number of reasons one being that the
055     * mappings have been altered. This implementation contains default
056     * mappings for US English.
057     */
058    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
059
060    /**
061     * This static variable contains an instance of the RefinedSoundex using
062     * the US_ENGLISH mapping.
063     */
064    public static final RefinedSoundex US_ENGLISH = new RefinedSoundex();
065
066    /**
067     * Every letter of the alphabet is "mapped" to a numerical value. This char
068     * array holds the values to which each letter is mapped. This
069     * implementation contains a default map for US_ENGLISH.
070     */
071    private final char[] soundexMapping;
072
073     /**
074     * Creates an instance of the RefinedSoundex object using the default US
075     * English mapping.
076     */
077    public RefinedSoundex() {
078        this.soundexMapping = US_ENGLISH_MAPPING;
079    }
080
081    /**
082     * Creates a refined Soundex instance using a custom mapping. This
083     * constructor can be used to customize the mapping, and/or possibly
084     * provide an internationalized mapping for a non-Western character set.
085     *
086     * @param mapping
087     *                  Mapping array to use when finding the corresponding code for
088     *                  a given character.
089     */
090    public RefinedSoundex(final char[] mapping) {
091        this.soundexMapping = mapping.clone();
092    }
093
094    /**
095     * Creates a refined Soundex instance using a custom mapping. This constructor can be used to customize the mapping,
096     * and/or possibly provide an internationalized mapping for a non-Western character set.
097     *
098     * @param mapping
099     *            Mapping string to use when finding the corresponding code for a given character.
100     * @since 1.4
101     */
102    public RefinedSoundex(final String mapping) {
103        this.soundexMapping = mapping.toCharArray();
104    }
105
106    /**
107     * Returns the number of characters in the two encoded Strings that are the
108     * same. This return value ranges from 0 to the length of the shortest
109     * encoded String: 0 indicates little or no similarity, and 4 out of 4 (for
110     * example) indicates strong similarity or identical values. For refined
111     * Soundex, the return value can be greater than 4.
112     *
113     * @param s1
114     *                  A String that will be encoded and compared.
115     * @param s2
116     *                  A String that will be encoded and compared.
117     * @return The number of characters in the two encoded Strings that are the
118     *             same from 0 to the length of the shortest encoded String.
119     *
120     * @see SoundexUtils#difference(StringEncoder,String,String)
121     * @see <a href="https://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
122     *          MS T-SQL DIFFERENCE</a>
123     *
124     * @throws EncoderException
125     *                  if an error occurs encoding one of the strings.
126     * @since 1.3
127     */
128    public int difference(final String s1, final String s2) throws EncoderException {
129        return SoundexUtils.difference(this, s1, s2);
130    }
131
132    /**
133     * Encodes an Object using the refined Soundex algorithm. This method is
134     * provided in order to satisfy the requirements of the Encoder interface,
135     * and will throw an EncoderException if the supplied object is not of type
136     * {@link String}.
137     *
138     * @param obj
139     *                  Object to encode.
140     * @return An object (or type {@link String}) containing the refined.
141     *             Soundex code which corresponds to the String supplied.
142     * @throws EncoderException
143     *                  if the parameter supplied is not of type {@link String}
144     */
145    @Override
146    public Object encode(final Object obj) throws EncoderException {
147        if (!(obj instanceof String)) {
148            throw new EncoderException("Parameter supplied to RefinedSoundex encode is not of type java.lang.String");
149        }
150        return soundex((String) obj);
151    }
152
153    /**
154     * Encodes a String using the refined Soundex algorithm.
155     *
156     * @param str
157     *                  A String object to encode.
158     * @return A Soundex code corresponding to the String supplied.
159     */
160    @Override
161    public String encode(final String str) {
162        return soundex(str);
163    }
164
165    /**
166     * Returns the mapping code for a given character. The mapping codes are
167     * maintained in an internal char array named soundexMapping, and the
168     * default values of these mappings are US English.
169     *
170     * @param c
171     *                  char to get mapping for.
172     * @return A character (really a numeral) to return for the given char.
173     */
174    char getMappingCode(final char c) {
175        if (!Character.isLetter(c)) {
176            return 0;
177        }
178        final int index = Character.toUpperCase(c) - 'A';
179        if (index < 0 || index >= this.soundexMapping.length) {
180            return 0;
181        }
182        return this.soundexMapping[index];
183    }
184
185    /**
186     * Retrieves the Refined Soundex code for a given String object.
187     *
188     * @param str
189     *                  String to encode using the Refined Soundex algorithm.
190     * @return A Soundex code for the String supplied.
191     */
192    public String soundex(String str) {
193        if (str == null) {
194            return null;
195        }
196        str = SoundexUtils.clean(str);
197        if (str.isEmpty()) {
198            return str;
199        }
200
201        final StringBuilder sBuf = new StringBuilder();
202        sBuf.append(str.charAt(0));
203
204        char last, current;
205        last = '*';
206
207        for (int i = 0; i < str.length(); i++) {
208
209            current = getMappingCode(str.charAt(i));
210            if (current == last) {
211                continue;
212            }
213            if (current != 0) {
214                sBuf.append(current);
215            }
216
217            last = current;
218
219        }
220
221        return sBuf.toString();
222    }
223}