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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.commons.codec.language;

import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.StringEncoder;

/**
 * Encodes a string into a Metaphone value.
 * 

* Initial Java implementation by William B. Brogden. December, 1997. * Permission given by wbrogden for code to be used anywhere. *

* Hanging on the Metaphone by Lawrence Philips in Computer Language of Dec. 1990, * p 39. *

* Note, that this does not match the algorithm that ships with PHP, or the algorithm found in the Perl implementations: *

* *

* They have had undocumented changes from the originally published algorithm. * For more information, see CODEC-57. *

* This class is conditionally thread-safe. * The instance field {@link #maxCodeLen} is mutable {@link #setMaxCodeLen(int)} * but is not volatile, and accesses are not synchronized. * If an instance of the class is shared between threads, the caller needs to ensure that suitable synchronization * is used to ensure safe publication of the value between threads, and must not invoke {@link #setMaxCodeLen(int)} * after initial setup. * * @version $Id$ */ public class Metaphone implements StringEncoder { /** * Five values in the English language */ private static final String VOWELS = "AEIOU"; /** * Variable used in Metaphone algorithm */ private static final String FRONTV = "EIY"; /** * Variable used in Metaphone algorithm */ private static final String VARSON = "CSPTG"; /** * The max code length for metaphone is 4 */ private int maxCodeLen = 4; /** * Creates an instance of the Metaphone encoder */ public Metaphone() { super(); } /** * Find the metaphone value of a String. This is similar to the * soundex algorithm, but better at finding similar sounding words. * All input is converted to upper case. * Limitations: Input format is expected to be a single ASCII word * with only characters in the A - Z range, no punctuation or numbers. * * @param txt String to find the metaphone code for * @return A metaphone code corresponding to the String supplied */ public String metaphone(final String txt) { boolean hard = false; int txtLength; if (txt == null || (txtLength = txt.length()) == 0) { return ""; } // single character is itself if (txtLength == 1) { return txt.toUpperCase(java.util.Locale.ENGLISH); } final char[] inwd = txt.toUpperCase(java.util.Locale.ENGLISH).toCharArray(); final StringBuilder local = new StringBuilder(40); // manipulate final StringBuilder code = new StringBuilder(10); // output // handle initial 2 characters exceptions switch(inwd[0]) { case 'K': case 'G': case 'P': /* looking for KN, etc*/ if (inwd[1] == 'N') { local.append(inwd, 1, inwd.length - 1); } else { local.append(inwd); } break; case 'A': /* looking for AE */ if (inwd[1] == 'E') { local.append(inwd, 1, inwd.length - 1); } else { local.append(inwd); } break; case 'W': /* looking for WR or WH */ if (inwd[1] == 'R') { // WR -> R local.append(inwd, 1, inwd.length - 1); break; } if (inwd[1] == 'H') { local.append(inwd, 1, inwd.length - 1); local.setCharAt(0, 'W'); // WH -> W } else { local.append(inwd); } break; case 'X': /* initial X becomes S */ inwd[0] = 'S'; local.append(inwd); break; default: local.append(inwd); } // now local has working string with initials fixed final int wdsz = local.length(); int n = 0; while (code.length() < this.getMaxCodeLen() && n < wdsz ) { // max code size of 4 works well final char symb = local.charAt(n); // remove duplicate letters except C if (symb != 'C' && isPreviousChar( local, n, symb ) ) { n++; } else { // not dup switch(symb) { case 'A': case 'E': case 'I': case 'O': case 'U': if (n == 0) { code.append(symb); } break; // only use vowel if leading char case 'B': if ( isPreviousChar(local, n, 'M') && isLastChar(wdsz, n) ) { // B is silent if word ends in MB break; } code.append(symb); break; case 'C': // lots of C special cases /* discard if SCI, SCE or SCY */ if ( isPreviousChar(local, n, 'S') && !isLastChar(wdsz, n) && FRONTV.indexOf(local.charAt(n + 1)) >= 0 ) { break; } if (regionMatch(local, n, "CIA")) { // "CIA" -> X code.append('X'); break; } if (!isLastChar(wdsz, n) && FRONTV.indexOf(local.charAt(n + 1)) >= 0) { code.append('S'); break; // CI,CE,CY -> S } if (isPreviousChar(local, n, 'S') && isNextChar(local, n, 'H') ) { // SCH->sk code.append('K'); break; } if (isNextChar(local, n, 'H')) { // detect CH if (n == 0 && wdsz >= 3 && isVowel(local,2) ) { // CH consonant -> K consonant code.append('K'); } else { code.append('X'); // CHvowel -> X } } else { code.append('K'); } break; case 'D': if (!isLastChar(wdsz, n + 1) && isNextChar(local, n, 'G') && FRONTV.indexOf(local.charAt(n + 2)) >= 0) { // DGE DGI DGY -> J code.append('J'); n += 2; } else { code.append('T'); } break; case 'G': // GH silent at end or before consonant if (isLastChar(wdsz, n + 1) && isNextChar(local, n, 'H')) { break; } if (!isLastChar(wdsz, n + 1) && isNextChar(local,n,'H') && !isVowel(local,n+2)) { break; } if (n > 0 && ( regionMatch(local, n, "GN") || regionMatch(local, n, "GNED") ) ) { break; // silent G } if (isPreviousChar(local, n, 'G')) { // NOTE: Given that duplicated chars are removed, I don't see how this can ever be true hard = true; } else { hard = false; } if (!isLastChar(wdsz, n) && FRONTV.indexOf(local.charAt(n + 1)) >= 0 && !hard) { code.append('J'); } else { code.append('K'); } break; case 'H': if (isLastChar(wdsz, n)) { break; // terminal H } if (n > 0 && VARSON.indexOf(local.charAt(n - 1)) >= 0) { break; } if (isVowel(local,n+1)) { code.append('H'); // Hvowel } break; case 'F': case 'J': case 'L': case 'M': case 'N': case 'R': code.append(symb); break; case 'K': if (n > 0) { // not initial if (!isPreviousChar(local, n, 'C')) { code.append(symb); } } else { code.append(symb); // initial K } break; case 'P': if (isNextChar(local,n,'H')) { // PH -> F code.append('F'); } else { code.append(symb); } break; case 'Q': code.append('K'); break; case 'S': if (regionMatch(local,n,"SH") || regionMatch(local,n,"SIO") || regionMatch(local,n,"SIA")) { code.append('X'); } else { code.append('S'); } break; case 'T': if (regionMatch(local,n,"TIA") || regionMatch(local,n,"TIO")) { code.append('X'); break; } if (regionMatch(local,n,"TCH")) { // Silent if in "TCH" break; } // substitute numeral 0 for TH (resembles theta after all) if (regionMatch(local,n,"TH")) { code.append('0'); } else { code.append('T'); } break; case 'V': code.append('F'); break; case 'W': case 'Y': // silent if not followed by vowel if (!isLastChar(wdsz,n) && isVowel(local,n+1)) { code.append(symb); } break; case 'X': code.append('K'); code.append('S'); break; case 'Z': code.append('S'); break; default: // do nothing break; } // end switch n++; } // end else from symb != 'C' if (code.length() > this.getMaxCodeLen()) { code.setLength(this.getMaxCodeLen()); } } return code.toString(); } private boolean isVowel(final StringBuilder string, final int index) { return VOWELS.indexOf(string.charAt(index)) >= 0; } private boolean isPreviousChar(final StringBuilder string, final int index, final char c) { boolean matches = false; if( index > 0 && index < string.length() ) { matches = string.charAt(index - 1) == c; } return matches; } private boolean isNextChar(final StringBuilder string, final int index, final char c) { boolean matches = false; if( index >= 0 && index < string.length() - 1 ) { matches = string.charAt(index + 1) == c; } return matches; } private boolean regionMatch(final StringBuilder string, final int index, final String test) { boolean matches = false; if( index >= 0 && index + test.length() - 1 < string.length() ) { final String substring = string.substring( index, index + test.length()); matches = substring.equals( test ); } return matches; } private boolean isLastChar(final int wdsz, final int n) { return n + 1 == wdsz; } /** * Encodes an Object using the metaphone algorithm. This method * is provided in order to satisfy the requirements of the * Encoder interface, and will throw an EncoderException if the * supplied object is not of type java.lang.String. * * @param obj Object to encode * @return An object (or type java.lang.String) containing the * metaphone code which corresponds to the String supplied. * @throws EncoderException if the parameter supplied is not * of type java.lang.String */ @Override public Object encode(final Object obj) throws EncoderException { if (!(obj instanceof String)) { throw new EncoderException("Parameter supplied to Metaphone encode is not of type java.lang.String"); } return metaphone((String) obj); } /** * Encodes a String using the Metaphone algorithm. * * @param str String object to encode * @return The metaphone code corresponding to the String supplied */ @Override public String encode(final String str) { return metaphone(str); } /** * Tests is the metaphones of two strings are identical. * * @param str1 First of two strings to compare * @param str2 Second of two strings to compare * @return true if the metaphones of these strings are identical, * false otherwise. */ public boolean isMetaphoneEqual(final String str1, final String str2) { return metaphone(str1).equals(metaphone(str2)); } /** * Returns the maxCodeLen. * @return int */ public int getMaxCodeLen() { return this.maxCodeLen; } /** * Sets the maxCodeLen. * @param maxCodeLen The maxCodeLen to set */ public void setMaxCodeLen(final int maxCodeLen) { this.maxCodeLen = maxCodeLen; } }





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