content: /*
   * 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,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.commons.codec.language;
  
  import org.apache.commons.codec.EncoderException;
  import org.apache.commons.codec.StringEncoder;
  
  /**
   * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
   * general purpose scheme to find word with similar phonemes.
   * 
   * @author Apache Software Foundation
   * @version $Id: Soundex.java 1064454 2011-01-28 04:40:02Z ggregory $
   */
  public class Soundex implements StringEncoder {
  
      /**
       * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
       * means do not encode.
       * <p>
       * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
       * up the value for the constant values page.)
       * </p>
       * 
       * @see #US_ENGLISH_MAPPING
       */
      public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
  
      /**
       * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
       * means do not encode.
       * 
       * @see Soundex#Soundex(char[])
       */
      private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
  
      /**
       * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
       * 
       * @see #US_ENGLISH_MAPPING
       */
      public static final Soundex US_ENGLISH = new Soundex();
  
  
      /**
       * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
       * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
       * identical values.
       * 
       * @param s1
       *                  A String that will be encoded and compared.
       * @param s2
       *                  A String that will be encoded and compared.
       * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
       * 
       * @see SoundexUtils#difference(StringEncoder,String,String)
       * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
       *          T-SQL DIFFERENCE </a>
       * 
       * @throws EncoderException
       *                  if an error occurs encoding one of the strings
       * @since 1.3
       */
      public int difference(String s1, String s2) throws EncoderException {
          return SoundexUtils.difference(this, s1, s2);
      }
  
      /**
       * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
       * 
       * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
       */
      private int maxLength = 4;
  
      /**
       * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
       * letter is mapped. This implementation contains a default map for US_ENGLISH
       */
      private final char[] soundexMapping;
  
      /**
       * Creates an instance using US_ENGLISH_MAPPING
       * 
       * @see Soundex#Soundex(char[])
       * @see Soundex#US_ENGLISH_MAPPING
       */
      public Soundex() {
          this.soundexMapping = US_ENGLISH_MAPPING;
      }
  
      /**
       * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
       * mapping for a non-Western character set.
       * 
       * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
       * letter is mapped. This implementation contains a default map for US_ENGLISH
       * 
       * @param mapping
       *                  Mapping array to use when finding the corresponding code for a given character
       */
      public Soundex(char[] mapping) {
          this.soundexMapping = new char[mapping.length];
          System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
      }
  
      /**
       * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
       * and/or possibly provide an internationalized mapping for a non-Western character set.
       * 
       * @param mapping
       *            Mapping string to use when finding the corresponding code for a given character
       * @since 1.4
       */
      public Soundex(String mapping) {
          this.soundexMapping = mapping.toCharArray();
      }
  
      /**
       * Encodes an Object using the soundex 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 pObject
       *                  Object to encode
       * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
       *             supplied.
       * @throws EncoderException
       *                  if the parameter supplied is not of type java.lang.String
       * @throws IllegalArgumentException
       *                  if a character is not mapped
       */
      public Object encode(Object pObject) throws EncoderException {
          if (!(pObject instanceof String)) {
              throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
          }
          return soundex((String) pObject);
      }
  
      /**
       * Encodes a String using the soundex algorithm.
       * 
       * @param pString
       *                  A String object to encode
       * @return A Soundex code corresponding to the String supplied
       * @throws IllegalArgumentException
       *                  if a character is not mapped
       */
      public String encode(String pString) {
          return soundex(pString);
      }
  
      /**
       * Used internally by the SoundEx algorithm.
       * 
       * Consonants from the same code group separated by W or H are treated as one.
       * 
       * @param str
       *                  the cleaned working string to encode (in upper case).
       * @param index
       *                  the character position to encode
       * @return Mapping code for a particular character
       * @throws IllegalArgumentException
       *                  if the character is not mapped
       */
      private char getMappingCode(String str, int index) {
          // map() throws IllegalArgumentException
          char mappedChar = this.map(str.charAt(index));
          // HW rule check
          if (index > 1 && mappedChar != '0') {
              char hwChar = str.charAt(index - 1);
              if ('H' == hwChar || 'W' == hwChar) {
                  char preHWChar = str.charAt(index - 2);
                  char firstCode = this.map(preHWChar);
                  if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
                      return 0;
                  }
              }
          }
          return mappedChar;
      }
  
      /**
       * Returns the maxLength. Standard Soundex
       * 
       * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
       * @return int
       */
      public int getMaxLength() {
          return this.maxLength;
      }
  
      /**
       * Returns the soundex mapping.
       * 
       * @return soundexMapping.
       */
      private char[] getSoundexMapping() {
          return this.soundexMapping;
      }
  
      /**
       * Maps the given upper-case character to its Soundex code.
       * 
       * @param ch
       *                  An upper-case character.
       * @return A Soundex code.
       * @throws IllegalArgumentException
       *                  Thrown if <code>ch</code> is not mapped.
       */
      private char map(char ch) {
          int index = ch - 'A';
          if (index < 0 || index >= this.getSoundexMapping().length) {
              throw new IllegalArgumentException("The character is not mapped: " + ch);
          }
          return this.getSoundexMapping()[index];
      }
  
      /**
       * Sets the maxLength.
       * 
       * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
       * @param maxLength
       *                  The maxLength to set
       */
      public void setMaxLength(int maxLength) {
          this.maxLength = maxLength;
      }
  
      /**
       * Retrieves the Soundex code for a given String object.
       * 
       * @param str
       *                  String to encode using the Soundex algorithm
       * @return A soundex code for the String supplied
       * @throws IllegalArgumentException
       *                  if a character is not mapped
       */
      public String soundex(String str) {
          if (str == null) {
              return null;
          }
          str = SoundexUtils.clean(str);
          if (str.length() == 0) {
              return str;
          }
          char out[] = {'0', '0', '0', '0'};
          char last, mapped;
          int incount = 1, count = 1;
          out[0] = str.charAt(0);
          // getMappingCode() throws IllegalArgumentException
          last = getMappingCode(str, 0);
          while ((incount < str.length()) && (count < out.length)) {
              mapped = getMappingCode(str, incount++);
              if (mapped != 0) {
                  if ((mapped != '0') && (mapped != last)) {
                      out[count++] = mapped;
                  }
                  last = mapped;
              }
          }
          return new String(out);
      }
  
  }
  