/*
    * 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.
   *
   * <p>This class is thread-safe.
   * Although not strictly immutable, the mutable fields are not actually used.</p>
   */
  public class Soundex implements StringEncoder {
  
      /**
       * The marker character used to indicate a silent (ignored) character.
       * These are ignored except when they appear as the first character.
       * <p>
       * Note: the {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism
       * because changing it might break existing code. Mappings that don't contain
       * a silent marker code are treated as though H and W are silent.
       * </p>
       * <p>
       * To override this, use the {@link #Soundex(String, boolean)} constructor.
       * </p>
       *
       * @since 1.11
       */
      public static final char SILENT_MARKER = '-';
  
      /**
       * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
       * means do not encode, but treat as a separator when it occurs between consonants with the same code.
       * <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>
       * <p>
       * <b>Note that letters H and W are treated specially.</b>
       * They are ignored (after the first letter) and don't act as separators
       * between consonants with the same code.
       * </p>
       */
      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} 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.
       * This treats H and W as silent letters.
       * Apart from when they appear as the first letter, they are ignored.
       * They don't act as separators between duplicate codes.
       *
       * @see #US_ENGLISH_MAPPING_STRING
       */
      public static final Soundex US_ENGLISH = new Soundex();
  
      /**
       * An instance of Soundex using the Simplified Soundex mapping, as described here:
       * http://west-penwith.org.uk/misc/soundex.htm
       * <p>
       * This treats H and W the same as vowels (AEIOUY).
       * Such letters aren't encoded (after the first), but they do
       * act as separators when dropping duplicate codes.
       * The mapping is otherwise the same as for {@link #US_ENGLISH}
       * </p>
       *
       * @since 1.11
       */
      public static final Soundex US_ENGLISH_SIMPLIFIED = new Soundex(US_ENGLISH_MAPPING_STRING, false);
  
      /**
       * An instance of Soundex using the mapping as per the Genealogy site:
       * http://www.genealogy.com/articles/research/00000060.html
       * <p>
       * This treats vowels (AEIOUY), H and W as silent letters.
      * Such letters are ignored (after the first) and do not
      * act as separators when dropping duplicate codes.
      * </p>
      * <p>
      * The codes for consonants are otherwise the same as for
      * {@link #US_ENGLISH_MAPPING_STRING} and {@link #US_ENGLISH_SIMPLIFIED}
      * </p>
      *
      * @since 1.11
      */
     public static final Soundex US_ENGLISH_GENEALOGY = new Soundex("-123-12--22455-12623-1-2-2");
     //                                                              ABCDEFGHIJKLMNOPQRSTUVWXYZ
 
     /**
      * 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.
      */
     @Deprecated
     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;
 
     /**
      * Should H and W be treated specially?
      * <p>
      * In versions of the code prior to 1.11,
      * the code always treated H and W as silent (ignored) letters.
      * If this field is false, H and W are no longer special-cased.
      * </p>
      */
     private final boolean specialCaseHW;
 
     /**
      * Creates an instance using US_ENGLISH_MAPPING
      *
      * @see Soundex#Soundex(char[])
      * @see Soundex#US_ENGLISH_MAPPING_STRING
      */
     public Soundex() {
         this.soundexMapping = US_ENGLISH_MAPPING;
         this.specialCaseHW = true;
     }
 
     /**
      * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
      * mapping for a non-Western character set.
      * <p>
      * 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
      * </p>
      * <p>
      * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
      * </p>
      *
      * @param mapping
      *                  Mapping array to use when finding the corresponding code for a given character
      */
     public Soundex(final char[] mapping) {
         this.soundexMapping = mapping.clone();
         this.specialCaseHW = !hasMarker(this.soundexMapping);
     }
 
     /**
      * 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.
      * <p>
      * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
      * </p>
      *
      * @param mapping
      *            Mapping string to use when finding the corresponding code for a given character
      * @since 1.4
      */
     public Soundex(final String mapping) {
         this.soundexMapping = mapping.toCharArray();
         this.specialCaseHW = !hasMarker(this.soundexMapping);
     }
 
     /**
      * 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
      * @param specialCaseHW if true, then
      * @since 1.11
      */
     public Soundex(final String mapping, final boolean specialCaseHW) {
         this.soundexMapping = mapping.toCharArray();
         this.specialCaseHW = specialCaseHW;
     }
 
     /**
      * 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="https://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(final String s1, final String s2) throws EncoderException {
         return SoundexUtils.difference(this, s1, s2);
     }
 
     /**
      * 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 {@link String}.
      *
      * @param obj
      *                  Object to encode
      * @return An object (or type {@link String}) containing the soundex code which corresponds to the String
      *             supplied.
      * @throws EncoderException
      *                  if the parameter supplied is not of type {@link String}
      * @throws IllegalArgumentException
      *                  if a character is not mapped
      */
     @Override
     public Object encode(final Object obj) throws EncoderException {
         if (!(obj instanceof String)) {
             throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
         }
         return soundex((String) obj);
     }
 
     /**
      * Encodes a String using the soundex algorithm.
      *
      * @param str
      *                  A String object to encode
      * @return A Soundex code corresponding to the String supplied
      * @throws IllegalArgumentException
      *                  if a character is not mapped
      */
     @Override
     public String encode(final String str) {
         return soundex(str);
     }
 
     /**
      * 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
      */
     @Deprecated
     public int getMaxLength() {
         return this.maxLength;
     }
 
     private boolean hasMarker(final char[] mapping) {
         for (final char ch : mapping) {
             if (ch == SILENT_MARKER) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * 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} is not mapped.
      */
     private char map(final char ch) {
         final int index = ch - 'A';
         if (index < 0 || index >= this.soundexMapping.length) {
             throw new IllegalArgumentException("The character is not mapped: " + ch + " (index=" + index + ")");
         }
         return this.soundexMapping[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
      */
     @Deprecated
     public void setMaxLength(final 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.isEmpty()) {
             return str;
         }
         final char[] out = { '0', '0', '0', '0' };
         int count = 0;
         final char first = str.charAt(0);
         out[count++] = first;
         char lastDigit = map(first); // previous digit
         for (int i = 1; i < str.length() && count < out.length; i++) {
             final char ch = str.charAt(i);
             if (this.specialCaseHW && (ch == 'H' || ch == 'W')) { // these are ignored completely
                 continue;
             }
             final char digit = map(ch);
             if (digit == SILENT_MARKER) {
                 continue;
             }
             if (digit != '0' && digit != lastDigit) { // don't store vowels or repeats
                 out[count++] = digit;
             }
             lastDigit = digit;
         }
         return new String(out);
     }
 
 }