/*
    * 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 java.util.Locale;
  
  import org.apache.commons.codec.EncoderException;
  import org.apache.commons.codec.StringEncoder;
  
  /**
   * Encodes a string into a Cologne Phonetic value.
   * <p>
   * Implements the <a href="http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik">K&ouml;lner Phonetik</a>
   * (Cologne Phonetic) algorithm issued by Hans Joachim Postel in 1969.
   * <p>
   * The <i>K&ouml;lner Phonetik</i> is a phonetic algorithm which is optimized for the German language.
   * It is related to the well-known soundex algorithm.
   * <p>
   *
   * <h2>Algorithm</h2>
   *
   * <ul>
   *
   * <li>
   * <h3>Step 1:</h3>
   * After preprocessing (conversion to upper case, transcription of <a
   * href="http://en.wikipedia.org/wiki/Germanic_umlaut">germanic umlauts</a>, removal of non alphabetical characters) the
   * letters of the supplied text are replaced by their phonetic code according to the following table.
   * <table border="1">
   * <tbody>
   * <tr>
   * <th>Letter</th>
   * <th>Context</th>
   * <th align="center">Code</th>
   * </tr>
   * <tr>
   * <td>A, E, I, J, O, U, Y</td>
   * <td></td>
   * <td align="center">0</td>
   * </tr>
   * <tr>
   *
   * <td>H</td>
   * <td></td>
   * <td align="center">-</td>
   * </tr>
   * <tr>
   * <td>B</td>
   * <td></td>
   * <td rowspan="2" align="center">1</td>
   * </tr>
   * <tr>
   * <td>P</td>
   * <td>not before H</td>
   *
   * </tr>
   * <tr>
   * <td>D, T</td>
   * <td>not before C, S, Z</td>
   * <td align="center">2</td>
   * </tr>
   * <tr>
   * <td>F, V, W</td>
   * <td></td>
   * <td rowspan="2" align="center">3</td>
   * </tr>
   * <tr>
   *
   * <td>P</td>
   * <td>before H</td>
   * </tr>
   * <tr>
   * <td>G, K, Q</td>
   * <td></td>
   * <td rowspan="3" align="center">4</td>
   * </tr>
   * <tr>
   * <td rowspan="2">C</td>
   * <td>at onset before A, H, K, L, O, Q, R, U, X</td>
   *
   * </tr>
   * <tr>
   * <td>before A, H, K, O, Q, U, X except after S, Z</td>
   * </tr>
  * <tr>
  * <td>X</td>
  * <td>not after C, K, Q</td>
  * <td align="center">48</td>
  * </tr>
  * <tr>
  * <td>L</td>
  * <td></td>
  *
  * <td align="center">5</td>
  * </tr>
  * <tr>
  * <td>M, N</td>
  * <td></td>
  * <td align="center">6</td>
  * </tr>
  * <tr>
  * <td>R</td>
  * <td></td>
  * <td align="center">7</td>
  * </tr>
  *
  * <tr>
  * <td>S, Z</td>
  * <td></td>
  * <td rowspan="6" align="center">8</td>
  * </tr>
  * <tr>
  * <td rowspan="3">C</td>
  * <td>after S, Z</td>
  * </tr>
  * <tr>
  * <td>at onset except before A, H, K, L, O, Q, R, U, X</td>
  * </tr>
  *
  * <tr>
  * <td>not before A, H, K, O, Q, U, X</td>
  * </tr>
  * <tr>
  * <td>D, T</td>
  * <td>before C, S, Z</td>
  * </tr>
  * <tr>
  * <td>X</td>
  * <td>after C, K, Q</td>
  * </tr>
  * </tbody>
  * </table>
  * <p>
  * <small><i>(Source: <a href= "http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik#Buchstabencodes" >Wikipedia (de):
  * K&ouml;lner Phonetik -- Buchstabencodes</a>)</i></small>
  * </p>
  *
  * <h4>Example:</h4>
  *
  * {@code "M}&uuml;{@code ller-L}&uuml;{@code denscheidt" => "MULLERLUDENSCHEIDT" => "6005507500206880022"}
  *
  * </li>
  *
  * <li>
  * <h3>Step 2:</h3>
  * Collapse of all multiple consecutive code digits.
  * <h4>Example:</h4>
  * {@code "6005507500206880022" => "6050750206802"}</li>
  *
  * <li>
  * <h3>Step 3:</h3>
  * Removal of all codes "0" except at the beginning. This means that two or more identical consecutive digits can occur
  * if they occur after removing the "0" digits.
  *
  * <h4>Example:</h4>
  * {@code "6050750206802" => "65752682"}</li>
  *
  * </ul>
  *
  * This class is thread-safe.
  *
  * @see <a href="http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik">Wikipedia (de): K&ouml;lner Phonetik (in German)</a>
  * @since 1.5
  */
 public class ColognePhonetic implements StringEncoder {
 
     // Predefined char arrays for better performance and less GC load
     private static final char[] AEIJOUY = new char[] { 'A', 'E', 'I', 'J', 'O', 'U', 'Y' };
     private static final char[] SCZ = new char[] { 'S', 'C', 'Z' };
     private static final char[] WFPV = new char[] { 'W', 'F', 'P', 'V' };
     private static final char[] GKQ = new char[] { 'G', 'K', 'Q' };
     private static final char[] CKQ = new char[] { 'C', 'K', 'Q' };
     private static final char[] AHKLOQRUX = new char[] { 'A', 'H', 'K', 'L', 'O', 'Q', 'R', 'U', 'X' };
     private static final char[] SZ = new char[] { 'S', 'Z' };
     private static final char[] AHOUKQX = new char[] { 'A', 'H', 'O', 'U', 'K', 'Q', 'X' };
     private static final char[] TDX = new char[] { 'T', 'D', 'X' };
 
     /**
      * This class is not thread-safe; the field {@link #length} is mutable.
      * However, it is not shared between threads, as it is constructed on demand
      * by the method {@link ColognePhonetic#colognePhonetic(String)}
      */
     private abstract class CologneBuffer {
 
         protected final char[] data;
 
         protected int length = 0;
 
         public CologneBuffer(final char[] data) {
             this.data = data;
             this.length = data.length;
         }
 
         public CologneBuffer(final int buffSize) {
             this.data = new char[buffSize];
             this.length = 0;
         }
 
         protected abstract char[] copyData(int start, final int length);
 
         public int length() {
             return length;
         }
 
         @Override
         public String toString() {
             return new String(copyData(0, length));
         }
     }
 
     private class CologneOutputBuffer extends CologneBuffer {
 
         public CologneOutputBuffer(final int buffSize) {
             super(buffSize);
         }
 
         public void addRight(final char chr) {
             data[length] = chr;
             length++;
         }
 
         @Override
         protected char[] copyData(final int start, final int length) {
             final char[] newData = new char[length];
             System.arraycopy(data, start, newData, 0, length);
             return newData;
         }
     }
 
     private class CologneInputBuffer extends CologneBuffer {
 
         public CologneInputBuffer(final char[] data) {
             super(data);
         }
 
         public void addLeft(final char ch) {
             length++;
             data[getNextPos()] = ch;
         }
 
         @Override
         protected char[] copyData(final int start, final int length) {
             final char[] newData = new char[length];
             System.arraycopy(data, data.length - this.length + start, newData, 0, length);
             return newData;
         }
 
         public char getNextChar() {
             return data[getNextPos()];
         }
 
         protected int getNextPos() {
             return data.length - length;
         }
 
         public char removeNext() {
             final char ch = getNextChar();
             length--;
             return ch;
         }
     }
 
     /**
      * Maps some Germanic characters to plain for internal processing. The following characters are mapped:
      * <ul>
      * <li>capital a, umlaut mark</li>
      * <li>capital u, umlaut mark</li>
      * <li>capital o, umlaut mark</li>
      * <li>small sharp s, German</li>
      * </ul>
      */
     private static final char[][] PREPROCESS_MAP = new char[][]{
         {'\u00C4', 'A'}, // capital a, umlaut mark
         {'\u00DC', 'U'}, // capital u, umlaut mark
         {'\u00D6', 'O'}, // capital o, umlaut mark
         {'\u00DF', 'S'} // small sharp s, German
     };
 
     /*
      * Returns whether the array contains the key, or not.
      */
     private static boolean arrayContains(final char[] arr, final char key) {
         for (final char element : arr) {
             if (element == key) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * <p>
      * Implements the <i>K&ouml;lner Phonetik</i> algorithm.
      * </p>
      * <p>
      * In contrast to the initial description of the algorithm, this implementation does the encoding in one pass.
      * </p>
      *
      * @param text
      * @return the corresponding encoding according to the <i>K&ouml;lner Phonetik</i> algorithm
      */
     public String colognePhonetic(String text) {
         if (text == null) {
             return null;
         }
 
         text = preprocess(text);
 
         final CologneOutputBuffer output = new CologneOutputBuffer(text.length() * 2);
         final CologneInputBuffer input = new CologneInputBuffer(text.toCharArray());
 
         char nextChar;
 
         char lastChar = '-';
         char lastCode = '/';
         char code;
         char chr;
 
         int rightLength = input.length();
 
         while (rightLength > 0) {
             chr = input.removeNext();
 
             if ((rightLength = input.length()) > 0) {
                 nextChar = input.getNextChar();
             } else {
                 nextChar = '-';
             }
 
             if (arrayContains(AEIJOUY, chr)) {
                 code = '0';
             } else if (chr == 'H' || chr < 'A' || chr > 'Z') {
                 if (lastCode == '/') {
                     continue;
                 }
                 code = '-';
             } else if (chr == 'B' || (chr == 'P' && nextChar != 'H')) {
                 code = '1';
             } else if ((chr == 'D' || chr == 'T') && !arrayContains(SCZ, nextChar)) {
                 code = '2';
             } else if (arrayContains(WFPV, chr)) {
                 code = '3';
             } else if (arrayContains(GKQ, chr)) {
                 code = '4';
             } else if (chr == 'X' && !arrayContains(CKQ, lastChar)) {
                 code = '4';
                 input.addLeft('S');
                 rightLength++;
             } else if (chr == 'S' || chr == 'Z') {
                 code = '8';
             } else if (chr == 'C') {
                 if (lastCode == '/') {
                     if (arrayContains(AHKLOQRUX, nextChar)) {
                         code = '4';
                     } else {
                         code = '8';
                     }
                 } else {
                     if (arrayContains(SZ, lastChar) || !arrayContains(AHOUKQX, nextChar)) {
                         code = '8';
                     } else {
                         code = '4';
                     }
                 }
             } else if (arrayContains(TDX, chr)) {
                 code = '8';
             } else if (chr == 'R') {
                 code = '7';
             } else if (chr == 'L') {
                 code = '5';
             } else if (chr == 'M' || chr == 'N') {
                 code = '6';
             } else {
                 code = chr;
             }
 
             if (code != '-' && (lastCode != code && (code != '0' || lastCode == '/') || code < '0' || code > '8')) {
                 output.addRight(code);
             }
 
             lastChar = chr;
             lastCode = code;
         }
         return output.toString();
     }
 
     @Override
     public Object encode(final Object object) throws EncoderException {
         if (!(object instanceof String)) {
             throw new EncoderException("This method's parameter was expected to be of the type " +
                 String.class.getName() +
                 ". But actually it was of the type " +
                 object.getClass().getName() +
                 ".");
         }
         return encode((String) object);
     }
 
     @Override
     public String encode(final String text) {
         return colognePhonetic(text);
     }
 
     public boolean isEncodeEqual(final String text1, final String text2) {
         return colognePhonetic(text1).equals(colognePhonetic(text2));
     }
 
     /**
      * Converts the string to upper case and replaces germanic characters as defined in {@link #PREPROCESS_MAP}.
      */
     private String preprocess(String text) {
         text = text.toUpperCase(Locale.GERMAN);
 
         final char[] chrs = text.toCharArray();
 
         for (int index = 0; index < chrs.length; index++) {
             if (chrs[index] > 'Z') {
                 for (final char[] element : PREPROCESS_MAP) {
                     if (chrs[index] == element[0]) {
                         chrs[index] = element[1];
                         break;
                     }
                 }
             }
         }
         return new String(chrs);
     }
 }