/*
    * 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
    *
    *      https://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.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Scanner;
  import java.util.Set;
  import java.util.regex.Pattern;
  
  import org.apache.commons.codec.CharEncoding;
  import org.apache.commons.codec.EncoderException;
  import org.apache.commons.codec.Resources;
  import org.apache.commons.codec.StringEncoder;
  
  /**
   * Encodes a string into a Daitch-Mokotoff Soundex value.
   * <p>
   * The Daitch-Mokotoff Soundex algorithm is a refinement of the Russel and American Soundex algorithms, yielding greater
   * accuracy in matching especially Slavish and Yiddish surnames with similar pronunciation but differences in spelling.
   * </p>
   * <p>
   * The main differences compared to the other Soundex variants are:
   * </p>
   * <ul>
   * <li>coded names are 6 digits long
   * <li>the initial character of the name is coded
   * <li>rules to encoded multi-character n-grams
   * <li>multiple possible encodings for the same name (branching)
   * </ul>
   * <p>
   * This implementation supports branching, depending on the used method:
   * <ul>
   * <li>{@link #encode(String)} - branching disabled, only the first code will be returned
   * <li>{@link #soundex(String)} - branching enabled, all codes will be returned, separated by '|'
   * </ul>
   * <p>
   * Note: This implementation has additional branching rules compared to the original description of the algorithm. The
   * rules can be customized by overriding the default rules contained in the resource file
   * {@code org/apache/commons/codec/language/dmrules.txt}.
   * </p>
   * <p>
   * This class is thread-safe.
   * </p>
   *
   * @see Soundex
   * @see <a href="https://en.wikipedia.org/wiki/Daitch%E2%80%93Mokotoff_Soundex"> Wikipedia - Daitch-Mokotoff Soundex</a>
   * @see <a href="http://www.avotaynu.com/soundex.htm">Avotaynu - Soundexing and Genealogy</a>
   * @since 1.10
   */
  public class DaitchMokotoffSoundex implements StringEncoder {
  
      /**
       * Inner class representing a branch during DM Soundex encoding.
       */
      private static final class Branch {
          private final StringBuilder builder;
          private String cachedString;
          private String lastReplacement;
  
          private Branch() {
              builder = new StringBuilder();
          }
  
          /**
           * Creates a new branch, identical to this branch.
           *
           * @return a new, identical branch
           */
          private Branch createBranch() {
              final Branch branch = new Branch();
              branch.builder.append(toString());
              branch.lastReplacement = this.lastReplacement;
              return branch;
          }
  
          @Override
          public boolean equals(final Object other) {
              if (this == other) {
                  return true;
             }
             if (!(other instanceof Branch)) {
                 return false;
             }
             return toString().equals(((Branch) other).toString());
         }
 
         /**
          * Finish this branch by appending '0's until the maximum code length has been reached.
          */
         private void finish() {
             while (builder.length() < MAX_LENGTH) {
                 builder.append('0');
                 cachedString = null;
             }
         }
 
         @Override
         public int hashCode() {
             return toString().hashCode();
         }
 
         /**
          * Process the next replacement to be added to this branch.
          *
          * @param replacement
          *            the next replacement to append.
          * @param forceAppend
          *            indicates if the default processing shall be overridden.
          */
         private void processNextReplacement(final String replacement, final boolean forceAppend) {
             final boolean append = lastReplacement == null || !lastReplacement.endsWith(replacement) || forceAppend;
             if (append && builder.length() < MAX_LENGTH) {
                 builder.append(replacement);
                 // remove all characters after the maximum length
                 if (builder.length() > MAX_LENGTH) {
                     builder.delete(MAX_LENGTH, builder.length());
                 }
                 cachedString = null;
             }
             lastReplacement = replacement;
         }
 
         @Override
         public String toString() {
             if (cachedString == null) {
                 cachedString = builder.toString();
             }
             return cachedString;
         }
     }
 
     /**
      * Inner class for storing rules.
      */
     private static final class Rule {
         private static final Pattern PIPE = Pattern.compile("\\|");
         private final String pattern;
         private final String[] replacementAtStart;
         private final String[] replacementBeforeVowel;
         private final String[] replacementDefault;
 
         private Rule(final String pattern, final String replacementAtStart, final String replacementBeforeVowel,
                 final String replacementDefault) {
             this.pattern = pattern;
             this.replacementAtStart = PIPE.split(replacementAtStart);
             this.replacementBeforeVowel = PIPE.split(replacementBeforeVowel);
             this.replacementDefault = PIPE.split(replacementDefault);
         }
 
         private int getPatternLength() {
             return pattern.length();
         }
 
         private String[] getReplacements(final String context, final boolean atStart) {
             if (atStart) {
                 return replacementAtStart;
             }
 
             final int nextIndex = getPatternLength();
             final boolean nextCharIsVowel = nextIndex < context.length() && isVowel(context.charAt(nextIndex));
             if (nextCharIsVowel) {
                 return replacementBeforeVowel;
             }
 
             return replacementDefault;
         }
 
         private boolean isVowel(final char ch) {
             return ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u';
         }
 
         private boolean matches(final String context) {
             return context.startsWith(pattern);
         }
 
         @Override
         public String toString() {
             return String.format("%s=(%s,%s,%s)", pattern, Arrays.asList(replacementAtStart),
                     Arrays.asList(replacementBeforeVowel), Arrays.asList(replacementDefault));
         }
     }
 
     /**
      * The NUL character.
      */
     private static final char NUL = '\0';
 
     private static final String COMMENT = "//";
 
     private static final String DOUBLE_QUOTE = "\"";
 
     private static final String MULTILINE_COMMENT_END = "*/";
 
     private static final String MULTILINE_COMMENT_START = "/*";
 
     /** The resource file containing the replacement and folding rules */
     private static final String RESOURCE_FILE = "/org/apache/commons/codec/language/dmrules.txt";
 
     /** The code length of a DM Soundex value. */
     private static final int MAX_LENGTH = 6;
 
     /** Transformation rules indexed by the first character of their pattern. */
     private static final Map<Character, List<Rule>> RULES = new HashMap<>();
 
     /** Folding rules. */
     private static final Map<Character, Character> FOLDINGS = new HashMap<>();
 
     private static final Pattern EQUAL = Pattern.compile("=");
 
     private static final Pattern SPACES = Pattern.compile("\\s+");
 
     static {
         try (Scanner scanner = new Scanner(Resources.getInputStream(RESOURCE_FILE), CharEncoding.UTF_8)) {
             parseRules(scanner, RESOURCE_FILE, RULES, FOLDINGS);
         }
         // sort RULES by pattern length in descending order
         RULES.forEach((k, v) -> v.sort((rule1, rule2) -> rule2.getPatternLength() - rule1.getPatternLength()));
     }
 
     private static void parseRules(final Scanner scanner, final String location, final Map<Character, List<Rule>> ruleMapping,
             final Map<Character, Character> asciiFoldings) {
         int currentLine = 0;
         boolean inMultilineComment = false;
         while (scanner.hasNextLine()) {
             currentLine++;
             final String rawLine = scanner.nextLine();
             String line = rawLine;
             if (inMultilineComment) {
                 if (line.endsWith(MULTILINE_COMMENT_END)) {
                     inMultilineComment = false;
                 }
                 continue;
             }
             if (line.startsWith(MULTILINE_COMMENT_START)) {
                 inMultilineComment = true;
             } else {
                 // discard comments
                 final int cmtI = line.indexOf(COMMENT);
                 if (cmtI >= 0) {
                     line = line.substring(0, cmtI);
                 }
                 // trim leading-trailing whitespace
                 line = line.trim();
                 if (line.isEmpty()) {
                     continue; // empty lines can be safely skipped
                 }
                 if (line.contains("=")) {
                     // folding
                     final String[] parts = EQUAL.split(line);
                     if (parts.length != 2) {
                         throw new IllegalArgumentException("Malformed folding statement split into " + parts.length + " parts: " + rawLine + " in " + location);
                     }
                     final String leftCharacter = parts[0];
                     final String rightCharacter = parts[1];
                     if (leftCharacter.length() != 1 || rightCharacter.length() != 1) {
                         throw new IllegalArgumentException(
                                 "Malformed folding statement - " + "patterns are not single characters: " + rawLine + " in " + location);
                     }
                     asciiFoldings.put(leftCharacter.charAt(0), rightCharacter.charAt(0));
                 } else {
                     // rule
                     final String[] parts = SPACES.split(line);
                     if (parts.length != 4) {
                         throw new IllegalArgumentException("Malformed rule statement split into " + parts.length + " parts: " + rawLine + " in " + location);
                     }
                     try {
                         final String pattern = stripQuotes(parts[0]);
                         final String replacement1 = stripQuotes(parts[1]);
                         final String replacement2 = stripQuotes(parts[2]);
                         final String replacement3 = stripQuotes(parts[3]);
                         final Rule r = new Rule(pattern, replacement1, replacement2, replacement3);
                         final char patternKey = r.pattern.charAt(0);
                         final List<Rule> rules = ruleMapping.computeIfAbsent(patternKey, k -> new ArrayList<>());
                         rules.add(r);
                     } catch (final IllegalArgumentException e) {
                         throw new IllegalStateException("Problem parsing line '" + currentLine + "' in " + location, e);
                     }
                 }
             }
         }
     }
 
     private static String stripQuotes(String str) {
         if (str.startsWith(DOUBLE_QUOTE)) {
             str = str.substring(1);
         }
         if (str.endsWith(DOUBLE_QUOTE)) {
             str = str.substring(0, str.length() - 1);
         }
         return str;
     }
 
     /** Whether to use ASCII folding prior to encoding. */
     private final boolean folding;
 
     /**
      * Creates a new instance with ASCII-folding enabled.
      */
     public DaitchMokotoffSoundex() {
         this(true);
     }
 
     /**
      * Creates a new instance.
      * <p>
      * With ASCII-folding enabled, certain accented characters will be transformed to equivalent ASCII characters, for example
      * è -&gt; e.
      * </p>
      *
      * @param folding
      *            if ASCII-folding shall be performed before encoding
      */
     public DaitchMokotoffSoundex(final boolean folding) {
         this.folding = folding;
     }
 
     /**
      * Performs a cleanup of the input string before the actual Soundex transformation.
      * <p>
      * Removes all whitespace characters and performs ASCII folding if enabled.
      * </p>
      *
      * @param input
      *            the input string to clean up.
      * @return a cleaned up string.
      */
     private String cleanup(final String input) {
         final StringBuilder sb = new StringBuilder();
         for (char ch : input.toCharArray()) {
             if (Character.isWhitespace(ch) || !Character.isLetter(ch)) {
                 continue;
             }
             ch = Character.toLowerCase(ch);
             final Character character = FOLDINGS.get(ch);
             if (folding && character != null) {
                 ch = character;
             }
             sb.append(ch);
         }
         return sb.toString();
     }
 
     /**
      * Encodes an Object using the Daitch-Mokotoff Soundex algorithm without branching.
      * <p>
      * 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}.
      * </p>
      *
      * @see #soundex(String)
      * @param obj
      *            Object to encode.
      * @return An object (of type {@link String}) containing the DM 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 DaitchMokotoffSoundex encode is not of type java.lang.String");
         }
         return encode((String) obj);
     }
 
     /**
      * Encodes a String using the Daitch-Mokotoff Soundex algorithm without branching.
      *
      * @see #soundex(String)
      * @param source
      *            A String object to encode.
      * @return A DM Soundex code corresponding to the String supplied.
      * @throws IllegalArgumentException
      *             if a character is not mapped.
      */
     @Override
     public String encode(final String source) {
         if (source == null) {
             return null;
         }
         return soundex(source, false)[0];
     }
 
     /**
      * Encodes a String using the Daitch-Mokotoff Soundex algorithm with branching.
      * <p>
      * In case a string is encoded into multiple codes (see branching rules), the result will contain all codes,
      * separated by '|'.
      * </p>
      * <p>
      * Example: the name "AUERBACH" is encoded as both
      * </p>
      * <ul>
      * <li>097400</li>
      * <li>097500</li>
      * </ul>
      * <p>
      * Thus the result will be "097400|097500".
      * </p>
      *
      * @param source
      *            A String object to encode.
      * @return A string containing a set of DM Soundex codes corresponding to the String supplied.
      * @throws IllegalArgumentException
      *             if a character is not mapped.
      */
     public String soundex(final String source) {
         return String.join("|", soundex(source, true));
     }
 
     /**
      * Perform the actual DM Soundex algorithm on the input string.
      *
      * @param source
      *            A String object to encode.
      * @param branching
      *            If branching shall be performed.
      * @return A string array containing all DM Soundex codes corresponding to the String supplied depending on the
      *         selected branching mode.
      */
     private String[] soundex(final String source, final boolean branching) {
         if (source == null) {
             return null;
         }
         final String input = cleanup(source);
         final Set<Branch> currentBranches = new LinkedHashSet<>();
         currentBranches.add(new Branch());
         char lastChar = NUL;
         for (int index = 0; index < input.length(); index++) {
             final char ch = input.charAt(index);
             final String inputContext = input.substring(index);
             final List<Rule> rules = RULES.get(ch);
             if (rules == null) {
                 continue;
             }
             // use an EMPTY_LIST to avoid false positive warnings wrt potential null pointer access
             final List<Branch> nextBranches = branching ? new ArrayList<>() : Collections.emptyList();
             for (final Rule rule : rules) {
                 if (rule.matches(inputContext)) {
                     if (branching) {
                         nextBranches.clear();
                     }
                     final String[] replacements = rule.getReplacements(inputContext, lastChar == '\0');
                     final boolean branchingRequired = replacements.length > 1 && branching;
                     for (final Branch branch : currentBranches) {
                         for (final String nextReplacement : replacements) {
                             // if we have multiple replacements, always create a new branch
                             final Branch nextBranch = branchingRequired ? branch.createBranch() : branch;
                             // special rule: occurrences of mn or nm are treated differently
                             final boolean force = lastChar == 'm' && ch == 'n' || lastChar == 'n' && ch == 'm';
                             nextBranch.processNextReplacement(nextReplacement, force);
                             if (!branching) {
                                 break;
                             }
                             nextBranches.add(nextBranch);
                         }
                     }
                     if (branching) {
                         currentBranches.clear();
                         currentBranches.addAll(nextBranches);
                     }
                     index += rule.getPatternLength() - 1;
                     break;
                 }
             }
             lastChar = ch;
         }
         final String[] result = new String[currentBranches.size()];
         int index = 0;
         for (final Branch branch : currentBranches) {
             branch.finish();
             result[index++] = branch.toString();
         }
         return result;
     }
 }