code: package zemberek.normalization;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.stream.Collectors;
  import zemberek.core.collections.FloatValueMap;
  import zemberek.core.collections.UIntMap;
  
  public class SingleWordSpellChecker {
  
    public static final Map<Character, String> TURKISH_FQ_NEAR_KEY_MAP = new HashMap<>();
    public static final Map<Character, String> TURKISH_Q_NEAR_KEY_MAP = new HashMap<>();
    static final float INSERTION_PENALTY = 1;
    static final float DELETION_PENALTY = 1;
    static final float SUBSTITUTION_PENALTY = 1;
    static final float NEAR_KEY_SUBSTITUTION_PENALTY = 0.5f;
    static final float TRANSPOSITION_PENALTY = 1;
    private static final AtomicInteger nodeIndexCounter = new AtomicInteger(0);
    private static final Locale tr = new Locale("tr");
  
    static {
      TURKISH_FQ_NEAR_KEY_MAP.put('a', "eüs");
      TURKISH_FQ_NEAR_KEY_MAP.put('b', "svn");
      TURKISH_FQ_NEAR_KEY_MAP.put('c', "vçx");
      TURKISH_FQ_NEAR_KEY_MAP.put('ç', "czö");
      TURKISH_FQ_NEAR_KEY_MAP.put('d', "orsf");
      TURKISH_FQ_NEAR_KEY_MAP.put('e', "iawr");
      TURKISH_FQ_NEAR_KEY_MAP.put('f', "gd");
      TURKISH_FQ_NEAR_KEY_MAP.put('g', "fğh");
      TURKISH_FQ_NEAR_KEY_MAP.put('ğ', "gıpü");
      TURKISH_FQ_NEAR_KEY_MAP.put('h', "npgj");
      TURKISH_FQ_NEAR_KEY_MAP.put('ı', "ğou");
      TURKISH_FQ_NEAR_KEY_MAP.put('i', "ueş");
      TURKISH_FQ_NEAR_KEY_MAP.put('j', "öhk");
      TURKISH_FQ_NEAR_KEY_MAP.put('k', "tmjl");
      TURKISH_FQ_NEAR_KEY_MAP.put('l', "mykş");
      TURKISH_FQ_NEAR_KEY_MAP.put('m', "klnö");
      TURKISH_FQ_NEAR_KEY_MAP.put('n', "rhbm");
      TURKISH_FQ_NEAR_KEY_MAP.put('o', "ıdp");
      TURKISH_FQ_NEAR_KEY_MAP.put('ö', "jvmç");
      TURKISH_FQ_NEAR_KEY_MAP.put('p', "hqoğ");
      TURKISH_FQ_NEAR_KEY_MAP.put('r', "dnet");
      TURKISH_FQ_NEAR_KEY_MAP.put('s', "zbad");
      TURKISH_FQ_NEAR_KEY_MAP.put('ş', "yli");
      TURKISH_FQ_NEAR_KEY_MAP.put('t', "ükry");
      TURKISH_FQ_NEAR_KEY_MAP.put('u', "iyı");
      TURKISH_FQ_NEAR_KEY_MAP.put('ü', "atğ");
      TURKISH_FQ_NEAR_KEY_MAP.put('v', "öcb");
      TURKISH_FQ_NEAR_KEY_MAP.put('y', "lştu");
      TURKISH_FQ_NEAR_KEY_MAP.put('z', "çsx");
      TURKISH_FQ_NEAR_KEY_MAP.put('x', "wzc");
      TURKISH_FQ_NEAR_KEY_MAP.put('q', "pqw");
      TURKISH_FQ_NEAR_KEY_MAP.put('w', "qxe");
    }
  
    static {
      TURKISH_Q_NEAR_KEY_MAP.put('a', "s");
      TURKISH_Q_NEAR_KEY_MAP.put('b', "vn");
      TURKISH_Q_NEAR_KEY_MAP.put('c', "vx");
      TURKISH_Q_NEAR_KEY_MAP.put('ç', "ö");
      TURKISH_Q_NEAR_KEY_MAP.put('d', "sf");
      TURKISH_Q_NEAR_KEY_MAP.put('e', "wr");
      TURKISH_Q_NEAR_KEY_MAP.put('f', "gd");
      TURKISH_Q_NEAR_KEY_MAP.put('g', "fh");
      TURKISH_Q_NEAR_KEY_MAP.put('ğ', "pü");
      TURKISH_Q_NEAR_KEY_MAP.put('h', "gj");
      TURKISH_Q_NEAR_KEY_MAP.put('ı', "ou");
      TURKISH_Q_NEAR_KEY_MAP.put('i', "ş");
      TURKISH_Q_NEAR_KEY_MAP.put('j', "hk");
      TURKISH_Q_NEAR_KEY_MAP.put('k', "jl");
      TURKISH_Q_NEAR_KEY_MAP.put('l', "kş");
      TURKISH_Q_NEAR_KEY_MAP.put('m', "nö");
      TURKISH_Q_NEAR_KEY_MAP.put('n', "bm");
      TURKISH_Q_NEAR_KEY_MAP.put('o', "ıp");
      TURKISH_Q_NEAR_KEY_MAP.put('ö', "mç");
      TURKISH_Q_NEAR_KEY_MAP.put('p', "oğ");
      TURKISH_Q_NEAR_KEY_MAP.put('r', "et");
      TURKISH_Q_NEAR_KEY_MAP.put('s', "ad");
      TURKISH_Q_NEAR_KEY_MAP.put('ş', "li");
      TURKISH_Q_NEAR_KEY_MAP.put('t', "ry");
      TURKISH_Q_NEAR_KEY_MAP.put('u', "yı");
      TURKISH_Q_NEAR_KEY_MAP.put('ü', "ğ");
      TURKISH_Q_NEAR_KEY_MAP.put('v', "cb");
      TURKISH_Q_NEAR_KEY_MAP.put('y', "tu");
      TURKISH_Q_NEAR_KEY_MAP.put('z', "x");
      TURKISH_Q_NEAR_KEY_MAP.put('x', "zc");
      TURKISH_Q_NEAR_KEY_MAP.put('q', "w");
      TURKISH_Q_NEAR_KEY_MAP.put('w', "qe");
    }
  
    public final float maxPenalty;
    public final boolean checkNearKeySubstitution;
    public Map<Character, String> nearKeyMap = new HashMap<>();
    private Node root = new Node(nodeIndexCounter.getAndIncrement(), (char) 0);
  
    public SingleWordSpellChecker(float maxPenalty) {
      this.maxPenalty = maxPenalty;
      this.checkNearKeySubstitution = false;
    }
  
    public SingleWordSpellChecker() {
      this.maxPenalty = 1;
      this.checkNearKeySubstitution = false;
    }
  
    public SingleWordSpellChecker(float maxPenalty, Map<Character, String> nearKeyMap) {
      this.maxPenalty = maxPenalty;
      this.nearKeyMap = Collections.unmodifiableMap(nearKeyMap);
      this.checkNearKeySubstitution = true;
    }
  
    public String process(String str) {
      return str.toLowerCase(tr).replace("['.]", "");
    }
  
    public void addWord(String word) {
      String clean = process(word);
      addChar(root, 0, clean, word);
    }
  
    public void addWords(String... words) {
      for (String word : words) {
        addWord(word);
      }
    }
  
    public void buildDictionary(List<String> vocabulary) {
      for (String s : vocabulary) {
        addWord(s);
      }
    }
  
    private Node addChar(Node currentNode, int index, String word, String actual) {
      char c = word.charAt(index);
      Node child = currentNode.addChild(c);
      if (index == word.length() - 1) {
        child.word = actual;
        return child;
      }
      index++;
      return addChar(child, index, word, actual);
    }
  
    private Set<Hypothesis> expand(Hypothesis hypothesis, String input,
        FloatValueMap<String> finished) {
  
      Set<Hypothesis> newHypotheses = new HashSet<>();
  
      int nextIndex = hypothesis.index + 1;
  
      // no-error
      if (nextIndex < input.length()) {
        if (hypothesis.node.hasChild(input.charAt(nextIndex))) {
          Hypothesis hyp = hypothesis.getNewMoveForward(
              hypothesis.node.getChild(input.charAt(nextIndex)),
              0,
              Operation.NE);
          if (nextIndex >= input.length() - 1) {
            if (hyp.node.word != null) {
              addHypothesis(finished, hyp);
            }
          } // TODO: below line may produce unnecessary hypotheses.
          newHypotheses.add(hyp);
        }
      } else if (hypothesis.node.word != null) {
        addHypothesis(finished, hypothesis);
      }
  
      // we don't need to explore further if we reached to max penalty
      if (hypothesis.penalty >= maxPenalty) {
        return newHypotheses;
      }
  
      // substitution
      if (nextIndex < input.length()) {
        for (Node childNode : hypothesis.node.getChildNodes()) {
  
          float penalty = 0;
          if (checkNearKeySubstitution) {
            char nextChar = input.charAt(nextIndex);
            if (childNode.chr != nextChar) {
              String nearCharactersString = nearKeyMap.get(childNode.chr);
              if (nearCharactersString != null && nearCharactersString.indexOf(nextChar) >= 0) {
                penalty = NEAR_KEY_SUBSTITUTION_PENALTY;
              } else {
                penalty = SUBSTITUTION_PENALTY;
              }
            }
          } else {
            penalty = SUBSTITUTION_PENALTY;
          }
  
          if (penalty > 0 && hypothesis.penalty + penalty <= maxPenalty) {
            Hypothesis hyp = hypothesis.getNewMoveForward(
                childNode,
                penalty,
                Operation.SUB);
            if (nextIndex == input.length() - 1) {
              if (hyp.node.word != null) {
                addHypothesis(finished, hyp);
              }
            } else {
              newHypotheses.add(hyp);
            }
          }
        }
      }
  
      if (hypothesis.penalty + DELETION_PENALTY > maxPenalty) {
        return newHypotheses;
      }
  
      // deletion
      newHypotheses
          .add(hypothesis.getNewMoveForward(hypothesis.node, DELETION_PENALTY, Operation.DEL));
  
      // insertion
      for (Node childNode : hypothesis.node.getChildNodes()) {
        newHypotheses.add(hypothesis.getNew(childNode, INSERTION_PENALTY, Operation.INS));
      }
  
      // transposition
      if (nextIndex < input.length() - 1) {
        char transpose = input.charAt(nextIndex + 1);
        Node nextNode = hypothesis.node.getChild(transpose);
        char nextChar = input.charAt(nextIndex);
        if (hypothesis.node.hasChild(transpose) && nextNode.hasChild(nextChar)) {
          Hypothesis hyp = hypothesis.getNew(
              nextNode.getChild(nextChar),
              TRANSPOSITION_PENALTY,
              nextIndex + 1,
              Operation.TR);
          if (nextIndex == input.length() - 1) {
            if (hyp.node.word != null) {
              addHypothesis(finished, hyp);
            }
          } else {
            newHypotheses.add(hyp);
          }
        }
      }
      return newHypotheses;
    }
  
    private void addHypothesis(FloatValueMap<String> result, Hypothesis hypothesis) {
      String hypWord = hypothesis.node.word;
      if (hypWord == null) {
        return;
      }
      if (!result.contains(hypWord)) {
        result.set(hypWord, hypothesis.penalty);
      } else if (result.get(hypWord) > hypothesis.penalty) {
        result.set(hypWord, hypothesis.penalty);
      }
    }
  
    public FloatValueMap<String> decode(String input) {
      Hypothesis hyp = new Hypothesis(null, root, 0, Operation.N_A);
      FloatValueMap<String> hypotheses = new FloatValueMap<>();
      Set<Hypothesis> next = expand(hyp, input, hypotheses);
      while (true) {
        HashSet<Hypothesis> newHyps = new HashSet<>();
        for (Hypothesis hypothesis : next) {
          newHyps.addAll(expand(hypothesis, input, hypotheses));
        }
        if (newHyps.size() == 0) {
          break;
        }
        next = newHyps;
      }
      return hypotheses;
    }
  
    /**
     * Returns suggestions sorted by penalty.
     */
    public List<ScoredString> getSuggestionsWithScores(String input) {
      FloatValueMap<String> results = decode(input);
  
      List<ScoredString> res = new ArrayList<>(results.size());
      for (String result : results) {
        res.add(new ScoredString(result, results.get(result)));
      }
      Collections.sort(res);
      return res;
    }
  
    public List<String> getSuggestions(String input) {
      return decode(input).getKeyList();
    }
  
    public List<String> getSuggestionsSorted(String input) {
      List<ScoredString> s = getSuggestionsWithScores(input);
      List<String> result = new ArrayList<>(s.size());
      result.addAll(s.stream().map(s1 -> s1.s).collect(Collectors.toList()));
      return result;
    }
  
    enum Operation {
      NE, INS, DEL, SUB, TR, N_A
    }
  
    public static class Node {
  
      int index;
      char chr;
      UIntMap<Node> nodes = new UIntMap<>(2);
      String word;
  
      public Node(int index, char chr) {
        this.index = index;
        this.chr = chr;
      }
  
      public Iterable<Node> getChildNodes() {
        return nodes.getValues();
      }
  
      public boolean hasChild(char c) {
        return nodes.containsKey(c);
      }
  
      public Node getChild(char c) {
        return nodes.get(c);
      }
  
      public Node addChild(char c) {
        Node node = nodes.get(c);
        if (node == null) {
          node = new Node(nodeIndexCounter.getAndIncrement(), c);
        }
        nodes.put(c, node);
        return node;
      }
  
      public void setWord(String word) {
        this.word = word;
      }
  
      @Override
      public boolean equals(Object o) {
        if (this == o) {
          return true;
        }
        if (o == null || getClass() != o.getClass()) {
          return false;
        }
        Node node = (Node) o;
        return index == node.index;
      }
  
      @Override
      public int hashCode() {
        return index;
      }
  
      @Override
      public String toString() {
        StringBuilder sb = new StringBuilder("[" + chr);
        char[] characters = new char[nodes.size()];
        int[] keys = nodes.getKeys();
        for (int i = 0; i < characters.length; i++) {
          characters[i] = (char) keys[i];
        }
        Arrays.sort(characters);
        if (nodes.size() > 0) {
          sb.append(" children=").append(Arrays.toString(characters));
        }
        if (word != null) {
          sb.append(" word=").append(word);
        }
        sb.append("]");
        return sb.toString();
      }
    }
  
    public static class ScoredString implements Comparable<ScoredString> {
  
      final String s;
      final float penalty;
  
      public ScoredString(String s, float penalty) {
        this.s = s;
        this.penalty = penalty;
      }
  
      @Override
      public boolean equals(Object o) {
        if (this == o) {
          return true;
        }
        if (o == null || getClass() != o.getClass()) {
          return false;
        }
  
        ScoredString result = (ScoredString) o;
  
        if (Float.compare(result.penalty, penalty) != 0) {
          return false;
        }
        if (!s.equals(result.s)) {
          return false;
        }
  
        return true;
      }
  
      @Override
      public int hashCode() {
        int result;
        long temp;
        result = s.hashCode();
        temp = Float.floatToIntBits(penalty);
        result = 31 * result + (int) (temp ^ (temp >>> 32));
        return result;
      }
  
      @Override
      public int compareTo(ScoredString o) {
        return Float.compare(penalty, o.penalty);
      }
    }
  
    static class Hypothesis implements Comparable<Hypothesis> {
  
      Operation operation;
      Hypothesis previous;
      Node node;
      float penalty;
      int index;
  
      Hypothesis(Hypothesis previous, Node node, float penalty, Operation operation) {
        this.previous = previous;
        this.node = node;
        this.penalty = penalty;
        this.index = -1;
        this.operation = operation;
      }
  
      Hypothesis(Hypothesis previous, Node node, float penalty, int index, Operation operation) {
        this.previous = previous;
        this.node = node;
        this.penalty = penalty;
        this.index = index;
        this.operation = operation;
      }
  
      String backTrack() {
        StringBuilder sb = new StringBuilder();
        Hypothesis p = previous;
        while (p.node.chr != 0) {
          if (p.node != p.previous.node) {
            sb.append(p.node.chr);
          }
          p = p.previous;
        }
        return sb.reverse().toString();
      }
  
      Hypothesis getNew(Node node, float penaltyToAdd, Operation operation) {
        return new Hypothesis(this, node, this.penalty + penaltyToAdd, index, operation);
      }
  
      Hypothesis getNewMoveForward(Node node, float penaltyToAdd, Operation operation) {
        return new Hypothesis(this, node, this.penalty + penaltyToAdd, index + 1, operation);
      }
  
      Hypothesis getNew(Node node, float penaltyToAdd, int index, Operation operation) {
        return new Hypothesis(this, node, this.penalty + penaltyToAdd, index, operation);
      }
  
      Hypothesis getNew(float penaltyToAdd, Operation operation) {
        return new Hypothesis(this, this.node, this.penalty + penaltyToAdd, index, operation);
      }
  
      @Override
      public int compareTo(Hypothesis o) {
        return Float.compare(penalty, o.penalty);
      }
  
      @Override
      public String toString() {
        return "Hypothesis{" +
            "previous=" + backTrack() + " " + previous.operation +
            ", node=" + node +
            ", penalty=" + penalty +
            ", index=" + index +
            ", OP=" + operation.name() +
            '}';
      }
  
      @Override
      public boolean equals(Object o) {
        if (this == o) {
          return true;
        }
        if (o == null || getClass() != o.getClass()) {
          return false;
        }
  
        Hypothesis that = (Hypothesis) o;
  
        if (index != that.index) {
          return false;
        }
        if (Double.compare(that.penalty, penalty) != 0) {
          return false;
        }
        if (!node.equals(that.node)) {
          return false;
        }
  
        return true;
      }
  
      @Override
      public int hashCode() {
        int result;
        long temp;
        result = node.hashCode();
        temp = Double.doubleToLongBits(penalty);
        result = 31 * result + (int) (temp ^ (temp >>> 32));
        result = 31 * result + index;
        return result;
      }
    }
  }
  