code: package zemberek.normalization;
  
  import com.google.common.io.Resources;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  import zemberek.core.ScoredItem;
  import zemberek.core.logging.Log;
  import zemberek.core.turkish.Turkish;
  import zemberek.core.turkish.TurkishAlphabet;
  import zemberek.lm.DummyLanguageModel;
  import zemberek.lm.LmVocabulary;
  import zemberek.lm.NgramLanguageModel;
  import zemberek.lm.compression.SmoothLm;
  import zemberek.morphology.TurkishMorphology;
  import zemberek.morphology.analysis.SingleAnalysis;
  import zemberek.morphology.analysis.WordAnalysis;
  import zemberek.morphology.analysis.WordAnalysisSurfaceFormatter;
  import zemberek.normalization.CharacterGraphDecoder.CharMatcher;
  import zemberek.tokenization.TurkishTokenizer;
  import zemberek.tokenization.Token;
  
  public class TurkishSpellChecker {
  
    private static final NgramLanguageModel DUMMY_LM = new DummyLanguageModel();
    private static final TurkishTokenizer tokenizer = TurkishTokenizer.DEFAULT;
    TurkishMorphology morphology;
    WordAnalysisSurfaceFormatter formatter = new WordAnalysisSurfaceFormatter();
    CharacterGraphDecoder decoder;
    NgramLanguageModel unigramModel;
  
    // Null means exact matcher will be used.
    CharMatcher charMatcher = null;
  
    // can be used for filtering analysis results.
    Predicate<SingleAnalysis> analysisPredicate;
  
    public NgramLanguageModel getUnigramLanguageModel() {
      return unigramModel;
    }
  
    public TurkishSpellChecker(TurkishMorphology morphology) throws IOException {
      this.morphology = morphology;
      StemEndingGraph graph = new StemEndingGraph(morphology);
      this.decoder = new CharacterGraphDecoder(graph.stemGraph);
      try (InputStream is = Resources.getResource("lm-unigram.slm").openStream()) {
        unigramModel = SmoothLm.builder(is).build();
      }
    }
  
    public TurkishSpellChecker(TurkishMorphology morphology, CharacterGraph graph) {
      this.morphology = morphology;
      this.decoder = new CharacterGraphDecoder(graph);
    }
  
    public TurkishSpellChecker(
        TurkishMorphology morphology,
        CharacterGraphDecoder decoder,
        CharMatcher matcher) {
      this.morphology = morphology;
      this.decoder = decoder;
      this.charMatcher = matcher;
    }
  
    // TODO: this is a temporary hack.
    public void setAnalysisPredicate(Predicate<SingleAnalysis> analysisPredicate) {
      this.analysisPredicate = analysisPredicate;
    }
  
    //TODO: this does not cover all token types.
    public static List<String> tokenizeForSpelling(String sentence) {
      List<Token> tokens = tokenizer.tokenize(sentence);
      List<String> result = new ArrayList<>(tokens.size());
      for (Token token : tokens) {
        if (token.getType() == Token.Type.Unknown ||
            token.getType() == Token.Type.UnknownWord ||
            token.getType() == Token.Type.Punctuation) {
          continue;
        }
        String w = token.getText();
        if (token.getType() == Token.Type.Word) {
          w = w.toLowerCase(Turkish.LOCALE);
        } else if (token.getType() == Token.Type.WordWithSymbol) {
          w = Turkish.capitalize(w);
        }
        result.add(w);
      }
      return result;
    }
  
    public boolean check(String input) {
      WordAnalysis analyses = morphology.analyze(input);
      WordAnalysisSurfaceFormatter.CaseType caseType = formatter.guessCase(input);
      for (SingleAnalysis analysis : analyses) {
        if (analysis.isUnknown()) {
          continue;
        }
        if (analysisPredicate != null && !analysisPredicate.test(analysis)) {
          continue;
        }
        String apostrophe = getApostrophe(input);
  
        if (formatter.canBeFormatted(analysis, caseType)) {
          String formatted = formatter.formatToCase(analysis, caseType, apostrophe);
          if (input.equals(formatted)) {
            return true;
          }
        }
      }
      return false;
    }
  
    private String getApostrophe(String input) {
      if (input.indexOf('’') > 0) {
        return "’";
      } else if (input.indexOf('\'') > 0) {
        return "'";
      }
      return null;
    }
  
    public List<String> suggestForWord(String word, NgramLanguageModel lm) {
      List<String> unRanked = getUnrankedSuggestions(word);
      return rankWithUnigramProbability(unRanked, lm);
    }
  
    private List<String> getUnrankedSuggestions(String word) {
      String normalized = TurkishAlphabet.INSTANCE.normalize(word.replaceAll("['’]", ""));
      List<String> strings = decoder.getSuggestions(normalized, charMatcher);
  
      WordAnalysisSurfaceFormatter.CaseType caseType = formatter.guessCase(word);
      if (caseType == WordAnalysisSurfaceFormatter.CaseType.MIXED_CASE ||
          caseType == WordAnalysisSurfaceFormatter.CaseType.LOWER_CASE) {
        caseType = WordAnalysisSurfaceFormatter.CaseType.DEFAULT_CASE;
      }
      Set<String> results = new LinkedHashSet<>(strings.size());
      for (String string : strings) {
        WordAnalysis analyses = morphology.analyze(string);
        for (SingleAnalysis analysis : analyses) {
          if (analysis.isUnknown()) {
            continue;
          }
          if (analysisPredicate != null && !analysisPredicate.test(analysis)) {
            continue;
          }
          String formatted = formatter.formatToCase(analysis, caseType, getApostrophe(word));
          results.add(formatted);
        }
      }
      return new ArrayList<>(results);
    }
  
    public List<String> suggestForWord(
        String word,
        String leftContext,
        String rightContext,
        NgramLanguageModel lm) {
      List<String> unRanked = getUnrankedSuggestions(word);
      if (lm == null) {
        Log.warn("No language model provided. Returning unraked results.");
        return unRanked;
      }
      if (lm.getOrder() < 2) {
        Log.warn("Language model order is 1. For context ranking it should be at least 2. " +
            "Unigram ranking will be applied.");
        return suggestForWord(word, lm);
      }
      LmVocabulary vocabulary = lm.getVocabulary();
      List<ScoredItem<String>> results = new ArrayList<>(unRanked.size());
      for (String str : unRanked) {
        if (leftContext == null) {
          leftContext = vocabulary.getSentenceStart();
        } else {
          leftContext = normalizeForLm(leftContext);
        }
        if (rightContext == null) {
          rightContext = vocabulary.getSentenceEnd();
        } else {
          rightContext = normalizeForLm(rightContext);
        }
        String w = normalizeForLm(str);
        int wordIndex = vocabulary.indexOf(w);
        int leftIndex = vocabulary.indexOf(leftContext);
        int rightIndex = vocabulary.indexOf(rightContext);
        float score;
        if (lm.getOrder() == 2) {
          score = lm.getProbability(leftIndex, wordIndex) + lm.getProbability(wordIndex, rightIndex);
        } else {
          score = lm.getProbability(leftIndex, wordIndex, rightIndex);
        }
        results.add(new ScoredItem<>(str, score));
      }
      results.sort(ScoredItem.STRING_COMP_DESCENDING);
      return results.stream().map(s -> s.item).collect(Collectors.toList());
  
    }
  
    private String normalizeForLm(String s) {
      if (s.indexOf('\'') > 0) {
        return Turkish.capitalize(s);
      } else {
        return s.toLowerCase(Turkish.LOCALE);
      }
    }
  
    public List<String> suggestForWord(String word) {
      return suggestForWord(word, unigramModel);
    }
  
    public CharacterGraphDecoder getDecoder() {
      return decoder;
    }
  
    public List<String> rankWithUnigramProbability(List<String> strings, NgramLanguageModel lm) {
      if (lm == null) {
        Log.warn("No language model provided. Returning unraked results.");
        return strings;
      }
      List<ScoredItem<String>> results = new ArrayList<>(strings.size());
      for (String string : strings) {
        String w = normalizeForLm(string);
        int wordIndex = lm.getVocabulary().indexOf(w);
        results.add(new ScoredItem<>(string, lm.getUnigramProbability(wordIndex)));
      }
      results.sort(ScoredItem.STRING_COMP_DESCENDING);
      return results.stream().map(s -> s.item).collect(Collectors.toList());
    }
  }
  