content: package zemberek.morphology.analysis;
  
  import static zemberek.core.turkish.PhoneticAttribute.ExpectsConsonant;
  import static zemberek.core.turkish.PhoneticAttribute.FirstLetterConsonant;
  import static zemberek.core.turkish.PhoneticAttribute.FirstLetterVowel;
  import static zemberek.core.turkish.PhoneticAttribute.HasNoVowel;
  import static zemberek.core.turkish.PhoneticAttribute.LastLetterConsonant;
  import static zemberek.core.turkish.PhoneticAttribute.LastLetterVoiced;
  import static zemberek.core.turkish.PhoneticAttribute.LastLetterVoiceless;
  import static zemberek.core.turkish.PhoneticAttribute.LastLetterVoicelessStop;
  import static zemberek.core.turkish.PhoneticAttribute.LastLetterVowel;
  import static zemberek.core.turkish.PhoneticAttribute.LastVowelBack;
  import static zemberek.core.turkish.PhoneticAttribute.LastVowelFrontal;
  import static zemberek.core.turkish.PhoneticAttribute.LastVowelRounded;
  import static zemberek.core.turkish.PhoneticAttribute.LastVowelUnrounded;
  
  import java.util.Arrays;
  import java.util.List;
  import zemberek.core.turkish.PhoneticAttribute;
  import zemberek.core.turkish.TurkicLetter;
  import zemberek.core.turkish.TurkishAlphabet;
  import zemberek.morphology.morphotactics.AttributeSet;
  
  /**
   * Helper class for calculating morphemic attributes.
   */
  public class AttributesHelper {
  
    private static final List<PhoneticAttribute> NO_VOWEL_ATTRIBUTES = Arrays
        .asList(LastLetterConsonant, FirstLetterConsonant, HasNoVowel);
  
    public static AttributeSet<PhoneticAttribute> getMorphemicAttributes(CharSequence seq) {
      return getMorphemicAttributes(seq, AttributeSet.emptySet());
    }
  
    private static TurkishAlphabet alphabet = TurkishAlphabet.INSTANCE;
  
    public static AttributeSet<PhoneticAttribute> getMorphemicAttributes(
        CharSequence seq,
        AttributeSet<PhoneticAttribute> predecessorAttrs) {
      if (seq.length() == 0) {
        return predecessorAttrs.copy();
      }
      AttributeSet<PhoneticAttribute> attrs = new AttributeSet<>();
      if (alphabet.containsVowel(seq)) {
  
        TurkicLetter last = alphabet.getLastLetter(seq);
        if (last.isVowel()) {
          attrs.add(LastLetterVowel);
        } else {
          attrs.add(LastLetterConsonant);
        }
  
        TurkicLetter lastVowel = last.isVowel() ? last : alphabet.getLastVowel(seq);
  
        if (lastVowel.isFrontal()) {
          attrs.add(LastVowelFrontal);
        } else {
          attrs.add(LastVowelBack);
        }
        if (lastVowel.isRounded()) {
          attrs.add(LastVowelRounded);
        } else {
          attrs.add(LastVowelUnrounded);
        }
  
        if (alphabet.getFirstLetter(seq).isVowel()) {
          attrs.add(FirstLetterVowel);
        } else {
          attrs.add(FirstLetterConsonant);
        }
      } else {
        // we transfer vowel attributes from the predecessor attributes.
        attrs.copyFrom(predecessorAttrs);
        attrs.addAll(NO_VOWEL_ATTRIBUTES);
        attrs.remove(LastLetterVowel);
        attrs.remove(ExpectsConsonant);
      }
  
      TurkicLetter last = alphabet.getLastLetter(seq);
  
      if (last.isVoiceless()) {
        attrs.add(LastLetterVoiceless);
        if (last.isStopConsonant()) {
          // kitap
          attrs.add(LastLetterVoicelessStop);
        }
      } else {
        attrs.add(LastLetterVoiced);
      }
      return attrs;
    }
  
  }
  