package io.atlassian.fugue.quickcheck;
   
   import com.pholser.junit.quickcheck.generator.ComponentizedGenerator;
   import com.pholser.junit.quickcheck.generator.GenerationStatus;
   import com.pholser.junit.quickcheck.random.SourceOfRandomness;
   import io.atlassian.fugue.Option;
   
   import java.util.Collections;
   import java.util.List;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  /**
   * Produces values of type {@link Option}.
   */
  public class OptionGenerator extends ComponentizedGenerator<Option<?>> {
  
    @SuppressWarnings("unchecked") public OptionGenerator() {
      super((Class) Option.class);
    }
  
    @Override public Option<?> generate(SourceOfRandomness random, GenerationStatus status) {
      double trial = random.nextDouble();
      if (trial < 0.25) {
        return Option.none();
      } else {
        Object item;
        do {
          item = componentGenerators().get(0).generate(random, status);
        } while (item == null);
        return Option.some(item);
      }
    }
  
    @Override public List<Option<?>> doShrink(SourceOfRandomness random, Option<?> larger) {
      return larger
        .fold(
          Collections::emptyList,
          largerItem -> Stream.concat(Stream.of(Option.none()),
            componentGenerators().get(0).shrink(random, largerItem).stream().filter(item -> item != null).map(Option::some)).collect(
            Collectors.toList()));
    }
  
    @Override public int numberOfNeededComponents() {
      return 1;
    }
  
  }