import java.util.*;
import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import static javax.lang.model.SourceVersion.*;
import javax.lang.model.element.*;
import javax.lang.model.util.*;

/**
 * An abstract annotation processor tailored to javac regression testing.
 */
public abstract class JavacTestingAbstractProcessor extends AbstractProcessor {
    private static final Set<String> allAnnotations;

    static { 
        Set<String> tmp = new HashSet<>();
        tmp.add("*");
        allAnnotations = Collections.unmodifiableSet(tmp);
    }

    protected Elements eltUtils;
    protected Elements elements;
    protected Types    typeUtils;
    protected Types    types;
    protected Filer    filer;
    protected Messager messager;
    protected Map<String, String> options;

    /**
     * Constructor for subclasses to call.
     */
    protected JavacTestingAbstractProcessor() {
        super();
    }

    /**
     * Return the latest source version. Unless this method is
     * overridden, an {@code IllegalStateException} will be thrown if a
     * subclass has a {@code SupportedSourceVersion} annotation.
     */
    @Override
    public SourceVersion getSupportedSourceVersion() {
        SupportedSourceVersion ssv = this.getClass().getAnnotation(SupportedSourceVersion.class);
        if (ssv != null)
            throw new IllegalStateException("SupportedSourceVersion annotation not supported here.");

        return SourceVersion.latest();
    }

    /**
     * If the processor class is annotated with {@link
     * SupportedAnnotationTypes}, return an unmodifiable set with the
     * same set of strings as the annotation.  If the class is not so
     * annotated, a one-element set containing {@code "*"} is returned
     * to indicate all annotations are processed.
     *
     * @return the names of the annotation types supported by this
     * processor, or an empty set if none
     */
    @Override
    public Set<String> getSupportedAnnotationTypes() {
        SupportedAnnotationTypes sat = this.getClass().getAnnotation(SupportedAnnotationTypes.class);
        if (sat != null)
            return super.getSupportedAnnotationTypes();
        else
            return allAnnotations;
    }

    @Override
    public void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        elements = eltUtils  = processingEnv.getElementUtils();
        types = typeUtils = processingEnv.getTypeUtils();
        filer     = processingEnv.getFiler();
        messager  = processingEnv.getMessager();
        options   = processingEnv.getOptions();
    }
}