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package de.tsl2.nano.annotation.extension;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;

import de.tsl2.nano.core.ManagedException;
import de.tsl2.nano.core.cls.BeanClass;

/**
 * This is a kind of workaround through the fact, that annotations cannot be
 * extended. If you want to create annotations, not known directly by the
 * underlying framework, the framework can provide a base annotation with only
 * one field: the factory class that will build something through the given
 * annotation.
 * 
 * This base annotation has to be followed by the specific (unknown to the
 * underlying framework) annotation, holding the desired values.
 * 
 * 
 * Example: @With(MyAnnotationFactory.class) @MySpecialAnnotation(myValue1="",
 * myValue2="")
 * 
 * @author Tom
 */
public interface AnnotationFactory {
    
	void build(I instance, A annotation);

	@SuppressWarnings({ "unchecked", "rawtypes" })
	public static void with(Object instance, AnnotatedElement annotationElment) {
		if (annotationElment.isAnnotationPresent(Withs.class)
		        || annotationElment.isAnnotationPresent(With.class)) {
			Annotation[] annotations = annotationElment.getAnnotations();
			With[] withs;
			for (int i = 0; i < annotations.length; i++) {
			    if (annotations[i] instanceof With) {
		            withs = new With[] {annotationElment.getAnnotation(With.class)};
			    } else if (annotations[i] instanceof Withs) {
			        withs = annotationElment.getAnnotation(Withs.class).value();
			    } else {
			        continue;
			    }
			    for (int j = 0; j < withs.length; j++) {
	                AnnotationFactory fact = BeanClass.createInstance(withs[j].value());
	                Annotation a = annotations[i + j + 1];
                    check(withs[j].value(), a);
	                fact.build(instance, a);
                }
			}
		}
	}

    static void check(Class> factory, Annotation annotation) {
        Class aType = annotation.annotationType();
        ManagedException.assertion(aType.isAnnotationPresent(With.class) && factory.equals(aType.getAnnotation(With.class).value()), 
            "The \"@With\" annotation-type " + annotation.annotationType() + " must be annotated with @With(" + factory.getName() + ".class)");
    }
}