package javax.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import javax.annotation.meta.TypeQualifier;
import javax.annotation.meta.TypeQualifierValidator;
import javax.annotation.meta.When;

/**
 * This annotation is used to annotate a value that should only contain
 * nonnegative values.
 * <p>
 * When this annotation is applied to a method it applies to the method return
 * value.
 */
@Documented
@TypeQualifier(applicableTo = Number.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface Nonnegative {
	When when() default When.ALWAYS;

	class Checker implements TypeQualifierValidator<Nonnegative> {

		public When forConstantValue(Nonnegative annotation, Object v) {
			if (!(v instanceof Number))
				return When.NEVER;
			boolean isNegative;
			Number value = (Number) v;
			if (value instanceof Long)
				isNegative = value.longValue() < 0;
			else if (value instanceof Double)
				isNegative = value.doubleValue() < 0;
			else if (value instanceof Float)
				isNegative = value.floatValue() < 0;
			else
				isNegative = value.intValue() < 0;

			if (isNegative)
				return When.NEVER;
			else
				return When.ALWAYS;

		}
	}
}