package javax.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

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

/**
 * This qualifier is used to denote String values that should be a Regular
 * expression.
 * <p>
 * When this annotation is applied to a method it applies to the method return
 * value.
 */
@Documented
@Syntax("RegEx")
@TypeQualifierNickname
@Retention(RetentionPolicy.RUNTIME)
public @interface RegEx {
	When when() default When.ALWAYS;

	static class Checker implements TypeQualifierValidator<RegEx> {

		public When forConstantValue(RegEx annotation, Object value) {
			if (!(value instanceof String))
				return When.NEVER;

			try {
				Pattern.compile((String) value);
			} catch (PatternSyntaxException e) {
				return When.NEVER;
			}
			return When.ALWAYS;

		}

	}

}
