LinkDescriptors.java

package fr.openwide.core.wicket.more.link.util;

import org.apache.wicket.model.IDetachable;

import fr.openwide.core.wicket.more.link.descriptor.generator.IImageResourceLinkGenerator;
import fr.openwide.core.wicket.more.link.descriptor.generator.ILinkGenerator;
import fr.openwide.core.wicket.more.link.descriptor.generator.IPageLinkGenerator;
import fr.openwide.core.wicket.more.link.descriptor.impl.DynamicBookmarkableLink;
import fr.openwide.core.wicket.more.link.descriptor.mapper.ILinkDescriptorMapper;

public final class LinkDescriptors {
	
	private LinkDescriptors() {
	}
	
	/**
	 * Returns an always-invalid link generator, i.e. one that will generate an always-disabled
	 * {@link DynamicBookmarkableLink} and will always throw exceptions when asked to render the URL or to redirect.
	 * <p>The returned generator implements {@link ILinkGenerator}, {@link IPageLinkGenerator}
	 * <em>and</em> {@link IImageResourceLinkGenerator}.
	 */
	public static InvalidLinkGenerator invalid() {
		return INVALID;
	}
	
	private static final InvalidLinkGenerator INVALID = new InvalidLinkGenerator() {
		private static final long serialVersionUID = 1L;
		private Object readResolve() {
			return LinkDescriptors.INVALID;
		}
	};

	/**
	 * Returns a mapper that will always return an invalid link generator.
	 * @see LinkDescriptors#invalid()
	 */
	public static ILinkDescriptorMapper<InvalidLinkGenerator, Object> invalidMapper() {
		return constantMapper(INVALID);
	}
	
	/**
	 * Returns a mapper that will only return the given link descriptor, regardless of parameters.
	 */
	public static <L> ILinkDescriptorMapper<L, Object> constantMapper(L descriptor) {
		return new ConstantLinkDescriptorMapper<>(descriptor);
	}
	
	private static class ConstantLinkDescriptorMapper<L> implements ILinkDescriptorMapper<L, Object> {
		
		private static final long serialVersionUID = -4926581483390516183L;
		
		private final L result;

		public ConstantLinkDescriptorMapper(L result) {
			super();
			this.result = result;
		}

		@Override
		public void detach() {
			if (result instanceof IDetachable) {
				((IDetachable)result).detach();
			}
		}

		@Override
		public L map(Object param) {
			return result;
		}
	}

}