java-util-observer/src/main/lombok/org/leumasjaffe/observer/ObserverDispatch.java

package org.leumasjaffe.observer;

import java.lang.ref.WeakReference;
import java.util.UUID;

import com.google.common.collect.LinkedListMultimap;
import com.google.common.collect.Multimap;

import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.experimental.FieldDefaults;
import lombok.experimental.UtilityClass;

@UtilityClass
@FieldDefaults(level=AccessLevel.PRIVATE, makeFinal=true)
public class ObserverDispatch {
	@AllArgsConstructor
	@FieldDefaults(level=AccessLevel.PRIVATE, makeFinal=true)
	private static class Pair {
		WeakReference<Object> obj;
		Subscriber sub;
	}
	
	Multimap<UUID, Pair> observers = LinkedListMultimap.create();
	
	public void subscribe(Observable target, Object src, Subscriber sub) {
		observers.put(target.observableId, new Pair(new WeakReference<>(src), sub));
	}
	
	public void unsubscribeAll(Object src) {
		if (src == null) return;
		observers.entries().removeIf( e -> e.getValue().obj == src );
	}
	
	public void notifySubscribers(Observable target, Object src) {
		observers.get(target.observableId).stream().filter( p -> p.obj.get() != src ).forEach( 
				p -> p.sub.notifyUpdate() );
	}
}