EventBus.java

package essentia.event;

import java.util.List;
import java.util.Map;

import essentia.util.collections.FastList;
import gnu.trove.map.hash.THashMap;

public class EventBus {
	
	public Map<Object, List<Object>> eventReceivers = new THashMap<>();
	
	@SuppressWarnings("unchecked")
	public void addNewReceiver(EventReceiver receiver) {
		for(Class<? extends Event<?>> event : receiver.getAllAvailableEvents()) {
			addNewreceiver((Class<Event<Object>>) event, receiver);
		}
	}
	
	public <T> void removeReceiver(Class<? extends Event<T>> clazz, T receiver) {
		List<Object> receivers = eventReceivers.get(clazz);
		if(receivers == null)
			return;
		receivers.remove(receiver);
	}
	
	public <T> void addNewReceiver(Class<? extends Event<T>> clazz, T receiver) {
		List<Object> receivers = eventReceivers.get(clazz);
		if(receivers == null) {
			receivers = new FastList<>();
			eventReceivers.put(clazz, receivers);
		}
		receivers.add(receiver);
	}
	
	@SuppressWarnings("unchecked")
	public <T> void executeEvent(Event<T> event) {
		List<T> receivers = (List<T>) eventReceivers.get(event.getClass());
		for(int i = 0; i < receivers.size(); ++i)
			event.execute(receivers.get(i));
	}
	
	public static interface Event<T> {

		public void execute(T eventReceiver);
	}
	
	public static interface EventReceiver {

		public Class<? extends Event<?>>[] getAllAvailableEvents();
		
	}
	
	public static class TestEvent implements Event<TestEventReceiver> {

		@Override
		public void execute(TestEventReceiver eventReceiver) {
			eventReceiver.executeEvent(this);
			
		}
	}
	
	public static class SecondTestEvent implements Event<SecondTestEventReceiver> {
		@Override
		public void execute(SecondTestEventReceiver eventReceiver) {
			eventReceiver.executeEvent(this);
			
		}
	}
	
	public abstract interface SecondTestEventReceiver {
		public void executeEvent(SecondTestEvent event);
	}
	
	public static class TestEventReceiver implements EventReceiver {

		public void executeEvent(TestEvent event) {
			// TODO Do some cool code with event
		}

		@SuppressWarnings("unchecked")
		@Override
		public Class<? extends Event<?>>[] getAllAvailableEvents() {
			return (Class<? extends Event<?>>[]) new Class[] {TestEvent.class};
		}
		
	}
	
	static {
		// Example code:
		EventBus bus = new EventBus();
		// Register single event:
		bus.addNewReceiver(TestEvent.class, new TestEventReceiver());
		// Register all events:
		bus.addNewReceiver(new TestEventReceiver());
		// Remove receiver from single event:
		bus.removeReceiver(TestEvent.class, new TestEventReceiver());
		// Execute event:
		bus.executeEvent(new TestEvent());
		// Lambda example
		bus.addNewReceiver(SecondTestEvent.class, (SecondTestEvent) -> {});
	}
}