refactoring EventManager

src/main/java/ghast/EventContext.java

@@ -0,0 +1,55 @@
+package ghast;
+
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import org.bukkit.Bukkit;
+import org.bukkit.event.Event;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BooleanSupplier;
+import java.util.function.Consumer;
+
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+@SuppressWarnings("unused")
+public class EventContext implements Listener {
+
+	private static final BooleanSupplier EMPTY_FILTER = () -> true;
+
+	private final Map<Class<? extends Event>, Consumer<?>> eventMap = new HashMap<>();
+	private BooleanSupplier filter = EMPTY_FILTER;
+
+	public EventContext filter(BooleanSupplier filter) {
+		this.filter = (filter != null ? filter : EMPTY_FILTER);
+		return this;
+	}
+
+	public <T extends Event> EventContext onEvent(Class<T> eventType, EventPriority eventPriority, Consumer<T> consumer) {
+		if (consumer == null) {
+			eventMap.remove(eventType);
+		} else {
+			eventMap.put(eventType, consumer);
+			Bukkit.getPluginManager().registerEvent(eventType, this, eventPriority,
+					this::eventExecute, GhastTools.getPlugin());
+		}
+		return this;
+	}
+
+	public <T extends Event> EventContext onEvent(Class<T> eventType, Consumer<T> consumer) {
+		return onEvent(eventType, EventPriority.NORMAL, consumer);
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	private void eventExecute(Listener listener, Event event) {
+		Consumer consumer = eventMap.get(event.getClass());
+		if (consumer != null && filter.getAsBoolean()) {
+			consumer.accept(event);
+		}
+	}
+
+	public static EventContext create() {
+		return new EventContext();
+	}
+}