Overhaul event handling (designed by WetABQ#3417)

src/main/java/emu/grasscutter/server/event/EventHandler.java

@@ -1,11 +1,79 @@
 package emu.grasscutter.server.event;
 
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
+import emu.grasscutter.Grasscutter;
 
-/**
- * Declares a class as an event listener/handler.
- */
-@Retention(RetentionPolicy.RUNTIME)
-public @interface EventHandler {
+import java.util.function.Consumer;
+
+public final class EventHandler<E extends Event> {
+    private E event;
+    
+    private Consumer<Event> listener;
+    private HandlerPriority priority;
+    private boolean handleCanceled;
+
+    /**
+     * Gets which event this handler is handling.
+     * @return An event class.
+     */
+    public Event handles() {
+        return this.event;
+    }
+
+    /**
+     * Returns the callback for the handler.
+     * @return A consumer callback.
+     */
+    public Consumer<Event> getCallback() {
+        return this.listener;
+    }
+
+    /**
+     * Returns the handler's priority.
+     * @return The priority of the handler.
+     */
+    public HandlerPriority getPriority() {
+        return this.priority;
+    }
+
+    /**
+     * Returns if the handler will ignore cancelled events.
+     * @return The ignore cancelled state.
+     */
+    public boolean ignoresCanceled() {
+        return this.handleCanceled;
+    }
+
+    /**
+     * Sets the callback method for when the event is invoked.
+     * @param listener An event handler method.
+     * @return Method chaining.
+     */
+    public EventHandler<E> listener(Consumer<Event> listener) {
+        this.listener = listener; return this;
+    }
+
+    /**
+     * Changes the handler's priority in handling events.
+     * @param priority The priority of the handler.
+     * @return Method chaining.
+     */
+    public EventHandler<E> priority(HandlerPriority priority) {
+        this.priority = priority; return this;
+    }
+
+    /**
+     * Sets if the handler will ignore cancelled events.
+     * @param ignore If the handler should ignore cancelled events.
+     * @return Method chaining.
+     */
+    public EventHandler<E> ignore(boolean ignore) {
+        this.handleCanceled = ignore; return this;
+    }
+
+    /**
+     * Registers the handler into the PluginManager.
+     */
+    public void register() {
+        Grasscutter.getPluginManager().registerListener(this);
+    }
 }