Simplify event registration and deregistration

Since Nashorn-created implementations of the org.bukkit.event.Listener
interface correctly implement Object.equals() (which was not the case
with Rhino), we can go back to instantiating a different Listener
instance per event handler and let the Bukkit API worry about the
details of RegisteredListeners.

Also, Nashorn automatically implements "functional interfaces" so
there is no need to explicitly create an EventExecutor.

Author: jonathanperret

src/main/java/bukkit/org/scriptcraftjs/bukkit/ScriptCraftPlugin.java

@@ -2,7 +2,6 @@
 
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandSender;
-import org.bukkit.event.Listener;
 import org.bukkit.plugin.java.JavaPlugin;
 
 import javax.script.Invocable;
@@ -12,7 +11,7 @@
 import java.util.ArrayList;
 import java.util.List;
 
-public class ScriptCraftPlugin extends JavaPlugin implements Listener
+public class ScriptCraftPlugin extends JavaPlugin
 {
     public boolean canary = false;
     public boolean bukkit = true;

src/main/js/lib/events-bukkit.js

@@ -1,16 +1,12 @@
 /*global Java, exports, org, __plugin */
 var bkEventPriority = org.bukkit.event.EventPriority,
-  bkEventExecutor = org.bukkit.plugin.EventExecutor,
-  bkRegisteredListener = org.bukkit.plugin.RegisteredListener;
+  bkHandlerList = org.bukkit.event.HandlerList,
+  bkPluginManager = org.bukkit.Bukkit.pluginManager;
 
-function getHandlerListForEventType(eventType) {
-  // Nashorn doesn't make inherited static methods accessible on derived
-  // classes (see https://stackoverflow.com/a/38258630), e.g.
-  // org.bukkit.event.block.BlockBreakEvent.getHandlerList() does not work.
-  // So to avoid this problem, call getHandlerList using java.lang.reflect
-  // methods.
-  return eventType.class.getMethod('getHandlerList').invoke(null);
-}
+// Ask Nashorn to generate a class implementing the Listener
+// interface, so that we may instantiate it to tag our event
+// handlers.
+var ScriptCraftListener = Java.extend(org.bukkit.event.Listener, {});
 
 exports.on = function(
   /* Java Class */
@@ -21,53 +17,45 @@ exports.on = function(
   /* (optional) String (HIGH, HIGHEST, LOW, LOWEST, NORMAL, MONITOR), */
   priority
 ) {
-  var handlerList, regd, eventExecutor;
-
   if (typeof priority == 'undefined') {
     priority = bkEventPriority.HIGHEST;
   } else {
     priority = bkEventPriority[priority.toUpperCase().trim()];
   }
-  handlerList = getHandlerListForEventType(eventType);
 
   var result = {};
-  eventExecutor = new bkEventExecutor({
-    execute: function(l, evt) {
-      function cancel() {
-        if (evt instanceof org.bukkit.event.Cancellable) {
-          evt.setCancelled(true);
-        }
-      }
-      /*
-       let handlers use this.cancel() to cancel the current event
-       or this.unregister() to unregister from future events.
-       */
-      var bound = {};
-      for (var i in result) {
-        bound[i] = result[i];
+  var eventExecutor = function(l, evt) {
+    function cancel() {
+      if (evt instanceof org.bukkit.event.Cancellable) {
+        evt.setCancelled(true);
       }
-      bound.cancel = cancel;
-      handler.call(bound, evt, cancel);
     }
-  });
-  /* 
-   wph 20130222 issue #64 bad interaction with Essentials plugin
-   if another plugin tries to unregister a Listener (not a Plugin or a RegisteredListener)
-   then BOOM! the other plugin will throw an error because Rhino can't coerce an
-   equals() method from an Interface.
-   The workaround is to make the ScriptCraftPlugin java class a Listener.
-   Should only unregister() registered plugins in ScriptCraft js code.
-   */
-  regd = new bkRegisteredListener(
-    __plugin,
-    eventExecutor,
+    /*
+     let handlers use this.cancel() to cancel the current event
+     or this.unregister() to unregister from future events.
+     */
+    var bound = {};
+    for (var i in result) {
+      bound[i] = result[i];
+    }
+    bound.cancel = cancel;
+    handler.call(bound, evt, cancel);
+  };
+
+  // Create an instance of our empty Listener implementation to track the handler
+  var listener = new ScriptCraftListener();
+
+  bkPluginManager.registerEvent(
+    eventType.class,
+    listener,
     priority,
-    __plugin,
-    false
+    eventExecutor,
+    __plugin
   );
-  handlerList.register(regd);
+
   result.unregister = function() {
-    handlerList.unregister(regd);
+    bkHandlerList.unregisterAll(listener);
   };
+
   return result;
 };