Add asynchronous event API from issue #200

api/src/main/java/net/md_5/bungee/api/event/AsyncEvent.java

@@ -0,0 +1,72 @@
+package net.md_5.bungee.api.event;
+
+import com.google.common.base.Preconditions;
+import java.util.Collections;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
+import net.md_5.bungee.api.Callback;
+import net.md_5.bungee.api.plugin.Event;
+import net.md_5.bungee.api.plugin.Plugin;
+
+/**
+ * Represents an event which depends on the result of asynchronous operations.
+ */
+@Data
+@ToString(callSuper = true)
+@EqualsAndHashCode(callSuper = true)
+public class AsyncEvent extends Event
+{
+
+    private final Callback done;
+    private final Set<Plugin> intents = Collections.newSetFromMap( new ConcurrentHashMap<Plugin, Boolean>() );
+    private final AtomicBoolean fired = new AtomicBoolean();
+    private final AtomicInteger latch = new AtomicInteger();
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public void postCall()
+    {
+        fired.set( true );
+        if ( latch.get() == 0 )
+        {
+            done.done( this, null );
+        }
+    }
+
+    /**
+     * Register an intent that this plugin will continue to perform work on a
+     * background task, and wishes to let the event proceed once the registered
+     * background task has completed.
+     *
+     * @param plugin the plugin registering this intent
+     */
+    public void registerIntent(Plugin plugin)
+    {
+        Preconditions.checkState( !fired.get(), "Event %s has already been fired", this );
+        Preconditions.checkState( !intents.contains( plugin ), "Plugin %s already registered intent for event %s", plugin, this );
+
+        intents.add( plugin );
+    }
+
+    /**
+     * Notifies this event that this plugin has done all its required processing
+     * and wishes to let the event proceed.
+     *
+     * @param plugin a plugin which has an intent registered for this evemt
+     */
+    @SuppressWarnings("unchecked")
+    public void completeIntent(Plugin plugin)
+    {
+        Preconditions.checkState( intents.contains( plugin ), "Plugin %s has not registered intent for event %s", plugin, this );
+        intents.remove( plugin );
+        if ( latch.decrementAndGet() == 0 )
+        {
+            done.done( this, null );
+        }
+    }
+}

api/src/main/java/net/md_5/bungee/api/plugin/Event.java

@@ -4,5 +4,12 @@ package net.md_5.bungee.api.plugin;
  * Dummy class which all callable events must extend.
  */
 public abstract class Event
+{
+
+    /**
+     * Method called after this event has been dispatched to all handlers.
+     */
+    public void postCall()
     {
     }
+}

api/src/main/java/net/md_5/bungee/api/plugin/PluginManager.java

@@ -227,8 +227,11 @@ public class PluginManager
      */
     public <T extends Event> T callEvent(T event)
     {
+        Preconditions.checkNotNull( event, "event" );
+
         long start = System.nanoTime();
         eventBus.post( event );
+        event.postCall();
         // TODO: No exceptions!
         if ( !( event instanceof LoginEvent ) )
         {

proxy/src/main/java/net/md_5/bungee/tablist/GlobalTabList.java

@@ -1,6 +1,7 @@
 package net.md_5.bungee.tablist;
 
-import java.util.Map;
+import java.util.Collections;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import net.md_5.bungee.BungeeCord;
 import net.md_5.bungee.UserConnection;
@@ -12,9 +13,7 @@ import net.md_5.bungee.packet.PacketC9PlayerListItem;
 public class GlobalTabList implements TabListHandler
 {
 
-    // Sweet trick to avoid locking, basically reimplement HashSet based on a ConcurrentHashMap
+    private final Set<ProxiedPlayer> sentPings = Collections.newSetFromMap( new ConcurrentHashMap<ProxiedPlayer, Boolean>() );
-    private static final Object PRESENT = new Object();
-    private final Map<ProxiedPlayer, Object> sentPings = new ConcurrentHashMap<>();
 
     @Override
     public void onConnect(ProxiedPlayer player)
@@ -30,10 +29,10 @@ public class GlobalTabList implements TabListHandler
     @Override
     public void onPingChange(ProxiedPlayer player, int ping)
     {
-        if ( !sentPings.containsKey( player ) )
+        if ( !sentPings.contains( player ) )
         {
             BungeeCord.getInstance().broadcast( new PacketC9PlayerListItem( player.getDisplayName(), true, player.getPing() ) );
-            sentPings.put( player, PRESENT );
+            sentPings.add( player );
         }
     }