Add Audiences#withPermission (#2215)

* Add Audiences#withPermission

* Add final and requireNonNull

Author: ImMorpheus

src/main/java/org/spongepowered/api/adventure/Audiences.java

@@ -27,6 +27,8 @@
 import net.kyori.adventure.audience.Audience;
 import org.spongepowered.api.Sponge;
 
+import java.util.Objects;
+
 /**
  * {@link Audience}s.
  */
@@ -47,7 +49,19 @@ public static Audience server() {
      * @return An audience
      */
     public static Audience onlinePlayers() {
-        return factory().onlinePlayers();
+        return Sponge.getRegistry().getFactoryRegistry().provideFactory(Factory.class).onlinePlayers();
+    }
+
+    /**
+     * Gets an {@link Audience} that targets all online players
+     * with the specified permission.
+     *
+     * @param permission The permission
+     * @return An audience
+     */
+    public static Audience withPermission(final String permission) {
+        Objects.requireNonNull(permission);
+        return Sponge.getRegistry().getFactoryRegistry().provideFactory(Factory.class).withPermission(permission);
     }
 
     /**
@@ -59,13 +73,14 @@ public static Audience system() {
         return Sponge.getGame().getSystemSubject();
     }
 
-    // TODO: withPermission
-
     private static Factory factory() {
         return Sponge.getRegistry().getFactoryRegistry().provideFactory(Factory.class);
     }
 
     public interface Factory {
+
         Audience onlinePlayers();
+
+        Audience withPermission(String permission);
     }
 }