changes to entity load handler keeping it backwards compatible

src/main/java/carpet/mixins/ServerWorld_scarpetMixin.java

@@ -23,6 +23,7 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
 
+import static carpet.script.CarpetEventServer.Event.ENTITY_HANDLER;
 import static carpet.script.CarpetEventServer.Event.ENTITY_LOAD;
 import static carpet.script.CarpetEventServer.Event.EXPLOSION;
 import static carpet.script.CarpetEventServer.Event.LIGHTNING;
@@ -43,24 +44,50 @@ public class ServerWorld_scarpetMixin implements ServerWorldInterface
         if (LIGHTNING.isNeeded()) LIGHTNING.onWorldEventFlag((ServerWorld) (Object)this, blockPos, bl2?1:0);
     }
 
+
+    private ThreadLocal<Boolean> entityJustLoaded = ThreadLocal.withInitial(() -> false);
+
     @Inject(method = "loadEntityUnchecked", at = @At(
             value = "INVOKE",
             target = "Lnet/minecraft/server/world/ServerChunkManager;loadEntity(Lnet/minecraft/entity/Entity;)V"
     ))
             private void onEntityAddedToWorld(Entity entity, CallbackInfo ci)
     {
-        CarpetEventServer.Event event = ENTITY_LOAD.get(entity.getType());
+        boolean justLoaded = entityJustLoaded.get();
+        entityJustLoaded.set(false);
+        CarpetEventServer.Event event = ENTITY_HANDLER.get(entity.getType());
         if (event != null)
         {
             if (event.isNeeded())
             {
-                event.onEntityAction(entity);
+                event.onEntityAction(entity, !justLoaded);
             }
         }
         else
         {
             CarpetSettings.LOG.error("Failed to handle entity "+entity.getType().getTranslationKey());
         }
+
+        // deprecated usage
+        event = ENTITY_LOAD.get(entity.getType());
+        if (event != null)
+        {
+            if (event.isNeeded())
+            {
+                event.onEntityAction(entity, true);
+            }
+        }
+        else
+        {
+            CarpetSettings.LOG.error("Failed to handle entity "+entity.getType().getTranslationKey());
+        }
+    }
+
+    // 1.16only
+    @Inject(method = "loadEntity", at= @At("HEAD"))
+    private void onSideLoaded(Entity entity, CallbackInfoReturnable<Boolean> cir)
+    {
+        entityJustLoaded.set(true);
     }
 
     @Inject(method = "createExplosion", at = @At("HEAD"))