Generate energy particle of the correct element for abilities.

src/main/java/emu/grasscutter/game/ability/AbilityManager.java

 package emu.grasscutter.game.ability;
 
+import java.util.Optional;
+
 import com.google.protobuf.InvalidProtocolBufferException;
 
+import emu.grasscutter.Grasscutter;
+
 import emu.grasscutter.data.GameData;
 import emu.grasscutter.data.custom.AbilityModifier.AbilityModifierAction;
+import emu.grasscutter.data.def.AvatarSkillDepotData;
 import emu.grasscutter.data.def.ItemData;
 import emu.grasscutter.data.custom.AbilityModifierEntry;
+import emu.grasscutter.game.avatar.Avatar;
+import emu.grasscutter.game.entity.EntityAvatar;
+import emu.grasscutter.game.entity.EntityClientGadget;
 import emu.grasscutter.game.entity.EntityItem;
 import emu.grasscutter.game.entity.GameEntity;
 import emu.grasscutter.game.player.Player;
+import emu.grasscutter.game.props.ElementType;
 import emu.grasscutter.net.proto.AbilityActionGenerateElemBallOuterClass.AbilityActionGenerateElemBall;
 import emu.grasscutter.net.proto.AbilityInvokeEntryHeadOuterClass.AbilityInvokeEntryHead;
 import emu.grasscutter.net.proto.AbilityInvokeEntryOuterClass.AbilityInvokeEntry;
@@ -18,6 +27,7 @@ import emu.grasscutter.net.proto.AbilityMixinCostStaminaOuterClass.AbilityMixinC
 import emu.grasscutter.net.proto.AbilityScalarValueEntryOuterClass.AbilityScalarValueEntry;
 import emu.grasscutter.net.proto.ModifierActionOuterClass.ModifierAction;
 import emu.grasscutter.utils.Position;
+import emu.grasscutter.utils.Utils;
 
 public class AbilityManager {
 	private Player player;
@@ -31,7 +41,7 @@ public class AbilityManager {
 	}
 
 	public void onAbilityInvoke(AbilityInvokeEntry invoke) throws Exception {
-		//System.out.println(invoke.getArgumentType() + " (" + invoke.getArgumentTypeValue() + "): " + Utils.bytesToHex(invoke.toByteArray()));
+		// Grasscutter.getLogger().info(invoke.getArgumentType() + " (" + invoke.getArgumentTypeValue() + "): " + Utils.bytesToHex(invoke.toByteArray()));
 		switch (invoke.getArgumentType()) {
 			case ABILITY_META_OVERRIDE_PARAM:
 				handleOverrideParam(invoke);
@@ -138,17 +148,88 @@ public class AbilityManager {
 		getPlayer().getStaminaManager().handleMixinCostStamina(costStamina.getIsSwim());
 	}
 	
+	private int getCastingAvatarIdForElemBall(int invokeEntityId) {
+		// To determine the avatar that has cast the skill that caused the energy particle to be generated,
+		// we have to look at the entity that has invoked the ability. This can either be that avatar directly, 
+		// or it can be an `EntityClientGadget`, owned (some way up the owner hierarchy) by the avatar 
+		// that cast the skill.
+		int res = 0;
+
+		// Try to get the invoking entity from the scene.
+		GameEntity entity = player.getScene().getEntityById(invokeEntityId);
+		
+		// If this entity is null, or not an `EntityClientGadget`, we assume that we are directly 
+		// looking at the casting avatar.
+		if (!(entity instanceof EntityClientGadget)) {
+			res = invokeEntityId;
+		}
+		// If the entity is a `EntityClientGadget`, we need to "walk up" the owner hierarchy,
+		// until the owner is no longer a gadget. This should then be the ID of the casting avatar.
+		else {	
+			while (entity instanceof EntityClientGadget gadget) {
+				res = gadget.getOwnerEntityId();
+				entity = player.getScene().getEntityById(gadget.getOwnerEntityId());
+			}
+		}
+		
+		return res;
+	}
+
 	private void handleGenerateElemBall(AbilityInvokeEntry invoke) throws InvalidProtocolBufferException {
+		// Get action info.
 		AbilityActionGenerateElemBall action = AbilityActionGenerateElemBall.parseFrom(invoke.getAbilityData());
 		if (action == null) {
 			return;
 		}
 		
-		ItemData itemData = GameData.getItemDataMap().get(2024);
+		// Determine the element of the energy particle that we have to generate.
+		// In case we can't, we default to an elementless particle.
+		// The element is the element of the avatar that has cast the ability.
+		// We can get that from the avatar's skill depot.
+		int itemId = 2024;
+		
+		// Try to fetch the avatar from the player's party and determine their element.
+		// ToDo: Does this work in co-op?
+		int avatarId = getCastingAvatarIdForElemBall(invoke.getEntityId());	
+		Optional<EntityAvatar> avatarEntity = player.getTeamManager().getActiveTeam()
+													.stream()
+													.filter(character -> character.getId() == avatarId)
+													.findFirst();
+
+		if (avatarEntity.isPresent()) {
+			Avatar avatar = avatarEntity.get().getAvatar();
+
+			if (avatar != null) {
+				AvatarSkillDepotData skillDepotData = avatar.getSkillDepot();
+
+				if (skillDepotData != null) {
+					ElementType element = skillDepotData.getElementType();
+
+					// If we found the element, we use it to deterine the ID of the
+					// energy particle that we have to generate.
+		 			if (element != null) {
+		 				itemId = switch (element) {
+							case Fire -> 2017;
+							case Water -> 2018; 
+							case Grass -> 2019;
+							case Electric -> 2020;
+							case Wind -> 2021;
+							case Ice -> 2022;
+							case Rock -> 2023;
+							default -> 2024;
+						};
+		 			}
+		 		}
+		 	}
+		}
+
+		// Get the item data for an energy particle of the correct element.
+		ItemData itemData = GameData.getItemDataMap().get(itemId);
 		if (itemData == null) {
 			return; // Should never happen
 		}
 		
+		// Generate entity.
 		EntityItem energyBall = new EntityItem(getPlayer().getScene(), getPlayer(), itemData, new Position(action.getPos()), 1);
 		energyBall.getRotation().set(action.getRot());