Add weapon acquisition and swapping systems with data handling

GameCore/Combat/WeaponAcquisitionSystem.cs

@@ -0,0 +1,39 @@
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+using GameCore.Player;
+
+namespace GameCore.Combat;
+
+public class WeaponAcquisitionSystem : ISystem
+{
+    private const string WeaponItemPrefix = "weapon_";
+    private readonly World _world;
+
+    public WeaponAcquisitionSystem(World world)
+    {
+        _world = world;
+        _world.Subscribe<AddItemToInventoryEvent>(OnItemAdded);
+    }
+
+    public void Update(World world, float deltaTime)
+    {
+    }
+
+    private void OnItemAdded(AddItemToInventoryEvent e)
+    {
+        if (!e.Item.ItemId.StartsWith(WeaponItemPrefix)) return;
+
+        var equipment = _world.GetComponent<EquipmentComponent>(e.Target);
+        if (equipment == null) return;
+
+        if (!equipment.EquippableWeaponItemIds.Contains(e.Item.ItemId))
+            equipment.EquippableWeaponItemIds.Add(e.Item.ItemId);
+
+        if (equipment.CurrentWeaponIndex == -1)
+        {
+            equipment.CurrentWeaponIndex = equipment.EquippableWeaponItemIds.Count - 1;
+            _world.PublishEvent(new EquipWeaponEvent(e.Target, e.Item.ItemId));
+        }
+    }
+}