Add weapon acquisition and swapping systems with data handling

GameCore/Combat/WeaponSwapSystem.cs

@@ -0,0 +1,50 @@
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+using GameCore.Input;
+using GameCore.Player;
+
+namespace GameCore.Combat;
+
+public class WeaponSwapSystem : ISystem
+{
+    public void Update(World world, float deltaTime)
+    {
+        var entities = world.GetEntitiesWith<InputStateComponent>();
+        foreach (var entity in entities)
+        {
+            var input = world.GetComponent<InputStateComponent>(entity);
+            var equipment = world.GetComponent<EquipmentComponent>(entity);
+
+            if (input == null || equipment == null || equipment.EquippableWeaponItemIds.Count <= 1)
+                continue;
+
+            var direction = SwapDirection.None;
+            if (input.IsSwapWeaponNext) direction = SwapDirection.Next;
+            if (input.IsSwapWeaponPrevious) direction = SwapDirection.Previous;
+
+            if (direction != SwapDirection.None)
+            {
+                var newIndex = equipment.CurrentWeaponIndex + (int)direction;
+                var weaponCount = equipment.EquippableWeaponItemIds.Count;
+
+                if (newIndex >= weaponCount) newIndex = 0;
+                if (newIndex < 0) newIndex = weaponCount - 1;
+
+                if (newIndex != equipment.CurrentWeaponIndex)
+                {
+                    equipment.CurrentWeaponIndex = newIndex;
+                    var newWeaponId = equipment.EquippableWeaponItemIds[newIndex];
+                    world.PublishEvent(new EquipWeaponEvent(entity, newWeaponId));
+                }
+            }
+        }
+    }
+
+    private enum SwapDirection
+    {
+        None = 0,
+        Next = 1,
+        Previous = -1
+    }
+}