Implement inventory system with item management and pickup functionality

GameCore/Inventory/InventoryComponent.cs

@@ -0,0 +1,46 @@
+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Inventory;
+
+public class InventoryComponent : IComponent
+{
+    private readonly Dictionary<string, Item> _items = new();
+
+    public bool AddItem(Item itemToAdd)
+    {
+        if (_items.TryGetValue(itemToAdd.ItemId, out var exisitingItem))
+        {
+            exisitingItem.Quantity += itemToAdd.Quantity;
+            _items[itemToAdd.ItemId] = exisitingItem;
+        }
+        else
+        {
+            _items.Add(itemToAdd.ItemId, itemToAdd);
+        }
+
+        return true;
+    }
+
+    public bool RemoveItem(string itemId, int quantity)
+    {
+        if (!_items.TryGetValue(itemId, out var existingItem) || existingItem.Quantity < quantity) return false;
+
+        existingItem.Quantity -= quantity;
+        if (existingItem.Quantity <= 0)
+            _items.Remove(itemId);
+        else
+            _items[itemId] = existingItem;
+
+        return true;
+    }
+
+    public int GetItemCount(string itemId)
+    {
+        return _items.TryGetValue(itemId, out var existingItem) ? existingItem.Quantity : 0;
+    }
+
+    public bool HasItem(string itemId, int quantity = 1)
+    {
+        return GetItemCount(itemId) >= quantity;
+    }
+}

GameCore/Inventory/InventorySystem.cs

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+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+
+namespace GameCore.Inventory;
+
+public class InventorySystem : ISystem
+{
+    private readonly World _world;
+
+    public InventorySystem(World world)
+    {
+        _world = world;
+        _world.Subscribe<AddItemToInventoryEvent>(OnAddItem);
+    }
+
+    public void Update(World world, float deltaTime)
+    {
+    }
+
+    private void OnAddItem(AddItemToInventoryEvent e)
+    {
+        var inventory = _world.GetComponent<InventoryComponent>(e.Target);
+        inventory?.AddItem(e.Item);
+    }
+}

GameCore/Inventory/Item.cs

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+namespace GameCore.Inventory;
+
+public struct Item(string itemId, int quantity)
+{
+    public string ItemId { get; set; } = itemId;
+    public int Quantity { get; set; } = quantity;
+}

GameCore/Inventory/PickupComponent.cs

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+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Inventory;
+
+public class PickupComponent : IComponent
+{
+    public string ItemId { get; set; }
+    public int Quantity { get; set; } = 1;
+    public bool IsInstantUse { get; set; } = false;
+}

GameCore/Inventory/PickupSystem.cs

@@ -0,0 +1,36 @@
+using GameCore.Combat;
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+using GameCore.Physics;
+using GameCore.Player;
+
+namespace GameCore.Inventory;
+
+public class PickupSystem : ISystem
+{
+    public void Update(World world, float deltaTime)
+    {
+        var entitiesWithCollisions = world.GetEntitiesWith<CollisionEventComponent>();
+        var withCollisions = entitiesWithCollisions.ToList();
+        foreach (var entity in withCollisions)
+        {
+            if (world.GetComponent<PlayerComponent>(entity) == null) return;
+
+            var collision = world.GetComponent<CollisionEventComponent>(entity);
+            if (collision == null) continue;
+
+            var pickup = world.GetComponent<PickupComponent>(entity);
+            var inventory = world.GetComponent<InventoryComponent>(entity);
+
+            if (pickup == null || inventory == null) continue;
+
+            var item = new Item(pickup.ItemId, pickup.Quantity);
+            // In the future, handle IsInstantUse items here
+            world.PublishEvent(new AddItemToInventoryEvent(entity, item));
+            world.AddComponent(collision.OtherEntity, new DeathComponent());
+        }
+
+        foreach (var entity in withCollisions) world.RemoveComponent<CollisionEventComponent>(entity);
+    }
+}