Add ammo consumption and item pickup systems

GameCore/Combat/Effects/ConsumeAmmoCost.cs

@@ -0,0 +1,19 @@
+using GameCore.Combat.Interfaces;
+using GameCore.Inventory;
+
+namespace GameCore.Combat.Effects;
+
+public class ConsumeAmmoCost(string ammoId, int amount) : ICostEffect
+{
+    public void Execute(EffectContext context)
+    {
+        var inventory = context.World.GetComponent<InventoryComponent>(context.Owner);
+        inventory?.RemoveItem(ammoId, amount);
+    }
+
+    public bool CanAfford(EffectContext context)
+    {
+        var inventory = context.World.GetComponent<InventoryComponent>(context.Owner);
+        return inventory != null && inventory.HasItem(ammoId, amount);
+    }
+}

GameCore/Combat/Interfaces/ICostEffect.cs

@@ -0,0 +1,8 @@
+using GameCore.Combat.Effects;
+
+namespace GameCore.Combat.Interfaces;
+
+public interface ICostEffect : IEffect
+{
+    bool CanAfford(EffectContext context);
+}

GameCore/Combat/WeaponComponent.cs

@@ -7,6 +7,7 @@ public class WeaponComponent : IComponent
 {
     public float FireRate { get; set; } = 1f;
 
+    public List<ICostEffect> FireCosts { get; set; } = [];
     public List<IEffect> OnFireEffects { get; set; } = [];
     public List<IEffect> OnHitEffects { get; set; } = [];
 

GameCore/Combat/WeaponSystem.cs

@@ -27,12 +27,21 @@ public class WeaponSystem : ISystem
 
             if (input.IsFiring && weapon.CooldownTimer <= 0f)
             {
-                // Check for ammo if applicable
-                
                 var context = new EffectContext { World = world, Owner = entity };
 
-                foreach (var effect in weapon.OnFireEffects) effect.Execute(context);
+                var canFire = true;
+                foreach (var cost in weapon.FireCosts)
+                    if (!cost.CanAfford(context))
+                    {
+                        canFire = false;
+                        //TODO: Publish an event or notify the player they can't fire
+                        break;
+                    }
 
+                if (!canFire) continue;
+
+                foreach (var cost in weapon.FireCosts) cost.Execute(context);
+                foreach (var effect in weapon.OnFireEffects) effect.Execute(context);
                 world.PublishEvent(new WeaponFiredEvent(entity, input.MuzzlePosition));
                 weapon.CooldownTimer = 1f / weapon.FireRate;
             }

GameCore/Events/ItemPickupAttemptEvent.cs

@@ -0,0 +1,17 @@
+using GameCore.ECS;
+using GameCore.Events.Interfaces;
+
+namespace GameCore.Events;
+
+public readonly struct ItemPickupAttemptEvent(
+    Entity picker,
+    Entity itemEntity,
+    string itemId,
+    int quantity
+) : IEvent
+{
+    public readonly Entity Picker = picker;
+    public readonly Entity ItemEntity = itemEntity;
+    public readonly string ItemId = itemId;
+    public readonly int Quantity = quantity;
+}

GameCore/Inventory/ItemAcquisitionSystem.cs

@@ -0,0 +1,47 @@
+using GameCore.Combat;
+using GameCore.Combat.Effects;
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+
+namespace GameCore.Inventory;
+
+public class ItemAcquisitionSystem : ISystem
+{
+    private readonly World _world;
+
+    public ItemAcquisitionSystem(World world)
+    {
+        _world = world;
+        _world.Subscribe<ItemPickupAttemptEvent>(OnItemPickupAttempt);
+    }
+
+    public void Update(World world, float deltaTime)
+    {
+    }
+
+    private void OnItemPickupAttempt(ItemPickupAttemptEvent e)
+    {
+        var pickupComponent = _world.GetComponent<PickupComponent>(e.ItemEntity);
+        if (pickupComponent == null) return;
+
+        if (pickupComponent.IsInstantUse)
+        {
+            var context = new EffectContext
+            {
+                World = _world,
+                Owner = e.Picker,
+                Target = e.Picker
+            };
+
+            foreach (var effect in pickupComponent.OnAcquireEffects) effect.Execute(context);
+        }
+        else
+        {
+            var item = new Item(e.ItemId, e.Quantity);
+            _world.PublishEvent(new AddItemToInventoryEvent(e.Picker, item));
+        }
+
+        _world.AddComponent(e.ItemEntity, new DeathComponent());
+    }
+}

GameCore/Inventory/PickupComponent.cs

@@ -1,3 +1,4 @@
+using GameCore.Combat.Interfaces;
 using GameCore.ECS.Interfaces;
 
 namespace GameCore.Inventory;
@@ -7,4 +8,5 @@ public class PickupComponent : IComponent
     public string ItemId { get; set; }
     public int Quantity { get; set; } = 1;
     public bool IsInstantUse { get; set; } = false;
+    public List<IEffect> OnAcquireEffects { get; set; } = [];
 }

GameCore/Inventory/PickupSystem.cs

@@ -1,4 +1,3 @@
-using GameCore.Combat;
 using GameCore.ECS;
 using GameCore.ECS.Interfaces;
 using GameCore.Events;
@@ -20,15 +19,17 @@ public class PickupSystem : ISystem
             var collision = world.GetComponent<CollisionEventComponent>(entity);
             if (collision == null) continue;
 
-            var pickup = world.GetComponent<PickupComponent>(entity);
+            var pickup = world.GetComponent<PickupComponent>(collision.OtherEntity);
             var inventory = world.GetComponent<InventoryComponent>(entity);
 
             if (pickup == null || inventory == null) continue;
 
-            var item = new Item(pickup.ItemId, pickup.Quantity);
+            world.PublishEvent(new ItemPickupAttemptEvent(
-            // In the future, handle IsInstantUse items here
+                entity,
-            world.PublishEvent(new AddItemToInventoryEvent(entity, item));
+                collision.OtherEntity,
-            world.AddComponent(collision.OtherEntity, new DeathComponent());
+                pickup.ItemId,
+                pickup.Quantity
+            ));
         }
 
         foreach (var entity in withCollisions) world.RemoveComponent<CollisionEventComponent>(entity);