upd

Code/Inventory/Usable/AmmoUseableBase.cs

@@ -0,0 +1,39 @@
+namespace Sasalka;
+
+public abstract class AmmoUseableBase : UseableBase
+{
+	protected InventoryItem AmmoItem => FindAmmoItem();
+
+	private InventoryItem FindAmmoItem()
+	{
+		// var ammoDefinition = new InventoryItemDefinition();
+
+		return Dedugan.Local.Inventory.Items.FirstOrDefault( i => i.Definition.Name == "Pistol Ammo" );
+	}
+
+	public override bool CanUse()
+	{
+		var ammo = AmmoItem;
+		return base.CanUse() && ammo != null && ammo.Count > 0;
+	}
+
+	public override void Use()
+	{
+		if ( !CanUse() )
+			return;
+
+		OnUse();
+
+		var ammo = AmmoItem;
+		if ( ammo != null )
+		{
+			ammo.Count--;
+			Log.Info( $"[AmmoUseableBase] Ammo left: {ammo.Count}" );
+
+			if ( ammo.Count <= 0 )
+			{
+				Dedugan.Local.Inventory.RemoveItem( ammo );
+			}
+		}
+	}
+}

Code/Inventory/Usable/IUseContext.cs

@@ -0,0 +1,6 @@
+namespace Sasalka;
+
+public interface IUseContext
+{
+	public IEnumerable<IUseable> GetUsables();
+}

Code/Inventory/Usable/IUseable.cs

@@ -0,0 +1,8 @@
+namespace Sasalka;
+
+public interface IUseable
+{
+	public void Use();
+	bool CanUse();
+	float Cooldown { get; }
+}

Code/Inventory/Usable/UseSystem.cs

@@ -0,0 +1,15 @@
+namespace Sasalka;
+
+public static class UseSystem
+{
+	public static void TryUse( IUseContext context )
+	{
+		foreach ( var useable in context.GetUsables() )
+		{
+			if ( useable.CanUse() )
+			{
+				useable.Use();
+			}
+		}
+	}
+}

Code/Inventory/Usable/UseableBase.cs

@@ -0,0 +1,31 @@
+using Sandbox;
+
+namespace Sasalka;
+
+public abstract class UseableBase : Component, IUseable
+{
+	[Property] public float Cooldown { get; set; } = 0.5f;
+
+	private TimeSince _timeSinceUsed;
+
+	protected override void OnStart()
+	{
+		_timeSinceUsed = Cooldown;
+	}
+
+	public virtual bool CanUse()
+	{
+		return _timeSinceUsed >= Cooldown && !Inventar.IsInventoryOpen;
+	}
+
+	public virtual void Use()
+	{
+		if ( !CanUse() )
+			return;
+
+		OnUse();
+		_timeSinceUsed = 0;
+	}
+
+	protected abstract void OnUse();
+}