AI pickup changes (#1811)

* AI pickup changes

Eating and drinking isn't spammed anymore.
AI can do InRangeUnobstructed checks for item pickups.
AI can open drink cans.

AI littering to be coded.

* #nullable enable

* github's nullable fails are actively shortening my lifespan

* Use a const instead

So it's easier to find given the performance implications.

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Server/AI/Operators/Nutrition/UseFoodInInventoryOperator.cs

@@ -0,0 +1,73 @@
+#nullable enable
+using Content.Server.GameObjects.Components.GUI;
+using Content.Server.GameObjects.Components.Items.Storage;
+using Content.Server.GameObjects.Components.Nutrition;
+using Content.Shared.GameObjects.Components.Nutrition;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Random;
+using Robust.Shared.IoC;
+using Robust.Shared.Random;
+
+namespace Content.Server.AI.Operators.Nutrition
+{
+    public class UseFoodInInventoryOperator : AiOperator
+    {
+        private readonly IEntity _owner;
+        private readonly IEntity _target;
+        private float _interactionCooldown;
+
+        public UseFoodInInventoryOperator(IEntity owner, IEntity target)
+        {
+            _owner = owner;
+            _target = target;
+        }
+
+        public override Outcome Execute(float frameTime)
+        {
+            if (_interactionCooldown >= 0)
+            {
+                _interactionCooldown -= frameTime;
+                return Outcome.Continuing;
+            }
+            
+            // TODO: Also have this check storage a la backpack etc.
+            if (_target.Deleted || 
+                !_owner.TryGetComponent(out HandsComponent handsComponent) ||
+                !_target.TryGetComponent(out ItemComponent itemComponent))
+            {
+                return Outcome.Failed;
+            }
+
+            FoodComponent? foodComponent = null;
+
+            foreach (var slot in handsComponent.ActivePriorityEnumerable())
+            {
+                if (handsComponent.GetItem(slot) != itemComponent) continue;
+                handsComponent.ActiveHand = slot;
+                if (!_target.TryGetComponent(out foodComponent))
+                {
+                    return Outcome.Failed;
+                }
+
+                // This should also implicitly open it.
+                handsComponent.ActivateItem();
+                _interactionCooldown = IoCManager.Resolve<IRobustRandom>().NextFloat() + 0.5f;
+            }
+
+            if (foodComponent == null)
+            {
+                return Outcome.Failed;
+            }
+            
+            if (_target.Deleted || 
+                foodComponent.UsesRemaining == 0 || 
+                _owner.TryGetComponent(out HungerComponent hungerComponent) && 
+                hungerComponent.CurrentHunger >= hungerComponent.HungerThresholds[HungerThreshold.Okay])
+            {
+                return Outcome.Success;
+            }
+
+            return Outcome.Continuing;
+        }
+    }
+}