moths can eat goat wool (#21704)

* add Wooly system

* add RequireDead to Food

* minor fix+cleanup and fix repeating

* minor fix+cleanup and fix repeating

* make goat wooly

---------

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Server/Animals/Systems/WoolySystem.cs

@@ -0,0 +1,56 @@
+using Content.Server.Animals.Components;
+using Content.Server.Nutrition;
+using Content.Shared.Chemistry.EntitySystems;
+using Content.Shared.Nutrition.Components;
+using Content.Shared.Nutrition.EntitySystems;
+using Robust.Shared.Timing;
+
+namespace Content.Server.Animals.Systems;
+
+/// <summary>
+/// Handles regeneration of an animal's wool solution when not hungry.
+/// Shearing is not currently possible so the only use is for moths to eat.
+/// </summary>
+public sealed class WoolySystem : EntitySystem
+{
+    [Dependency] private readonly HungerSystem _hunger = default!;
+    [Dependency] private readonly IGameTiming _timing = default!;
+    [Dependency] private readonly SolutionContainerSystem _solutionContainer = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<WoolyComponent, BeforeFullyEatenEvent>(OnBeforeFullyEaten);
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var query = EntityQueryEnumerator<WoolyComponent, HungerComponent>();
+        var now = _timing.CurTime;
+        while (query.MoveNext(out var uid, out var comp, out var hunger))
+        {
+            if (now < comp.NextGrowth)
+                continue;
+
+            comp.NextGrowth = now + comp.GrowthDelay;
+
+            // Is there enough nutrition to produce reagent?
+            if (_hunger.GetHungerThreshold(hunger) < HungerThreshold.Peckish)
+                continue;
+
+            if (!_solutionContainer.TryGetSolution(uid, comp.Solution, out var solution))
+                continue;
+
+            _solutionContainer.TryAddReagent(uid, solution, comp.ReagentId, comp.Quantity, out _);
+        }
+    }
+
+    private void OnBeforeFullyEaten(Entity<WoolyComponent> ent, ref BeforeFullyEatenEvent args)
+    {
+        // don't want moths to delete goats after eating them
+        args.Cancel();
+    }
+}