New science unlock: the H.A.R.M.P.A.C.K (#38824)

Content.Shared/Hands/Components/ExtraHandsEquipmentComponent.cs

@@ -0,0 +1,18 @@
+using Robust.Shared.GameStates;
+using Content.Shared.Hands.EntitySystems;
+
+namespace Content.Shared.Hands.Components;
+
+/// <summary>
+/// An entity with this component will give you extra hands when you equip it in your inventory.
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+[Access(typeof(ExtraHandsEquipmentSystem))]
+public sealed partial class ExtraHandsEquipmentComponent : Component
+{
+    /// <summary>
+    /// Dictionary relating a unique hand ID corresponding to a container slot on the attached entity to a struct containing information about the Hand itself.
+    /// </summary>
+    [DataField]
+    public Dictionary<string, Hand> Hands = new();
+}

Content.Shared/Hands/EntitySystems/ExtraHandsEquipmentSystem.cs

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+using Content.Shared.Hands.Components;
+using Content.Shared.Inventory.Events;
+
+namespace Content.Shared.Hands.EntitySystems;
+
+public sealed class ExtraHandsEquipmentSystem : EntitySystem
+{
+    [Dependency] private readonly SharedHandsSystem _hands = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<ExtraHandsEquipmentComponent, GotEquippedEvent>(OnEquipped);
+        SubscribeLocalEvent<ExtraHandsEquipmentComponent, GotUnequippedEvent>(OnUnequipped);
+    }
+
+    private void OnEquipped(Entity<ExtraHandsEquipmentComponent> ent, ref GotEquippedEvent args)
+    {
+        if (!TryComp<HandsComponent>(args.Equipee, out var handsComp))
+            return;
+
+        foreach (var (handName, hand) in ent.Comp.Hands)
+        {
+            // add the NetEntity id to the container name to prevent multiple items with this component from conflicting
+            var handId = $"{GetNetEntity(ent.Owner).Id}-{handName}";
+            _hands.AddHand((args.Equipee, handsComp), handId, hand.Location);
+        }
+    }
+
+    private void OnUnequipped(Entity<ExtraHandsEquipmentComponent> ent, ref GotUnequippedEvent args)
+    {
+        if (!TryComp<HandsComponent>(args.Equipee, out var handsComp))
+            return;
+
+        foreach (var handName in ent.Comp.Hands.Keys)
+        {
+            // add the NetEntity id to the container name to prevent multiple items with this component from conflicting
+            var handId = $"{GetNetEntity(ent.Owner).Id}-{handName}";
+            _hands.RemoveHand((args.Equipee, handsComp), handId);
+        }
+    }
+}