Add hot potato (#14204)

Co-authored-by: AJCM <AJCM@tutanota.com>

Content.Shared/HotPotato/ActiveHotPotatoComponent.cs

@@ -0,0 +1,23 @@
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.HotPotato;
+
+/// <summary>
+/// Added to an activated hot potato. Controls hot potato transfer on server / effect spawning on client.
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+[Access(typeof(SharedHotPotatoSystem))]
+public sealed class ActiveHotPotatoComponent : Component
+{
+    /// <summary>
+    /// Hot potato effect spawn cooldown in seconds
+    /// </summary>
+    [DataField("effectCooldown"), ViewVariables(VVAccess.ReadWrite)]
+    public float EffectCooldown = 0.3f;
+
+    /// <summary>
+    /// Moment in time next effect will be spawned
+    /// </summary>
+    [ViewVariables(VVAccess.ReadWrite)]
+    public TimeSpan TargetTime = TimeSpan.Zero;
+}

Content.Shared/HotPotato/HotPotatoComponent.cs

@@ -0,0 +1,20 @@
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.HotPotato;
+
+/// <summary>
+/// Similar to <see cref="Content.Shared.Interaction.Components.UnremoveableComponent"/>
+/// except entities with this component can be removed in specific case: <see cref="CanTransfer"/>
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+[AutoGenerateComponentState]
+[Access(typeof(SharedHotPotatoSystem))]
+public sealed partial class HotPotatoComponent : Component
+{
+    /// <summary>
+    /// If set to true entity can be removed by hitting entities if they have hands
+    /// </summary>
+    [DataField("canTransfer"), ViewVariables(VVAccess.ReadWrite)]
+    [AutoNetworkedField]
+    public bool CanTransfer = true;
+}

Content.Shared/HotPotato/SharedHotPotatoSystem.cs

@@ -0,0 +1,18 @@
+using Robust.Shared.Containers;
+
+namespace Content.Shared.HotPotato;
+
+public abstract class SharedHotPotatoSystem : EntitySystem
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<HotPotatoComponent, ContainerGettingRemovedAttemptEvent>(OnRemoveAttempt);
+    }
+
+    private void OnRemoveAttempt(EntityUid uid, HotPotatoComponent comp, ContainerGettingRemovedAttemptEvent args)
+    {
+        if (!comp.CanTransfer)
+            args.Cancel();
+    }
+}