Migrate cuffing to an uncuff attempt event and allow self-uncuff again (#4725)

* Migrate cuffing to an uncuff attempt event and allow self-uncuff again

* Uncuff attempt event: Use more SubscribeLocalEvent and Dependency attributes

Content.Server/Cuffs/CuffableSystem.cs

@@ -1,20 +1,72 @@
 using Content.Server.Cuffs.Components;
 using Content.Server.Hands.Components;
 using Content.Shared.Hands.Components;
+using Content.Shared.ActionBlocker;
+using Content.Shared.MobState;
 using Content.Shared.Cuffs;
+using Content.Shared.Popups;
 using JetBrains.Annotations;
 using Robust.Shared.GameObjects;
+using Robust.Shared.Localization;
+using Robust.Shared.IoC;
 
 namespace Content.Server.Cuffs
 {
     [UsedImplicitly]
     internal sealed class CuffableSystem : SharedCuffableSystem
     {
+        [Dependency] private readonly SharedPopupSystem _popupSystem = default!;
+        [Dependency] private readonly ActionBlockerSystem _actionBlockerSystem = default!;
+
         public override void Initialize()
         {
             base.Initialize();
 
-            EntityManager.EventBus.SubscribeEvent<HandCountChangedEvent>(EventSource.Local, this, OnHandCountChanged);
+            SubscribeLocalEvent<HandCountChangedEvent>(OnHandCountChanged);
+            SubscribeLocalEvent<UncuffAttemptEvent>(OnUncuffAttempt);
+        }
+
+        private void OnUncuffAttempt(UncuffAttemptEvent args)
+        {
+            if (args.Cancelled)
+            {
+                return;
+            }
+            if (!EntityManager.TryGetEntity(args.User, out var userEntity))
+            {
+                // Should this even be possible?
+                args.Cancel();
+                return;
+            }
+            // If the user is the target, special logic applies.
+            // This is because the CanInteract blocking of the cuffs prevents self-uncuff.
+            if (args.User == args.Target)
+            {
+                if (userEntity.TryGetComponent<IMobStateComponent>(out var state))
+                {
+                    // Manually check this.
+                    if (state.IsIncapacitated())
+                    {
+                        args.Cancel();
+                    }
+                }
+                else
+                {
+                    // Uh... let it go through???
+                }
+            }
+            else
+            {
+                // Check if the user can interact.
+                if (!_actionBlockerSystem.CanInteract(userEntity))
+                {
+                    args.Cancel();
+                }
+            }
+            if (args.Cancelled)
+            {
+                _popupSystem.PopupEntity(Loc.GetString("cuffable-component-cannot-interact-message"), args.Target, _popupSystem.GetFilterFromEntity(userEntity));
+            }
         }
 
         /// <summary>
@@ -49,4 +101,20 @@ namespace Content.Server.Cuffs
             }
         }
     }
+
+    /// <summary>
+    /// Event fired on the User when the User attempts to cuff the Target.
+    /// Should generate popups on the User.
+    /// </summary>
+    public class UncuffAttemptEvent : CancellableEntityEventArgs
+    {
+        public readonly EntityUid User;
+        public readonly EntityUid Target;
+
+        public UncuffAttemptEvent(EntityUid user, EntityUid target)
+        {
+            User = user;
+            Target = target;
+        }
+    }
 }