Reduce action blocker uses and add target entity to CanInteract (#6655)

Content.Shared/ActionBlocker/ActionBlockerSystem.cs

@@ -16,7 +16,7 @@ namespace Content.Shared.ActionBlocker
     /// Utility methods to check if a specific entity is allowed to perform an action.
     /// </summary>
     [UsedImplicitly]
-    public class ActionBlockerSystem : EntitySystem
+    public sealed class ActionBlockerSystem : EntitySystem
     {
         public bool CanMove(EntityUid uid)
         {
@@ -26,26 +26,54 @@ namespace Content.Shared.ActionBlocker
             return !ev.Cancelled;
         }
 
-        public bool CanInteract(EntityUid uid)
+        /// <summary>
+        ///     Raises an event directed at both the user and the target entity to check whether a user is capable of
+        ///     interacting with this entity.
+        /// </summary>
+        /// <remarks>
+        ///     If this is a generic interaction without a target (e.g., stop-drop-and-roll when burning), the target
+        ///     may be null. Note that this is checked by <see cref="SharedInteractionSystem"/>. In the majority of
+        ///     cases, systems that provide interactions will not need to check this themselves, though they may need to
+        ///     check other blockers like <see cref="CanPickup(EntityUid)"/>
+        /// </remarks>
+        /// <returns></returns>
+        public bool CanInteract(EntityUid user, EntityUid? target)
         {
-            var ev = new InteractionAttemptEvent(uid);
-            RaiseLocalEvent(uid, ev);
+            var ev = new InteractionAttemptEvent(user, target);
+            RaiseLocalEvent(user, ev);
+
+            if (ev.Cancelled)
+                return false;
+
+            if (target == null)
+                return true;
+
+            var targetEv = new GettingInteractedWithAttemptEvent(user, target);
+            RaiseLocalEvent(target.Value, targetEv);
+
+            return !targetEv.Cancelled;
+        }
+
+        /// <summary>
+        ///     Can a user utilize the entity that they are currently holding in their hands.
+        /// </summary>>
+        /// <remarks>
+        ///     This event is automatically checked by <see cref="SharedInteractionSystem"/> for any interactions that
+        ///     involve using a held entity. In the majority of cases, systems that provide interactions will not need
+        ///     to check this themselves.
+        /// </remarks>
+        public bool CanUseHeldEntity(EntityUid user)
+        {
+            var ev = new UseAttemptEvent(user);
+            RaiseLocalEvent(user, ev);
 
             return !ev.Cancelled;
         }
 
-        public bool CanUse(EntityUid uid)
+        public bool CanThrow(EntityUid user)
         {
-            var ev = new UseAttemptEvent(uid);
-            RaiseLocalEvent(uid, ev);
-
-            return !ev.Cancelled;
-        }
-
-        public bool CanThrow(EntityUid uid)
-        {
-            var ev = new ThrowAttemptEvent(uid);
-            RaiseLocalEvent(uid, ev);
+            var ev = new ThrowAttemptEvent(user);
+            RaiseLocalEvent(user, ev);
 
             return !ev.Cancelled;
         }