Fix duplicate mech footstep sounds (#12972)

* Fix duplicate mech footstep sounds

We just add a new component for relay targets so we can use that for audio prediction.

* Fix cwash

* woop

Content.Shared/Movement/Systems/SharedMoverController.Relay.cs

@@ -12,6 +12,10 @@ public abstract partial class SharedMoverController
         SubscribeLocalEvent<RelayInputMoverComponent, ComponentGetState>(OnRelayGetState);
         SubscribeLocalEvent<RelayInputMoverComponent, ComponentHandleState>(OnRelayHandleState);
         SubscribeLocalEvent<RelayInputMoverComponent, ComponentShutdown>(OnRelayShutdown);
+
+        SubscribeLocalEvent<MovementRelayTargetComponent, ComponentGetState>(OnTargetRelayGetState);
+        SubscribeLocalEvent<MovementRelayTargetComponent, ComponentHandleState>(OnTargetRelayHandleState);
+        SubscribeLocalEvent<MovementRelayTargetComponent, ComponentShutdown>(OnTargetRelayShutdown);
     }
 
     /// <summary>
@@ -20,7 +24,7 @@ public abstract partial class SharedMoverController
     /// </summary>
     public void SetRelay(EntityUid uid, EntityUid relayEntity, RelayInputMoverComponent? component = null)
     {
-        if (!Resolve(uid, ref component))
+        if (!Resolve(uid, ref component) || component.RelayEntity == relayEntity)
             return;
 
         if (uid == relayEntity)
@@ -29,14 +33,38 @@ public abstract partial class SharedMoverController
             return;
         }
 
+        if (TryComp<MovementRelayTargetComponent>(relayEntity, out var targetComp))
+        {
+            targetComp.Entities.Remove(uid);
+
+            if (targetComp.Entities.Count == 0)
+                RemComp<MovementRelayTargetComponent>(relayEntity);
+        }
+
         component.RelayEntity = relayEntity;
+        targetComp = EnsureComp<MovementRelayTargetComponent>(relayEntity);
+        targetComp.Entities.Add(uid);
         Dirty(component);
+        Dirty(targetComp);
     }
 
     private void OnRelayShutdown(EntityUid uid, RelayInputMoverComponent component, ComponentShutdown args)
     {
         // If relay is removed then cancel all inputs.
-        if (!TryComp<InputMoverComponent>(component.RelayEntity, out var inputMover)) return;
+        if (!TryComp<InputMoverComponent>(component.RelayEntity, out var inputMover))
+            return;
+
+        if (TryComp<MovementRelayTargetComponent>(component.RelayEntity, out var targetComp) &&
+            targetComp.LifeStage < ComponentLifeStage.Stopping)
+        {
+            targetComp.Entities.Remove(uid);
+
+            if (targetComp.Entities.Count == 0)
+                RemCompDeferred<MovementRelayTargetComponent>(component.RelayEntity.Value);
+            else
+                Dirty(targetComp);
+        }
+
         SetMoveInput(inputMover, MoveButtons.None);
     }
 
@@ -56,9 +84,59 @@ public abstract partial class SharedMoverController
         };
     }
 
+    #region Target Relay
+
+    private void OnTargetRelayShutdown(EntityUid uid, MovementRelayTargetComponent component, ComponentShutdown args)
+    {
+        if (component.Entities.Count == 0)
+            return;
+
+        var relayQuery = GetEntityQuery<RelayInputMoverComponent>();
+
+        foreach (var ent in component.Entities)
+        {
+            if (!relayQuery.TryGetComponent(ent, out var relay))
+                continue;
+
+            DebugTools.Assert(relay.RelayEntity == uid);
+
+            if (relay.RelayEntity != uid)
+                continue;
+
+            RemCompDeferred<RelayInputMoverComponent>(ent);
+        }
+    }
+
+    private void OnTargetRelayHandleState(EntityUid uid, MovementRelayTargetComponent component, ref ComponentHandleState args)
+    {
+        if (args.Current is not MovementRelayTargetComponentState state)
+            return;
+
+        component.Entities.Clear();
+        component.Entities.AddRange(state.Entities);
+    }
+
+    private void OnTargetRelayGetState(EntityUid uid, MovementRelayTargetComponent component, ref ComponentGetState args)
+    {
+        args.State = new MovementRelayTargetComponentState(component.Entities);
+    }
+
+    #endregion
+
     [Serializable, NetSerializable]
     private sealed class RelayInputMoverComponentState : ComponentState
     {
         public EntityUid? Entity;
     }
+
+    [Serializable, NetSerializable]
+    private sealed class MovementRelayTargetComponentState : ComponentState
+    {
+        public List<EntityUid> Entities;
+
+        public MovementRelayTargetComponentState(List<EntityUid> entities)
+        {
+            Entities = entities;
+        }
+    }
 }