Climbing refactor (#20516)

Content.Shared/DragDrop/SharedDragDropSystem.cs

@@ -1,6 +1,51 @@
-namespace Content.Shared.DragDrop;
+using Content.Shared.ActionBlocker;
+using Content.Shared.Interaction;
+
+namespace Content.Shared.DragDrop;
 
 public abstract class SharedDragDropSystem : EntitySystem
 {
+    [Dependency] private readonly ActionBlockerSystem _actionBlockerSystem = default!;
+    [Dependency] private readonly SharedInteractionSystem _interaction = default!;
 
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeAllEvent<DragDropRequestEvent>(OnDragDropRequestEvent);
+    }
+
+    private void OnDragDropRequestEvent(DragDropRequestEvent msg, EntitySessionEventArgs args)
+    {
+        var dragged = GetEntity(msg.Dragged);
+        var target = GetEntity(msg.Target);
+
+        if (Deleted(dragged) || Deleted(target))
+            return;
+
+        var user = args.SenderSession.AttachedEntity;
+
+        if (user == null || !_actionBlockerSystem.CanInteract(user.Value, target))
+            return;
+
+        // must be in range of both the target and the object they are drag / dropping
+        // Client also does this check but ya know we gotta validate it.
+        if (!_interaction.InRangeUnobstructed(user.Value, dragged, popup: true)
+            || !_interaction.InRangeUnobstructed(user.Value, target, popup: true))
+        {
+            return;
+        }
+
+        var dragArgs = new DragDropDraggedEvent(user.Value, target);
+
+        // trigger dragdrops on the dropped entity
+        RaiseLocalEvent(dragged, ref dragArgs);
+
+        if (dragArgs.Handled)
+            return;
+
+        var dropArgs = new DragDropTargetEvent(user.Value, dragged);
+
+        // trigger dragdrops on the target entity (what you are dropping onto)
+        RaiseLocalEvent(GetEntity(msg.Target), ref dropArgs);
+    }
 }