Construction graph improvements (#17960)

Content.Shared/Construction/IGraphNodeEntity.cs

@@ -0,0 +1,29 @@
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Construction;
+
+public interface IGraphNodeEntity
+{
+    /// <summary>
+    ///     Gets the <see cref="EntityPrototype"/> ID for a node, given the <see cref="EntityUid"/> of both the
+    ///     construction entity and the user entity.
+    ///     If the construction entity is null, then we are dealing with a "start construction" for an entity that
+    ///     does not exist yet.
+    ///     If the user entity is null, this node was reached through means other some sort of "user interaction".
+    /// </summary>
+    /// <param name="uid">Uid of the construction entity.</param>
+    /// <param name="userUid">Uid of the user that caused the transition to the node.</param>
+    /// <param name="args">Arguments with useful instances, etc.</param>
+    /// <returns></returns>
+    public string? GetId(EntityUid? uid, EntityUid? userUid, GraphNodeEntityArgs args);
+}
+
+public readonly struct GraphNodeEntityArgs
+{
+    public readonly IEntityManager EntityManager;
+
+    public GraphNodeEntityArgs(IEntityManager entityManager)
+    {
+        EntityManager = entityManager;
+    }
+}