Construction graph improvements (#17960)

Content.Server/Construction/NodeEntities/BoardNodeEntity.cs

@@ -0,0 +1,41 @@
+using Content.Server.Construction.Components;
+using Content.Shared.Construction;
+using Content.Shared.Construction.Components;
+using JetBrains.Annotations;
+using Robust.Server.Containers;
+
+namespace Content.Server.Construction.NodeEntities;
+
+/// <summary>
+///     Works for both <see cref="ComputerBoardComponent"/> and <see cref="MachineBoardComponent"/>
+///     because duplicating code just for this is really stinky.
+/// </summary>
+[UsedImplicitly]
+[DataDefinition]
+public sealed class BoardNodeEntity : IGraphNodeEntity
+{
+    [DataField("container")] public string Container { get; private set; } = string.Empty;
+
+    public string? GetId(EntityUid? uid, EntityUid? userUid, GraphNodeEntityArgs args)
+    {
+        if (uid == null)
+            return null;
+
+        var containerSystem = args.EntityManager.EntitySysManager.GetEntitySystem<ContainerSystem>();
+
+        if (!containerSystem.TryGetContainer(uid.Value, Container, out var container)
+            || container.ContainedEntities.Count == 0)
+            return null;
+
+        var board = container.ContainedEntities[0];
+
+        // There should not be a case where both of these components exist on the same entity...
+        if (args.EntityManager.TryGetComponent(board, out MachineBoardComponent? machine))
+            return machine.Prototype;
+
+        if(args.EntityManager.TryGetComponent(board, out ComputerBoardComponent? computer))
+            return computer.Prototype;
+
+        return null;
+    }
+}