Protect referenced feeder structures from deletion

tests/distribution-board-structure-project-command.repository.test.ts

@@ -219,6 +219,54 @@ describe("distribution-board structure project command", () => {
     }
   });
 
+  it("blocks undo from removing an empty board used as a feeder", () => {
+    const context = createTestDatabase();
+    try {
+      const repository =
+        new DistributionBoardStructureProjectCommandRepository(context.db);
+      const upstream = createDistributionBoardStructureSnapshot(
+        "project-1",
+        "NSHV"
+      );
+      const inserted = repository.execute({
+        projectId: "project-1",
+        expectedRevision: 0,
+        source: "user",
+        command: createDistributionBoardInsertProjectCommand(upstream),
+      });
+      const downstream = createDistributionBoardStructureSnapshot(
+        "project-1",
+        "UV-01"
+      );
+      context.db.insert(distributionBoards).values({
+        ...downstream.distributionBoard,
+        boardNumber: "UV-01",
+        feedingDistributionBoardId: upstream.distributionBoard.id,
+      }).run();
+      context.db.insert(circuitLists).values(downstream.circuitList).run();
+      context.db.insert(circuitSections).values(downstream.sections).run();
+      context.db.insert(distributionBoardComponents)
+        .values(downstream.components).run();
+
+      assert.throws(
+        () => repository.execute({
+          projectId: "project-1",
+          expectedRevision: 1,
+          source: "undo",
+          historyTargetChangeSetId: inserted.revision.changeSetId,
+          command: inserted.inverse,
+        }),
+        /Speist UV-01 – erst Einspeisung ändern\./
+      );
+      assert.ok(
+        context.db.select().from(distributionBoards)
+          .where(eq(distributionBoards.id, upstream.distributionBoard.id)).get()
+      );
+    } finally {
+      context.close();
+    }
+  });
+
   it("allows only supply types enabled in the project", () => {
     const context = createTestDatabase();
     try {