From d1eb648b73d26a65f37c9597532c8085f24c3059 Mon Sep 17 00:00:00 2001
From: Yisroel Baum <yisroel.d.baum@gmail.com>
Date: Sat, 21 Feb 2026 22:44:18 +0200
Subject: [PATCH] test and impl that only one root node exists per text

in practice this means only one node with a null parentNode
---
 app/Node/UseCases/CreateNode.php            | 21 +++++++++++++++++++++
 tests/Unit/Node/UseCases/CreateNodeTest.php | 16 ++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/app/Node/UseCases/CreateNode.php b/app/Node/UseCases/CreateNode.php
index 25882f0..dcb8afa 100644
--- a/app/Node/UseCases/CreateNode.php
+++ b/app/Node/UseCases/CreateNode.php
@@ -15,6 +15,9 @@ class CreateNode
         private TextRepository $textRepo,
     ) {}
 
+    /**
+     * @throws DomainException
+     */
     public function execute(CreateNodeRequest $request): Node
     {
         $textId = $request->textId;
@@ -23,6 +26,7 @@ class CreateNode
             throw new DomainException("Text with id: $textId doesnt exist");
         }
         if ($request->parentNodeId === null) {
+            $this->validateNoOtherRootNodeExists($textId);
             return $this->nodeRepo->create(new CreateNodeDto(
                 text: $text,
                 title: $request->title,
@@ -41,4 +45,21 @@ class CreateNode
             parentNode: $parentNode,
         ));
     }
+
+    /**
+     * @throws DomainException
+     */
+    private function validateNoOtherRootNodeExists(int $textId): void
+    {
+        $nodesOfText = $this->nodeRepo->findByTextId($textId);
+        $exists = array_find(
+            $nodesOfText,
+            function (Node $node) {
+                return $node->getParentNode() === null;
+            }
+        );
+        if ($exists) {
+            throw new DomainException('A root node already exists for this text');
+        }
+    }
 }
diff --git a/tests/Unit/Node/UseCases/CreateNodeTest.php b/tests/Unit/Node/UseCases/CreateNodeTest.php
index 38ae268..e617079 100644
--- a/tests/Unit/Node/UseCases/CreateNodeTest.php
+++ b/tests/Unit/Node/UseCases/CreateNodeTest.php
@@ -95,4 +95,20 @@ class CreateNodeTest extends TestCase
             parentNodeId: 0,
         ));
     }
+
+    public function test_one_root_node_per_text(): void
+    {
+        $this->expectException(DomainException::class);
+        $this->expectExceptionMessage('A root node already exists for this text');
+        $this->useCase->execute(new CreateNodeRequest(
+            textId: 0,
+            title: 'test',
+            parentNodeId: null,
+        ));
+        $this->useCase->execute(new CreateNodeRequest(
+            textId: 0,
+            title: 'test',
+            parentNodeId: null,
+        ));
+    }
 }