feat: first cut at menu editor

tests/renderer/components/menuTreeMove.test.ts

@@ -0,0 +1,81 @@
+import { describe, expect, it } from 'vitest';
+import { applyTreeMove, type MenuTreeItem } from '../../../src/renderer/components/MenuEditorView/menuTreeMove';
+
+function createTree(): MenuTreeItem[] {
+  return [
+    {
+      id: 'home',
+      title: 'Home',
+      kind: 'page',
+      children: [],
+    },
+    {
+      id: 'docs',
+      title: 'Docs',
+      kind: 'submenu',
+      children: [
+        {
+          id: 'about',
+          title: 'About',
+          kind: 'page',
+          children: [],
+        },
+      ],
+    },
+    {
+      id: 'blog',
+      title: 'Blog',
+      kind: 'submenu',
+      children: [
+        {
+          id: 'post-1',
+          title: 'Post 1',
+          kind: 'page',
+          children: [],
+        },
+        {
+          id: 'post-2',
+          title: 'Post 2',
+          kind: 'page',
+          children: [],
+        },
+      ],
+    },
+  ];
+}
+
+describe('applyTreeMove', () => {
+  it('moves a page into a submenu', () => {
+    const moved = applyTreeMove(createTree(), {
+      dragIds: ['home'],
+      parentId: 'docs',
+      index: 1,
+    });
+
+    const docs = moved.find((item) => item.id === 'docs');
+    expect(docs?.children.map((child) => child.id)).toEqual(['about', 'home']);
+    expect(moved.map((item) => item.id)).toEqual(['docs', 'blog']);
+  });
+
+  it('moves a whole subtree without losing children', () => {
+    const moved = applyTreeMove(createTree(), {
+      dragIds: ['blog'],
+      parentId: null,
+      index: 0,
+    });
+
+    expect(moved[0].id).toBe('blog');
+    expect(moved[0].children.map((child) => child.id)).toEqual(['post-1', 'post-2']);
+  });
+
+  it('reorders siblings within same parent', () => {
+    const moved = applyTreeMove(createTree(), {
+      dragIds: ['post-2'],
+      parentId: 'blog',
+      index: 0,
+    });
+
+    const blog = moved.find((item) => item.id === 'blog');
+    expect(blog?.children.map((child) => child.id)).toEqual(['post-2', 'post-1']);
+  });
+});