feat(ui/templates): replace flat tree model with TmplNode discriminated by kind

src/ScadaLink.CentralUI/Components/Pages/Design/Templates.razor

@@ -293,22 +293,98 @@
         _loading = false;
     }
 
-    private record TmplTreeNode(Template Template, List<TmplTreeNode> Children);
+    private enum TmplNodeKind { Folder, Template, Composition }
 
-    private List<TmplTreeNode> _templateTreeRoots = new();
+    private record TmplNode(
+        string Key,
+        TmplNodeKind Kind,
+        int EntityId,
+        string Label,
+        int? ParentFolderId,
+        int? OwnerTemplateId,
+        Template? Template,
+        TemplateComposition? Composition,
+        List<TmplNode> Children);
+
+    private List<TmplNode> _treeRoots = new();
 
     private void BuildTemplateTree()
     {
-        _templateTreeRoots = BuildTmplChildren(null);
+        // 1. Folder nodes keyed by id
+        var folderNodes = _folders.ToDictionary(
+            f => f.Id,
+            f => new TmplNode(
+                Key: $"f:{f.Id}",
+                Kind: TmplNodeKind.Folder,
+                EntityId: f.Id,
+                Label: f.Name,
+                ParentFolderId: f.ParentFolderId,
+                OwnerTemplateId: null,
+                Template: null,
+                Composition: null,
+                Children: new List<TmplNode>()));
+
+        // 2. Attach folder nodes by ParentFolderId
+        var roots = new List<TmplNode>();
+        foreach (var f in _folders.OrderBy(f => f.Name, StringComparer.OrdinalIgnoreCase))
+        {
+            var node = folderNodes[f.Id];
+            if (f.ParentFolderId is int pid && folderNodes.TryGetValue(pid, out var parent))
+                parent.Children.Add(node);
+            else
+                roots.Add(node);
+        }
+
+        // 3. Template nodes with composition leaves
+        foreach (var t in _templates.OrderBy(t => t.Name, StringComparer.OrdinalIgnoreCase))
+        {
+            var compChildren = t.Compositions
+                .OrderBy(c => c.InstanceName, StringComparer.OrdinalIgnoreCase)
+                .Select(c => new TmplNode(
+                    Key: $"c:{c.Id}",
+                    Kind: TmplNodeKind.Composition,
+                    EntityId: c.Id,
+                    Label: c.InstanceName,
+                    ParentFolderId: null,
+                    OwnerTemplateId: t.Id,
+                    Template: null,
+                    Composition: c,
+                    Children: new List<TmplNode>()))
+                .ToList();
+
+            var tNode = new TmplNode(
+                Key: $"t:{t.Id}",
+                Kind: TmplNodeKind.Template,
+                EntityId: t.Id,
+                Label: t.Name,
+                ParentFolderId: t.FolderId,
+                OwnerTemplateId: null,
+                Template: t,
+                Composition: null,
+                Children: compChildren);
+
+            if (t.FolderId is int fid && folderNodes.TryGetValue(fid, out var parentFolder))
+                parentFolder.Children.Add(tNode);
+            else
+                roots.Add(tNode);
+        }
+
+        // 4. Sort each level: folders before templates, alphabetical
+        SortChildren(roots);
+        foreach (var node in folderNodes.Values)
+            SortChildren(node.Children);
+
+        _treeRoots = roots;
     }
 
-    private List<TmplTreeNode> BuildTmplChildren(int? parentId)
+    private static void SortChildren(List<TmplNode> children)
     {
-        return _templates
-            .Where(t => t.ParentTemplateId == parentId)
-            .OrderBy(t => t.Name)
-            .Select(t => new TmplTreeNode(t, BuildTmplChildren(t.Id)))
-            .ToList();
+        children.Sort((a, b) =>
+        {
+            var kindOrder = (int)a.Kind - (int)b.Kind;
+            if (kindOrder != 0) return kindOrder;
+            return string.Compare(a.Label, b.Label, StringComparison.OrdinalIgnoreCase);
+        });
     }
 
     private async Task SelectTemplate(int templateId)