feat(template-folder): move with cycle detection and sibling uniqueness

src/ScadaLink.TemplateEngine/Services/TemplateFolderService.cs

@@ -67,4 +67,55 @@ public class TemplateFolderService
 
         return Result<TemplateFolder>.Success(folder);
     }
+
+    public async Task<Result<TemplateFolder>> MoveFolderAsync(
+        int folderId, int? newParentId, string user,
+        CancellationToken cancellationToken = default)
+    {
+        var folder = await _repository.GetFolderByIdAsync(folderId, cancellationToken);
+        if (folder == null)
+            return Result<TemplateFolder>.Failure($"Folder with ID {folderId} not found.");
+
+        if (newParentId.HasValue)
+        {
+            if (newParentId.Value == folderId)
+                return Result<TemplateFolder>.Failure("Cannot move a folder into itself (cycle).");
+
+            var newParent = await _repository.GetFolderByIdAsync(newParentId.Value, cancellationToken);
+            if (newParent == null)
+                return Result<TemplateFolder>.Failure($"Target folder with ID {newParentId.Value} not found.");
+
+            var all = await _repository.GetAllFoldersAsync(cancellationToken);
+            // Walk up from newParentId — if we encounter folderId, the move would create a cycle.
+            var byId = all.ToDictionary(f => f.Id);
+            var cursor = newParentId;
+            while (cursor.HasValue)
+            {
+                if (cursor.Value == folderId)
+                    return Result<TemplateFolder>.Failure("Cannot move a folder under one of its descendants (cycle).");
+                cursor = byId.TryGetValue(cursor.Value, out var node) ? node.ParentFolderId : null;
+            }
+
+            // Sibling-name uniqueness in destination.
+            if (all.Any(f => f.Id != folderId
+                             && f.ParentFolderId == newParentId
+                             && string.Equals(f.Name, folder.Name, StringComparison.OrdinalIgnoreCase)))
+                return Result<TemplateFolder>.Failure($"A folder named '{folder.Name}' already exists in the target folder.");
+        }
+        else
+        {
+            var all = await _repository.GetAllFoldersAsync(cancellationToken);
+            if (all.Any(f => f.Id != folderId
+                             && f.ParentFolderId == null
+                             && string.Equals(f.Name, folder.Name, StringComparison.OrdinalIgnoreCase)))
+                return Result<TemplateFolder>.Failure($"A folder named '{folder.Name}' already exists at the root.");
+        }
+
+        folder.ParentFolderId = newParentId;
+        await _repository.UpdateFolderAsync(folder, cancellationToken);
+        await _repository.SaveChangesAsync(cancellationToken);
+        await _auditService.LogAsync(user, "Move", "TemplateFolder", folder.Id.ToString(), folder.Name, folder, cancellationToken);
+
+        return Result<TemplateFolder>.Success(folder);
+    }
 }