Avoids circular dependency in profile groups

Adds cycle detection to prevent infinite loops when evaluating profile groups.

This ensures that profile group configurations don't result in stack overflow errors when groups reference each other, directly or indirectly.

v2rayN/ServiceLib/Models/ProfileItem.cs

@@ -109,6 +109,42 @@ public class ProfileItem : ReactiveObject
         return true;
     }
 
+    public async Task<bool> HasCycle(HashSet<string> visited, HashSet<string> stack)
+    {
+        if (ConfigType < EConfigType.Group)
+            return false;
+
+        if (stack.Contains(IndexId))
+            return true;
+
+        if (visited.Contains(IndexId))
+            return false;
+
+        visited.Add(IndexId);
+        stack.Add(IndexId);
+
+        if (ProfileGroupItemManager.Instance.TryGet(IndexId, out var group)
+            && !group.ChildItems.IsNullOrEmpty())
+        {
+            var childProfiles = (await Task.WhenAll(
+                    Utils.String2List(group.ChildItems)
+                        .Where(p => !p.IsNullOrEmpty())
+                        .Select(AppManager.Instance.GetProfileItem)
+                ))
+                .Where(p => p != null)
+                .ToList();
+
+            foreach (var child in childProfiles)
+            {
+                if (await child.HasCycle(visited, stack))
+                    return true;
+            }
+        }
+
+        stack.Remove(IndexId);
+        return false;
+    }
+
     #endregion function
 
     [PrimaryKey]

v2rayN/ServiceLib/Services/CoreConfig/Singbox/SingboxOutboundService.cs

@@ -217,9 +217,15 @@ public partial class CoreConfigSingboxService
             {
                 return -1;
             }
+
+            var hasCycle = await node.HasCycle(new HashSet<string>(), new HashSet<string>());
+            if (hasCycle)
+            {
+                return -1;
+            }
+
             // remove custom nodes
             // remove group nodes for proxy chain
-            // avoid self-reference
             var childProfiles = (await Task.WhenAll(
                     Utils.String2List(profileGroupItem.ChildItems)
                         .Where(p => !p.IsNullOrEmpty())
@@ -230,7 +236,6 @@ public partial class CoreConfigSingboxService
                     && p.IsValid()
                     && p.ConfigType != EConfigType.Custom
                     && (node.ConfigType == EConfigType.PolicyGroup || p.ConfigType < EConfigType.Group)
-                    && p.IndexId != node.IndexId
                 )
                 .ToList();
 

v2rayN/ServiceLib/Services/CoreConfig/V2ray/V2rayOutboundService.cs

@@ -493,6 +493,13 @@ public partial class CoreConfigV2rayService
             {
                 return -1;
             }
+
+            var hasCycle = await node.HasCycle(new HashSet<string>(), new HashSet<string>());
+            if (hasCycle)
+            {
+                return -1;
+            }
+
             // remove custom nodes
             // remove group nodes for proxy chain
             var childProfiles = (await Task.WhenAll(