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routlin/validation.py

@@ -267,32 +267,22 @@ def derive_vlan_id(subnet, prefix):
         return None
 
 
-def resolve_vlan_derived_fields(data):
-    """Return a deep copy of data with vlan_id and interface computed for every VLAN.
-
-    WireGuard VLANs are assigned wg0/wg1/... in ascending vlan_id order for
-    deterministic interface naming regardless of JSON list order.
-    Does not mutate the input dict.
-    """
-    import copy
-    result = copy.deepcopy(data)
-    lan    = result.get("general", {}).get("lan_interface", "eth0")
-    vlans  = result.get("vlans", [])
-
-    for vlan in vlans:
-        vlan["vlan_id"] = derive_vlan_id(vlan.get("subnet", ""), vlan.get("subnet_mask", 24))
-
-    wg_entries = [(i, v) for i, v in enumerate(vlans) if is_wg(v)]
-    wg_sorted  = sorted(wg_entries, key=lambda x: (x[1].get("vlan_id") is None, x[1].get("vlan_id") or 0))
-    for wg_idx, (_, vlan) in enumerate(wg_sorted):
-        vlan["interface"] = f"wg{wg_idx}"
-
-    for vlan in vlans:
-        if not is_wg(vlan):
-            vid = vlan.get("vlan_id", 1)
-            vlan["interface"] = lan if vid == 1 else f"{lan}.{vid}"
-
-    return result
+def derive_interface(vlan, data):
+    """Derive the interface name for a VLAN without mutating data."""
+    lan = data.get('general', {}).get('lan_interface', 'eth0')
+    if is_wg(vlan):
+        wg_vlans = [v for v in data.get('vlans', []) if is_wg(v)]
+        wg_sorted = sorted(
+            wg_vlans,
+            key=lambda v: (
+                derive_vlan_id(v.get('subnet', ''), v.get('subnet_mask', 24)) is None,
+                derive_vlan_id(v.get('subnet', ''), v.get('subnet_mask', 24)) or 0,
+            )
+        )
+        idx = next((i for i, v in enumerate(wg_sorted) if v is vlan), 0)
+        return f'wg{idx}'
+    vid = derive_vlan_id(vlan.get('subnet', ''), vlan.get('subnet_mask', 24))
+    return lan if vid == 1 else f'{lan}.{vid}'
 
 
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