refactor(dbus): Move system configuration methods to revpi_config.py

Centralized `ConfigActions`, `configure_gui`, and `simple_systemd` into
`revpi_config.py` to eliminate duplication and improve maintainability.
Updated `interface_config.py` to import these methods, ensuring
consistent functionality across modules.

src/revpi_middleware/dbus_middleware1/system_config/interface_config.py

@@ -3,12 +3,9 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 """D-Bus interfaces for hardware configuration."""
 from collections import namedtuple
-from enum import Enum
 from logging import getLogger
-from os import X_OK, access
-
-from pydbus import SystemBus
 
+from .revpi_config import ConfigActions, configure_gui, simple_systemd
 from ..dbus_helper import DbusInterface
 
 log = getLogger(__name__)
@@ -16,13 +13,6 @@ log = getLogger(__name__)
 FeatureFunction = namedtuple("FeatureFunction", ["function", "args"])
 
 
-class ConfigActions(Enum):
-    ENABLE = "enable"
-    DISABLE = "disable"
-    STATUS = "status"
-    AVAILABLE = "available"
-
-
 class InterfaceRevpiConfig(DbusInterface):
     """
     <node>
@@ -71,28 +61,6 @@ class InterfaceRevpiConfig(DbusInterface):
         return list(AVAILABLE_FEATURES.keys())
 
 
-def configure_gui(action: ConfigActions):
-    gui_available = access("/usr/bin/startx", X_OK)
-
-    if action is ConfigActions.AVAILABLE:
-        return gui_available
-
-    bus = SystemBus()
-    systemd_manager = bus.get(".systemd1")
-
-    if action is ConfigActions.ENABLE:
-        systemd_manager.SetDefaultTarget("graphical.target", True)
-
-    elif action is ConfigActions.DISABLE:
-        systemd_manager.SetDefaultTarget("multi-user.target", True)
-
-    elif action is ConfigActions.STATUS:
-        return systemd_manager.GetDefaultTarget() == "graphical.target"
-
-    else:
-        raise ValueError(f"action {action} not supported")
-
-
 def get_feature(feature: str) -> FeatureFunction:
     if feature not in AVAILABLE_FEATURES:
         raise ValueError(f"feature {feature} does not exist")
@@ -102,43 +70,6 @@ def get_feature(feature: str) -> FeatureFunction:
     return feature_function
 
 
-def simple_systemd(action: ConfigActions, unit: str):
-    bus = SystemBus()
-    systemd_manager = bus.get(".systemd1")
-
-    if action is ConfigActions.ENABLE:
-        systemd_manager.UnmaskUnitFiles([unit], False)
-        systemd_manager.EnableUnitFiles([unit], False, False)
-        systemd_manager.StartUnit(unit, "replace")
-
-    elif action is ConfigActions.DISABLE:
-        systemd_manager.StopUnit(unit, "replace")
-        systemd_manager.DisableUnitFiles([unit], False)
-
-    elif action is ConfigActions.STATUS:
-        try:
-            unit_path = systemd_manager.LoadUnit(unit)
-            properties = bus.get(".systemd1", unit_path)
-        except Exception:
-            log.warning(f"could not get systemd unit {unit}")
-            return False
-
-        return properties.UnitFileState == "enabled" and properties.ActiveState == "active"
-
-    elif action is ConfigActions.AVAILABLE:
-        try:
-            unit_path = systemd_manager.LoadUnit(unit)
-            properties = bus.get(".systemd1", unit_path)
-        except Exception:
-            log.warning(f"could not get systemd unit {unit}")
-            return False
-
-        return properties.LoadState != "not-found"
-
-    else:
-        raise ValueError(f"action {action} not supported")
-
-
 AVAILABLE_FEATURES = {
     "gui": FeatureFunction(configure_gui, []),
     "revpi-con-can": False,