implement config layering

owrx/config/classic.py

@@ -0,0 +1,30 @@
+from owrx.property import PropertyReadOnly, PropertyLayer
+from owrx.config.migration import Migrator
+import importlib.util
+
+
+class ClassicConfig(PropertyReadOnly):
+    def __init__(self):
+        pm = ClassicConfig._loadConfig()
+        Migrator.migrate(pm)
+        super().__init__(pm)
+
+    @staticmethod
+    def _loadConfig():
+        for file in ["/etc/openwebrx/config_webrx.py", "./config_webrx.py"]:
+            try:
+                return ClassicConfig._loadPythonFile(file)
+            except FileNotFoundError:
+                pass
+
+    @staticmethod
+    def _loadPythonFile(file):
+        spec = importlib.util.spec_from_file_location("config_webrx", file)
+        cfg = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(cfg)
+        pm = PropertyLayer()
+        for name, value in cfg.__dict__.items():
+            if name.startswith("__"):
+                continue
+            pm[name] = value
+        return pm