implement config layering

owrx/config/migration.py

@@ -1,5 +1,9 @@
 from abc import ABC, abstractmethod
 
+import logging
+
+logger = logging.getLogger(__name__)
+
 
 class ConfigMigrator(ABC):
     @abstractmethod
@@ -26,11 +30,30 @@ class ConfigMigratorVersion1(ConfigMigrator):
         self.renameKey(config, "wsjt_queue_length", "decoding_queue_length")
 
         config["version"] = 2
-        return config
 
 
 class ConfigMigratorVersion2(ConfigMigrator):
     def migrate(self, config):
         if "waterfall_colors" in config and any(v > 0xFFFFFF for v in config["waterfall_colors"]):
             config["waterfall_colors"] = [v >> 8 for v in config["waterfall_colors"]]
-        return config
+
+        config["version"] = 3
+
+
+class Migrator(object):
+    currentVersion = 3
+    migrators = {
+        1: ConfigMigratorVersion1(),
+        2: ConfigMigratorVersion2(),
+    }
+
+    @staticmethod
+    def migrate(config):
+        version = config["version"] if "version" in config else 1
+        if version == Migrator.currentVersion:
+            return config
+
+        logger.debug("migrating config from version %i", version)
+        migrators = [Migrator.migrators[i] for i in range(version, Migrator.currentVersion)]
+        for migrator in migrators:
+            migrator.migrate(config)