refactor: add equipment registry

backend/core/basic/equipment_registry.py

@@ -0,0 +1,22 @@
+from functools import cache
+from pathlib import Path
+
+from database.connect import BACKEND_DIR
+
+
+class EquipmentRegistry:
+    def __init__(self, equipment_cls):
+        self.equipment_cls = equipment_cls
+
+    @cache
+    def get(self, version: str = '0'):
+        normalized = version or '0'
+        if not self._version_exists(normalized):
+            if normalized == '0':
+                return self.equipment_cls(normalized)
+            return self.get('0')
+        return self.equipment_cls(normalized)
+
+    def _version_exists(self, version: str) -> bool:
+        db_path = Path(BACKEND_DIR) / 'dataFiles' / f'dcalc_{version}.db'
+        return db_path.exists()