db.Session: Add

Add database session API to db. This is a breaking change, because
from this commit on, a session object has to be passed to every
query.

This commit also removes any reference to Cmds / App objects. An
instantiated database object can be worked with outside of an App.

Signed-off-by: Jan Lindemann <jan@janware.com>

tools/python/jwutils/db/DataBase.py

@@ -3,21 +3,27 @@
 from typing import Any
 
 import abc
+from contextlib import contextmanager
 
 from jwutils.Config import Config
 from jwutils.db.schema.Schema import Schema
 from jwutils import Cmds
+from .Session import Session
+from ..log import *
 
 class DataBase(abc.ABC):
 
-    def __init__(self, schema: Schema, conf: Config, app: Any) -> None:
+    def __init__(self, schema: Schema, conf: Config) -> None:
         self.__conf = conf
-        self.__app = app
         self.__schema = schema
+        conf.dump(NOTICE, "Initializing database with configuration")
 
-    @property
-    def app(self) -> Cmds:
-        return self.__app
+    @abc.abstractmethod
+    def _create_session(self):
+        pass
+
+    def _delete_session(self, session: Session):
+        del session
 
     @property
     def schema(self):
@@ -26,3 +32,11 @@ class DataBase(abc.ABC):
     @property
     def conf(self):
         return self.__conf
+
+    @contextmanager
+    def session(self):
+        ret = self._create_session()
+        try:
+           yield ret
+        finally:
+            self._delete_session(ret)