refactor: Database class

src/arcaea_offline/database.py

@@ -1,22 +1,48 @@
-from sqlalchemy import Engine
-from sqlalchemy.orm import Session
+from sqlalchemy import Engine, select
+from sqlalchemy.orm import sessionmaker
 
 from .models.common import *
 from .models.scores import *
 from .models.songs import *
+from .singleton import Singleton
 
 
-def init(engine: Engine, checkfirst: bool = True):
-    # sqlalchemy-utils issue #396
-    # view.create_view() causes DuplicateTableError on Base.metadata.create_all(checkfirst=True)
-    # https://github.com/kvesteri/sqlalchemy-utils/issues/396
-    if checkfirst:
-        ScoresViewBase.metadata.drop_all(engine)
+class Database(metaclass=Singleton):
+    def __init__(self, engine: Engine):
+        self.engine = engine
 
-    SongsBase.metadata.create_all(engine, checkfirst=checkfirst)
-    ScoresBase.metadata.create_all(engine, checkfirst=checkfirst)
-    ScoresViewBase.metadata.create_all(engine)
-    CommonBase.metadata.create_all(engine, checkfirst=checkfirst)
-    with Session(engine) as session:
-        session.add(Property(id="version", value="2"))
-        session.commit()
+    @property
+    def engine(self):
+        return self.__engine
+
+    @engine.setter
+    def engine(self, value: Engine):
+        if not isinstance(value, Engine):
+            raise ValueError("Database.engine only accepts sqlalchemy.Engine")
+        self.__engine = value
+        self.__sessionmaker = sessionmaker(self.__engine)
+
+    @property
+    def sessionmaker(self):
+        return self.__sessionmaker
+
+    def init(self, checkfirst: bool = True):
+        # create tables & views
+        if checkfirst:
+            # > https://github.com/kvesteri/sqlalchemy-utils/issues/396
+            # > view.create_view() causes DuplicateTableError on Base.metadata.create_all(checkfirst=True)
+            # so if `checkfirst` is True, drop these views before creating
+            ScoresViewBase.metadata.drop_all(self.engine)
+
+        SongsBase.metadata.create_all(self.engine, checkfirst=checkfirst)
+        ScoresBase.metadata.create_all(self.engine, checkfirst=checkfirst)
+        ScoresViewBase.metadata.create_all(self.engine)
+        CommonBase.metadata.create_all(self.engine, checkfirst=checkfirst)
+
+        # insert version property
+        with self.sessionmaker() as session:
+            stmt = select(Property.value).where(Property.key == "version")
+            result = session.execute(stmt).fetchone()
+            if not checkfirst or not result:
+                session.add(Property(key="version", value="2"))
+                session.commit()