From 003e1a7289526f4727af71175955f7749cf8cf51 Mon Sep 17 00:00:00 2001
From: 283375 <bilibili283375@163.com>
Date: Sat, 26 Aug 2023 16:52:19 +0800
Subject: [PATCH] refactor: `Database` class

---
 src/arcaea_offline/database.py      | 56 +++++++++++++++++++++--------
 src/arcaea_offline/models/common.py |  2 +-
 src/arcaea_offline/models/scores.py |  3 ++
 src/arcaea_offline/singleton.py     | 12 +++++++
 4 files changed, 57 insertions(+), 16 deletions(-)
 create mode 100644 src/arcaea_offline/singleton.py

diff --git a/src/arcaea_offline/database.py b/src/arcaea_offline/database.py
index 9a0e20f..b366e1a 100644
--- a/src/arcaea_offline/database.py
+++ b/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()
diff --git a/src/arcaea_offline/models/common.py b/src/arcaea_offline/models/common.py
index 435c075..85fba75 100644
--- a/src/arcaea_offline/models/common.py
+++ b/src/arcaea_offline/models/common.py
@@ -14,5 +14,5 @@ class CommonBase(DeclarativeBase):
 class Property(CommonBase):
     __tablename__ = "property"
 
-    id: Mapped[str] = mapped_column(TEXT(), primary_key=True)
+    key: Mapped[str] = mapped_column(TEXT(), primary_key=True)
     value: Mapped[str] = mapped_column(TEXT())
diff --git a/src/arcaea_offline/models/scores.py b/src/arcaea_offline/models/scores.py
index 10c6b72..6ac279a 100644
--- a/src/arcaea_offline/models/scores.py
+++ b/src/arcaea_offline/models/scores.py
@@ -104,6 +104,7 @@ class Calculated(ScoresViewBase):
             & (Chart.rating_class == Score.rating_class),
         ),
         metadata=ScoresViewBase.metadata,
+        cascade_on_drop=False,
     )
 
 
@@ -131,6 +132,7 @@ class Best(ScoresViewBase):
         .group_by(Calculated.song_id, Calculated.rating_class)
         .order_by(Calculated.potential.desc()),
         metadata=ScoresViewBase.metadata,
+        cascade_on_drop=False,
     )
 
 
@@ -147,4 +149,5 @@ class CalculatedPotential(ScoresViewBase):
         name="calculated_potential",
         selectable=select(func.avg(_select_bests_subquery.c.b30_sum).label("b30")),
         metadata=ScoresViewBase.metadata,
+        cascade_on_drop=False,
     )
diff --git a/src/arcaea_offline/singleton.py b/src/arcaea_offline/singleton.py
new file mode 100644
index 0000000..6776678
--- /dev/null
+++ b/src/arcaea_offline/singleton.py
@@ -0,0 +1,12 @@
+from typing import Generic, TypeVar
+
+T = TypeVar("T")
+
+
+class Singleton(type, Generic[T]):
+    _instance = None
+
+    def __call__(cls, *args, **kwargs) -> T:
+        if cls._instance is None:
+            cls._instance = super().__call__(*args, **kwargs)
+        return cls._instance