add project structure

app/db.py

@@ -0,0 +1,44 @@
+from typing import Generator
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+
+from app.config import get_settings
+
+engine = None
+SessionLocal = sessionmaker(autocommit=False, autoflush=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def _build_engine(database_url: str):
+    connect_args = {"check_same_thread": False} if database_url.startswith("sqlite") else {}
+    return create_engine(database_url, connect_args=connect_args)
+
+
+def configure_database(database_url: str | None = None) -> None:
+    global engine
+
+    settings = get_settings()
+    resolved_database_url = database_url or settings.database_url
+    engine = _build_engine(resolved_database_url)
+    SessionLocal.configure(bind=engine)
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def init_db(database_url: str | None = None) -> None:
+    from app import models
+
+    if engine is None or database_url is not None:
+        configure_database(database_url)
+
+    Base.metadata.create_all(bind=engine)