Initial commit

app/database.py

@@ -0,0 +1,50 @@
+"""
+Database engine/session management.
+
+Uses SQLAlchemy so the storage backend is a config change, not a code
+change. Today DB_URL points at a local SQLite file. When you're ready
+to move to the MariaDB LXC, set DB_URL in .env to something like:
+
+    mysql+pymysql://user:[email protected]:3306/order_manager
+
+and install PyMySQL (pip install pymysql). Nothing else in the app
+needs to change.
+"""
+from __future__ import annotations
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, Session
+
+from app import config
+from app.models import Base
+
+_engine = None
+_SessionLocal = None
+
+
+def get_engine():
+    global _engine
+    if _engine is None:
+        db_url = config.get("DB_URL", config.DEFAULT_DB_URL)
+        connect_args = {}
+        if db_url.startswith("sqlite"):
+            # allow use across the QThread worker and the UI thread
+            connect_args = {"check_same_thread": False}
+        _engine = create_engine(db_url, connect_args=connect_args, future=True)
+    return _engine
+
+
+def get_session_factory():
+    global _SessionLocal
+    if _SessionLocal is None:
+        _SessionLocal = sessionmaker(bind=get_engine(), future=True, expire_on_commit=False)
+    return _SessionLocal
+
+
+def init_db() -> None:
+    """Create tables that don't exist yet. Safe to call every startup."""
+    Base.metadata.create_all(get_engine())
+
+
+def get_session() -> Session:
+    return get_session_factory()()