Implement Monlet MVP stack and UI updates

server/monlet_server/db.py

@@ -0,0 +1,43 @@
+from collections.abc import AsyncIterator
+
+from sqlalchemy.ext.asyncio import (
+    AsyncEngine,
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+
+from .settings import get_settings
+
+_engine: AsyncEngine | None = None
+_sessionmaker: async_sessionmaker[AsyncSession] | None = None
+
+
+def get_engine() -> AsyncEngine:
+    global _engine, _sessionmaker
+    if _engine is None:
+        s = get_settings()
+        _engine = create_async_engine(s.database_url, pool_pre_ping=True, future=True)
+        _sessionmaker = async_sessionmaker(_engine, expire_on_commit=False)
+    return _engine
+
+
+def get_sessionmaker() -> async_sessionmaker[AsyncSession]:
+    if _sessionmaker is None:
+        get_engine()
+    assert _sessionmaker is not None
+    return _sessionmaker
+
+
+async def dispose_engine() -> None:
+    global _engine, _sessionmaker
+    if _engine is not None:
+        await _engine.dispose()
+    _engine = None
+    _sessionmaker = None
+
+
+async def get_session() -> AsyncIterator[AsyncSession]:
+    sm = get_sessionmaker()
+    async with sm() as session:
+        yield session