Implement FastAPI Temporal MVP pipeline

app/infra/db/session.py

@@ -0,0 +1,65 @@
+"""Async database engine and session helpers."""
+
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker, create_async_engine
+
+from app.config.settings import get_settings
+from app.infra.db.base import Base
+
+_engine: AsyncEngine | None = None
+_session_factory: async_sessionmaker[AsyncSession] | None = None
+
+
+def get_async_engine() -> AsyncEngine:
+    """Return the lazily created async SQLAlchemy engine."""
+
+    global _engine
+    if _engine is None:
+        _engine = create_async_engine(
+            get_settings().database_url,
+            future=True,
+            echo=False,
+        )
+    return _engine
+
+
+def get_session_factory() -> async_sessionmaker[AsyncSession]:
+    """Return the lazily created async session factory."""
+
+    global _session_factory
+    if _session_factory is None:
+        _session_factory = async_sessionmaker(get_async_engine(), expire_on_commit=False)
+    return _session_factory
+
+
+async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
+    """Yield a database session for FastAPI dependencies."""
+
+    async with get_session_factory()() as session:
+        yield session
+
+
+async def init_database() -> None:
+    """Create database tables when running the MVP without migrations."""
+
+    from app.infra.db.models.asset import AssetORM
+    from app.infra.db.models.order import OrderORM
+    from app.infra.db.models.review_task import ReviewTaskORM
+    from app.infra.db.models.workflow_run import WorkflowRunORM
+    from app.infra.db.models.workflow_step import WorkflowStepORM
+
+    del AssetORM, OrderORM, ReviewTaskORM, WorkflowRunORM, WorkflowStepORM
+
+    async with get_async_engine().begin() as connection:
+        await connection.run_sync(Base.metadata.create_all)
+
+
+async def dispose_database() -> None:
+    """Dispose the active engine and clear cached session objects."""
+
+    global _engine, _session_factory
+    if _engine is not None:
+        await _engine.dispose()
+    _engine = None
+    _session_factory = None