feat: backend FastAPI Smart App City — auth JWT, IoT, GIS, notifications, reporting

smart-app-city/backend/app/database.py

@@ -0,0 +1,57 @@
+"""Async SQLAlchemy database setup for Smart City Digital Twin."""
+
+from collections.abc import AsyncGenerator
+from typing import NoReturn
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+
+# ── Declarative base ──────────────────────────────────────────────────
+class Base(DeclarativeBase):
+    pass
+
+
+# ── Engine ───────────────────────────────────────────────────────────
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=False,
+    pool_size=10,
+    max_overflow=20,
+)
+
+# ── Session factory ──────────────────────────────────────────────────
+AsyncSessionLocal = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+# ── Dependency: per-request session ──────────────────────────────────
+async def get_session() -> AsyncGenerator[AsyncSession, None]:
+    """Yield an async session and close it when the request is done."""
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+# ── Startup: create tables ───────────────────────────────────────────
+async def init_db() -> None:
+    """Create all tables defined via ``Base`` models (idempotent)."""
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+
+# ── Shutdown: release connections ────────────────────────────────────
+async def close_db() -> None:
+    """Dispose the engine and release all pooled connections."""
+    await engine.dispose()