SLM config now sync to SLMM, SLMM caches configs for speed

backend/routers/slmm.py

@@ -5,9 +5,11 @@ Proxies requests from SFM to the standalone SLMM backend service.
 SLMM runs on port 8100 and handles NL43/NL53 sound level meter communication.
 """
 
-from fastapi import APIRouter, HTTPException, Request, Response
+from fastapi import APIRouter, HTTPException, Request, Response, WebSocket, WebSocketDisconnect
 from fastapi.responses import StreamingResponse
 import httpx
+import websockets
+import asyncio
 import logging
 import os
 
@@ -17,6 +19,8 @@ router = APIRouter(prefix="/api/slmm", tags=["slmm"])
 
 # SLMM backend URL - configurable via environment variable
 SLMM_BASE_URL = os.getenv("SLMM_BASE_URL", "http://localhost:8100")
+# WebSocket URL derived from HTTP URL
+SLMM_WS_BASE_URL = SLMM_BASE_URL.replace("http://", "ws://").replace("https://", "wss://")
 
 
 @router.get("/health")
@@ -61,6 +65,173 @@ async def check_slmm_health():
         }
 
 
+# WebSocket routes MUST come before the catch-all route
+@router.websocket("/{unit_id}/stream")
+async def proxy_websocket_stream(websocket: WebSocket, unit_id: str):
+    """
+    Proxy WebSocket connections to SLMM's /stream endpoint.
+
+    This allows real-time streaming of measurement data from NL43 devices
+    through the SFM unified interface.
+    """
+    await websocket.accept()
+    logger.info(f"WebSocket connection accepted for SLMM unit {unit_id}")
+
+    # Build target WebSocket URL
+    target_ws_url = f"{SLMM_WS_BASE_URL}/api/nl43/{unit_id}/stream"
+    logger.info(f"Connecting to SLMM WebSocket: {target_ws_url}")
+
+    backend_ws = None
+
+    try:
+        # Connect to SLMM backend WebSocket
+        backend_ws = await websockets.connect(target_ws_url)
+        logger.info(f"Connected to SLMM backend WebSocket for {unit_id}")
+
+        # Create tasks for bidirectional communication
+        async def forward_to_backend():
+            """Forward messages from client to SLMM backend"""
+            try:
+                while True:
+                    data = await websocket.receive_text()
+                    await backend_ws.send(data)
+            except WebSocketDisconnect:
+                logger.info(f"Client WebSocket disconnected for {unit_id}")
+            except Exception as e:
+                logger.error(f"Error forwarding to backend: {e}")
+
+        async def forward_to_client():
+            """Forward messages from SLMM backend to client"""
+            try:
+                async for message in backend_ws:
+                    await websocket.send_text(message)
+            except websockets.exceptions.ConnectionClosed:
+                logger.info(f"Backend WebSocket closed for {unit_id}")
+            except Exception as e:
+                logger.error(f"Error forwarding to client: {e}")
+
+        # Run both forwarding tasks concurrently
+        await asyncio.gather(
+            forward_to_backend(),
+            forward_to_client(),
+            return_exceptions=True
+        )
+
+    except websockets.exceptions.WebSocketException as e:
+        logger.error(f"WebSocket error connecting to SLMM backend: {e}")
+        try:
+            await websocket.send_json({
+                "error": "Failed to connect to SLMM backend",
+                "detail": str(e)
+            })
+        except Exception:
+            pass
+    except Exception as e:
+        logger.error(f"Unexpected error in WebSocket proxy for {unit_id}: {e}")
+        try:
+            await websocket.send_json({
+                "error": "Internal server error",
+                "detail": str(e)
+            })
+        except Exception:
+            pass
+    finally:
+        # Clean up connections
+        if backend_ws:
+            try:
+                await backend_ws.close()
+            except Exception:
+                pass
+        try:
+            await websocket.close()
+        except Exception:
+            pass
+        logger.info(f"WebSocket proxy closed for {unit_id}")
+
+
+@router.websocket("/{unit_id}/live")
+async def proxy_websocket_live(websocket: WebSocket, unit_id: str):
+    """
+    Proxy WebSocket connections to SLMM's /live endpoint.
+
+    Alternative WebSocket endpoint that may be used by some frontend components.
+    """
+    await websocket.accept()
+    logger.info(f"WebSocket connection accepted for SLMM unit {unit_id} (live endpoint)")
+
+    # Build target WebSocket URL - try /stream endpoint as SLMM uses that for WebSocket
+    target_ws_url = f"{SLMM_WS_BASE_URL}/api/nl43/{unit_id}/stream"
+    logger.info(f"Connecting to SLMM WebSocket: {target_ws_url}")
+
+    backend_ws = None
+
+    try:
+        # Connect to SLMM backend WebSocket
+        backend_ws = await websockets.connect(target_ws_url)
+        logger.info(f"Connected to SLMM backend WebSocket for {unit_id} (live endpoint)")
+
+        # Create tasks for bidirectional communication
+        async def forward_to_backend():
+            """Forward messages from client to SLMM backend"""
+            try:
+                while True:
+                    data = await websocket.receive_text()
+                    await backend_ws.send(data)
+            except WebSocketDisconnect:
+                logger.info(f"Client WebSocket disconnected for {unit_id} (live)")
+            except Exception as e:
+                logger.error(f"Error forwarding to backend (live): {e}")
+
+        async def forward_to_client():
+            """Forward messages from SLMM backend to client"""
+            try:
+                async for message in backend_ws:
+                    await websocket.send_text(message)
+            except websockets.exceptions.ConnectionClosed:
+                logger.info(f"Backend WebSocket closed for {unit_id} (live)")
+            except Exception as e:
+                logger.error(f"Error forwarding to client (live): {e}")
+
+        # Run both forwarding tasks concurrently
+        await asyncio.gather(
+            forward_to_backend(),
+            forward_to_client(),
+            return_exceptions=True
+        )
+
+    except websockets.exceptions.WebSocketException as e:
+        logger.error(f"WebSocket error connecting to SLMM backend (live): {e}")
+        try:
+            await websocket.send_json({
+                "error": "Failed to connect to SLMM backend",
+                "detail": str(e)
+            })
+        except Exception:
+            pass
+    except Exception as e:
+        logger.error(f"Unexpected error in WebSocket proxy for {unit_id} (live): {e}")
+        try:
+            await websocket.send_json({
+                "error": "Internal server error",
+                "detail": str(e)
+            })
+        except Exception:
+            pass
+    finally:
+        # Clean up connections
+        if backend_ws:
+            try:
+                await backend_ws.close()
+            except Exception:
+                pass
+        try:
+            await websocket.close()
+        except Exception:
+            pass
+        logger.info(f"WebSocket proxy closed for {unit_id} (live)")
+
+
+# HTTP catch-all route MUST come after specific routes (including WebSocket routes)
 @router.api_route("/{path:path}", methods=["GET", "POST", "PUT", "DELETE", "PATCH"])
 async def proxy_to_slmm(path: str, request: Request):
     """