feat: add realtime GNSS monitor with telemetry websocket

backend/app/api/deps.py

@@ -27,7 +27,7 @@ SessionDep = Annotated[Session, Depends(get_db)]
 TokenDep = Annotated[str, Depends(reusable_oauth2)]
 
 
-def get_current_user(session: SessionDep, token: TokenDep) -> User:
+def resolve_user_from_token(*, session: Session, token: str) -> User:
     try:
         payload = jwt.decode(
             token, settings.SECRET_KEY, algorithms=[security.ALGORITHM]
@@ -46,6 +46,10 @@ def get_current_user(session: SessionDep, token: TokenDep) -> User:
     return user
 
 
+def get_current_user(session: SessionDep, token: TokenDep) -> User:
+    return resolve_user_from_token(session=session, token=token)
+
+
 CurrentUser = Annotated[User, Depends(get_current_user)]
 
 

backend/app/api/main.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 
-from app.api.routes import locations, login, private, users, utils
+from app.api.routes import locations, login, private, telemetry, users, utils
 from app.core.config import settings
 
 api_router = APIRouter()
@@ -8,8 +8,8 @@ api_router.include_router(login.router)
 api_router.include_router(users.router)
 api_router.include_router(utils.router)
 api_router.include_router(locations.router)
+api_router.include_router(telemetry.router)
 
 
 if settings.ENVIRONMENT == "local":
     api_router.include_router(private.router)
-

backend/app/api/routes/telemetry.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+import asyncio
+from typing import Any
+
+from fastapi import APIRouter, HTTPException, Query, WebSocket, status
+from fastapi.encoders import jsonable_encoder
+from fastapi.websockets import WebSocketDisconnect
+from sqlmodel import Session
+
+from app.api.deps import CurrentUser, SessionDep, resolve_user_from_token
+from app.core.db import engine
+from app.mqtt.telemetry import build_telemetry_snapshot
+
+router = APIRouter(prefix="/telemetry", tags=["telemetry"])
+STREAM_INTERVAL_SECONDS = 1.0
+
+
+@router.get("/latest")
+def read_telemetry_latest(
+    session: SessionDep,
+    _current_user: CurrentUser,
+    device_id: str | None = None,
+    limit: int = Query(default=50, ge=1, le=200),
+) -> dict[str, Any]:
+    """
+    Return the latest parsed GNSS telemetry snapshot.
+    """
+    return build_telemetry_snapshot(session=session, device_id=device_id, limit=limit)
+
+
+@router.websocket("/ws")
+async def telemetry_websocket(
+    websocket: WebSocket,
+    token: str | None = Query(default=None),
+    device_id: str | None = Query(default=None),
+    limit: int = Query(default=50, ge=1, le=200),
+) -> None:
+    if not token:
+        await websocket.close(code=status.WS_1008_POLICY_VIOLATION)
+        return
+
+    with Session(engine) as session:
+        try:
+            resolve_user_from_token(session=session, token=token)
+        except HTTPException:
+            await websocket.close(code=status.WS_1008_POLICY_VIOLATION)
+            return
+
+    await websocket.accept()
+
+    try:
+        while True:
+            with Session(engine) as session:
+                payload = build_telemetry_snapshot(
+                    session=session,
+                    device_id=device_id,
+                    limit=limit,
+                )
+            await websocket.send_json(jsonable_encoder(payload))
+            await asyncio.sleep(STREAM_INTERVAL_SECONDS)
+    except (WebSocketDisconnect, RuntimeError):
+        return