refactor: #85 T4 extrait le domaine backups vers backend/routers + sse partage (comportement inchange)

backend/sse.py

@@ -0,0 +1,54 @@
+"""Server-Sent Events manager (ROADMAP #85, tranche 4).
+
+Singleton extrait de :mod:`backend.main` sans changement de comportement :
+les routers montés par ``main`` partagent la même instance (les clients SSE
+connectés sur ``/api/events`` reçoivent les broadcasts émis depuis
+n'importe quel router).
+"""
+
+from __future__ import annotations
+
+import asyncio
+import json as _json
+import logging
+
+logger = logging.getLogger("obsigate")
+
+
+class SSEManager:
+    """Manages SSE client connections and broadcasts events."""
+
+    def __init__(self):
+        self._clients: list[asyncio.Queue] = []
+
+    async def connect(self) -> asyncio.Queue:
+        """Register a new SSE client and return its message queue."""
+        queue: asyncio.Queue = asyncio.Queue()
+        self._clients.append(queue)
+        logger.debug(f"SSE client connected (total: {len(self._clients)})")
+        return queue
+
+    def disconnect(self, queue: asyncio.Queue):
+        """Remove a disconnected SSE client."""
+        if queue in self._clients:
+            self._clients.remove(queue)
+        logger.debug(f"SSE client disconnected (total: {len(self._clients)})")
+
+    async def broadcast(self, event_type: str, data: dict):
+        """Send an event to all connected SSE clients."""
+        message = _json.dumps(data, ensure_ascii=False)
+        dead: list[asyncio.Queue] = []
+        for q in self._clients:
+            try:
+                q.put_nowait({"event": event_type, "data": message})
+            except asyncio.QueueFull:
+                dead.append(q)
+        for q in dead:
+            self.disconnect(q)
+
+    @property
+    def client_count(self) -> int:
+        return len(self._clients)
+
+
+sse_manager = SSEManager()