Initial commit - Phase 3/4

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/backend/websocket/manager.py

@@ -0,0 +1,71 @@
+"""WebSocket connection manager for real-time notifications."""
+import asyncio
+import json
+from datetime import datetime, timezone
+from typing import Set
+from fastapi import WebSocket
+
+
+class ConnectionManager:
+    """Manages WebSocket connections and broadcasts."""
+
+    def __init__(self):
+        self._connections: Set[WebSocket] = set()
+        self._lock = asyncio.Lock()
+
+    async def connect(self, websocket: WebSocket) -> None:
+        """Accept and track a new WebSocket connection."""
+        await websocket.accept()
+        async with self._lock:
+            self._connections.add(websocket)
+
+        # Send initial connected event
+        await self._send_to_client(websocket, {
+            "type": "event",
+            "event": "connected",
+            "data": {"message": "Connected to Dangerous Pi event stream"},
+            "timestamp": datetime.now(timezone.utc).isoformat()
+        })
+
+    async def disconnect(self, websocket: WebSocket) -> None:
+        """Remove a disconnected WebSocket."""
+        async with self._lock:
+            self._connections.discard(websocket)
+
+    async def broadcast(self, event_type: str, data: dict) -> None:
+        """Broadcast an event to all connected clients."""
+        message = {
+            "type": "event",
+            "event": event_type,
+            "data": data,
+            "timestamp": datetime.now(timezone.utc).isoformat()
+        }
+
+        async with self._lock:
+            dead_connections: Set[WebSocket] = set()
+            for connection in self._connections:
+                try:
+                    await asyncio.wait_for(
+                        self._send_to_client(connection, message),
+                        timeout=5.0
+                    )
+                except asyncio.TimeoutError:
+                    dead_connections.add(connection)
+                except Exception:
+                    dead_connections.add(connection)
+
+            # Remove dead connections
+            self._connections -= dead_connections
+
+    async def _send_to_client(self, websocket: WebSocket, message: dict) -> None:
+        """Send a message to a specific client."""
+        await websocket.send_json(message)
+
+    @property
+    def connection_count(self) -> int:
+        """Return number of active connections."""
+        return len(self._connections)
+
+
+# Global singleton instance
+ws_manager = ConnectionManager()