Complete Forgejo discussion MVP

update_events.py

@@ -0,0 +1,64 @@
+from __future__ import annotations
+
+import asyncio
+import json
+import time
+from collections.abc import AsyncIterator
+from typing import Any
+
+
+class UpdateBroker:
+    def __init__(self) -> None:
+        self._subscribers: set[asyncio.Queue[dict[str, object]]] = set()
+
+    def subscribe(self) -> asyncio.Queue[dict[str, object]]:
+        queue: asyncio.Queue[dict[str, object]] = asyncio.Queue(maxsize=20)
+        self._subscribers.add(queue)
+        return queue
+
+    def unsubscribe(self, queue: asyncio.Queue[dict[str, object]]) -> None:
+        self._subscribers.discard(queue)
+
+    async def publish(self, event: str, payload: dict[str, object] | None = None) -> None:
+        message = {
+            "event": event,
+            "data": {
+                "type": event,
+                "published_at": time.time(),
+                **(payload or {}),
+            },
+        }
+        stale_queues: list[asyncio.Queue[dict[str, object]]] = []
+        for queue in tuple(self._subscribers):
+            try:
+                queue.put_nowait(message)
+            except asyncio.QueueFull:
+                stale_queues.append(queue)
+
+        for queue in stale_queues:
+            self.unsubscribe(queue)
+
+
+async def stream_sse_events(
+    broker: UpdateBroker,
+) -> AsyncIterator[str]:
+    queue = broker.subscribe()
+    try:
+        yield _sse_event("connected", {"type": "connected", "published_at": time.time()})
+        while True:
+            try:
+                message = await asyncio.wait_for(queue.get(), timeout=25)
+            except TimeoutError:
+                yield ": keepalive\n\n"
+                continue
+
+            yield _sse_event(
+                str(message.get("event", "message")),
+                message.get("data") if isinstance(message.get("data"), dict) else {},
+            )
+    finally:
+        broker.unsubscribe(queue)
+
+
+def _sse_event(event: str, payload: dict[str, Any]) -> str:
+    return f"event: {event}\ndata: {json.dumps(payload, separators=(',', ':'))}\n\n"