feat: publish shared task and reply activities through MCP

src/features/activities/http-events.server.ts

@@ -0,0 +1,65 @@
+/** Invalidate browser snapshots after a commit, including on reconnect. */
+export function activityEvents(
+  request: Request,
+  subscribe: (listener: () => void) => () => void,
+  isAuthorized: () => boolean,
+) {
+  if (!isAuthorized()) return new Response(null, { status: 401 });
+  const encoder = new TextEncoder();
+  let dispose = () => {};
+  let flush = () => {};
+  const stream = new ReadableStream<Uint8Array>({
+    start(controller) {
+      let closed = false;
+      let dirty = true;
+      let unsubscribe = () => {};
+      let heartbeat: ReturnType<typeof setInterval> | undefined;
+      const close = () => {
+        if (closed) return;
+        dispose();
+        controller.close();
+      };
+      dispose = () => {
+        if (closed) return;
+        closed = true;
+        clearInterval(heartbeat);
+        unsubscribe();
+        request.signal.removeEventListener("abort", close);
+      };
+      flush = () => {
+        if (closed) return;
+        if (!isAuthorized()) return close();
+        if (dirty && (controller.desiredSize ?? 0) > 0) {
+          dirty = false;
+          controller.enqueue(encoder.encode("event: change\ndata: {}\n\n"));
+        }
+      };
+      if (request.signal.aborted) return close();
+      unsubscribe = subscribe(() => {
+        dirty = true;
+        flush();
+      });
+      request.signal.addEventListener("abort", close, { once: true });
+      heartbeat = setInterval(() => {
+        flush();
+        if (!closed && !dirty && (controller.desiredSize ?? 0) > 0)
+          controller.enqueue(encoder.encode(": keepalive\n\n"));
+      }, 15_000);
+      heartbeat.unref?.();
+      flush();
+    },
+    pull() {
+      flush();
+    },
+    cancel() {
+      dispose();
+    },
+  });
+  return new Response(stream, {
+    headers: {
+      "Content-Type": "text/event-stream; charset=utf-8",
+      "Cache-Control": "no-cache, no-transform",
+      "X-Accel-Buffering": "no",
+    },
+  });
+}