Fix: use ReadableStream cancel() to cleanup interval (avoid controller.signal TS error)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app/routes/api/price-stream.ts

@@ -0,0 +1,60 @@
+import { fetchLatestBar } from "../../lib/alpacaClient";
+
+export async function loader({ request }: { request: Request }) {
+  const url = new URL(request.url);
+  const ticker = (url.searchParams.get("ticker") || "").toUpperCase();
+  if (!ticker) return new Response("ticker required", { status: 400 });
+  const timeframe = url.searchParams.get("timeframe") || "1Min"; // default to 1Min bars for live price
+  const mode = url.searchParams.get("mode") === "live" ? 'live' : 'paper';
+
+  const headers = new Headers({
+    "Content-Type": "text/event-stream",
+    "Cache-Control": "no-cache",
+    Connection: "keep-alive",
+  });
+
+  // Create a ReadableStream that polls latest bar every second and pushes SSE
+  let closed = false;
+  let interval: any;
+  const stream = new ReadableStream({
+    start(controller) {
+      // helper to push SSE event
+      function pushEvent(obj: any) {
+        try {
+          const payload = `data: ${JSON.stringify(obj)}\n\n`;
+          controller.enqueue(new TextEncoder().encode(payload));
+        } catch (e) {
+          console.warn("price-stream: failed to enqueue", e);
+        }
+      }
+
+      // initial ping
+      pushEvent({ event: "connected", ticker, timeframe });
+
+      interval = setInterval(async () => {
+        if (closed) return;
+        try {
+          const last = await fetchLatestBar(ticker, timeframe, mode);
+          const price = last ? (last.ClosePrice ?? last.c ?? null) : null;
+          if (price != null) {
+            pushEvent({ price, ts: Date.now(), timeframe });
+          } else {
+            pushEvent({ error: "no_bar", ts: Date.now() });
+          }
+        } catch (err) {
+          console.error("price-stream: error fetching latest bar", err);
+          pushEvent({ error: String(err), ts: Date.now() });
+          // keep trying
+        }
+      }, 1000);
+
+      // no-op here; cleanup handled in cancel
+    },
+    cancel() {
+      closed = true;
+      clearInterval(interval);
+    },
+  });
+
+  return new Response(stream, { headers });
+}