feat: implement websocket realtime data streaming

src/web/websocket.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, it, afterAll, beforeAll } from "bun:test";
+import { WebServer } from "./server";
+
+describe("WebSocket Server", () => {
+    // Start server on a random port
+    const port = 0;
+
+    beforeAll(() => {
+        WebServer.start(port);
+    });
+
+    afterAll(() => {
+        WebServer.stop();
+    });
+
+    it("should accept websocket connection and send welcome message", async () => {
+        // We need to know the actual port assigned by Bun if we passed 0.
+        // But WebServer stores it in private static server. 
+        // We can't access it easily unless we expose it or use a known port.
+        // Let's rely on the fact that if we pass 0, we can't easily know the port without exposing it.
+        // So for this test, let's pick a random high port to avoid conflict: 40000 + Math.floor(Math.random() * 1000)
+
+        // Actually, let's restart with a known port 8081 for testing
+        WebServer.stop();
+        const testPort = 8081;
+        WebServer.start(testPort);
+
+        const ws = new WebSocket(`ws://localhost:${testPort}/ws`);
+
+        const messagePromise = new Promise<any>((resolve) => {
+            ws.onmessage = (event) => {
+                resolve(JSON.parse(event.data as string));
+            };
+        });
+
+        const msg = await messagePromise;
+        expect(msg.type).toBe("WELCOME");
+        expect(msg.message).toContain("Connected");
+
+        ws.close();
+    });
+
+    it("should reject non-ws upgrade requests on /ws endpoint via http", async () => {
+        const testPort = 8081;
+        // Just a normal fetch to /ws should fail with 426 Upgrade Required usually, 
+        // but our implementation returns "WebSocket upgrade failed" 500 or undefined -> 101 Switching Protocols if valid.
+        // If we send a normal GET request to /ws without Upgrade headers, server.upgrade(req) returns false.
+        // So it returns status 500 "WebSocket upgrade failed" based on our code.
+
+        const res = await fetch(`http://localhost:${testPort}/ws`);
+        expect(res.status).toBe(500);
+        expect(await res.text()).toBe("WebSocket upgrade failed");
+    });
+});