push updated state to clients over SSE (ISS-129)

app/api/events/route.test.ts

@@ -0,0 +1,41 @@
+import fs from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { GET } from './route';
+
+let dir: string;
+
+beforeAll(async () => {
+  // Same pattern as app/api/state/route.test.ts: point the DB singleton at a throwaway file so
+  // this test never touches ./db/flight.db. getGameDb() reads the env var on first call, and
+  // vitest gives each test file its own module registry (fresh singleton).
+  dir = await fs.mkdtemp(path.join(os.tmpdir(), 'flight-events-'));
+  process.env.FLIGHT_DB_PATH = path.join(dir, 'events.db');
+});
+
+afterAll(async () => {
+  delete process.env.FLIGHT_DB_PATH;
+  await fs.rm(dir, { recursive: true, force: true });
+});
+
+describe('GET /api/events', () => {
+  it('streams SSE with the current snapshot as the first event', async () => {
+    const res = await GET();
+    expect(res.status).toBe(200);
+    expect(res.headers.get('content-type')).toContain('text/event-stream');
+    expect(res.headers.get('cache-control')).toBe('no-cache');
+    expect(res.headers.get('x-accel-buffering')).toBe('no');
+
+    const reader = (res.body as ReadableStream<Uint8Array>).getReader();
+    try {
+      const { value } = await reader.read(); // first chunk: the initial snapshot event
+      const text = new TextDecoder().decode(value);
+      expect(text.startsWith('data: ')).toBe(true);
+      const snap = JSON.parse(text.slice('data: '.length)) as Record<string, unknown>;
+      expect(typeof (snap.simState as { clockMs: number }).clockMs).toBe('number');
+    } finally {
+      await reader.cancel(); // → stream cancel → unsubscribe from the registry
+    }
+  });
+});