import { test, expect } from '@playwright/test';

// ISS-129 (v0.57.0): /api/events pushes full state snapshots over SSE — the current snapshot on
// connect, then one after every sim tick (~1 s; the background tick runs even while idle since
// v0.56.0, so no scale hook is needed). Reached via the same base URL as playwright.config.ts
// (E2E_BASE_URL, defaulting to the live instance) — node-side fetch, no browser involved.
const baseUrl = process.env.E2E_BASE_URL ?? 'https://flight.dev.kkhost.pl';

interface StateBody {
  simState: { clockMs: number };
}

test('GET /api/events streams state snapshots over SSE', async () => {
  const res = await fetch(`${baseUrl}/api/events`, { headers: { Accept: 'text/event-stream' } });
  expect(res.status).toBe(200);
  expect(res.headers.get('content-type')).toContain('text/event-stream');
  expect(res.body).not.toBeNull();

  const reader = res.body!.getReader();
  const decoder = new TextDecoder();
  let buffer = '';
  const clocks: number[] = []; // simState.clockMs of each parsed snapshot event

  try {
    // Collect two snapshot events: the initial one, then at least one pushed by a background tick.
    const deadline = Date.now() + 15_000;
    while (clocks.length < 2 && Date.now() < deadline) {
      let chunk: ReadableStreamReadResult<Uint8Array>;
      try {
        chunk = await Promise.race([
          reader.read(),
          new Promise<never>((_, reject) =>
            setTimeout(() => reject(new Error('SSE stream stalled')), Math.max(1, deadline - Date.now())),
          ),
        ]);
      } catch {
        break; // stalled or past the deadline — let the length assertion report it
      }
      if (chunk.done) break; // stream ended early — same
      buffer += decoder.decode(chunk.value, { stream: true });
      let sep: number;
      while ((sep = buffer.indexOf('\n\n')) >= 0) {
        const frame = buffer.slice(0, sep);
        buffer = buffer.slice(sep + 2);
        for (const line of frame.split('\n')) {
          if (!line.startsWith('data: ')) continue; // heartbeats are comment lines (" : ping")
          const snap = JSON.parse(line.slice('data: '.length)) as StateBody;
          clocks.push(snap.simState.clockMs);
        }
      }
    }
  } finally {
    await reader.cancel(); // close the stream → server unsubscribes
  }

  // The initial snapshot arrives on connect; the second comes from a background tick within ~1 s.
  expect(clocks.length).toBeGreaterThanOrEqual(2);
  expect(clocks[1]).toBeGreaterThan(clocks[0]); // clock advanced between pushes — real updates, not replays
});