import { test, expect } from "@playwright/test";
import { resetData, writeSettings } from "./helpers";

// /api/pulse is the change token the global auto-refresh polls instead of
// re-rendering the page tree on a timer. Its entire justification is that it is
// cheap enough to ask constantly, so "cheap" is a contract, not an aspiration:
// in-memory job/queue/worker state plus two stat() calls, and NO corpus
// contact on the idle path.
//
// If someone later adds a channel walk, a snapshot read or a directory listing
// to it, these fail — which is the point.

test.describe("/api/pulse", () => {
  test.beforeEach(async () => {
    await resetData("channel-with-counts");
  });

  test("is fast, and stays fast when asked repeatedly", async ({ request }) => {
    // Warm-up: the first hit in a dev server pays compilation, which is not
    // what's being measured.
    const first = await request.get("/api/pulse");
    expect(first.ok()).toBe(true);
    const body = await first.json();
    expect(typeof body.rev).toBe("string");
    expect(body.rev.length).toBeGreaterThan(0);
    // A first call with no known rev must return the full payload.
    expect(body.changed).toBe(true);
    expect(typeof body.cleanableBytes).toBe("number");

    // The idle path: hand back the rev we were just given. Nothing has changed,
    // so the endpoint must say so without recomputing anything expensive.
    const started = Date.now();
    const rounds = 5;
    for (let i = 0; i < rounds; i++) {
      const res = await request.get(
        `/api/pulse?rev=${encodeURIComponent(body.rev)}`,
      );
      expect(res.ok()).toBe(true);
      const idle = await res.json();
      expect(idle.rev).toBe(body.rev);
      expect(idle.changed).toBe(false);
    }
    const perCall = (Date.now() - started) / rounds;
    // Generous versus the ~2 ms the handler actually costs — this is a
    // tripwire for "someone put a corpus walk in the poller", not a benchmark,
    // and it runs on a shared machine.
    expect(perCall, `idle pulse averaged ${perCall}ms per call`).toBeLessThan(
      250,
    );
  });

  test("the token moves when something the editor displays changes", async ({
    request,
  }) => {
    const before = await (await request.get("/api/pulse")).json();

    // settings.json's mtime is part of the token — this is what makes editing
    // settings repaint the sidebar without a reload.
    await writeSettings({
      autoRefreshIntervalSeconds: 5,
      adminTitle: "Pulse Moved",
    });

    await expect
      .poll(
        async () => (await (await request.get("/api/pulse")).json()).rev,
        { timeout: 5_000 },
      )
      .not.toBe(before.rev);
  });

  test("the token is stable when nothing changes", async ({ request }) => {
    const a = await (await request.get("/api/pulse")).json();
    await new Promise((r) => setTimeout(r, 1_200));
    const b = await (await request.get("/api/pulse")).json();
    expect(b.rev).toBe(a.rev);
  });
});