frontend/tests/refocus-sync.test.ts

/**
 * Refocus re-sync guard tests.
 *
 * Exercises createRefocusSync across the four liveness cases it must
 * distinguish on tab refocus, plus the offline grace release. Uses fake
 * timers and a fake provider/editor - no network, no browser.
 */
import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
import {
  createRefocusSync,
  type RefocusProviderLike,
  type RefocusEditorLike,
} from "../src/editor/refocus-sync";

interface Fakes {
  provider: RefocusProviderLike & { emit: (event: string) => void };
  editor: RefocusEditorLike & { setEditable: ReturnType<typeof vi.fn> };
  socket: { status: string; webSocket: { readyState: number }; lastMessageReceived: number };
}

function makeFakes(opts: {
  synced?: boolean;
  status?: string;
  readyState?: number;
  /** Simulate a healthy socket: forceSync draws a server reply that advances lastMessageReceived. */
  replyOnForceSync?: boolean;
} = {}): Fakes {
  const listeners: Record<string, Array<(...a: any[]) => void>> = {};
  const socket = {
    status: opts.status ?? "connected",
    webSocket: { readyState: opts.readyState ?? 1 },
    lastMessageReceived: 0,
  };

  const provider: Fakes["provider"] = {
    synced: opts.synced ?? true,
    configuration: { websocketProvider: socket },
    connect: vi.fn(() => Promise.resolve()),
    forceSync: vi.fn(() => {
      if (opts.replyOnForceSync) socket.lastMessageReceived += 1;
    }),
    on: (event, cb) => {
      (listeners[event] ??= []).push(cb);
    },
    off: (event, cb) => {
      listeners[event] = (listeners[event] ?? []).filter((f) => f !== cb);
    },
    emit: (event) => {
      (listeners[event] ?? []).forEach((f) => f());
    },
  };

  const editor: Fakes["editor"] = {
    isEditable: true,
    isDestroyed: false,
    setEditable: vi.fn(function (this: unknown, editable: boolean) {
      editor.isEditable = editable;
    }),
  };

  return { provider, editor, socket };
}

function lastEditableArg(setEditable: ReturnType<typeof vi.fn>): boolean | undefined {
  const call = setEditable.mock.calls.at(-1);
  return call ? (call[0] as boolean) : undefined;
}

describe("createRefocusSync", () => {
  beforeEach(() => vi.useFakeTimers());
  afterEach(() => vi.useRealTimers());

  it("healthy + synced socket: forces a sync but never locks", () => {
    const { provider, editor } = makeFakes({ synced: true, replyOnForceSync: true });
    const { onVisibility } = createRefocusSync({ provider, editor });

    onVisibility();

    expect(provider.connect).toHaveBeenCalled();
    expect(provider.forceSync).toHaveBeenCalled();
    expect(editor.setEditable).not.toHaveBeenCalled();

    // Probe window passes; reply advanced lastMessageReceived -> still no lock.
    vi.advanceTimersByTime(2000);
    expect(editor.setEditable).not.toHaveBeenCalledWith(false);
  });

  it("disconnected socket: locks immediately, unlocks on synced", () => {
    const { provider, editor } = makeFakes({ synced: false, status: "disconnected" });
    const { onVisibility } = createRefocusSync({ provider, editor });

    onVisibility();
    expect(editor.setEditable).toHaveBeenCalledWith(false);
    expect(editor.isEditable).toBe(false);

    provider.emit("synced");
    expect(lastEditableArg(editor.setEditable)).toBe(true);
    expect(editor.isEditable).toBe(true);
  });

  it("closed readyState while status says connected: locks", () => {
    const { provider, editor } = makeFakes({ synced: true, status: "connected", readyState: 3 });
    const { onVisibility } = createRefocusSync({ provider, editor });

    onVisibility();
    expect(editor.setEditable).toHaveBeenCalledWith(false);
  });

  it("offline: never traps the user, releases after the grace window", () => {
    const { provider, editor } = makeFakes({ synced: false });
    createRefocusSync({ provider, editor }).onVisibility();

    expect(editor.isEditable).toBe(false);
    vi.advanceTimersByTime(4000);
    expect(lastEditableArg(editor.setEditable)).toBe(true);
    expect(editor.isEditable).toBe(true);
  });

  it("half-open socket: looks alive but no reply -> locks after probe", () => {
    const { provider, editor } = makeFakes({
      synced: true,
      status: "connected",
      readyState: 1,
      replyOnForceSync: false,
    });
    const { onVisibility } = createRefocusSync({ provider, editor });

    onVisibility();
    // Looks alive, so no immediate lock.
    expect(editor.setEditable).not.toHaveBeenCalledWith(false);

    // No message landed within the probe window -> declare it stale.
    vi.advanceTimersByTime(2000);
    expect(editor.setEditable).toHaveBeenCalledWith(false);
    expect(provider.connect).toHaveBeenCalledTimes(2); // initial + probe reconnect
  });

  it("dispose detaches the synced listener and releases the lock", () => {
    const { provider, editor } = makeFakes({ synced: false });
    const { onVisibility, dispose } = createRefocusSync({ provider, editor });

    onVisibility();
    expect(editor.isEditable).toBe(false);

    dispose();
    expect(editor.isEditable).toBe(true);

    // A late synced event must not touch a disposed editor.
    editor.setEditable.mockClear();
    provider.emit("synced");
    expect(editor.setEditable).not.toHaveBeenCalled();
  });
});