/**

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 *

 * @emails react-core

 *

 * @jest-environment node

 */

'use strict';

let useSyncExternalStore;

let React;

let ReactDOM;

let ReactDOMServer;

let Scheduler;

let assertLog;

// This tests the userspace shim of `useSyncExternalStore` in a server-rendering

// (Node) environment

describe('useSyncExternalStore (userspace shim, server rendering)', () => {

  beforeEach(() => {

    jest.resetModules();

    // Remove useSyncExternalStore from the React imports so that we use the

    // shim instead. Also removing startTransition, since we use that to detect

    // outdated 18 alphas that don't yet include useSyncExternalStore.

    //

    // Longer term, we'll probably test this branch using an actual build of

    // React 17.

    jest.mock('react', () => {

      const {

        // eslint-disable-next-line no-unused-vars

        startTransition: _,

        // eslint-disable-next-line no-unused-vars

        useSyncExternalStore: __,

        ...otherExports

      } = jest.requireActual('react');

      return otherExports;

    });

    React = require('react');

    ReactDOM = require('react-dom');

    ReactDOMServer = require('react-dom/server');

    Scheduler = require('scheduler');

    const InternalTestUtils = require('internal-test-utils');

    assertLog = InternalTestUtils.assertLog;

    useSyncExternalStore =

      require('use-sync-external-store/shim').useSyncExternalStore;

  });

  function Text({text}) {

    Scheduler.log(text);

    return text;

  }

  function createExternalStore(initialState) {

    const listeners = new Set();

    let currentState = initialState;

    return {

      set(text) {

        currentState = text;

        ReactDOM.unstable_batchedUpdates(() => {

          listeners.forEach(listener => listener());

        });

      },

      subscribe(listener) {

        listeners.add(listener);

        return () => listeners.delete(listener);

      },

      getState() {

        return currentState;

      },

      getSubscriberCount() {

        return listeners.size;

      },

    };

  }

  test('basic server render', async () => {

    const store = createExternalStore('client');

    function App() {

      const text = useSyncExternalStore(

        store.subscribe,

        store.getState,

        () => 'server',

      );

      return <Text text={text} />;

    }

    const html = ReactDOMServer.renderToString(<App />);

    // We don't call getServerSnapshot in the shim

    assertLog(['client']);

    expect(html).toEqual('client');

  });

});