feat: show empty state on posts pages [BD-38] [TNL-9484] [SE-5347] (#65)

When a user browses the discussion pages, show a page showing
that there is no data, rather than a blank page.

This PR implements the designs for this page while refactoring the
DiscussionHome component so that it doesn't get much larger.

- Created a hooks file and move some of the larger hooks in there.
- Added selectors for the state that would be needed for the
  components.
- Split the DiscussionHome into DiscussionContent and
  DiscussionSidebar to make it clearer where certain things get
  rendered.
- Adds a message to the sidebar to display No Results when
  appropriate.
- Added the NoResults component to show when filtering posts and there
  is nothing to show.

src/discussions/empty-posts/EmptyPage.jsx

@@ -0,0 +1,51 @@
+import React from 'react';
+import propTypes from 'prop-types';
+
+import classNames from 'classnames';
+
+import { Button } from '@edx/paragon';
+
+import { ReactComponent as EmptyIcon } from '../../assets/empty.svg';
+
+function EmptyPage({
+  title,
+  subTitle = null,
+  action = null,
+  actionText = null,
+  fullWidth = false,
+}) {
+  const containerClasses = classNames(
+    'align-content-start align-items-center d-flex w-100 flex-column pt-5',
+    { 'bg-light-300': !fullWidth },
+  );
+
+  return (
+    <div className={containerClasses}>
+      <EmptyIcon />
+      <h3 className="pt-3">{title}</h3>
+      {subTitle && <p className="pb-2">{subTitle}</p>}
+      {action && actionText && (
+        <Button onClick={action} variant="outline-dark">
+          {actionText}
+        </Button>
+      )}
+    </div>
+  );
+}
+
+EmptyPage.propTypes = {
+  title: propTypes.string.isRequired,
+  subTitle: propTypes.string,
+  action: propTypes.func,
+  actionText: propTypes.string,
+  fullWidth: propTypes.bool,
+};
+
+EmptyPage.defaultProps = {
+  subTitle: null,
+  action: null,
+  fullWidth: false,
+  actionText: null,
+};
+
+export default EmptyPage;

src/discussions/empty-posts/EmptyPosts.jsx

@@ -0,0 +1,59 @@
+import React from 'react';
+import propTypes from 'prop-types';
+
+import { useDispatch, useSelector } from 'react-redux';
+
+import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+
+import { useIsOnDesktop } from '../data/hooks';
+import { selectAreThreadsFiltered, selectPostThreadCount } from '../data/selectors';
+import messages from '../messages';
+import { messages as postMessages, showPostEditor } from '../posts';
+import EmptyPage from './EmptyPage';
+
+function EmptyPosts({ intl, subTitleMessage }) {
+  const dispatch = useDispatch();
+
+  const isFiltered = useSelector(selectAreThreadsFiltered);
+  const totalThreads = useSelector(selectPostThreadCount);
+  const isOnDesktop = useIsOnDesktop();
+
+  function addPost() {
+    return dispatch(showPostEditor());
+  }
+
+  let title = messages.noPostSelected;
+  let subTitle = null;
+  let action = null;
+  let actionText = null;
+  let fullWidth = false;
+
+  const isEmpty = [0, null].includes(totalThreads) && !isFiltered;
+
+  if (!(isOnDesktop || isEmpty)) {
+    return null;
+  } if (isEmpty) {
+    subTitle = subTitleMessage;
+    title = messages.emptyTitle;
+    action = addPost;
+    actionText = postMessages.addAPost;
+    fullWidth = true;
+  }
+
+  return (
+    <EmptyPage
+      title={intl.formatMessage(title)}
+      subTitle={subTitle ? intl.formatMessage(subTitle) : null}
+      action={action}
+      actionText={actionText ? intl.formatMessage(actionText) : null}
+      fullWidth={fullWidth}
+    />
+  );
+}
+
+EmptyPosts.propTypes = {
+  subTitleMessage: propTypes.string.isRequired,
+  intl: intlShape.isRequired,
+};
+
+export default injectIntl(EmptyPosts);

src/discussions/empty-posts/EmptyPosts.test.jsx

@@ -0,0 +1,78 @@
+import { render, screen } from '@testing-library/react';
+import MockAdapter from 'axios-mock-adapter';
+import { IntlProvider } from 'react-intl';
+import { Context as ResponsiveContext } from 'react-responsive';
+import { MemoryRouter } from 'react-router';
+import { Factory } from 'rosie';
+
+import { initializeMockApp } from '@edx/frontend-platform';
+import { getAuthenticatedHttpClient } from '@edx/frontend-platform/auth';
+import { AppProvider } from '@edx/frontend-platform/react';
+
+import { initializeStore } from '../../store';
+import { executeThunk } from '../../test-utils';
+import messages from '../messages';
+import { threadsApiUrl } from '../posts/data/api';
+import { fetchThreads } from '../posts/data/thunks';
+import EmptyPosts from './EmptyPosts';
+
+import '../posts/data/__factories__';
+
+let store;
+const courseId = 'course-v1:edX+DemoX+Demo_Course';
+
+function renderComponent(location = `/${courseId}/`) {
+  return render(
+    <IntlProvider locale="en">
+      <ResponsiveContext.Provider value={{ width: 1280 }}>
+        <AppProvider store={store}>
+          <MemoryRouter initialEntries={[location]}>
+            <EmptyPosts subTitleMessage={messages.emptyMyPosts} />
+          </MemoryRouter>
+        </AppProvider>
+      </ResponsiveContext.Provider>
+    </IntlProvider>,
+  );
+}
+
+function mockFetchThreads() {
+  const axiosMock = new MockAdapter(getAuthenticatedHttpClient());
+  axiosMock.onGet(threadsApiUrl).reply(200, Factory.build('threadsResult'));
+
+  return executeThunk(fetchThreads(courseId), store.dispatch, store.getState);
+}
+
+describe('EmptyPage', () => {
+  beforeEach(async () => {
+    initializeMockApp({
+      authenticatedUser: {
+        userId: 3,
+        username: 'abc123',
+        administrator: true,
+        roles: [],
+      },
+    });
+
+    store = initializeStore();
+  });
+
+  test('"posts youve interacted with" message shown when no posts in system', async () => {
+    renderComponent(`/${courseId}/my-posts/`);
+    expect(
+      screen.queryByText(messages.emptyMyPosts.defaultMessage),
+    ).toBeInTheDocument();
+
+    expect(
+      screen.queryByRole('button', { name: 'Add a post' }),
+    ).toBeInTheDocument();
+  });
+
+  test('"no post selected" text shown when posts are in system', async () => {
+    await mockFetchThreads();
+    renderComponent(`/${courseId}/my-posts/`);
+
+    expect(
+      screen.queryByText(messages.noPostSelected.defaultMessage),
+    ).toBeInTheDocument();
+  });
+});

src/discussions/empty-posts/EmptyTopics.jsx

@@ -0,0 +1,71 @@
+import React from 'react';
+
+import { useDispatch, useSelector } from 'react-redux';
+import { useRouteMatch } from 'react-router';
+
+import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+
+import { ALL_ROUTES } from '../../data/constants';
+import { useIsOnDesktop, useTotalTopicThreadCount } from '../data/hooks';
+import { selectTopicThreadCount } from '../data/selectors';
+import messages from '../messages';
+import { messages as postMessages, showPostEditor } from '../posts';
+import EmptyPage from './EmptyPage';
+
+function EmptyTopics({ intl }) {
+  const match = useRouteMatch(ALL_ROUTES);
+  const dispatch = useDispatch();
+
+  const hasGlobalThreads = useTotalTopicThreadCount() > 0;
+  const topicThreadCount = useSelector(selectTopicThreadCount(match.params.topicId));
+
+  function addPost() {
+    return dispatch(showPostEditor());
+  }
+
+  const isOnDesktop = useIsOnDesktop();
+
+  let title = messages.emptyTitle;
+  let fullWidth = false;
+  let subTitle;
+  let action;
+  let actionText;
+
+  if (!isOnDesktop) {
+    return null;
+  }
+
+  if (match.params.topicId) {
+    if (topicThreadCount > 0) {
+      title = messages.noPostSelected;
+    } else {
+      action = addPost;
+      actionText = postMessages.addAPost;
+      subTitle = messages.emptyTopic;
+      fullWidth = true;
+    }
+  } else if (hasGlobalThreads) {
+    title = messages.noTopicSelected;
+  } else {
+    action = addPost;
+    actionText = postMessages.addAPost;
+    subTitle = messages.emptyAllTopics;
+    fullWidth = true;
+  }
+
+  return (
+    <EmptyPage
+      title={intl.formatMessage(title)}
+      subTitle={subTitle ? intl.formatMessage(subTitle) : null}
+      action={action}
+      actionText={actionText ? intl.formatMessage(actionText) : null}
+      fullWidth={fullWidth}
+    />
+  );
+}
+
+EmptyTopics.propTypes = {
+  intl: intlShape.isRequired,
+};
+
+export default injectIntl(EmptyTopics);

src/discussions/empty-posts/EmptyTopics.test.jsx

@@ -0,0 +1,77 @@
+import { render, screen } from '@testing-library/react';
+import MockAdapter from 'axios-mock-adapter';
+import { IntlProvider } from 'react-intl';
+import { Context as ResponsiveContext } from 'react-responsive';
+import { MemoryRouter } from 'react-router';
+import { Factory } from 'rosie';
+
+import { initializeMockApp } from '@edx/frontend-platform';
+import { getAuthenticatedHttpClient } from '@edx/frontend-platform/auth';
+import { AppProvider } from '@edx/frontend-platform/react';
+
+import { API_BASE_URL } from '../../data/constants';
+import { initializeStore } from '../../store';
+import { executeThunk } from '../../test-utils';
+import messages from '../messages';
+import { fetchCourseTopics } from '../topics/data/thunks';
+import EmptyTopics from './EmptyTopics';
+
+import '../topics/data/__factories__';
+
+let store;
+const courseId = 'course-v1:edX+DemoX+Demo_Course';
+const topicsApiUrl = `${API_BASE_URL}/api/discussion/v1/course_topics/${courseId}`;
+
+function renderComponent(location = `/${courseId}/topics/`) {
+  return render(
+    <IntlProvider locale="en">
+      <ResponsiveContext.Provider value={{ width: 1280 }}>
+        <AppProvider store={store}>
+          <MemoryRouter initialEntries={[location]}>
+            <EmptyTopics />
+          </MemoryRouter>
+        </AppProvider>
+      </ResponsiveContext.Provider>
+    </IntlProvider>,
+  );
+}
+
+async function setupMockResponse() {
+  const axiosMock = new MockAdapter(getAuthenticatedHttpClient());
+  axiosMock
+    .onGet(topicsApiUrl)
+    .reply(200, {
+      courseware_topics: Factory.buildList('category', 2),
+      non_courseware_topics: Factory.buildList('topic.withThreads', 3, {}, { topicPrefix: 'ncw' }),
+    });
+  await executeThunk(fetchCourseTopics(courseId), store.dispatch, store.getState);
+}
+
+describe('EmptyTopics', () => {
+  beforeEach(async () => {
+    initializeMockApp({
+      authenticatedUser: {
+        userId: 3,
+        username: 'abc123',
+        administrator: true,
+        roles: [],
+      },
+    });
+
+    store = initializeStore({ config: { provider: 'legacy' } });
+  });
+
+  test('"no topic selected" text shown when viewing topics page', async () => {
+    renderComponent(`/${courseId}/topics/`);
+    expect(screen.queryByText(messages.emptyTitle.defaultMessage))
+      .toBeInTheDocument();
+  });
+
+  test('"no post selected" text shown when viewing a specific topic', async () => {
+    await setupMockResponse();
+    renderComponent(`/${courseId}/topics/ncwtopic-3/`);
+
+    expect(screen.queryByText(messages.noPostSelected.defaultMessage))
+      .toBeInTheDocument();
+  });
+});

src/discussions/empty-posts/index.js

@@ -0,0 +1,3 @@
+export { default as EmptyPage } from './EmptyPage';
+export { default as EmptyPosts } from './EmptyPosts';
+export { default as EmptyTopics } from './EmptyTopics';