Add graphs and retention metrics to admin dashboard (#16829)

app/javascript/mastodon/components/admin/Trends.js

@@ -0,0 +1,73 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import api from 'mastodon/api';
+import { FormattedMessage } from 'react-intl';
+import classNames from 'classnames';
+import Hashtag from 'mastodon/components/hashtag';
+
+export default class Trends extends React.PureComponent {
+
+  static propTypes = {
+    limit: PropTypes.number.isRequired,
+  };
+
+  state = {
+    loading: true,
+    data: null,
+  };
+
+  componentDidMount () {
+    const { limit } = this.props;
+
+    api().get('/api/v1/admin/trends', { params: { limit } }).then(res => {
+      this.setState({
+        loading: false,
+        data: res.data,
+      });
+    }).catch(err => {
+      console.error(err);
+    });
+  }
+
+  render () {
+    const { limit } = this.props;
+    const { loading, data } = this.state;
+
+    let content;
+
+    if (loading) {
+      content = (
+        <div>
+          {Array.from(Array(limit)).map((_, i) => (
+            <Hashtag key={i} />
+          ))}
+        </div>
+      );
+    } else {
+      content = (
+        <div>
+          {data.map(hashtag => (
+            <Hashtag
+              key={hashtag.name}
+              name={hashtag.name}
+              href={`/admin/tags/${hashtag.id}`}
+              people={hashtag.history[0].accounts * 1 + hashtag.history[1].accounts * 1}
+              uses={hashtag.history[0].uses * 1 + hashtag.history[1].uses * 1}
+              history={hashtag.history.reverse().map(day => day.uses)}
+              className={classNames(hashtag.requires_review && 'trends__item--requires-review', !hashtag.trendable && !hashtag.requires_review && 'trends__item--disabled')}
+            />
+          ))}
+        </div>
+      );
+    }
+
+    return (
+      <div className='trends trends--compact'>
+        <h4><FormattedMessage id='trends.trending_now' defaultMessage='Trending now' /></h4>
+
+        {content}
+      </div>
+    );
+  }
+
+}