Migrate AutoUpdateTime to functional component

src/components/AutoUpdateTime.js

@@ -3,7 +3,13 @@
  * The time auto-update logic is extracted to this component to avoid re-rendering a more complex component, e.g. DetailsPage.
  */
 import {View} from 'react-native';
-import React, {PureComponent} from 'react';
+import React, {
+    useCallback,
+    useEffect,
+    useMemo,
+    useRef,
+    useState,
+} from 'react';
 import PropTypes from 'prop-types';
 import styles from '../styles/styles';
 import DateUtils from '../libs/DateUtils';
@@ -22,85 +28,60 @@ const propTypes = {
     ...withLocalizePropTypes,
 };
 
-class AutoUpdateTime extends PureComponent {
-    constructor(props) {
-        super(props);
-        this.getCurrentUserLocalTime = this.getCurrentUserLocalTime.bind(this);
-        this.updateCurrentTime = this.updateCurrentTime.bind(this);
-        this.getTimezoneName = this.getTimezoneName.bind(this);
-        this.state = {
-            currentUserLocalTime: this.getCurrentUserLocalTime(),
-        };
-    }
-
-    componentDidMount() {
-        this.updateCurrentTime();
-    }
-
-    componentDidUpdate() {
-        // Make sure the interval is up to date every time the component updates
-        this.updateCurrentTime();
-    }
-
-    componentWillUnmount() {
-        clearTimeout(this.timer);
-    }
-
+function AutoUpdateTime(props) {
     /**
      * @returns {moment} Returns the locale moment object
      */
-    getCurrentUserLocalTime() {
-        return DateUtils.getLocalMomentFromDatetime(
-            this.props.preferredLocale,
+    const getCurrentUserLocalTime = useCallback(() => (
+        DateUtils.getLocalMomentFromDatetime(
+            props.preferredLocale,
             null,
-            this.props.timezone.selected,
-        );
-    }
+            props.timezone.selected,
+        )
+    ), [props.preferredLocale, props.timezone.selected]);
 
-    /**
-     * @returns {string} Returns the timezone name in string, e.g.: GMT +07
-     */
-    getTimezoneName() {
+    const [currentUserLocalTime, setCurrentUserLocalTime] = useState(getCurrentUserLocalTime);
+    const minuteRef = useRef(new Date().getMinutes());
+    const timezoneName = useMemo(() => {
         // With non-GMT timezone, moment.zoneAbbr() will return the name of that timezone, so we can use it directly.
-        if (Number.isNaN(Number(this.state.currentUserLocalTime.zoneAbbr()))) {
-            return this.state.currentUserLocalTime.zoneAbbr();
+        if (Number.isNaN(Number(currentUserLocalTime.zoneAbbr()))) {
+            return currentUserLocalTime.zoneAbbr();
         }
 
         // With GMT timezone, moment.zoneAbbr() will return a number, so we need to display it as GMT {abbreviations} format, e.g.: GMT +07
-        return `GMT ${this.state.currentUserLocalTime.zoneAbbr()}`;
-    }
+        return `GMT ${currentUserLocalTime.zoneAbbr()}`;
+    }, [currentUserLocalTime]);
 
-    /**
-     * Update the user's local time at the top of every minute
-     */
-    updateCurrentTime() {
-        if (this.timer) {
-            clearTimeout(this.timer);
-            this.timer = null;
-        }
-        const millisecondsUntilNextMinute = (60 - this.state.currentUserLocalTime.seconds()) * 1000;
-        this.timer = setTimeout(() => {
-            this.setState({
-                currentUserLocalTime: this.getCurrentUserLocalTime(),
-            });
-        }, millisecondsUntilNextMinute);
-    }
+    useEffect(() => {
+        // If the any of the props that getCurrentUserLocalTime depends on change, we want to update the displayed time immediately
+        setCurrentUserLocalTime(getCurrentUserLocalTime());
+
+        // Also, if the user leaves this page open, we want to make sure the displayed time is updated every minute when the clock changes
+        // To do this we create an interval to check if the minute has changed every second and update the displayed time if it has
+        const interval = setInterval(() => {
+            const currentMinute = new Date().getMinutes();
+            if (currentMinute !== minuteRef.current) {
+                setCurrentUserLocalTime(getCurrentUserLocalTime());
+                minuteRef.current = currentMinute;
+            }
+        }, 1000);
+        return () => clearInterval(interval);
+    }, [getCurrentUserLocalTime]);
 
-    render() {
-        return (
-            <View style={[styles.mb6, styles.detailsPageSectionContainer]}>
-                <Text style={[styles.textLabelSupporting, styles.mb1]} numberOfLines={1}>
-                    {this.props.translate('detailsPage.localTime')}
-                </Text>
-                <Text numberOfLines={1}>
-                    {this.state.currentUserLocalTime.format('LT')}
-                    {' '}
-                    {this.getTimezoneName()}
-                </Text>
-            </View>
-        );
-    }
+    return (
+        <View style={[styles.mb6, styles.detailsPageSectionContainer]}>
+            <Text style={[styles.textLabelSupporting, styles.mb1]} numberOfLines={1}>
+                {props.translate('detailsPage.localTime')}
+            </Text>
+            <Text numberOfLines={1}>
+                {currentUserLocalTime.format('LT')}
+                {' '}
+                {timezoneName}
+            </Text>
+        </View>
+    );
 }
 
 AutoUpdateTime.propTypes = propTypes;
+AutoUpdateTime.displayName = 'AutoUpdateTime';
 export default withLocalize(AutoUpdateTime);