Use spring to animate lightbox thumbnails

stylesheets/components/Lightbox.scss

@@ -52,10 +52,6 @@
     }
   }
 
-  &__thumbnails_placeholder {
-    height: 44px;
-  }
-
   &__thumbnail {
     @include button-reset;
     position: relative;

ts/components/Lightbox.tsx

@@ -4,7 +4,6 @@
 import type { ReactNode } from 'react';
 import React, { useCallback, useEffect, useRef, useState } from 'react';
 import classNames from 'classnames';
-import moment from 'moment';
 import { createPortal } from 'react-dom';
 import { noop } from 'lodash';
 import { useSpring, animated, to } from '@react-spring/web';
@@ -20,9 +19,11 @@ import * as GoogleChrome from '../util/GoogleChrome';
 import * as log from '../logging/log';
 import { Avatar, AvatarSize } from './Avatar';
 import { IMAGE_PNG, isImage, isVideo } from '../types/MIME';
+import { formatDateTimeForAttachment } from '../util/timestamp';
 import { formatDuration } from '../util/formatDuration';
 import { isGIF } from '../types/Attachment';
 import { useRestoreFocus } from '../hooks/useRestoreFocus';
+import { usePrevious } from '../hooks/usePrevious';
 
 export type PropsType = {
   children?: ReactNode;
@@ -56,6 +57,17 @@ const INITIAL_IMAGE_TRANSFORM = {
   },
 };
 
+const THUMBNAIL_SPRING_CONFIG = {
+  mass: 1,
+  tension: 986,
+  friction: 64,
+  velocity: 0,
+};
+
+const THUMBNAIL_WIDTH = 44;
+const THUMBNAIL_PADDING = 8;
+const THUMBNAIL_FULL_WIDTH = THUMBNAIL_WIDTH + THUMBNAIL_PADDING;
+
 export function Lightbox({
   children,
   closeLightbox,
@@ -73,6 +85,9 @@ export function Lightbox({
   hasNextMessage,
   hasPrevMessage,
 }: PropsType): JSX.Element | null {
+  const hasThumbnails = media.length > 1;
+  const hadThumbnails = usePrevious(hasThumbnails, hasThumbnails);
+  const justGotThumbnails = !hadThumbnails && hasThumbnails;
   const [root, setRoot] = React.useState<HTMLElement | undefined>();
 
   const [videoElement, setVideoElement] = useState<HTMLVideoElement | null>(
@@ -271,6 +286,43 @@ export function Lightbox({
     () => INITIAL_IMAGE_TRANSFORM
   );
 
+  const thumbnailsMarginLeft =
+    0 - (selectedIndex * THUMBNAIL_FULL_WIDTH + THUMBNAIL_WIDTH / 2);
+
+  const [thumbnailsStyle, thumbnailsAnimation] = useSpring(
+    {
+      config: THUMBNAIL_SPRING_CONFIG,
+      to: {
+        marginLeft: thumbnailsMarginLeft,
+        opacity: hasThumbnails ? 1 : 0,
+      },
+    },
+    [selectedIndex, hasThumbnails]
+  );
+
+  useEffect(() => {
+    if (!justGotThumbnails) {
+      return;
+    }
+
+    thumbnailsAnimation.stop();
+    thumbnailsAnimation.set({
+      marginLeft:
+        thumbnailsMarginLeft +
+        (selectedIndex === 0 ? -1 : 1) * THUMBNAIL_FULL_WIDTH,
+      opacity: 0,
+    });
+    thumbnailsAnimation.start({
+      marginLeft: thumbnailsMarginLeft,
+      opacity: 1,
+    });
+  }, [
+    justGotThumbnails,
+    selectedIndex,
+    thumbnailsMarginLeft,
+    thumbnailsAnimation,
+  ]);
+
   const maxBoundsLimiter = useCallback(
     (x: number, y: number): [number, number] => {
       const zoomCache = zoomCacheRef.current;
@@ -643,16 +695,13 @@ export function Lightbox({
               {caption ? (
                 <div className="Lightbox__caption">{caption}</div>
               ) : null}
-              {media.length > 1 ? (
               <div className="Lightbox__thumbnails--container">
-                  <div
+                <animated.div
                   className="Lightbox__thumbnails"
-                    style={{
-                      marginLeft:
-                        0 - (selectedIndex * 44 + selectedIndex * 8 + 22),
-                    }}
+                  style={thumbnailsStyle}
                 >
-                    {media.map((item, index) => (
+                  {hasThumbnails
+                    ? media.map((item, index) => (
                         <button
                           className={classNames({
                             Lightbox__thumbnail: true,
@@ -662,7 +711,10 @@ export function Lightbox({
                           key={item.thumbnailObjectUrl}
                           type="button"
                           onClick={(
-                          event: React.MouseEvent<HTMLButtonElement, MouseEvent>
+                            event: React.MouseEvent<
+                              HTMLButtonElement,
+                              MouseEvent
+                            >
                           ) => {
                             event.stopPropagation();
                             event.preventDefault();
@@ -679,13 +731,11 @@ export function Lightbox({
                             <div className="Lightbox__thumbnail--unavailable" />
                           )}
                         </button>
-                    ))}
+                      ))
+                    : undefined}
+                </animated.div>
               </div>
             </div>
-              ) : (
-                <div className="Lightbox__thumbnails_placeholder" />
-              )}
-            </div>
           </div>
         </div>,
         root
@@ -704,6 +754,8 @@ function LightboxHeader({
 }): JSX.Element {
   const conversation = getConversation(message.conversationId);
 
+  const now = Date.now();
+
   return (
     <div className="Lightbox__header--container">
       <div className="Lightbox__header--avatar">
@@ -726,7 +778,7 @@ function LightboxHeader({
       <div className="Lightbox__header--content">
         <div className="Lightbox__header--name">{conversation.title}</div>
         <div className="Lightbox__header--timestamp">
-          {moment(message.received_at_ms).format('L LT')}
+          {formatDateTimeForAttachment(i18n, message.received_at_ms ?? now)}
         </div>
       </div>
     </div>

ts/util/durations/duration-in-seconds.ts

@@ -34,5 +34,6 @@ export namespace DurationInSeconds {
   export const HOUR = DurationInSeconds.fromHours(1);
   export const MINUTE = DurationInSeconds.fromMinutes(1);
   export const DAY = DurationInSeconds.fromDays(1);
+  export const WEEK = DurationInSeconds.fromWeeks(1);
 }
 /* eslint-enable @typescript-eslint/no-namespace, @typescript-eslint/no-redeclare */

ts/util/timestamp.ts

@@ -74,6 +74,49 @@ export function formatDateTimeShort(
   }).format(timestamp);
 }
 
+export function formatDateTimeForAttachment(
+  i18n: LocalizerType,
+  rawTimestamp: RawTimestamp
+): string {
+  const timestamp = rawTimestamp.valueOf();
+
+  const now = Date.now();
+  const diff = now - timestamp;
+
+  const locale = window.getPreferredSystemLocales();
+
+  if (diff < HOUR || isToday(timestamp)) {
+    return formatTime(i18n, rawTimestamp, now);
+  }
+
+  const m = moment(timestamp);
+
+  if (diff < WEEK && m.isSame(now, 'month')) {
+    return new Intl.DateTimeFormat(locale, {
+      weekday: 'short',
+      hour: 'numeric',
+      minute: 'numeric',
+    }).format(timestamp);
+  }
+
+  if (m.isSame(now, 'year')) {
+    return new Intl.DateTimeFormat(locale, {
+      day: 'numeric',
+      month: 'short',
+      hour: 'numeric',
+      minute: 'numeric',
+    }).format(timestamp);
+  }
+
+  return new Intl.DateTimeFormat(locale, {
+    day: 'numeric',
+    month: 'short',
+    year: 'numeric',
+    hour: 'numeric',
+    minute: 'numeric',
+  }).format(timestamp);
+}
+
 export function formatDateTimeLong(
   i18n: LocalizerType,
   rawTimestamp: RawTimestamp