update folds

package-lock.json

@@ -32,7 +32,7 @@
         "emojibase-data": "15.3.2",
         "file-saver": "2.0.5",
         "focus-trap-react": "10.0.2",
-        "folds": "2.3.0",
+        "folds": "2.5.0",
         "html-dom-parser": "4.0.0",
         "html-react-parser": "4.2.0",
         "i18next": "23.12.2",
@@ -7157,9 +7157,9 @@
       }
     },
     "node_modules/folds": {
-      "version": "2.3.0",
+      "version": "2.5.0",
-      "resolved": "https://registry.npmjs.org/folds/-/folds-2.3.0.tgz",
+      "resolved": "https://registry.npmjs.org/folds/-/folds-2.5.0.tgz",
-      "integrity": "sha512-1KoM21jrg5daxvKrmSY0V04wa946KlNT0z6h017Rsnw2fdtNC6J0f34Ce5GF46Tzi00gZ/7SvCDXMzW/7e5s0w==",
+      "integrity": "sha512-UJhvXAQ1XnZ9w10KJwSW+frvzzWE/zcF0dH3fDVCD70RFHAxwEi0UkkVS8CaZGxZF2Wvt3qTJyTS5LW3LwwUAw==",
       "license": "Apache-2.0",
       "peerDependencies": {
         "@vanilla-extract/css": "1.9.2",

package.json

@@ -43,7 +43,7 @@
     "emojibase-data": "15.3.2",
     "file-saver": "2.0.5",
     "focus-trap-react": "10.0.2",
-    "folds": "2.3.0",
+    "folds": "2.5.0",
     "html-dom-parser": "4.0.0",
     "html-react-parser": "4.2.0",
     "i18next": "23.12.2",

src/app/components/message/Time.css.ts

@@ -0,0 +1,6 @@
+import { style } from '@vanilla-extract/css';
+
+export const Time = style({
+  fontWeight: 'inherit',
+  flexShrink: 0,
+});

src/app/components/message/Time.tsx

@@ -1,12 +1,15 @@
 import React, { ComponentProps } from 'react';
 import { Text, as } from 'folds';
+import classNames from 'classnames';
 import { timeDayMonYear, timeHourMinute, today, yesterday } from '../../utils/time';
+import * as css from './Time.css';
 
 export type TimeProps = {
   compact?: boolean;
   ts: number;
   hour24Clock: boolean;
   dateFormatString: string;
+  inheritPriority?: boolean;
 };
 
 /**
@@ -22,7 +25,7 @@ export type TimeProps = {
  * @returns {React.ReactElement} A <Text as="time"> element with the formatted date/time.
  */
 export const Time = as<'span', TimeProps & ComponentProps<typeof Text>>(
-  ({ compact, hour24Clock, dateFormatString, ts, ...props }, ref) => {
+  ({ compact, hour24Clock, dateFormatString, ts, inheritPriority, className, ...props }, ref) => {
     const formattedTime = timeHourMinute(ts, hour24Clock);
 
     let time = '';
@@ -33,11 +36,18 @@ export const Time = as<'span', TimeProps & ComponentProps<typeof Text>>(
     } else if (yesterday(ts)) {
       time = `Yesterday ${formattedTime}`;
     } else {
-      time = `${timeDayMonYear(ts, dateFormatString)} ${formattedTime}`;
+      time = `${timeDayMonYear(ts, dateFormatString)}, ${formattedTime}`;
     }
 
     return (
-      <Text as="time" style={{ flexShrink: 0 }} size="T200" priority="300" {...props} ref={ref}>
+      <Text
+        as="time"
+        className={classNames(css.Time, className)}
+        size="T200"
+        priority={inheritPriority ? undefined : '300'}
+        {...props}
+        ref={ref}
+      >
         {time}
       </Text>
     );

src/app/features/room/Room.tsx

@@ -13,6 +13,8 @@ import { useKeyDown } from '../../hooks/useKeyDown';
 import { markAsRead } from '../../utils/notifications';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { useRoomMembers } from '../../hooks/useRoomMembers';
+import { ThreadView } from './thread-view';
+import { useActiveThread } from '../../state/hooks/roomToActiveThread';
 
 export function Room() {
   const { eventId } = useParams();
@@ -25,6 +27,8 @@ export function Room() {
   const powerLevels = usePowerLevels(room);
   const members = useRoomMembers(mx, room.roomId);
 
+  const threadId = useActiveThread(room.roomId);
+
   useKeyDown(
     window,
     useCallback(
@@ -41,11 +45,19 @@ export function Room() {
     <PowerLevelsContextProvider value={powerLevels}>
       <Box grow="Yes">
         <RoomView room={room} eventId={eventId} />
-        {screenSize === ScreenSize.Desktop && isDrawer && (
+        {threadId ? (
+          <>
+            <Line variant="Surface" direction="Vertical" size="300" />
+            <ThreadView threadId={threadId} />
+          </>
+        ) : (
+          screenSize === ScreenSize.Desktop &&
+          isDrawer && (
             <>
               <Line variant="Background" direction="Vertical" size="300" />
               <MembersDrawer key={room.roomId} room={room} members={members} />
             </>
+          )
         )}
       </Box>
     </PowerLevelsContextProvider>

src/app/features/room/RoomTimeline.tsx

@@ -77,6 +77,7 @@ import {
   decryptAllTimelineEvent,
   getEditedEvent,
   getEventReactions,
+  getEventThreadDetail,
   getLatestEditableEvt,
   getMemberDisplayName,
   getReactionContent,
@@ -126,6 +127,18 @@ import { useAccessiblePowerTagColors, useGetMemberPowerTag } from '../../hooks/u
 import { useTheme } from '../../hooks/useTheme';
 import { useRoomCreatorsTag } from '../../hooks/useRoomCreatorsTag';
 import { usePowerLevelTags } from '../../hooks/usePowerLevelTags';
+import { ThreadSelector, ThreadSelectorContainer } from './message/thread-selector';
+import {
+  getEventIdAbsoluteIndex,
+  getFirstLinkedTimeline,
+  getLinkedTimelines,
+  getTimelineAndBaseIndex,
+  getTimelineEvent,
+  getTimelineRelativeIndex,
+  getTimelinesEventsCount,
+  timelineToEventsCount,
+} from './utils';
+import { useThreadSelector } from '../../state/hooks/roomToActiveThread';
 
 const TimelineFloat = as<'div', css.TimelineFloatVariants>(
   ({ position, className, ...props }, ref) => (
@@ -150,79 +163,6 @@ const TimelineDivider = as<'div', { variant?: ContainerColor | 'Inherit' }>(
   )
 );
 
-export const getLiveTimeline = (room: Room): EventTimeline =>
-  room.getUnfilteredTimelineSet().getLiveTimeline();
-
-export const getEventTimeline = (room: Room, eventId: string): EventTimeline | undefined => {
-  const timelineSet = room.getUnfilteredTimelineSet();
-  return timelineSet.getTimelineForEvent(eventId) ?? undefined;
-};
-
-export const getFirstLinkedTimeline = (
-  timeline: EventTimeline,
-  direction: Direction
-): EventTimeline => {
-  const linkedTm = timeline.getNeighbouringTimeline(direction);
-  if (!linkedTm) return timeline;
-  return getFirstLinkedTimeline(linkedTm, direction);
-};
-
-export const getLinkedTimelines = (timeline: EventTimeline): EventTimeline[] => {
-  const firstTimeline = getFirstLinkedTimeline(timeline, Direction.Backward);
-  const timelines: EventTimeline[] = [];
-
-  for (
-    let nextTimeline: EventTimeline | null = firstTimeline;
-    nextTimeline;
-    nextTimeline = nextTimeline.getNeighbouringTimeline(Direction.Forward)
-  ) {
-    timelines.push(nextTimeline);
-  }
-  return timelines;
-};
-
-export const timelineToEventsCount = (t: EventTimeline) => t.getEvents().length;
-export const getTimelinesEventsCount = (timelines: EventTimeline[]): number => {
-  const timelineEventCountReducer = (count: number, tm: EventTimeline) =>
-    count + timelineToEventsCount(tm);
-  return timelines.reduce(timelineEventCountReducer, 0);
-};
-
-export const getTimelineAndBaseIndex = (
-  timelines: EventTimeline[],
-  index: number
-): [EventTimeline | undefined, number] => {
-  let uptoTimelineLen = 0;
-  const timeline = timelines.find((t) => {
-    uptoTimelineLen += t.getEvents().length;
-    if (index < uptoTimelineLen) return true;
-    return false;
-  });
-  if (!timeline) return [undefined, 0];
-  return [timeline, uptoTimelineLen - timeline.getEvents().length];
-};
-
-export const getTimelineRelativeIndex = (absoluteIndex: number, timelineBaseIndex: number) =>
-  absoluteIndex - timelineBaseIndex;
-
-export const getTimelineEvent = (timeline: EventTimeline, index: number): MatrixEvent | undefined =>
-  timeline.getEvents()[index];
-
-export const getEventIdAbsoluteIndex = (
-  timelines: EventTimeline[],
-  eventTimeline: EventTimeline,
-  eventId: string
-): number | undefined => {
-  const timelineIndex = timelines.findIndex((t) => t === eventTimeline);
-  if (timelineIndex === -1) return undefined;
-  const eventIndex = eventTimeline.getEvents().findIndex((evt) => evt.getId() === eventId);
-  if (eventIndex === -1) return undefined;
-  const baseIndex = timelines
-    .slice(0, timelineIndex)
-    .reduce((accValue, timeline) => timeline.getEvents().length + accValue, 0);
-  return baseIndex + eventIndex;
-};
-
 type RoomTimelineProps = {
   room: Room;
   eventId?: string;
@@ -232,6 +172,14 @@ type RoomTimelineProps = {
 
 const PAGINATION_LIMIT = 80;
 
+export const getLiveTimeline = (room: Room): EventTimeline =>
+  room.getUnfilteredTimelineSet().getLiveTimeline();
+
+export const getEventTimeline = (room: Room, eventId: string): EventTimeline | undefined => {
+  const timelineSet = room.getUnfilteredTimelineSet();
+  return timelineSet.getTimelineForEvent(eventId) ?? undefined;
+};
+
 type Timeline = {
   linkedTimelines: EventTimeline[];
   range: ItemRange;
@@ -482,6 +430,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
   const spoilerClickHandler = useSpoilerClickHandler();
   const openUserRoomProfile = useOpenUserRoomProfile();
   const space = useSpaceOptionally();
+  const handleThreadClick = useThreadSelector(room.roomId);
 
   const imagePackRooms: Room[] = useImagePackRooms(room.roomId, roomToParents);
 
@@ -1014,6 +963,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
     },
     [editor]
   );
+
   const { t } = useTranslation();
 
   const renderMatrixEvent = useMatrixEventRenderer<
@@ -1034,6 +984,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
         const senderId = mEvent.getSender() ?? '';
         const senderDisplayName =
           getMemberDisplayName(room, senderId) ?? getMxIdLocalPart(senderId) ?? senderId;
+        const threadDetail = getEventThreadDetail(mEvent);
 
         return (
           <Message
@@ -1107,6 +1058,20 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
                 outlineAttachment={messageLayout === MessageLayout.Bubble}
               />
             )}
+
+            {threadDetail && (
+              <ThreadSelectorContainer>
+                <ThreadSelector
+                  room={room}
+                  threadId={mEventId}
+                  threadDetail={threadDetail}
+                  hour24Clock={hour24Clock}
+                  dateFormatString={dateFormatString}
+                  outlined={messageLayout === MessageLayout.Bubble}
+                  onClick={handleThreadClick}
+                />
+              </ThreadSelectorContainer>
+            )}
           </Message>
         );
       },

src/app/features/room/RoomViewHeader.tsx

@@ -69,6 +69,7 @@ import { useRoomNavigate } from '../../hooks/useRoomNavigate';
 import { useRoomCreators } from '../../hooks/useRoomCreators';
 import { useRoomPermissions } from '../../hooks/useRoomPermissions';
 import { InviteUserPrompt } from '../../components/invite-user-prompt';
+import { ThreadsMenu } from './threads-menu';
 
 type RoomMenuProps = {
   room: Room;
@@ -263,6 +264,7 @@ export function RoomViewHeader() {
   const space = useSpaceOptionally();
   const [menuAnchor, setMenuAnchor] = useState<RectCords>();
   const [pinMenuAnchor, setPinMenuAnchor] = useState<RectCords>();
+  const [threadsMenuAnchor, setThreadsMenuAnchor] = useState<RectCords>();
   const mDirects = useAtomValue(mDirectAtom);
 
   const pinnedEvents = useRoomPinnedEvents(room);
@@ -295,6 +297,10 @@ export function RoomViewHeader() {
     setPinMenuAnchor(evt.currentTarget.getBoundingClientRect());
   };
 
+  const handleOpenThreadsMenu: MouseEventHandler<HTMLButtonElement> = (evt) => {
+    setThreadsMenuAnchor(evt.currentTarget.getBoundingClientRect());
+  };
+
   return (
     <PageHeader balance={screenSize === ScreenSize.Mobile}>
       <Box grow="Yes" gap="300">
@@ -424,6 +430,27 @@ export function RoomViewHeader() {
               </IconButton>
             )}
           </TooltipProvider>
+
+          <TooltipProvider
+            position="Bottom"
+            offset={4}
+            tooltip={
+              <Tooltip>
+                <Text>My Threads</Text>
+              </Tooltip>
+            }
+          >
+            {(triggerRef) => (
+              <IconButton
+                style={{ position: 'relative' }}
+                onClick={handleOpenThreadsMenu}
+                ref={triggerRef}
+                aria-pressed={!!threadsMenuAnchor}
+              >
+                <Icon size="400" src={Icons.Thread} filled={!!threadsMenuAnchor} />
+              </IconButton>
+            )}
+          </TooltipProvider>
           <PopOut
             anchor={pinMenuAnchor}
             position="Bottom"
@@ -443,6 +470,25 @@ export function RoomViewHeader() {
               </FocusTrap>
             }
           />
+          <PopOut
+            anchor={threadsMenuAnchor}
+            position="Bottom"
+            content={
+              <FocusTrap
+                focusTrapOptions={{
+                  initialFocus: false,
+                  returnFocusOnDeactivate: false,
+                  onDeactivate: () => setThreadsMenuAnchor(undefined),
+                  clickOutsideDeactivates: true,
+                  isKeyForward: (evt: KeyboardEvent) => evt.key === 'ArrowDown',
+                  isKeyBackward: (evt: KeyboardEvent) => evt.key === 'ArrowUp',
+                  escapeDeactivates: stopPropagation,
+                }}
+              >
+                <ThreadsMenu room={room} requestClose={() => setThreadsMenuAnchor(undefined)} />
+              </FocusTrap>
+            }
+          />
           {screenSize === ScreenSize.Desktop && (
             <TooltipProvider
               position="Bottom"

src/app/features/room/message/thread-selector/ThreadSelector.tsx

@@ -0,0 +1,83 @@
+import { Box, Icon, Icons, Line, Text } from 'folds';
+import React, { ReactNode } from 'react';
+import classNames from 'classnames';
+import { IThreadBundledRelationship, Room } from 'matrix-js-sdk';
+import * as css from './styles.css';
+import { getMemberDisplayName } from '../../../../utils/room';
+import { getMxIdLocalPart } from '../../../../utils/matrix';
+import { Time } from '../../../../components/message';
+
+export function ThreadSelectorContainer({ children }: { children: ReactNode }) {
+  return <Box className={css.ThreadSelectorContainer}>{children}</Box>;
+}
+
+type ThreadSelectorProps = {
+  room: Room;
+  threadId: string;
+  threadDetail: IThreadBundledRelationship;
+  outlined?: boolean;
+  hour24Clock: boolean;
+  dateFormatString: string;
+  onClick?: (threadId: string) => void;
+};
+
+export function ThreadSelector({
+  room,
+  threadId,
+  threadDetail,
+  outlined,
+  hour24Clock,
+  dateFormatString,
+  onClick,
+}: ThreadSelectorProps) {
+  const latestEvent = threadDetail.latest_event;
+
+  const latestSenderId = latestEvent.sender;
+  const latestDisplayName =
+    getMemberDisplayName(room, latestSenderId) ??
+    getMxIdLocalPart(latestSenderId) ??
+    latestSenderId;
+
+  const latestEventTs = latestEvent.origin_server_ts;
+
+  return (
+    <Box
+      as="button"
+      type="button"
+      className={classNames(css.ThreadSelector, outlined && css.ThreadSectorOutlined)}
+      alignItems="Center"
+      gap="300"
+      onClick={() => onClick?.(threadId)}
+    >
+      <Box className={css.ThreadRepliesCount} shrink="No" alignItems="Center" gap="200">
+        <Icon size="100" src={Icons.Thread} filled />
+        <Text size="L400">
+          {threadDetail.count} {threadDetail.count === 1 ? 'Reply' : 'Replies'}
+        </Text>
+      </Box>
+      {latestSenderId && (
+        <>
+          <Line
+            className={css.ThreadSelectorDivider}
+            direction="Vertical"
+            variant="SurfaceVariant"
+          />
+          <Box gap="200" alignItems="Inherit">
+            <Text size="T200" truncate>
+              <span>Last reply by </span>
+              <b>{latestDisplayName}</b>
+              <span> — </span>
+              <Time
+                hour24Clock={hour24Clock}
+                dateFormatString={dateFormatString}
+                ts={latestEventTs}
+                inheritPriority
+              />
+            </Text>
+            <Icon size="100" src={Icons.ChevronRight} />
+          </Box>
+        </>
+      )}
+    </Box>
+  );
+}

src/app/features/room/message/thread-selector/index.ts

@@ -0,0 +1 @@
+export * from './ThreadSelector';

src/app/features/room/message/thread-selector/styles.css.ts

@@ -0,0 +1,37 @@
+import { style } from '@vanilla-extract/css';
+import { color, config, toRem } from 'folds';
+import { ContainerColor } from '../../../../styles/ContainerColor.css';
+
+export const ThreadSelectorContainer = style({
+  marginTop: config.space.S200,
+});
+
+export const ThreadSelector = style([
+  ContainerColor({ variant: 'SurfaceVariant' }),
+  {
+    padding: config.space.S200,
+    borderRadius: config.radii.R400,
+    cursor: 'pointer',
+
+    selectors: {
+      '&:hover, &:focus-visible': {
+        backgroundColor: color.SurfaceVariant.ContainerHover,
+      },
+      '&:active': {
+        backgroundColor: color.SurfaceVariant.ContainerActive,
+      },
+    },
+  },
+]);
+
+export const ThreadSectorOutlined = style({
+  borderWidth: config.borderWidth.B300,
+});
+
+export const ThreadSelectorDivider = style({
+  height: toRem(16),
+});
+
+export const ThreadRepliesCount = style({
+  color: color.Primary.Main,
+});

src/app/features/room/thread-view/ThreadView.tsx

@@ -0,0 +1,79 @@
+import React from 'react';
+import { Box, Icon, IconButton, Icons, Scroll, Text, Tooltip, TooltipProvider } from 'folds';
+import classNames from 'classnames';
+import FocusTrap from 'focus-trap-react';
+import { Page, PageHeader } from '../../../components/page';
+import * as css from './styles.css';
+import { useRoom } from '../../../hooks/useRoom';
+import { useThreadClose } from '../../../state/hooks/roomToActiveThread';
+import { ScreenSize, useScreenSizeContext } from '../../../hooks/useScreenSize';
+
+type ThreadViewProps = {
+  threadId: string;
+};
+export function ThreadView({ threadId }: ThreadViewProps) {
+  const room = useRoom();
+  const screenSize = useScreenSizeContext();
+  const floating = screenSize !== ScreenSize.Desktop;
+
+  const closeThread = useThreadClose(room.roomId);
+
+  const thread = room.getThread(threadId);
+  const events = thread?.events ?? [];
+
+  return (
+    <FocusTrap
+      paused={!floating}
+      focusTrapOptions={{
+        initialFocus: false,
+        clickOutsideDeactivates: true,
+        onDeactivate: floating ? closeThread : undefined,
+      }}
+    >
+      <Page
+        className={classNames(css.ThreadView, {
+          [css.ThreadViewFloating]: floating,
+        })}
+      >
+        <PageHeader>
+          <Box grow="Yes" alignItems="Center" gap="200">
+            <Box grow="Yes">
+              <Text size="H5" truncate>
+                Thread
+              </Text>
+            </Box>
+            <Box shrink="No" alignItems="Center">
+              <TooltipProvider
+                position="Bottom"
+                align="End"
+                offset={4}
+                tooltip={
+                  <Tooltip>
+                    <Text>Close</Text>
+                  </Tooltip>
+                }
+              >
+                {(triggerRef) => (
+                  <IconButton ref={triggerRef} variant="Surface" onClick={closeThread}>
+                    <Icon src={Icons.Cross} />
+                  </IconButton>
+                )}
+              </TooltipProvider>
+            </Box>
+          </Box>
+        </PageHeader>
+        <Box grow="Yes" direction="Column">
+          <Scroll visibility="Hover" hideTrack>
+            <div>
+              {events.map((mEvent) => (
+                <p style={{ padding: `8px 16px` }} key={mEvent.getId()}>
+                  {mEvent.sender?.name}: {mEvent.getContent().body}
+                </p>
+              ))}
+            </div>
+          </Scroll>
+        </Box>
+      </Page>
+    </FocusTrap>
+  );
+}

src/app/features/room/thread-view/index.tsx

@@ -0,0 +1 @@
+export * from './ThreadView';

src/app/features/room/thread-view/styles.css.ts

@@ -0,0 +1,21 @@
+import { style } from '@vanilla-extract/css';
+import { config, toRem } from 'folds';
+
+export const ThreadView = style({
+  width: toRem(456),
+  flexShrink: 0,
+  flexGrow: 0,
+});
+
+export const ThreadViewFloating = style({
+  position: 'absolute',
+  right: 0,
+  top: 0,
+  bottom: 0,
+  zIndex: 1,
+
+  maxWidth: toRem(456),
+  flexShrink: 1,
+  width: '100vw',
+  boxShadow: config.shadow.E400,
+});

src/app/features/room/threads-menu/ThreadsError.tsx

@@ -0,0 +1,32 @@
+import React from 'react';
+import { Box, Icon, Icons, toRem, Text, config } from 'folds';
+import { ContainerColor } from '../../../styles/ContainerColor.css';
+import { BreakWord } from '../../../styles/Text.css';
+
+export function ThreadsError({ error }: { error: Error }) {
+  return (
+    <Box
+      className={ContainerColor({ variant: 'SurfaceVariant' })}
+      style={{
+        marginBottom: config.space.S200,
+        padding: `${config.space.S700} ${config.space.S400} ${toRem(60)}`,
+        borderRadius: config.radii.R300,
+      }}
+      grow="Yes"
+      direction="Column"
+      gap="400"
+      justifyContent="Center"
+      alignItems="Center"
+    >
+      <Icon src={Icons.Warning} size="600" />
+      <Box style={{ maxWidth: toRem(300) }} direction="Column" gap="200" alignItems="Center">
+        <Text size="H4" align="Center">
+          {error.name}
+        </Text>
+        <Text className={BreakWord} size="T400" align="Center">
+          {error.message}
+        </Text>
+      </Box>
+    </Box>
+  );
+}

src/app/features/room/threads-menu/ThreadsLoading.tsx

@@ -0,0 +1,23 @@
+import { Box, config, Spinner } from 'folds';
+import React from 'react';
+import { ContainerColor } from '../../../styles/ContainerColor.css';
+
+export function ThreadsLoading() {
+  return (
+    <Box
+      className={ContainerColor({ variant: 'SurfaceVariant' })}
+      style={{
+        marginBottom: config.space.S200,
+        padding: config.space.S700,
+        borderRadius: config.radii.R300,
+      }}
+      grow="Yes"
+      direction="Column"
+      gap="400"
+      justifyContent="Center"
+      alignItems="Center"
+    >
+      <Spinner variant="Secondary" />
+    </Box>
+  );
+}

src/app/features/room/threads-menu/ThreadsMenu.css.ts

@@ -0,0 +1,18 @@
+import { style } from '@vanilla-extract/css';
+import { config, toRem } from 'folds';
+
+export const ThreadsMenu = style({
+  display: 'flex',
+  maxWidth: toRem(548),
+  width: '100vw',
+  maxHeight: '90vh',
+});
+
+export const ThreadsMenuHeader = style({
+  paddingLeft: config.space.S400,
+  paddingRight: config.space.S200,
+});
+
+export const ThreadsMenuContent = style({
+  paddingLeft: config.space.S200,
+});

src/app/features/room/threads-menu/ThreadsMenu.tsx

@@ -0,0 +1,99 @@
+/* eslint-disable react/destructuring-assignment */
+import React, { forwardRef, useMemo } from 'react';
+import { EventTimelineSet, Room } from 'matrix-js-sdk';
+import { Box, config, Header, Icon, IconButton, Icons, Menu, Scroll, Text, toRem } from 'folds';
+import * as css from './ThreadsMenu.css';
+import { ContainerColor } from '../../../styles/ContainerColor.css';
+import { useRoomMyThreads } from '../../../hooks/useRoomThreads';
+import { AsyncStatus } from '../../../hooks/useAsyncCallback';
+import { getLinkedTimelines, getTimelinesEventsCount } from '../utils';
+import { ThreadsTimeline } from './ThreadsTimeline';
+import { ThreadsLoading } from './ThreadsLoading';
+import { ThreadsError } from './ThreadsError';
+
+const getTimelines = (timelineSet: EventTimelineSet) => {
+  const liveTimeline = timelineSet.getLiveTimeline();
+  const linkedTimelines = getLinkedTimelines(liveTimeline);
+
+  return linkedTimelines;
+};
+
+function NoThreads() {
+  return (
+    <Box
+      className={ContainerColor({ variant: 'SurfaceVariant' })}
+      style={{
+        marginBottom: config.space.S200,
+        padding: `${config.space.S700} ${config.space.S400} ${toRem(60)}`,
+        borderRadius: config.radii.R300,
+      }}
+      grow="Yes"
+      direction="Column"
+      gap="400"
+      justifyContent="Center"
+      alignItems="Center"
+    >
+      <Icon src={Icons.Thread} size="600" />
+      <Box style={{ maxWidth: toRem(300) }} direction="Column" gap="200" alignItems="Center">
+        <Text size="H4" align="Center">
+          No Threads Yet
+        </Text>
+        <Text size="T400" align="Center">
+          Threads you’re participating in will appear here.
+        </Text>
+      </Box>
+    </Box>
+  );
+}
+
+type ThreadsMenuProps = {
+  room: Room;
+  requestClose: () => void;
+};
+export const ThreadsMenu = forwardRef<HTMLDivElement, ThreadsMenuProps>(
+  ({ room, requestClose }, ref) => {
+    const threadsState = useRoomMyThreads(room);
+    const threadsTimelineSet =
+      threadsState.status === AsyncStatus.Success ? threadsState.data : undefined;
+
+    const linkedTimelines = useMemo(() => {
+      if (!threadsTimelineSet) return undefined;
+      return getTimelines(threadsTimelineSet);
+    }, [threadsTimelineSet]);
+
+    const hasEvents = linkedTimelines && getTimelinesEventsCount(linkedTimelines) > 0;
+
+    return (
+      <Menu ref={ref} className={css.ThreadsMenu}>
+        <Box grow="Yes" direction="Column">
+          <Header className={css.ThreadsMenuHeader} size="500">
+            <Box grow="Yes">
+              <Text size="H5">My Threads</Text>
+            </Box>
+            <Box shrink="No">
+              <IconButton size="300" onClick={requestClose} radii="300">
+                <Icon src={Icons.Cross} size="400" />
+              </IconButton>
+            </Box>
+          </Header>
+          <Box grow="Yes">
+            {threadsState.status === AsyncStatus.Success && hasEvents ? (
+              <ThreadsTimeline timelines={linkedTimelines} requestClose={requestClose} />
+            ) : (
+              <Scroll size="300" hideTrack visibility="Hover">
+                <Box className={css.ThreadsMenuContent} direction="Column" gap="100">
+                  {(threadsState.status === AsyncStatus.Loading ||
+                    threadsState.status === AsyncStatus.Idle) && <ThreadsLoading />}
+                  {threadsState.status === AsyncStatus.Success && !hasEvents && <NoThreads />}
+                  {threadsState.status === AsyncStatus.Error && (
+                    <ThreadsError error={threadsState.error} />
+                  )}
+                </Box>
+              </Scroll>
+            )}
+          </Box>
+        </Box>
+      </Menu>
+    );
+  }
+);

src/app/features/room/threads-menu/ThreadsTimeline.tsx

@@ -0,0 +1,488 @@
+/* eslint-disable react/destructuring-assignment */
+import React, { MouseEventHandler, useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { Direction, EventTimeline, MatrixEvent, Room } from 'matrix-js-sdk';
+import { Avatar, Box, Chip, config, Icon, Icons, Scroll, Text } from 'folds';
+import { Opts as LinkifyOpts } from 'linkifyjs';
+import { HTMLReactParserOptions } from 'html-react-parser';
+import { useVirtualizer } from '@tanstack/react-virtual';
+import { SequenceCard } from '../../../components/sequence-card';
+import { useMediaAuthentication } from '../../../hooks/useMediaAuthentication';
+import {
+  AvatarBase,
+  ImageContent,
+  MessageNotDecryptedContent,
+  MessageUnsupportedContent,
+  ModernLayout,
+  MSticker,
+  RedactedContent,
+  Reply,
+  Time,
+  Username,
+  UsernameBold,
+} from '../../../components/message';
+import { UserAvatar } from '../../../components/user-avatar';
+import { getMxIdLocalPart, mxcUrlToHttp } from '../../../utils/matrix';
+import { useMatrixClient } from '../../../hooks/useMatrixClient';
+import {
+  getEditedEvent,
+  getEventThreadDetail,
+  getMemberAvatarMxc,
+  getMemberDisplayName,
+} from '../../../utils/room';
+import { GetContentCallback, MessageEvent } from '../../../../types/matrix/room';
+import { useMentionClickHandler } from '../../../hooks/useMentionClickHandler';
+import { useSpoilerClickHandler } from '../../../hooks/useSpoilerClickHandler';
+import {
+  factoryRenderLinkifyWithMention,
+  getReactCustomHtmlParser,
+  LINKIFY_OPTS,
+  makeMentionCustomProps,
+  renderMatrixMention,
+} from '../../../plugins/react-custom-html-parser';
+import { RenderMatrixEvent, useMatrixEventRenderer } from '../../../hooks/useMatrixEventRenderer';
+import { RenderMessageContent } from '../../../components/RenderMessageContent';
+import { useSetting } from '../../../state/hooks/settings';
+import { settingsAtom } from '../../../state/settings';
+import * as customHtmlCss from '../../../styles/CustomHtml.css';
+import { EncryptedContent } from '../message';
+import { Image } from '../../../components/media';
+import { ImageViewer } from '../../../components/image-viewer';
+import { useRoomNavigate } from '../../../hooks/useRoomNavigate';
+import { usePowerLevelsContext } from '../../../hooks/usePowerLevels';
+import { usePowerLevelTags } from '../../../hooks/usePowerLevelTags';
+import { useTheme } from '../../../hooks/useTheme';
+import { PowerIcon } from '../../../components/power';
+import colorMXID from '../../../../util/colorMXID';
+import { useIsDirectRoom, useRoom } from '../../../hooks/useRoom';
+import { useRoomCreators } from '../../../hooks/useRoomCreators';
+import {
+  GetMemberPowerTag,
+  getPowerTagIconSrc,
+  useAccessiblePowerTagColors,
+  useGetMemberPowerTag,
+} from '../../../hooks/useMemberPowerTag';
+import { useRoomCreatorsTag } from '../../../hooks/useRoomCreatorsTag';
+import { ThreadSelector, ThreadSelectorContainer } from '../message/thread-selector';
+import {
+  getTimelineAndBaseIndex,
+  getTimelineEvent,
+  getTimelineRelativeIndex,
+  getTimelinesEventsCount,
+} from '../utils';
+import { ThreadsLoading } from './ThreadsLoading';
+import { VirtualTile } from '../../../components/virtualizer';
+import { useAlive } from '../../../hooks/useAlive';
+import * as css from './ThreadsMenu.css';
+
+type ThreadMessageProps = {
+  room: Room;
+  event: MatrixEvent;
+  renderContent: RenderMatrixEvent<[string, MatrixEvent, string, GetContentCallback]>;
+  onOpen: (roomId: string, eventId: string) => void;
+  getMemberPowerTag: GetMemberPowerTag;
+  accessibleTagColors: Map<string, string>;
+  legacyUsernameColor: boolean;
+  hour24Clock: boolean;
+  dateFormatString: string;
+};
+function ThreadMessage({
+  room,
+  event,
+  renderContent,
+  onOpen,
+  getMemberPowerTag,
+  accessibleTagColors,
+  legacyUsernameColor,
+  hour24Clock,
+  dateFormatString,
+}: ThreadMessageProps) {
+  const useAuthentication = useMediaAuthentication();
+  const mx = useMatrixClient();
+
+  const handleOpenClick: MouseEventHandler = (evt) => {
+    evt.stopPropagation();
+    const evtId = evt.currentTarget.getAttribute('data-event-id');
+    if (!evtId) return;
+    onOpen(room.roomId, evtId);
+  };
+
+  const renderOptions = () => (
+    <Box shrink="No" gap="200" alignItems="Center">
+      <Chip
+        data-event-id={event.getId()}
+        onClick={handleOpenClick}
+        variant="Secondary"
+        radii="Pill"
+      >
+        <Text size="T200">Open</Text>
+      </Chip>
+    </Box>
+  );
+
+  const sender = event.getSender()!;
+  const displayName = getMemberDisplayName(room, sender) ?? getMxIdLocalPart(sender) ?? sender;
+  const senderAvatarMxc = getMemberAvatarMxc(room, sender);
+  const getContent = (() => event.getContent()) as GetContentCallback;
+
+  const memberPowerTag = getMemberPowerTag(sender);
+  const tagColor = memberPowerTag?.color
+    ? accessibleTagColors?.get(memberPowerTag.color)
+    : undefined;
+  const tagIconSrc = memberPowerTag?.icon
+    ? getPowerTagIconSrc(mx, useAuthentication, memberPowerTag.icon)
+    : undefined;
+
+  const usernameColor = legacyUsernameColor ? colorMXID(sender) : tagColor;
+
+  const mEventId = event.getId();
+
+  if (!mEventId) return null;
+
+  return (
+    <ModernLayout
+      before={
+        <AvatarBase>
+          <Avatar size="300">
+            <UserAvatar
+              userId={sender}
+              src={
+                senderAvatarMxc
+                  ? mxcUrlToHttp(mx, senderAvatarMxc, useAuthentication, 48, 48, 'crop') ??
+                    undefined
+                  : undefined
+              }
+              alt={displayName}
+              renderFallback={() => <Icon size="200" src={Icons.User} filled />}
+            />
+          </Avatar>
+        </AvatarBase>
+      }
+    >
+      <Box gap="300" justifyContent="SpaceBetween" alignItems="Center" grow="Yes">
+        <Box gap="200" alignItems="Baseline">
+          <Box alignItems="Center" gap="200">
+            <Username style={{ color: usernameColor }}>
+              <Text as="span" truncate>
+                <UsernameBold>{displayName}</UsernameBold>
+              </Text>
+            </Username>
+            {tagIconSrc && <PowerIcon size="100" iconSrc={tagIconSrc} />}
+          </Box>
+          <Time ts={event.getTs()} hour24Clock={hour24Clock} dateFormatString={dateFormatString} />
+        </Box>
+        {renderOptions()}
+      </Box>
+      {event.replyEventId && (
+        <Reply
+          room={room}
+          replyEventId={event.replyEventId}
+          threadRootId={event.threadRootId}
+          onClick={handleOpenClick}
+          getMemberPowerTag={getMemberPowerTag}
+          accessibleTagColors={accessibleTagColors}
+          legacyUsernameColor={legacyUsernameColor}
+        />
+      )}
+      {renderContent(event.getType(), false, mEventId, event, displayName, getContent)}
+    </ModernLayout>
+  );
+}
+
+type ThreadsTimelineProps = {
+  timelines: EventTimeline[];
+  requestClose: () => void;
+};
+export function ThreadsTimeline({ timelines, requestClose }: ThreadsTimelineProps) {
+  const mx = useMatrixClient();
+  const { navigateRoom } = useRoomNavigate();
+  const alive = useAlive();
+  const scrollRef = useRef<HTMLDivElement>(null);
+
+  const room = useRoom();
+  const powerLevels = usePowerLevelsContext();
+  const creators = useRoomCreators(room);
+
+  const creatorsTag = useRoomCreatorsTag();
+  const powerLevelTags = usePowerLevelTags(room, powerLevels);
+  const getMemberPowerTag = useGetMemberPowerTag(room, creators, powerLevels);
+
+  const theme = useTheme();
+  const accessibleTagColors = useAccessiblePowerTagColors(theme.kind, creatorsTag, powerLevelTags);
+
+  const useAuthentication = useMediaAuthentication();
+  const [mediaAutoLoad] = useSetting(settingsAtom, 'mediaAutoLoad');
+  const [urlPreview] = useSetting(settingsAtom, 'urlPreview');
+
+  const direct = useIsDirectRoom();
+  const [legacyUsernameColor] = useSetting(settingsAtom, 'legacyUsernameColor');
+
+  const [hour24Clock] = useSetting(settingsAtom, 'hour24Clock');
+  const [dateFormatString] = useSetting(settingsAtom, 'dateFormatString');
+
+  const mentionClickHandler = useMentionClickHandler(room.roomId);
+  const spoilerClickHandler = useSpoilerClickHandler();
+
+  const linkifyOpts = useMemo<LinkifyOpts>(
+    () => ({
+      ...LINKIFY_OPTS,
+      render: factoryRenderLinkifyWithMention((href) =>
+        renderMatrixMention(mx, room.roomId, href, makeMentionCustomProps(mentionClickHandler))
+      ),
+    }),
+    [mx, room, mentionClickHandler]
+  );
+  const htmlReactParserOptions = useMemo<HTMLReactParserOptions>(
+    () =>
+      getReactCustomHtmlParser(mx, room.roomId, {
+        linkifyOpts,
+        useAuthentication,
+        handleSpoilerClick: spoilerClickHandler,
+        handleMentionClick: mentionClickHandler,
+      }),
+    [mx, room, linkifyOpts, mentionClickHandler, spoilerClickHandler, useAuthentication]
+  );
+
+  const renderMatrixEvent = useMatrixEventRenderer<
+    [string, MatrixEvent, string, GetContentCallback]
+  >(
+    {
+      [MessageEvent.RoomMessage]: (eventId, event, displayName, getContent) => {
+        if (event.isRedacted()) {
+          return <RedactedContent reason={event.getUnsigned().redacted_because?.content.reason} />;
+        }
+
+        const threadDetail = getEventThreadDetail(event);
+
+        return (
+          <>
+            <RenderMessageContent
+              displayName={displayName}
+              msgType={event.getContent().msgtype ?? ''}
+              ts={event.getTs()}
+              getContent={getContent}
+              edited={!!event.replacingEvent()}
+              mediaAutoLoad={mediaAutoLoad}
+              urlPreview={urlPreview}
+              htmlReactParserOptions={htmlReactParserOptions}
+              linkifyOpts={linkifyOpts}
+              outlineAttachment
+            />
+            {threadDetail && (
+              <ThreadSelectorContainer>
+                <ThreadSelector
+                  room={room}
+                  threadId={eventId}
+                  threadDetail={threadDetail}
+                  outlined
+                  hour24Clock={hour24Clock}
+                  dateFormatString={dateFormatString}
+                />
+              </ThreadSelectorContainer>
+            )}
+          </>
+        );
+      },
+      [MessageEvent.RoomMessageEncrypted]: (eventId, mEvent, displayName) => {
+        const evtTimeline = room.getTimelineForEvent(eventId);
+
+        return (
+          <EncryptedContent mEvent={mEvent}>
+            {() => {
+              if (mEvent.isRedacted()) return <RedactedContent />;
+              if (mEvent.getType() === MessageEvent.Sticker)
+                return (
+                  <MSticker
+                    content={mEvent.getContent()}
+                    renderImageContent={(props) => (
+                      <ImageContent
+                        {...props}
+                        autoPlay={mediaAutoLoad}
+                        renderImage={(p) => <Image {...p} loading="lazy" />}
+                        renderViewer={(p) => <ImageViewer {...p} />}
+                      />
+                    )}
+                  />
+                );
+              if (mEvent.getType() === MessageEvent.RoomMessage) {
+                const editedEvent =
+                  evtTimeline && getEditedEvent(eventId, mEvent, evtTimeline.getTimelineSet());
+                const getContent = (() =>
+                  editedEvent?.getContent()['m.new_content'] ??
+                  mEvent.getContent()) as GetContentCallback;
+
+                return (
+                  <RenderMessageContent
+                    displayName={displayName}
+                    msgType={mEvent.getContent().msgtype ?? ''}
+                    ts={mEvent.getTs()}
+                    edited={!!editedEvent || !!mEvent.replacingEvent()}
+                    getContent={getContent}
+                    mediaAutoLoad={mediaAutoLoad}
+                    urlPreview={urlPreview}
+                    htmlReactParserOptions={htmlReactParserOptions}
+                    linkifyOpts={linkifyOpts}
+                  />
+                );
+              }
+              if (mEvent.getType() === MessageEvent.RoomMessageEncrypted)
+                return (
+                  <Text>
+                    <MessageNotDecryptedContent />
+                  </Text>
+                );
+              return (
+                <Text>
+                  <MessageUnsupportedContent />
+                </Text>
+              );
+            }}
+          </EncryptedContent>
+        );
+      },
+      [MessageEvent.Sticker]: (eventId, event, displayName, getContent) => {
+        if (event.isRedacted()) {
+          return <RedactedContent reason={event.getUnsigned().redacted_because?.content.reason} />;
+        }
+
+        const threadDetail = getEventThreadDetail(event);
+
+        return (
+          <>
+            <MSticker
+              content={getContent()}
+              renderImageContent={(props) => (
+                <ImageContent
+                  {...props}
+                  autoPlay={mediaAutoLoad}
+                  renderImage={(p) => <Image {...p} loading="lazy" />}
+                  renderViewer={(p) => <ImageViewer {...p} />}
+                />
+              )}
+            />
+            {threadDetail && (
+              <ThreadSelectorContainer>
+                <ThreadSelector
+                  room={room}
+                  threadId={eventId}
+                  threadDetail={threadDetail}
+                  outlined
+                  hour24Clock={hour24Clock}
+                  dateFormatString={dateFormatString}
+                />
+              </ThreadSelectorContainer>
+            )}
+          </>
+        );
+      },
+    },
+    undefined,
+    (eventId, event) => {
+      if (event.isRedacted()) {
+        return <RedactedContent reason={event.getUnsigned().redacted_because?.content.reason} />;
+      }
+      return (
+        <Box grow="Yes" direction="Column">
+          <Text size="T400" priority="300">
+            <code className={customHtmlCss.Code}>{event.getType()}</code>
+            {' event'}
+          </Text>
+        </Box>
+      );
+    }
+  );
+
+  const handleOpen = (roomId: string, eventId: string) => {
+    navigateRoom(roomId, eventId);
+    requestClose();
+  };
+
+  const eventsLength = getTimelinesEventsCount(timelines);
+  const timelineToPaginate = timelines[timelines.length - 1];
+  const [paginationToken, setPaginationToken] = useState(
+    timelineToPaginate.getPaginationToken(Direction.Backward)
+  );
+
+  const virtualizer = useVirtualizer({
+    count: eventsLength,
+    getScrollElement: () => scrollRef.current,
+    estimateSize: () => 122,
+    overscan: 10,
+  });
+  const vItems = virtualizer.getVirtualItems();
+
+  const paginate = useCallback(async () => {
+    const moreToLoad = await mx.paginateEventTimeline(timelineToPaginate, {
+      backwards: true,
+      limit: 30,
+    });
+
+    if (alive()) {
+      setPaginationToken(
+        moreToLoad ? timelineToPaginate.getPaginationToken(Direction.Backward) : null
+      );
+    }
+  }, [mx, alive, timelineToPaginate]);
+
+  // auto paginate when scroll reach bottom
+  useEffect(() => {
+    const lastVItem = vItems.length > 0 ? vItems[vItems.length - 1] : undefined;
+    if (paginationToken && lastVItem && lastVItem.index === eventsLength - 1) {
+      paginate();
+    }
+  }, [vItems, paginationToken, eventsLength, paginate]);
+
+  return (
+    <Scroll ref={scrollRef} size="300" hideTrack visibility="Hover">
+      <Box className={css.ThreadsMenuContent} direction="Column" gap="100">
+        <div
+          style={{
+            position: 'relative',
+            height: virtualizer.getTotalSize(),
+          }}
+        >
+          {vItems.map((vItem) => {
+            const reverseTimelineIndex = eventsLength - vItem.index - 1;
+
+            const [timeline, baseIndex] = getTimelineAndBaseIndex(timelines, reverseTimelineIndex);
+            if (!timeline) return null;
+            const event = getTimelineEvent(
+              timeline,
+              getTimelineRelativeIndex(reverseTimelineIndex, baseIndex)
+            );
+
+            if (!event?.getId()) return null;
+
+            return (
+              <VirtualTile
+                virtualItem={vItem}
+                style={{ paddingBottom: config.space.S200 }}
+                ref={virtualizer.measureElement}
+                key={vItem.index}
+              >
+                <SequenceCard
+                  key={event.getId()}
+                  style={{ padding: config.space.S400, borderRadius: config.radii.R300 }}
+                  variant="SurfaceVariant"
+                  direction="Column"
+                >
+                  <ThreadMessage
+                    room={room}
+                    event={event}
+                    renderContent={renderMatrixEvent}
+                    onOpen={handleOpen}
+                    getMemberPowerTag={getMemberPowerTag}
+                    accessibleTagColors={accessibleTagColors}
+                    legacyUsernameColor={legacyUsernameColor || direct}
+                    hour24Clock={hour24Clock}
+                    dateFormatString={dateFormatString}
+                  />
+                </SequenceCard>
+              </VirtualTile>
+            );
+          })}
+        </div>
+        {paginationToken && <ThreadsLoading />}
+      </Box>
+    </Scroll>
+  );
+}

src/app/features/room/threads-menu/index.ts

@@ -0,0 +1 @@
+export * from './ThreadsMenu';

src/app/features/room/utils/index.ts

@@ -0,0 +1 @@
+export * from './timeline';

src/app/features/room/utils/timeline.ts

@@ -0,0 +1,66 @@
+import { Room, EventTimeline, Direction, MatrixEvent } from 'matrix-js-sdk';
+
+export const getFirstLinkedTimeline = (
+  timeline: EventTimeline,
+  direction: Direction
+): EventTimeline => {
+  const linkedTm = timeline.getNeighbouringTimeline(direction);
+  if (!linkedTm) return timeline;
+  return getFirstLinkedTimeline(linkedTm, direction);
+};
+
+export const getLinkedTimelines = (timeline: EventTimeline): EventTimeline[] => {
+  const firstTimeline = getFirstLinkedTimeline(timeline, Direction.Backward);
+  const timelines: EventTimeline[] = [];
+
+  for (
+    let nextTimeline: EventTimeline | null = firstTimeline;
+    nextTimeline;
+    nextTimeline = nextTimeline.getNeighbouringTimeline(Direction.Forward)
+  ) {
+    timelines.push(nextTimeline);
+  }
+  return timelines;
+};
+
+export const timelineToEventsCount = (t: EventTimeline) => t.getEvents().length;
+export const getTimelinesEventsCount = (timelines: EventTimeline[]): number => {
+  const timelineEventCountReducer = (count: number, tm: EventTimeline) =>
+    count + timelineToEventsCount(tm);
+  return timelines.reduce(timelineEventCountReducer, 0);
+};
+
+export const getTimelineAndBaseIndex = (
+  timelines: EventTimeline[],
+  index: number
+): [EventTimeline | undefined, number] => {
+  let uptoTimelineLen = 0;
+  const timeline = timelines.find((t) => {
+    uptoTimelineLen += t.getEvents().length;
+    if (index < uptoTimelineLen) return true;
+    return false;
+  });
+  if (!timeline) return [undefined, 0];
+  return [timeline, uptoTimelineLen - timeline.getEvents().length];
+};
+
+export const getTimelineRelativeIndex = (absoluteIndex: number, timelineBaseIndex: number) =>
+  absoluteIndex - timelineBaseIndex;
+
+export const getTimelineEvent = (timeline: EventTimeline, index: number): MatrixEvent | undefined =>
+  timeline.getEvents()[index];
+
+export const getEventIdAbsoluteIndex = (
+  timelines: EventTimeline[],
+  eventTimeline: EventTimeline,
+  eventId: string
+): number | undefined => {
+  const timelineIndex = timelines.findIndex((t) => t === eventTimeline);
+  if (timelineIndex === -1) return undefined;
+  const eventIndex = eventTimeline.getEvents().findIndex((evt) => evt.getId() === eventId);
+  if (eventIndex === -1) return undefined;
+  const baseIndex = timelines
+    .slice(0, timelineIndex)
+    .reduce((accValue, timeline) => timeline.getEvents().length + accValue, 0);
+  return baseIndex + eventIndex;
+};

src/app/hooks/useRoomThreads.ts

@@ -0,0 +1,20 @@
+import { useCallback } from 'react';
+import { EventTimelineSet, Room } from 'matrix-js-sdk';
+import { AsyncState, useAsyncCallbackValue } from './useAsyncCallback';
+
+export const useRoomMyThreads = (room: Room): AsyncState<EventTimelineSet, Error> => {
+  const [threadsState] = useAsyncCallbackValue<EventTimelineSet, Error>(
+    useCallback(async () => {
+      await room.createThreadsTimelineSets();
+      await room.fetchRoomThreads();
+
+      const timelineSet = room.threadsTimelineSets[0];
+      if (timelineSet === undefined) {
+        throw new Error('Failed to fetch My Threads!');
+      }
+      return timelineSet;
+    }, [room])
+  );
+
+  return threadsState;
+};

src/app/pages/client/ClientInitStorageAtom.tsx

@@ -8,6 +8,8 @@ import { makeNavToActivePathAtom } from '../../state/navToActivePath';
 import { NavToActivePathProvider } from '../../state/hooks/navToActivePath';
 import { makeOpenedSidebarFolderAtom } from '../../state/openedSidebarFolder';
 import { OpenedSidebarFolderProvider } from '../../state/hooks/openedSidebarFolder';
+import { makeRoomToActiveThreadAtom } from '../../state/roomToActiveThread';
+import { RoomToActiveThreadProvider } from '../../state/hooks/roomToActiveThread';
 
 type ClientInitStorageAtomProps = {
   children: ReactNode;
@@ -22,15 +24,19 @@ export function ClientInitStorageAtom({ children }: ClientInitStorageAtomProps)
 
   const navToActivePathAtom = useMemo(() => makeNavToActivePathAtom(userId), [userId]);
 
+  const roomToActiveThreadAtom = useMemo(() => makeRoomToActiveThreadAtom(userId), [userId]);
+
   const openedSidebarFolderAtom = useMemo(() => makeOpenedSidebarFolderAtom(userId), [userId]);
 
   return (
     <ClosedNavCategoriesProvider value={closedNavCategoriesAtom}>
       <ClosedLobbyCategoriesProvider value={closedLobbyCategoriesAtom}>
         <NavToActivePathProvider value={navToActivePathAtom}>
+          <RoomToActiveThreadProvider value={roomToActiveThreadAtom}>
             <OpenedSidebarFolderProvider value={openedSidebarFolderAtom}>
               {children}
             </OpenedSidebarFolderProvider>
+          </RoomToActiveThreadProvider>
         </NavToActivePathProvider>
       </ClosedLobbyCategoriesProvider>
     </ClosedNavCategoriesProvider>

src/app/state/hooks/roomToActiveThread.ts

@@ -0,0 +1,55 @@
+import { createContext, useCallback, useContext } from 'react';
+import { useAtomValue, useSetAtom } from 'jotai';
+import { RoomToActiveThreadAtom } from '../roomToActiveThread';
+
+const RoomToActiveThreadAtomContext = createContext<RoomToActiveThreadAtom | null>(null);
+export const RoomToActiveThreadProvider = RoomToActiveThreadAtomContext.Provider;
+
+export const useRoomToActiveThreadAtom = (): RoomToActiveThreadAtom => {
+  const anAtom = useContext(RoomToActiveThreadAtomContext);
+
+  if (!anAtom) {
+    throw new Error('RoomToActiveThreadAtom is not provided!');
+  }
+
+  return anAtom;
+};
+
+export const useThreadSelector = (roomId: string): ((threadId: string) => void) => {
+  const roomToActiveThreadAtom = useRoomToActiveThreadAtom();
+  const setRoomToActiveThread = useSetAtom(roomToActiveThreadAtom);
+
+  const onThreadSelect = useCallback(
+    (threadId: string) => {
+      setRoomToActiveThread({
+        type: 'PUT',
+        roomId,
+        threadId,
+      });
+    },
+    [roomId, setRoomToActiveThread]
+  );
+
+  return onThreadSelect;
+};
+
+export const useActiveThread = (roomId: string): string | undefined => {
+  const roomToActiveThreadAtom = useRoomToActiveThreadAtom();
+  const roomToActiveThread = useAtomValue(roomToActiveThreadAtom);
+
+  return roomToActiveThread.get(roomId);
+};
+
+export const useThreadClose = (roomId: string): (() => void) => {
+  const roomToActiveThreadAtom = useRoomToActiveThreadAtom();
+  const setRoomToActiveThread = useSetAtom(roomToActiveThreadAtom);
+
+  const closeThread = useCallback(() => {
+    setRoomToActiveThread({
+      type: 'DELETE',
+      roomId,
+    });
+  }, [roomId, setRoomToActiveThread]);
+
+  return closeThread;
+};

src/app/state/roomToActiveThread.ts

@@ -0,0 +1,75 @@
+import { atom, WritableAtom } from 'jotai';
+import produce from 'immer';
+import {
+  atomWithLocalStorage,
+  getLocalStorageItem,
+  setLocalStorageItem,
+} from './utils/atomWithLocalStorage';
+
+const ROOM_TO_ACTIVE_THREAD = 'roomToActiveThread';
+
+const getStoreKey = (userId: string): string => `${ROOM_TO_ACTIVE_THREAD}${userId}`;
+
+type RoomToActiveThread = Map<string, string>;
+
+type RoomToActiveThreadAction =
+  | {
+      type: 'PUT';
+      roomId: string;
+      threadId: string;
+    }
+  | {
+      type: 'DELETE';
+      roomId: string;
+    };
+
+export type RoomToActiveThreadAtom = WritableAtom<
+  RoomToActiveThread,
+  [RoomToActiveThreadAction],
+  undefined
+>;
+
+export const makeRoomToActiveThreadAtom = (userId: string): RoomToActiveThreadAtom => {
+  const storeKey = getStoreKey(userId);
+
+  const baseRoomToActiveThread = atomWithLocalStorage<RoomToActiveThread>(
+    storeKey,
+    (key) => {
+      const obj: Record<string, string> = getLocalStorageItem(key, {});
+      return new Map(Object.entries(obj));
+    },
+    (key, value) => {
+      const obj: Record<string, string> = Object.fromEntries(value);
+      setLocalStorageItem(key, obj);
+    }
+  );
+
+  const navToActivePathAtom = atom<RoomToActiveThread, [RoomToActiveThreadAction], undefined>(
+    (get) => get(baseRoomToActiveThread),
+    (get, set, action) => {
+      if (action.type === 'DELETE') {
+        set(
+          baseRoomToActiveThread,
+          produce(get(baseRoomToActiveThread), (draft) => {
+            draft.delete(action.roomId);
+          })
+        );
+        return;
+      }
+      if (action.type === 'PUT') {
+        set(
+          baseRoomToActiveThread,
+          produce(get(baseRoomToActiveThread), (draft) => {
+            draft.set(action.roomId, action.threadId);
+          })
+        );
+      }
+    }
+  );
+
+  return navToActivePathAtom;
+};
+
+export const clearRoomToActiveThreadStore = (userId: string) => {
+  localStorage.removeItem(getStoreKey(userId));
+};

src/app/utils/room.ts

@@ -8,6 +8,7 @@ import {
   IPowerLevelsContent,
   IPushRule,
   IPushRules,
+  IThreadBundledRelationship,
   JoinRule,
   MatrixClient,
   MatrixEvent,
@@ -16,6 +17,7 @@ import {
   RelationType,
   Room,
   RoomMember,
+  THREAD_RELATION_TYPE,
 } from 'matrix-js-sdk';
 import { CryptoBackend } from 'matrix-js-sdk/lib/common-crypto/CryptoBackend';
 import { AccountDataEvent } from '../../types/matrix/accountData';
@@ -201,6 +203,7 @@ export const isNotificationEvent = (mEvent: MatrixEvent) => {
 
   if (mEvent.isRedacted()) return false;
   if (mEvent.getRelation()?.rel_type === 'm.replace') return false;
+  if (mEvent.getRelation()?.rel_type === 'm.thread') return false;
 
   return true;
 };
@@ -551,3 +554,13 @@ export const guessPerfectParent = (
 
   return perfectParent;
 };
+
+export const getEventThreadDetail = (
+  mEvent: MatrixEvent
+): IThreadBundledRelationship | undefined => {
+  const details = mEvent.getServerAggregatedRelation<IThreadBundledRelationship>(
+    THREAD_RELATION_TYPE.name
+  );
+
+  return details;
+};

src/client/initMatrix.ts

@@ -2,6 +2,7 @@ import { createClient, MatrixClient, IndexedDBStore, IndexedDBCryptoStore } from
 
 import { cryptoCallbacks } from './secretStorageKeys';
 import { clearNavToActivePathStore } from '../app/state/navToActivePath';
+import { clearRoomToActiveThreadStore } from '../app/state/roomToActiveThread';
 
 type Session = {
   baseUrl: string;
@@ -42,12 +43,14 @@ export const initClient = async (session: Session): Promise<MatrixClient> => {
 export const startClient = async (mx: MatrixClient) => {
   await mx.startClient({
     lazyLoadMembers: true,
+    threadSupport: true,
   });
 };
 
 export const clearCacheAndReload = async (mx: MatrixClient) => {
   mx.stopClient();
   clearNavToActivePathStore(mx.getSafeUserId());
+  clearRoomToActiveThreadStore(mx.getSafeUserId());
   await mx.store.deleteAllData();
   window.location.reload();
 };