Restore scroll position when returning to the timeline

.changeset/cool-clouds-flash.md

@@ -0,0 +1,5 @@
+---
+"nostrudel": minor
+---
+
+Restore scroll position when returning to the timeline

src/components/timeline-page/generic-note-timeline/index.tsx

@@ -1,7 +1,8 @@
-import { ReactNode, memo, useEffect, useState } from "react";
+import { ReactNode, memo, useCallback, useEffect, useRef, useState } from "react";
 import { Box, Button, Text } from "@chakra-ui/react";
 import { Kind } from "nostr-tools";
 import dayjs from "dayjs";
+import { useLocation } from "react-router-dom";
 
 import useSubject from "../../../hooks/use-subject";
 import TimelineLoader from "../../../classes/timeline-loader";
@@ -14,11 +15,18 @@ import { ErrorBoundary } from "../../error-boundary";
 import { getEventUID, isReply } from "../../../helpers/nostr/events";
 import ReplyNote from "./reply-note";
 import RelayRecommendation from "./relay-recommendation";
-import { ExtendedIntersectionObserverEntry, useIntersectionObserver } from "../../../providers/intersection-observer";
+import {
+  ExtendedIntersectionObserverEntry,
+  useIntersectionObserver,
+  useRegisterIntersectionEntity,
+} from "../../../providers/intersection-observer";
 import BadgeAwardCard from "../../../views/badges/components/badge-award-card";
 import ArticleNote from "./article-note";
 
-function RenderEvent({ event }: { event: NostrEvent }) {
+function RenderEvent({ event, visible, minHeight }: { event: NostrEvent; visible: boolean; minHeight?: number }) {
+  const ref = useRef<HTMLDivElement | null>(null);
+  useRegisterIntersectionEntity(ref, getEventUID(event));
+
   let content: ReactNode | null = null;
   switch (event.kind) {
     case Kind.Text:
@@ -44,23 +52,56 @@ function RenderEvent({ event }: { event: NostrEvent }) {
       break;
   }
 
-  return content && <ErrorBoundary>{content}</ErrorBoundary>;
+  return (
+    <ErrorBoundary>
+      <Box minHeight={minHeight} ref={ref}>
+        {visible && content}
+      </Box>
+    </ErrorBoundary>
+  );
 }
 const RenderEventMemo = memo(RenderEvent);
 
-const PRELOAD_NOTES = 5;
+const NOTE_BUFFER = 5;
+const timelineNoteMinHeightCache = new WeakMap<TimelineLoader, Record<string, Record<string, number>>>();
+
 function GenericNoteTimeline({ timeline }: { timeline: TimelineLoader }) {
   const notesArray = useSubject(timeline.timeline);
   const [latest, setLatest] = useState(() => dayjs().unix());
   const { subject } = useIntersectionObserver();
 
-  const [minDate, setMinDate] = useState(timeline.timeline.value[PRELOAD_NOTES]?.created_at ?? 0);
+  const location = useLocation();
+  const setCachedNumber = useCallback(
+    (id: string, value: number) => {
+      let timelineData = timelineNoteMinHeightCache.get(timeline);
+      if (!timelineData) {
+        timelineData = {};
+        timelineNoteMinHeightCache.set(timeline, timelineData);
+      }
+      if (!timelineData[location.key]) timelineData[location.key] = {};
+      timelineData[location.key][id] = value;
+    },
+    [location.key, timeline],
+  );
+  const getCachedNumber = useCallback(
+    (id: string) => {
+      const timelineData = timelineNoteMinHeightCache.get(timeline);
+      if (!timelineData) return undefined;
+      return timelineData[location.key]?.[id] ?? undefined;
+    },
+    [location.key, timeline],
+  );
+  const [maxDate, setMaxDate] = useState(getCachedNumber("max") ?? -Infinity);
+  const [minDate, setMinDate] = useState(
+    getCachedNumber("min") ?? timeline.timeline.value[NOTE_BUFFER]?.created_at ?? 0,
+  );
 
   // reset the latest and minDate when timeline changes
   useEffect(() => {
     setLatest(dayjs().unix());
-    setMinDate(timeline.timeline.value[PRELOAD_NOTES]?.created_at ?? 0);
+    setMaxDate(getCachedNumber("max") ?? -Infinity);
-  }, [timeline, setMinDate, setLatest]);
+    setMinDate(getCachedNumber("min") ?? timeline.timeline.value[NOTE_BUFFER]?.created_at ?? 0);
+  }, [timeline, setMinDate, setLatest, getCachedNumber]);
 
   const newNotes: NostrEvent[] = [];
   const notes: NostrEvent[] = [];
@@ -69,13 +110,29 @@ function GenericNoteTimeline({ timeline }: { timeline: TimelineLoader }) {
     else if (note.created_at > minDate) notes.push(note);
   }
 
+  const updateNoteMinHeight = useCallback(
+    (id: string, element: Element) => {
+      const rect = element.getBoundingClientRect();
+      const current = getCachedNumber(id);
+      setCachedNumber(id, Math.max(current ?? 0, rect.height));
+    },
+    [setCachedNumber, getCachedNumber],
+  );
+
+  // TODO: break this out into its own component or hook, this is pretty ugly
   const [intersectionEntryCache] = useState(() => new Map<string, IntersectionObserverEntry>());
   useEffect(() => {
     const listener = (entities: ExtendedIntersectionObserverEntry[]) => {
-      for (const entity of entities) entity.id && intersectionEntryCache.set(entity.id, entity.entry);
+      for (const entity of entities) {
+        if (entity.id) {
+          intersectionEntryCache.set(entity.id, entity.entry);
+          updateNoteMinHeight(entity.id, entity.entry.target);
+        }
+      }
 
       let min: number = Infinity;
-      let preload = PRELOAD_NOTES;
+      let max: number = -Infinity;
+      let preload = NOTE_BUFFER;
       let foundVisible = false;
       for (const event of timeline.timeline.value) {
         if (event.created_at > latest) continue;
@@ -92,17 +149,25 @@ function GenericNoteTimeline({ timeline }: { timeline: TimelineLoader }) {
         } else {
           // found visible event
           foundVisible = true;
+
+          const bufferEvent =
+            timeline.timeline.value[Math.max(timeline.timeline.value.indexOf(event) - NOTE_BUFFER)] || event;
+          if (bufferEvent.created_at > max) max = bufferEvent.created_at;
         }
       }
 
       setMinDate((v) => Math.min(v, min));
+      setMaxDate(max);
+
+      setCachedNumber("max", max);
+      setCachedNumber("min", Math.min(getCachedNumber("min") ?? Infinity, min));
     };
 
     subject.subscribe(listener);
     return () => {
       subject.unsubscribe(listener);
     };
-  }, [setMinDate, intersectionEntryCache, latest, timeline]);
+  }, [setMinDate, intersectionEntryCache, updateNoteMinHeight, setCachedNumber, getCachedNumber, latest, timeline]);
 
   return (
     <>
@@ -120,7 +185,12 @@ function GenericNoteTimeline({ timeline }: { timeline: TimelineLoader }) {
         </Box>
       )}
       {notes.map((note) => (
-        <RenderEventMemo key={note.id} event={note} />
+        <RenderEventMemo
+          key={note.id}
+          event={note}
+          visible={note.created_at <= maxDate}
+          minHeight={getCachedNumber(getEventUID(note))}
+        />
       ))}
     </>
   );

src/helpers/regexp.ts

@@ -1,7 +1,8 @@
 export const getMatchNostrLink = () =>
   /(nostr:|@)?((npub|note|nprofile|nevent|nrelay|naddr)1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{58,})/gi;
 export const getMatchHashtag = () => /(^|[^\p{L}])#([\p{L}\p{N}\p{M}]+)/gu;
-export const getMatchLink = () => /https?:\/\/([a-zA-Z0-9\.\-]+\.[a-zA-Z]+)([\p{L}\p{N}\p{M}&\.-\/\?=#\-@%\+_,:!~]*)/gu;
+export const getMatchLink = () =>
+  /https?:\/\/([a-zA-Z0-9\.\-]+\.[a-zA-Z]+)([\p{L}\p{N}\p{M}&\.-\/\?=#\-@%\+_,:!~*]*)/gu;
 export const getMatchEmoji = () => /:([a-zA-Z0-9_-]+):/gi;
 export const getMatchCashu = () => /cashuA[A-z0-9]+/g;