perf(home): stop popular threads rerenders after load

src/hooks/__tests__/browser-hooks.test.tsx

@@ -82,4 +82,19 @@ describe('browser hooks', () => {
 
     expect(latestValue).toBe(1_704_067_230);
   });
+
+  it('can leave the current time frozen without scheduling updates', () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2024-01-01T00:00:00Z'));
+
+    expect(renderHookValue(() => useCurrentTime(false))).toBe(1_704_067_200);
+
+    act(() => {
+      vi.setSystemTime(new Date('2024-01-01T00:01:00Z'));
+      vi.advanceTimersByTime(60_000);
+    });
+
+    expect(latestValue).toBe(1_704_067_200);
+    expect(vi.getTimerCount()).toBe(0);
+  });
 });

src/hooks/use-current-time.ts

@@ -8,10 +8,14 @@ import { useState, useEffect } from 'react';
  * For visual updates like blinking animations, CSS handles that independently.
  * This hook is for time-based calculations that don't need millisecond precision.
  */
-export const useCurrentTime = (updateIntervalSeconds = 60) => {
+export const useCurrentTime = (updateIntervalSeconds: number | false = 60) => {
   const [currentTime, setCurrentTime] = useState(() => Date.now() / 1000);
 
   useEffect(() => {
+    if (updateIntervalSeconds === false) {
+      return;
+    }
+
     // Update periodically
     const intervalId = setInterval(() => {
       setCurrentTime(Date.now() / 1000);

src/hooks/use-popular-posts.ts

@@ -58,6 +58,10 @@ function shuffleBoardAddresses(boardAddresses: string[]): string[] {
   return shuffledBoardAddresses;
 }
 
+function getPopularPostsInputKey(communityAddresses: string[]): string {
+  return [...communityAddresses].sort().join(',');
+}
+
 function getPopularPostsCacheEntry(inputKey: string, communityAddresses: string[]): PopularPostsCacheEntry {
   const cachedEntry = popularPostsCacheByInputKey.get(inputKey);
   if (cachedEntry) {
@@ -73,6 +77,11 @@ function getPopularPostsCacheEntry(inputKey: string, communityAddresses: string[
   return cacheEntry;
 }
 
+export function getRevealedPopularPosts(communityAddresses: string[]): Comment[] | undefined {
+  const cacheEntry = popularPostsCacheByInputKey.get(getPopularPostsInputKey(communityAddresses));
+  return cacheEntry?.revealed ? cacheEntry.posts : undefined;
+}
+
 export function clearPopularPostsCacheForTest() {
   popularPostsCacheByInputKey.clear();
 }
@@ -86,10 +95,10 @@ export function clearPopularPostsCacheForTest() {
  * the board filter, so threads never disappear during background loads.
  */
 const usePopularPosts = (communities: Array<Community | undefined>, communityAddresses: string[]) => {
-  const inputKey = [...communityAddresses].sort().join(',');
+  const inputKey = getPopularPostsInputKey(communityAddresses);
   const cacheEntry = getPopularPostsCacheEntry(inputKey, communityAddresses);
 
-  const currentTime = useCurrentTime(cacheEntry.revealed ? 300 : 5);
+  const currentTime = useCurrentTime(cacheEntry.revealed ? false : 5);
   const nowSeconds = Math.floor(currentTime);
   const loadingStartTimestamps = useCommunitiesLoadingStartTimestamps(communityAddresses);