refactor(feed): gate feed cache to infinite scroll mode

src/stores/__tests__/use-feed-cache-store.test.ts

@@ -0,0 +1,71 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import useFeedCacheStore from '../use-feed-cache-store';
+
+describe('useFeedCacheStore', () => {
+  beforeEach(() => {
+    useFeedCacheStore.getState().clearFeeds();
+  });
+
+  afterEach(() => {
+    useFeedCacheStore.getState().clearFeeds();
+  });
+
+  it('accessFeed adds entries', () => {
+    const { accessFeed } = useFeedCacheStore.getState();
+
+    accessFeed('plebbit/board', 'board');
+    const afterFirst = useFeedCacheStore.getState().cachedFeeds;
+    expect(afterFirst.length).toBe(1);
+    expect(afterFirst[0].key).toBe('plebbit/board');
+    expect(afterFirst[0].type).toBe('board');
+
+    accessFeed('plebbit/catalog', 'catalog');
+    const afterSecond = useFeedCacheStore.getState().cachedFeeds;
+    expect(afterSecond.length).toBe(2);
+    expect(afterSecond.some((f) => f.key === 'plebbit/catalog' && f.type === 'catalog')).toBe(true);
+  });
+
+  it('evicts least recently accessed when cache exceeds maxCacheSize (2)', () => {
+    const { accessFeed, isFeedCached } = useFeedCacheStore.getState();
+    vi.useFakeTimers();
+
+    accessFeed('a', 'board');
+    vi.advanceTimersByTime(1);
+    accessFeed('b', 'board');
+    vi.advanceTimersByTime(1);
+    accessFeed('c', 'board');
+
+    expect(isFeedCached('a')).toBe(false);
+    expect(isFeedCached('b')).toBe(true);
+    expect(isFeedCached('c')).toBe(true);
+
+    vi.useRealTimers();
+  });
+
+  it('clearFeeds empties cache', () => {
+    const { accessFeed, clearFeeds } = useFeedCacheStore.getState();
+
+    accessFeed('plebbit/board', 'board');
+    accessFeed('other/board', 'catalog');
+    expect(useFeedCacheStore.getState().cachedFeeds.length).toBe(2);
+
+    clearFeeds();
+    const after = useFeedCacheStore.getState().cachedFeeds;
+    expect(after.length).toBe(0);
+    expect(after).toEqual([]);
+  });
+
+  it('clearFeeds is idempotent when already empty', () => {
+    const { clearFeeds } = useFeedCacheStore.getState();
+
+    expect(useFeedCacheStore.getState().cachedFeeds.length).toBe(0);
+
+    clearFeeds();
+    clearFeeds();
+    clearFeeds();
+
+    const after = useFeedCacheStore.getState().cachedFeeds;
+    expect(after.length).toBe(0);
+    expect(after).toEqual([]);
+  });
+});