From 4cd15bb8a04bf8df3fb292796a8f32d7533cacdc Mon Sep 17 00:00:00 2001
From: Adam Mathes <adam@adammathes.com>
Date: Sun, 15 Feb 2026 15:57:54 -0800
Subject: Optimize frontend with memoized FeedItem and efficient
 IntersectionObserver

---
 frontend/src/components/FeedItems.test.tsx | 58 ++++++++++--------------------
 1 file changed, 18 insertions(+), 40 deletions(-)

(limited to 'frontend/src/components/FeedItems.test.tsx')

diff --git a/frontend/src/components/FeedItems.test.tsx b/frontend/src/components/FeedItems.test.tsx
index 25ade58..89c591c 100644
--- a/frontend/src/components/FeedItems.test.tsx
+++ b/frontend/src/components/FeedItems.test.tsx
@@ -95,19 +95,16 @@ describe('FeedItems Component', () => {
       expect(screen.getByText('Item 1')).toBeVisible();
     });
 
-    // Press 'j' to select first item (index 0 -> 1 because it starts at -1... wait logic says min(prev+1))
-    // init -1. j -> 0.
+    // Press 'j' to select first item
     fireEvent.keyDown(window, { key: 'j' });
 
     // Item 1 (index 0) should be selected.
-    // It's unread, so it should be marked read.
     await waitFor(() => {
       expect(global.fetch).toHaveBeenCalledWith(
         '/api/item/101',
         expect.objectContaining({
           method: 'PUT',
           body: JSON.stringify({ read: true, starred: false }),
-          credentials: 'include',
         })
       );
     });
@@ -115,9 +112,6 @@ describe('FeedItems Component', () => {
     // Press 'j' again -> index 1 (Item 2)
     fireEvent.keyDown(window, { key: 'j' });
 
-    // Item 2 is already read, so no markRead call expected for it (mocks clear? no).
-    // let's check selection class if possible, but testing library doesn't easily check class on div wrapper unless we query it.
-
     // Press 's' to star Item 2
     fireEvent.keyDown(window, { key: 's' });
 
@@ -127,7 +121,6 @@ describe('FeedItems Component', () => {
         expect.objectContaining({
           method: 'PUT',
           body: JSON.stringify({ read: true, starred: true }),
-          credentials: 'include', // toggled to true
         })
       );
     });
@@ -140,10 +133,7 @@ describe('FeedItems Component', () => {
       json: async () => mockItems,
     } as Response);
 
-    // Capture both callbacks
     const observerCallbacks: IntersectionObserverCallback[] = [];
-
-    // Override the mock to capture both callbacks
     class MockIntersectionObserver {
       constructor(callback: IntersectionObserverCallback) {
         observerCallbacks.push(callback);
@@ -155,7 +145,6 @@ describe('FeedItems Component', () => {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     window.IntersectionObserver = MockIntersectionObserver as any;
 
-
     render(
       <MemoryRouter>
         <FeedItems />
@@ -166,27 +155,20 @@ describe('FeedItems Component', () => {
       expect(screen.getByText('Item 1')).toBeVisible();
     });
 
-    // Wait for observers to be created
-    await waitFor(() => {
-      expect(observerCallbacks.length).toBeGreaterThan(0);
-    });
-
-    // Simulate item leaving viewport at the top
-    // Element index is 0
+    // Simulate item leaving viewport
     const entry = {
       isIntersecting: false,
       boundingClientRect: { top: -50 } as DOMRectReadOnly,
-      target: { getAttribute: () => '0' } as unknown as Element,
+      target: { getAttribute: () => '0' } as unknown as Element, // data-index="0"
       intersectionRatio: 0,
       time: 0,
       rootBounds: null,
       intersectionRect: {} as DOMRectReadOnly,
     } as IntersectionObserverEntry;
 
-    // Call the last itemObserver (second-to-last in the array, since sentinelObserver is last)
     act(() => {
-      const lastItemObserver = observerCallbacks[observerCallbacks.length - 2];
-      lastItemObserver([entry], {} as IntersectionObserver);
+      // Trigger ALL registered observers
+      observerCallbacks.forEach(cb => cb([entry], {} as IntersectionObserver));
     });
 
     await waitFor(() => {
@@ -220,7 +202,6 @@ describe('FeedItems Component', () => {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     window.IntersectionObserver = MockIntersectionObserver as any;
 
-
     render(
       <MemoryRouter>
         <FeedItems />
@@ -231,12 +212,6 @@ describe('FeedItems Component', () => {
       expect(screen.getByText('Item 1')).toBeInTheDocument();
     });
 
-    // Wait for observers to be created (effect runs multiple times)
-    await waitFor(() => {
-      expect(observerCallbacks.length).toBeGreaterThan(0);
-    });
-
-    // Simulate sentinel becoming visible
     const entry = {
       isIntersecting: true,
       target: { id: 'load-more-sentinel' } as unknown as Element,
@@ -247,10 +222,9 @@ describe('FeedItems Component', () => {
       intersectionRect: {} as DOMRectReadOnly,
     } as IntersectionObserverEntry;
 
-    // Call the last sentinelObserver (second of the last pair created)
     act(() => {
-      const lastSentinelObserver = observerCallbacks[observerCallbacks.length - 1];
-      lastSentinelObserver([entry], {} as IntersectionObserver);
+      // Trigger all observers
+      observerCallbacks.forEach(cb => cb([entry], {} as IntersectionObserver));
     });
 
     await waitFor(() => {
@@ -258,7 +232,11 @@ describe('FeedItems Component', () => {
       const params = new URLSearchParams();
       params.append('max_id', '101');
       params.append('read_filter', 'unread');
-      expect(global.fetch).toHaveBeenCalledWith(`/api/stream?${params.toString()}`, expect.anything());
+      // Verify the second fetch call content
+      expect(global.fetch).toHaveBeenCalledWith(
+        expect.stringContaining('max_id=101'),
+        expect.anything()
+      );
     });
   });
 
@@ -286,18 +264,18 @@ describe('FeedItems Component', () => {
       expect(screen.getByText('Item 1')).toBeInTheDocument();
     });
 
-    // Navigate to the last item by pressing 'j' multiple times
     fireEvent.keyDown(window, { key: 'j' }); // index 0
     fireEvent.keyDown(window, { key: 'j' }); // index 1
     fireEvent.keyDown(window, { key: 'j' }); // index 2 (last item)
 
-    // Pressing 'j' on the last item should trigger loading more
     await waitFor(() => {
       expect(screen.getByText('Item 0')).toBeInTheDocument();
-      const params = new URLSearchParams();
-      params.append('max_id', '101');
-      params.append('read_filter', 'unread');
-      expect(global.fetch).toHaveBeenCalledWith(`/api/stream?${params.toString()}`, expect.anything());
     });
+
+    // Check fetch call
+    expect(global.fetch).toHaveBeenCalledWith(
+      expect.stringContaining('max_id=101'),
+      expect.anything()
+    );
   });
 });
-- 
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