fix(ui): coalesce lyric refreshes with in-flight requests

Signed-off-by: ranokay <github@ranokay.com>

ui/src/audioplayer/useEnhancedLyrics.js

@@ -153,8 +153,13 @@ const useEnhancedLyrics = ({
 
   const refresh = useCallback(() => {
     if (!trackId || disabled || !requested) return
+    // Coalesce with an unsettled request: its answer is at least as fresh as
+    // one started now, and restarting it would strand slow responses behind
+    // the poll interval.
+    const entry = inFlight.get(cacheKey)
+    if (entry && !entry.settled) return
     setRefreshToken((current) => current + 1)
-  }, [disabled, requested, trackId])
+  }, [cacheKey, disabled, requested, trackId])
 
   useEffect(() => {
     if (!trackId || disabled || !requested) {

ui/src/audioplayer/useEnhancedLyrics.test.js

@@ -344,6 +344,29 @@ describe('useEnhancedLyrics', () => {
     expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(2)
   })
 
+  it('coalesces a refresh with a request that is still in flight', async () => {
+    const pending = createDeferred()
+    subsonic.getLyricsBySongId.mockReturnValueOnce(pending.promise)
+
+    const { result } = renderLyrics({ trackId: 'song-coalesce' })
+
+    expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(1)
+
+    act(() => {
+      result.current.refresh()
+    })
+    expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(1)
+
+    act(() => {
+      pending.resolve(
+        responseForEntries([sourceEntry('NetEase', 'NetEase line')]),
+      )
+    })
+
+    await expectLyric(result, 'NetEase line')
+    expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(1)
+  })
+
   it('keeps current lyrics when a refresh fails', async () => {
     subsonic.getLyricsBySongId
       .mockResolvedValueOnce(

ui/src/audioplayer/usePlayerLyrics.test.jsx

@@ -195,29 +195,32 @@ describe('usePlayerLyrics', () => {
     vi.useFakeTimers()
     subsonic.getLyricsBySongId.mockResolvedValue(variantsResponse())
 
+    const flushMicrotasks = () =>
+      act(async () => {
+        await Promise.resolve()
+        await Promise.resolve()
+      })
+
     const { result } = renderPlayerLyrics()
     act(() => result.current.toolbarLyricsProps.onToggleLyrics())
-    await act(async () => {
-      await Promise.resolve()
-    })
+    await flushMicrotasks()
     expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(1)
 
     act(() => result.current.desktopLyricsProps.onSourceMenuOpenChange(true))
     expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(2)
 
-    await act(async () => {
-      vi.advanceTimersByTime(5_000)
-    })
-    expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(3)
-
-    for (let step = 0; step < 11; step += 1) {
+    let expectedCalls = 2
+    for (let step = 0; step < 12; step += 1) {
+      await flushMicrotasks()
       await act(async () => {
         vi.advanceTimersByTime(5_000)
       })
+      expectedCalls += 1
+      expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(expectedCalls)
     }
-    expect(subsonic.getLyricsBySongId).toHaveBeenCalledTimes(14)
 
     act(() => result.current.desktopLyricsProps.onSourceMenuOpenChange(false))
+    await flushMicrotasks()
     await act(async () => {
       vi.advanceTimersByTime(15_000)
     })