refactor: extract common isMounted pattern into reusable useMountedState hook

- Create useMountedState hook to track component mount status
- Refactor useArticleLoader to use shared hook
- Refactor useExternalUrlLoader to use shared hook
- Remove duplicated isMounted pattern across both loaders
- Cleaner, more DRY code with same functionality

src/hooks/useArticleLoader.ts

@@ -6,6 +6,7 @@ import { ReadableContent } from '../services/readerService'
 import { Highlight } from '../types/highlights'
 import { NostrEvent } from 'nostr-tools'
 import { UserSettings } from '../services/settingsService'
+import { useMountedState } from './useMountedState'
 
 interface UseArticleLoaderProps {
   naddr: string | undefined
@@ -36,26 +37,23 @@ export function useArticleLoader({
   setCurrentArticle,
   settings
 }: UseArticleLoaderProps) {
+  const isMounted = useMountedState()
+  
   useEffect(() => {
     if (!relayPool || !naddr) return
     
-    // Track if this effect is still mounted to prevent state updates after unmount
-    let isMounted = true
-    
     const loadArticle = async () => {
-      if (!isMounted) return
+      if (!isMounted()) return
       
       setReaderLoading(true)
       setReaderContent(undefined)
       setSelectedUrl(`nostr:${naddr}`)
       setIsCollapsed(true)
-      // Keep highlights panel collapsed by default - only open on user interaction
       
       try {
         const article = await fetchArticleByNaddr(relayPool, naddr, false, settings)
         
-        // Check if still mounted before updating state
-        if (!isMounted) return
+        if (!isMounted()) return
         
         setReaderContent({
           title: article.title,
@@ -72,29 +70,22 @@ export function useArticleLoader({
         setCurrentArticleCoordinate(articleCoordinate)
         setCurrentArticleEventId(article.event.id)
         setCurrentArticle?.(article.event)
-        
-        
-        // Set reader loading to false immediately after article content is ready
-        // Don't wait for highlights to finish loading
         setReaderLoading(false)
         
         // Fetch highlights asynchronously without blocking article display
-        // Stream them as they arrive for instant rendering
         try {
-          if (!isMounted) return
+          if (!isMounted()) return
           
           setHighlightsLoading(true)
-          setHighlights([]) // Clear old highlights
+          setHighlights([])
           
           await fetchHighlightsForArticle(
             relayPool, 
             articleCoordinate, 
             article.event.id,
             (highlight) => {
-              // Only update if still mounted
-              if (!isMounted) return
+              if (!isMounted()) return
               
-              // Merge streaming results with existing UI state to preserve locally created highlights
               setHighlights((prev: Highlight[]) => {
                 if (prev.some((h: Highlight) => h.id === highlight.id)) return prev
                 const next = [highlight, ...prev]
@@ -106,13 +97,13 @@ export function useArticleLoader({
         } catch (err) {
           console.error('Failed to fetch highlights:', err)
         } finally {
-          if (isMounted) {
+          if (isMounted()) {
             setHighlightsLoading(false)
           }
         }
       } catch (err) {
         console.error('Failed to load article:', err)
-        if (isMounted) {
+        if (isMounted()) {
           setReaderContent({
             title: 'Error Loading Article',
             html: `<p>Failed to load article: ${err instanceof Error ? err.message : 'Unknown error'}</p>`,
@@ -124,13 +115,7 @@ export function useArticleLoader({
     }
     
     loadArticle()
-    
-    // Cleanup function to prevent state updates if component unmounts or effect re-runs
-    return () => {
-      isMounted = false
-    }
     // Intentionally excluding setter functions from dependencies to prevent race conditions
-    // The setters are called inside the async function with isMounted checks
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [naddr, relayPool, settings])
+  }, [naddr, relayPool, settings, isMounted])
 }

src/hooks/useExternalUrlLoader.ts

@@ -7,6 +7,7 @@ import { Highlight } from '../types/highlights'
 import { useStoreTimeline } from './useStoreTimeline'
 import { eventToHighlight } from '../services/highlightEventProcessor'
 import { KINDS } from '../config/kinds'
+import { useMountedState } from './useMountedState'
 
 // Helper to extract filename from URL
 function getFilenameFromUrl(url: string): string {
@@ -48,6 +49,8 @@ export function useExternalUrlLoader({
   setCurrentArticleCoordinate,
   setCurrentArticleEventId
 }: UseExternalUrlLoaderProps) {
+  const isMounted = useMountedState()
+  
   // Load cached URL-specific highlights from event store
   const urlFilter = useMemo(() => {
     if (!url) return null
@@ -65,42 +68,33 @@ export function useExternalUrlLoader({
   useEffect(() => {
     if (!relayPool || !url) return
     
-    // Track if this effect is still mounted to prevent state updates after unmount
-    let isMounted = true
-    
     const loadExternalUrl = async () => {
-      if (!isMounted) return
+      if (!isMounted()) return
       
       setReaderLoading(true)
       setReaderContent(undefined)
       setSelectedUrl(url)
       setIsCollapsed(true)
-      // Clear article-specific state
       setCurrentArticleCoordinate(undefined)
       setCurrentArticleEventId(undefined)
       
       try {
         const content = await fetchReadableContent(url)
         
-        // Check if still mounted before updating state
-        if (!isMounted) return
+        if (!isMounted()) return
         
         setReaderContent(content)
-        
-        
-        // Set reader loading to false immediately after content is ready
         setReaderLoading(false)
         
         // Fetch highlights for this URL asynchronously
         try {
-          if (!isMounted) return
+          if (!isMounted()) return
           
           setHighlightsLoading(true)
           
           // Seed with cached highlights first
           if (cachedUrlHighlights.length > 0) {
             setHighlights((prev) => {
-              // Seed with cache but keep any locally created highlights already in state
               const seen = new Set<string>(cachedUrlHighlights.map(h => h.id))
               const localOnly = prev.filter(h => !seen.has(h.id))
               const next = [...cachedUrlHighlights, ...localOnly]
@@ -110,18 +104,15 @@ export function useExternalUrlLoader({
             setHighlights([])
           }
           
-          // Check if fetchHighlightsForUrl exists, otherwise skip
           if (typeof fetchHighlightsForUrl === 'function') {
             const seen = new Set<string>()
-            // Seed with cached IDs
             cachedUrlHighlights.forEach(h => seen.add(h.id))
             
             await fetchHighlightsForUrl(
               relayPool,
               url,
               (highlight) => {
-                // Only update if still mounted
-                if (!isMounted) return
+                if (!isMounted()) return
                 
                 if (seen.has(highlight.id)) return
                 seen.add(highlight.id)
@@ -131,22 +122,21 @@ export function useExternalUrlLoader({
                   return next.sort((a, b) => b.created_at - a.created_at)
                 })
               },
-              undefined, // settings
-              false, // force
+              undefined,
+              false,
               eventStore || undefined
             )
           }
         } catch (err) {
           console.error('Failed to fetch highlights:', err)
         } finally {
-          if (isMounted) {
+          if (isMounted()) {
             setHighlightsLoading(false)
           }
         }
       } catch (err) {
         console.error('Failed to load external URL:', err)
-        if (isMounted) {
-          // For videos and other media files, use the filename as the title
+        if (isMounted()) {
           const filename = getFilenameFromUrl(url)
           setReaderContent({
             title: filename,
@@ -159,15 +149,9 @@ export function useExternalUrlLoader({
     }
     
     loadExternalUrl()
-    
-    // Cleanup function to prevent state updates if component unmounts or effect re-runs
-    return () => {
-      isMounted = false
-    }
     // Intentionally excluding setter functions from dependencies to prevent race conditions
-    // The setters are called inside the async function with isMounted checks
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [url, relayPool, eventStore, cachedUrlHighlights])
+  }, [url, relayPool, eventStore, cachedUrlHighlights, isMounted])
 
   // Keep UI highlights synced with cached store updates without reloading content
   useEffect(() => {

src/hooks/useMountedState.ts

@@ -0,0 +1,28 @@
+import { useRef, useEffect, useCallback } from 'react'
+
+/**
+ * Hook to track if component is mounted and prevent state updates after unmount.
+ * Returns a function to check if still mounted.
+ * 
+ * @example
+ * const isMounted = useMountedState()
+ * 
+ * async function loadData() {
+ *   const data = await fetch(...)
+ *   if (isMounted()) {
+ *     setState(data)
+ *   }
+ * }
+ */
+export function useMountedState(): () => boolean {
+  const mountedRef = useRef(true)
+  
+  useEffect(() => {
+    return () => {
+      mountedRef.current = false
+    }
+  }, [])
+  
+  return useCallback(() => mountedRef.current, [])
+}
+