fix(filen-mobile): prevent concurrent thumbnail generation with isGeneratingRef guard

Add a ref-based mutex to prevent overlapping generate() calls when
multiple triggers fire (AppState, httpStore, recycling). Reset the
flag in all cleanup paths (recycling, background, port loss, unmount)
to avoid stale locks after abort.

Author: Dwynr

packages/filen-mobile/src/components/drive/item/thumbnail.tsx

@@ -29,7 +29,8 @@ const Thumbnail = memo(
 		className?: string
 	}) => {
 		const abortControllerRef = useRef<AbortController | null>(null)
-		const errorRetryCountRef = useRef(0)
+		const errorRetryCountRef = useRef<number>(0)
+		const isGeneratingRef = useRef<boolean>(false)
 
 		const [localPath, setLocalPath] = useRecyclingState<string | null>(
 			() => {
@@ -53,6 +54,7 @@ const Thumbnail = memo(
 
 				abortControllerRef.current = null
 				errorRetryCountRef.current = 0
+				isGeneratingRef.current = false
 			}
 		)
 
@@ -63,54 +65,72 @@ const Thumbnail = memo(
 		}, [localPath])
 
 		const generate = useCallback(async () => {
-			if (
-				localPathRef.current ||
-				(item.type !== "file" && item.type !== "sharedFile") ||
-				!thumbnails.canGenerate(item) ||
-				AppState.currentState !== "active"
-			) {
-				return
-			}
+			const result = await run(async defer => {
+				if (isGeneratingRef.current) {
+					return
+				}
 
-			abortControllerRef.current?.abort()
-			errorRetryCountRef.current = 0
-			abortControllerRef.current = new AbortController()
+				isGeneratingRef.current = true
 
-			const signal = abortControllerRef.current.signal
-			let lastError: unknown
+				defer(() => {
+					isGeneratingRef.current = false
+				})
 
-			for (let attempt = 0; attempt < MAX_GENERATE_RETRIES; attempt++) {
-				if (signal.aborted || AppState.currentState !== "active") {
+				if (
+					localPathRef.current ||
+					(item.type !== "file" && item.type !== "sharedFile") ||
+					!thumbnails.canGenerate(item) ||
+					AppState.currentState !== "active"
+				) {
 					return
 				}
 
-				const result = await run(async () => {
-					return await thumbnails.generate({
-						item,
-						signal
+				abortControllerRef.current?.abort()
+				errorRetryCountRef.current = 0
+				abortControllerRef.current = new AbortController()
+
+				const signal = abortControllerRef.current.signal
+				let lastError: unknown
+
+				for (let attempt = 0; attempt < MAX_GENERATE_RETRIES; attempt++) {
+					if (signal.aborted || AppState.currentState !== "active") {
+						return
+					}
+
+					const result = await run(async () => {
+						return await thumbnails.generate({
+							item,
+							signal
+						})
 					})
-				})
 
-				if (signal.aborted) {
-					return
-				}
+					if (signal.aborted) {
+						return
+					}
 
-				if (result.success) {
-					cache.availableThumbnails.set(item.data.uuid, true)
+					if (result.success) {
+						cache.availableThumbnails.set(item.data.uuid, true)
 
-					setLocalPath(result.data)
+						setLocalPath(result.data)
 
-					return
+						return
+					}
+
+					lastError = result.error
+
+					await new Promise<void>(resolve => setTimeout(resolve, 1000))
 				}
 
-				lastError = result.error
+				console.error(lastError)
 
-				await new Promise<void>(resolve => setTimeout(resolve, 1000))
-			}
+				cache.availableThumbnails.set(item.data.uuid, false)
+			})
 
-			console.error(lastError)
+			if (!result.success) {
+				console.error(result.error)
 
-			cache.availableThumbnails.set(item.data.uuid, false)
+				return
+			}
 		}, [item, setLocalPath])
 
 		const generateRef = useRef(generate)
@@ -157,6 +177,7 @@ const Thumbnail = memo(
 
 						abortControllerRef.current = null
 						errorRetryCountRef.current = 0
+						isGeneratingRef.current = false
 					}
 				})
 
@@ -174,6 +195,7 @@ const Thumbnail = memo(
 
 							abortControllerRef.current = null
 							errorRetryCountRef.current = 0
+							isGeneratingRef.current = false
 						}
 					}
 				)
@@ -194,6 +216,7 @@ const Thumbnail = memo(
 
 				abortControllerRef.current = null
 				errorRetryCountRef.current = 0
+				isGeneratingRef.current = false
 			}
 		}, [])