Engineering joy: Building the celebration system on the Home tab of the LINE app on Android

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3PCVTU*NQMFNFOUBUJPO // Metadata Download Worker: Fetch event configurations if (retryUntil
< now) { return failure() } val event = fetchEventMetadata(eventId) // error -> retry saveEventMetadata(event) // error -> retry scheduleAssetDownload(event) // success -> next step .FUBEBUB%PXOMPBE8PSLFS'FUDIFWFOUDPOGJHVSBUJPOT

3PCVTU*NQMFNFOUBUJPO // Asset Worker: Download and validate celebration assets if
(retryUntil < now) { return failure() } val asset = downloadAsset(event) // error -> retry validateAsset(asset, event.checksum) // error -> retry fileStorage.extractAndSave(eventId, asset) // error -> retry // success scheduleShowtime() scheduleCleanup() "TTFU8PSLFS%PXOMPBEBOEWBMJEBUFDFMFCSBUJPOBTTFUT

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&MFHBOU4JNQMJDJUZ // WorkManager: One simple state change eventRepository.updateEventState(eventId, READY) //
Everything else happens automatically: // Room → Flow → UI updates seamlessly

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3FBM*NQBDU$PNQMFY-PHJDJO4JNQMF$PEF // All three building blocks working together: val displayableEventFlow
= combine( homeEventEffectDao.getDisplayableEventsFlow(), // Room: reactive queries homeTabVisibilityFlow // Flow: UI state tracking ) { events, isHomeVisible -> events.takeIf { isHomeVisible } // Timing: only when visible ?.maxByOrNull { it.priority } // Priority: personal > cultural } // Worker updates Room → Room triggers Flow → Flow updates UI displayableEventFlow.collect { event -> showEffect(event) }

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Engineering joy: Building the celebration syste...

Engineering joy: Building the celebration system on the Home tab of the LINE app on Android

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