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tasks/android-production/23-offline-sync.md

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+# 23. Offline Sync & Conflict Resolution
+
+meta:
+  id: android-production-23
+  feature: android-production
+  priority: P2
+  depends_on: [android-production-21]
+  tags: [backend, offline, production]
+
+objective:
+- Implement robust offline mode with sync conflict resolution for all user actions
+
+deliverables:
+- Offline queue improvements
+- Sync conflict resolution strategy
+- Offline UI indicators
+- Data consistency guarantees
+
+steps:
+1. Audit existing offline support:
+   - Review android/app/.../data/sync/SyncManager.kt
+   - Review OfflineWorker.kt
+   - Review PendingRequestQueue.kt
+   - Identify gaps in offline handling
+2. Improve offline queue:
+   - Support all mutation types (add, update, delete)
+   - Add request deduplication
+   - Add request ordering (dependencies)
+   - Increase max retry count with exponential backoff
+3. Implement conflict resolution:
+   - Define strategy per data type:
+     - Server wins for most data (alerts, exposures)
+     - Last write wins for user preferences
+     - Merge for watchlist items
+   - Add conflict detection (version numbers or timestamps)
+   - Show conflict UI for manual resolution (if needed)
+4. Add offline UI:
+   - Offline indicator in status bar
+   - Disabled actions when offline
+   - "Sync pending" badges on modified items
+   - Pull-to-refresh with offline state
+5. Implement data consistency:
+   - Optimistic updates (update UI immediately, sync in background)
+   - Rollback on sync failure
+   - Verify server state after sync
+   - Handle partial sync failures
+6. Add background sync:
+   - Process queue on app foreground
+   - Process queue on network restoration
+   - Schedule periodic sync attempts
+7. Test offline scenarios:
+   - Create watchlist item offline → syncs when online
+   - Delete exposure offline → syncs when online
+   - Modify settings offline → syncs when online
+   - Conflicting edits on multiple devices
+
+tests:
+- Unit: Test queue ordering and deduplication
+- Integration: Test sync after offline period
+- E2E: Test conflicting edits resolution
+
+acceptance_criteria:
+- All mutations queued when offline
+- Queue processed automatically when online
+- Optimistic updates show immediately
+- Failed operations roll back UI changes
+- Conflict resolution strategy defined per data type
+- Offline indicator visible in UI
+- Sync pending badges on modified items
+- No data loss during sync failures
+- Background sync on app foreground and network restore
+- Unit tests for all offline scenarios
+
+validation:
+- Enable airplane mode → create watchlist item → badge shows
+- Disable airplane mode → item syncs → badge clears
+- Edit same item on web and Android → conflict resolved correctly
+- Kill app during sync → queue persists, resumes on relaunch
+
+notes:
+- SyncManager.kt and OfflineWorker.kt already exist but may need enhancement
+- Room database can help with offline queue persistence
+- Simple server-wins strategy is acceptable for MVP
+- Consider using WorkManager for reliable background sync