Add data persistence and sync strategy for offline-first experience

[SahilKumar75]

Problem

The app relies heavily on AsyncStorage for persistence but lacks a comprehensive offline-first strategy, proper data sync, and conflict resolution.

Issues Identified

1. Data Persistence Gaps

• No offline queue: Actions fail when offline, not queued for retry
• Inconsistent persistence: Some data persisted, some lost on app close
• No data versioning: Cannot migrate data when schema changes
• Large data in AsyncStorage: Performance issues with big datasets
• No data expiration: Stale data never cleaned up

2. Sync Issues

• No sync status: Users do not know if data is synced
• No conflict resolution: Last-write-wins can lose data
• No optimistic updates: UI waits for server response
• No background sync: Data only syncs when app is open
• No partial sync: All-or-nothing sync approach

3. Data Integrity

• No validation: Corrupted data can crash app
• No backup: Data loss if storage corrupted
• No encryption: Sensitive data stored in plain text
• No data limits: Can fill device storage
• No data export: Users cannot backup their data

Proposed Solutions

1. Offline-First Architecture

• Implement action queue system for offline actions
• Add optimistic UI updates
• Queue failed requests for retry
• Show pending state indicators

2. Data Sync Strategy

• Add sync status indicator in UI
• Implement conflict resolution (last-write-wins with merge)
• Set up background sync with expo-background-fetch
• Add partial sync for large datasets

3. Data Storage Strategy

• Multi-layer storage: Memory cache, AsyncStorage, SQLite
• Data migration system for schema changes
• Storage limits and cleanup routines
• Data validation on load

4. Data Security

• Use expo-secure-store for sensitive data
• Encrypt auth tokens and personal data
• Validate data structure on import
• Implement secure backup/restore

5. Data Management Features

• Export user data as JSON
• Import data with validation
• Storage usage dashboard
• Clear cache functionality

Implementation Plan

Phase 1: Foundation

• Implement action queue system
• Add network status detection
• Create sync status indicator
• Add data versioning

Phase 2: Sync

• Implement optimistic updates
• Add conflict resolution
• Set up background sync
• Add sync retry logic

Phase 3: Storage

• Implement multi-layer storage
• Add data migration system
• Set up SQLite for large datasets
• Add data validation

Phase 4: Security and Management

• Implement encryption for sensitive data
• Add data export/import
• Create storage management UI
• Add data cleanup routines

Acceptance Criteria

• App works fully offline
• Actions queued when offline
• Automatic sync when online
• Sync status visible to users
• Conflicts resolved gracefully
• Data migrations work
• Export/import functional
• Sensitive data encrypted

Priority

High - Critical for reliability and user trust