Flutter SyncEngine

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Version: 1.0.0

SyncEngine is a lightweight Flutter/Dart package that helps developers sync data between local storage and remote backends.
It is flexible and backend-agnostic, allowing you to use any storage (File, Hive, SQLite, etc.) and any transport (REST API, dummy transport, or custom).

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Features

• Push and pull data to/from a backend.
• Local storage support (File, Hive, SQLite, or custom).
• Conflict resolution support (LastWriteWins by default, custom resolvers allowed).
• Backend-agnostic: transport can be REST, GraphQL, WebSocket, or custom.
• Minimal dependencies – you can choose your storage/transport freely.

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Installation

Add to your pubspec.yaml:

dependencies:
  flutter_sync_engine: ^1.0.0

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Usage

1️⃣ Import the package

import 'package:flutter_sync_engine/flutter_sync_engine.dart';

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2️⃣ Initialize a store and transport

final store = await FileSyncStore.create('notes.json'); // File store
final transport = DummyTransport(); // Dummy transport

final engine = SyncEngine(store: store, transport: transport);
engine.registerCollection(name: 'notes', conflictResolver: const LastWriteWins());

You can replace FileSyncStore with HiveSyncStore or SQLiteSyncStore.
You can replace DummyTransport with RestTransport or a custom backend.

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3️⃣ Add and sync data

// Add note locally
final note = {
  'id': '1',
  'title': 'Note 1',
  'content': 'This is a note',
  'updatedAt': DateTime.now().toIso8601String(),
};
await store.saveEntity('notes', note);
await store.logOperation(SyncOperation(
  collection: 'notes',
  entityId: note['id']!,
  type: OperationType.create,
  timestamp: DateTime.now(),
  data: note,
));

// Sync with backend
await engine.sync();

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4️⃣ RestTransport example (sync with dummy REST API)

final transport = RestTransport('https://jsonplaceholder.typicode.com');

await engine.sync(); // Push local notes and pull remote notes

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5️⃣ Conflict Resolution

By default, LastWriteWins is used:

class LastWriteWins implements ConflictResolver {
  @override
  Map<String, dynamic> resolve({
    required Map<String, dynamic> local,
    required Map<String, dynamic> remote,
  }) {
    final localUpdated = DateTime.parse(local['updatedAt'] ?? '1970-01-01');
    final remoteUpdated = DateTime.parse(remote['updatedAt'] ?? '1970-01-01');
    return localUpdated.isAfter(remoteUpdated) ? local : remote;
  }
}

You can also implement a custom resolver per collection:

engine.registerCollection(
  name: 'notes',
  conflictResolver: MyCustomResolver(),
);

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Example App

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  
  final store = await FileSyncStore.create('notes.json');
  final transport = DummyTransport();

  final engine = SyncEngine(store: store, transport: transport);
  engine.registerCollection(name: 'notes', conflictResolver: const LastWriteWins());

  runApp(MyApp(engine));
}

• Supports File, Hive, SQLite storage.
• Supports DummyTransport or any custom backend.
• Easy to extend and integrate into any Flutter app.

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Store Options

Store Type	Description
FileSyncStore	Simple JSON file storage (default for example apps)
HiveSyncStore	Persistent NoSQL storage using Hive
SQLiteSyncStore	Relational storage using SQLite
Custom	You can implement SyncStore interface for your own storage

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Transport Options

Transport Type	Description
DummyTransport	In-memory backend for testing
RestTransport	Connects to a REST API
Custom	Implement SyncTransport for your own backend

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Installation Notes

• No dependencies on Hive or SQLite in the package itself.
• Example app includes optional implementations for testing and demonstration.
• You can use your preferred database without modifying the package.

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License

MIT License