SDK: Flutter/Dart bindings via flutter_rust_bridge

[saltyskip]

Overview

Add a Flutter/Dart SDK by wrapping the existing core/ crate with a flutter_ffi/ crate using flutter_rust_bridge v2. Ships as a standalone pub.dev plugin package.

Architecture

The core/ crate already has no FFI dependency — no business logic needs to be duplicated.

core/         ← unchanged, pure Rust (attribution, identify, deferred deep links)
ffi/          ← UniFFI → Swift + Kotlin (existing native iOS/Android)
flutter_ffi/  ← flutter_rust_bridge → Dart (new)

Key work

1. client/mobile/flutter_ffi/ crate

• Depends on rift_sdk_core
• Mirrors the ffi/ public API surface using #[frb] annotations
• Replicate all public methods: attributeLink, setUserId, checkDeferredDeepLink, pendingPresentation, dismissPresentation, showPresentation, etc.

2. RiftStorage equivalent for Dart

UniFFI's foreign trait pattern doesn't exist in flutter_rust_bridge. Instead, accept storage callbacks at init time backed by shared_preferences on the Dart side:

pub struct FlutterStorage {
    get: Arc<dyn Fn(String) -> Option<String> + Send + Sync>,
    set: Arc<dyn Fn(String, String) + Send + Sync>,
    remove: Arc<dyn Fn(String) + Send + Sync>,
}

final sdk = await RiftSdk.init(
  publishableKey: 'pk_live_...',
  storage: RiftStorage(
    get: (key) => prefs.getString(key),
    set: (key, val) => prefs.setString(key, val),
    remove: (key) => prefs.remove(key),
  ),
);

3. Flutter plugin package

• flutter_rust_bridge_codegen generate produces Dart bindings
• Plugin bundles compiled .so (Android) and .a (iOS) from the same Rust workspace
• Publish to pub.dev

4. CI

• Add Flutter build steps to sdk-ci.yml and sdk-release.yml alongside existing UniFFI bindgen
• Triggered by sdk/flutter/ path changes

Out of scope

• Native iOS/Android SDK changes (UniFFI path unchanged)
• Any new business logic — all logic stays in core/