iktakahiro/fargon2

1. What this repository is

- fargon2 is a Flutter plugin package, not a standalone app.

- Its purpose is to expose Argon2 password hashing to Dart code while executing the actual hashing natively on Android and iOS.

2. Public API boundary

- The main package surface is lib/fargon2.dart.

- That Dart layer is the only code consumers are meant to call directly; the README example shows creating a Fargon2 instance and calling hash(...).

3. Cross-platform execution model

- The architecture is split into three layers:

- Dart API in Flutter

- Native platform plugin code

- Platform-specific hashing implementation

- Data flows from Dart inputs such as passphrase, salt, mode, and tuning parameters into native code, and the computed hash string returns back to Dart.

4. Android subsystem

- Android implementation lives under android/.

- The plugin entrypoint is android/src/main/kotlin/dev/iktakahiro/fargon2/Fargon2Plugin.kt.

- This is the Android boundary where Flutter method calls are received and forwarded into the native hashing logic.

5. iOS subsystem

- iOS implementation lives under ios/.

- The plugin code is split across ios/Classes/Fargon2Plugin.h, ios/Classes/Fargon2Plugin.m, and ios/Classes/SwiftFargon2Plugin.swift.

- This suggests an iOS plugin boundary with a Swift implementation plus Objective-C compatibility/registration glue.

6. Hashing domain

- The core domain concept is Argon2 hashing, with support for the Argon2 variants mentioned in the README: argon2id, argon2i, and argon2d.

- The plugin accepts Argon2 cost parameters such as hash length, iterations, parallelism, and memory size, which are central to the runtime behavior and output.

7. Platform-native dependency boundary

- The repository is a wrapper around platform-native Argon2-capable libraries rather than implementing the algorithm entirely in Dart.

- The README credits CatCrypto and argon2kt, indicating the real hashing work is delegated to native dependencies or their equivalents under the hood.

8. Example application

- example/ is a full Flutter app used to demonstrate and validate the plugin on both platforms.

- It contains its own Android and iOS host projects plus example/lib/main.dart and a widget test, so it serves as the integration reference for consumers.

9. Testing and CI

- Repository-level tests live in test/fargon2_test.dart.

- GitHub Actions workflow /.github/workflows/test.yaml runs Flutter tests, making the CI boundary focused on package validation rather than deployment.

10. Build and packaging structure

- pubspec.yaml, analysis_options.yaml, and .fvm/fvm_config.json define the Dart/Flutter toolchain and style constraints.

- Android and iOS subprojects are configured as plugin host builds, with Gradle and CocoaPods metadata present in each platform folder.

11. Platform integration details

- The plugin is packaged for Android with Gradle files and an AndroidManifest.xml, and for iOS with a .podspec, Xcode project files, and Flutter xcconfig assets.

- This is the standard Flutter plugin layout for shipping one Dart package with two native implementations.

12. Operationally important diagram view

- If you draw the architecture, the main arrow should be: Flutter app code → fargon2 Dart API → Android/iOS plugin layer → Argon2 native implementation → hashed result back to Dart.

- The example app is a separate consumer of that same path, and CI/test files validate the package boundary.