ipatool is a cross-platform command-line tool that acts as an unofficial Apple App Store client. It enables searching, purchasing, and downloading iOS/iPadOS/tvOS/watchOS/visionOS/macOS applications and packages directly from Apple's servers. The tool implements Apple's private SAP authentication and signing protocol by emulating Apple's StoreAgent binary in-process using the Unicorn CPU emulator, allowing it to generate kbsync blobs and decrypt macOS packages. It also includes low-level parsers for Apple's proprietary formats (AEA encrypted archives, APFS filesystems, dyld shared caches) to extract assets from macOS restore images. The architecture is modular: a CLI layer (using cobra) dispatches to domain logic in pkg/appstore, which relies on a generic HTTP client (pkg/http), keychain storage (pkg/keychain), and platform abstractions (pkg/util). An MCP (Model Context Protocol) server subcommand exposes the same functionality over stdio. The codebase is heavily tested with unit and integration tests, and CI builds for macOS, Linux, Windows, and iOS. While primarily an application, it contains significant reverse-engineering and protocol-analysis components, giving it a hybrid character.
BetterLyrics is a feature-rich WinUI3 desktop application for Windows that displays and customizes synchronized song lyrics. The application serves as both a lyrics visualizer and a music player, supporting multiple display modes (standard, fullscreen, desktop wallpaper, docked, taskbar) with GPU-accelerated rendering via Win2D and ComputeSharp pixel shaders. It integrates with the Windows Global System Media Transport Controls (GSMTC) to work with external players like Spotify, Apple Music, and NetEase, and provides its own local media playback engine with a music library browser and playlist management. The architecture follows MVVM (CommunityToolkit.Mvvm) with a service layer and dependency injection, separating platform-agnostic logic in 'BetterLyrics.Core', UI in 'BetterLyrics.WinUI3', and a plugin SDK in 'BetterLyrics.Sdk'. Core data flows include lyrics retrieval from multiple providers (QQ, Netease, Kugou, Apple Music, LrcLib) with caching, metadata extraction via TagLib, and analytics tracking stored in LiteDB. The plugin SDK allows third-party developers to extend lyrics sources, translations, transliterations, and AI services via isolated AssemblyLoadContext. Reusable components include generic helpers (Debouncer, ValueTransition, FullyObservableCollection), a comprehensive lyrics format parser (LRC, TTML, QRC/KRC), and a plugin framework with auto-generated settings UI.