SpotiFLAC-Mobile is a cross-platform mobile application (Android and iOS) that enables users to download and play high-fidelity music in lossless formats such as FLAC and DSD. It operates through an extension-based architecture where community-provided plugins supply download sources, metadata, lyrics, and cover art. The application integrates with streaming services like Deezer, Tidal, Qobuz, and Spotify via these extensions, handling authentication, rate limiting, and content resolution. The system is built on a multi-language stack: a core Rust backend handles audio processing, metadata tagging, library management, and network communication; a Flutter (Dart) frontend provides the user interface; and platform-specific code in Kotlin (Android) and Swift (iOS) bridges native features like file system access, USB audio output, and system audio routing. The Rust backend is exposed to mobile languages via UniFFI-generated bindings. Key data flows include: extension-based download orchestration with cancellation and progress reporting, audio file finalization (metadata embedding, ReplayGain scanning, cover art insertion), incremental library scanning with SQLite persistence, and multi-provider lyrics fetching with caching. The application also features hi-res audio authenticity verification using STFT analysis, direct USB audio output for bit-perfect playback, and a comprehensive extension management system with sandboxed JavaScript runtimes. External dependencies include FFmpeg for audio conversion, libusb for USB audio transport, and various web APIs (Deezer, MusicBrainz, LRCLib, Apple Music, etc.) for metadata and lyrics enrichment. The project demonstrates strong engineering practices with extensive unit and integration tests, a modular crate architecture, and reusable patterns for cancellation, progress tracking, and caching.
SpotiFLAC is a cross-platform desktop application (built with Wails v2) that enables users to download high-quality FLAC audio from streaming services (Tidal, Qobuz, Amazon Music, Deezer) by leveraging Spotify metadata. The user inputs a Spotify track, album, playlist, or artist URL; the backend fetches metadata via Spotify's internal GraphQL API using reverse-engineered TOTP authentication, resolves streaming URLs through Songlink/Songstats, then downloads from the chosen service. The app includes a comprehensive suite of audio processing tools: audio analysis (spectrogram, FFT), BPM/key detection (Essentia.js), format conversion, resampling, ReplayGain tagging, lyrics management (LRCLIB), metadata enrichment, and file management. The frontend is built with React 19, TypeScript, Tailwind CSS, and shadcn/ui components, communicating with the Go backend via Wails bindings. The backend handles persistent storage (BoltDB for queue, history, caches), FFmpeg integration, and community API sessions for Tidal/Qobuz/Amazon. The architecture is a monolith desktop app with a clear separation between frontend UI and backend services, but the backend modules are tightly coupled to the app's specific workflow. The app is open-source (MIT) with a Patreon funding model and has a large internationalization footprint (11 languages). Key entry points include the SearchBar for URL input, the download queue for batch processing, and various tool pages (Audio Analysis, Converter, Resampler, ReplayGain, File Manager, Lyrics Manager). External dependencies include Spotify's undocumented API, Tidal/Qobuz/Amazon community APIs, Songlink, LRCLIB, MusicBrainz, FFmpeg, and Essentia.js. The codebase demonstrates significant reverse-engineering effort but carries maintenance risks due to reliance on fragile third-party APIs and hardcoded secrets.