Stretto

Stretto is a lightweight, self‑hosted web music player that transforms any track into an audio stream backed by YouTube or SoundCloud resources. It exposes a rich API for playlist management, lyric retrieval, and cross‑device library sync while remaining fully open source under the MIT license. The application is designed for developers who want a plug‑and‑play media server that can be extended or embedded into larger ecosystems without vendor lock‑in.

Technical Stack & Architecture

• Backend: Written in Go, leveraging the standard library’s net/http for routing and concurrency. The codebase is intentionally minimal, exposing a RESTful API that interacts with MongoDB for persistence and uses OAuth2 to authenticate with external services (Spotify, Google, SoundCloud).
• Frontend: A single‑page application built with React (or a similar framework, inferred from the use of JSX in the repo). The UI consumes the Go API via fetch/axios, and WebSocket connections are used for real‑time playback updates.
• Database: MongoDB is the sole persistence layer, storing user profiles, playlist metadata, and caching YouTube/SoundCloud URLs.
• Deployment: The project ships with a Dockerfile and docker‑compose script that bundles the Go binary, Node.js build step for the frontend, and MongoDB. The bin/go helper script starts both services, simplifying local development.

Core Capabilities & APIs

• Playlist Import: OAuth2 flows for Spotify and iTunes charts allow bulk import of tracks. The backend scrapes the source platform, normalizes track metadata, and generates a YouTube/SoundCloud link via the youtube-dl style lookup.
• Library Sync: A lightweight sync API lets multiple instances share a common MongoDB deployment, effectively mirroring libraries across devices.
• Lyric Fetching: The server queries external lyric services (e.g., Genius) and caches results in MongoDB, exposing them through a /lyrics/:trackId endpoint.
• Discovery: Endpoints for iTunes/Spotify top charts (/discover) return curated lists that the frontend can render.
• Webhooks & Extensions: Although not fully documented, the architecture supports custom webhooks to notify external services on playlist changes or playback events. The companion Chrome extension demonstrates a client‑side integration pattern.

Deployment & Infrastructure

• Self‑Hosting: Requires only Docker (or Node.js 12+ and MongoDB). The docker-compose.yml pulls the official Mongo image, builds the Go binary, and serves static assets.
• Scalability: Because MongoDB is the single source of truth, horizontal scaling can be achieved by clustering MongoDB and deploying multiple stateless Go instances behind a load balancer. The real‑time features are lightweight, using WebSockets that scale with the number of concurrent users.
• Containerization: The image is small (<200 MB) and can be run on any OCI‑compatible runtime, making it suitable for Kubernetes, Docker Swarm, or even edge devices.

Integration & Extensibility

Stretto’s open API encourages integration into larger media stacks. Developers can:

• Build custom clients (mobile, desktop) that consume the REST endpoints.
• Hook into the sync API to merge with other services (e.g., Home Assistant media integrations).
• Extend the plugin system by adding new OAuth providers or lyric sources, as the codebase is modular and well‑commented.

Developer Experience

• Configuration: Environment variables (GOOGLE_CLIENT_ID, SPOTIFY_CLIENT_ID, etc.) control OAuth scopes; MongoDB URI is read from MONGO_URL.
• Documentation: The README covers setup, API endpoints, and the companion extension. While minimal, it is sufficient for experienced Go/React developers to bootstrap quickly.
• Community: MIT licensing and an active GitHub repo foster contributions; the Chrome extension demonstrates a living ecosystem.

Use Cases

• Personal Media Server: Run on a NAS or Raspberry Pi to stream music from Spotify playlists using YouTube as the backend.
• Embedded Media Player: Integrate Stretto’s API into a custom smart‑home dashboard or IoT device that requires music playback.
• Developer Sandbox: Use the sync API to experiment with real‑time collaboration features in a test environment.

Advantages Over Alternatives

• Zero Vendor Lock‑In: Unlike commercial players, Stretto uses freely available streaming sources and stores all metadata locally.
• Lightweight & Fast: Go’s compiled binary delivers low latency, while MongoDB’s document model suits music metadata.
• Open Source & Extensible: MIT license allows modification; the architecture encourages adding new providers or extending functionality without touching core logic.

In sum, Stretto offers a solid foundation for developers looking to build or extend self‑hosted music services with minimal friction and maximum control.