Feature Request: Google Cast Support via SharpCaster #39

I would like to propose adding support for browsing and controlling Google Cast devices within smoc. This would allow users to cast their music to speakers, TVs, and other Cast-enabled devices directly from the CLI.

High-Level Plan

1. Device Discovery: Integrate SharpCaster to discover devices on the local network.
2. Audio Service Implementation: Create a new IAudioService implementation (CastAudioService) that targets a selected Cast device.
3. Playback Service Implementation: Create a CastPlaybackService that implements IPlaybackService to control remote playback.
4. Local Stream Proxy: Since smoc handles audio as Stream objects, implement a lightweight HTTP proxy to serve these streams to the Cast device.
5. UI Integration: Implement a command (e.g., :output) to list and select output devices via the command line interface.

Detailed Implementation Plan

1. Core Services

• ICastDiscoveryService:
  • Task<IEnumerable<Chromecast>> DiscoverDevicesAsync()
  • Uses SharpCaster.DeviceFinder.
• CastPlaybackService (implements IPlaybackService):
  • Wraps SharpCaster.ChromecastClient and its MediaStatus.
  • Bridges MediaStatus updates to PositionChanged and PlaybackStateChanged events.
  • Implements Play(), Pause(), Stop(), and Seek() by calling the respective SharpCaster methods.
• CastAudioService (implements IAudioService):
  • Acts as the factory for CastPlaybackService.
  • Manages the connection to the specific Chromecast device.
  • Manages the lifecycle of a local HttpListener to proxy the Stream from IStreamingClient to the Chromecast's required URL.

2. Streaming Proxy

• A StreamProxyService that:
  • Listens on a random local port.
  • Generates a transient URL (e.g., http://<local-ip>:<port>/stream/<guid>).
  • When the URL is requested, it pipes the Stream from IStreamingClient to the HTTP response.
  • This ensures that any smoc supported stream (Subsonic, etc.) can be played on the Cast device even if the device doesn't have direct access to the source.

3. UI/UX Changes

• Implement a new command :output in the command bar.
• Running :output without arguments lists available devices (Local, discovered Cast devices).
• Running :output <name> (with auto-completion support) switches the active output device.
• Display the current output device in the status bar or playback info area.
• Update StandardPlaybackQueueService to switch the underlying IAudioService implementation when a new device is selected via the command.

Dependencies

• SharpCaster (NuGet) - Latest version (3.0.0)