feat: Introduce IGuildMusicService for guild-specific music management

CLAUDE.md

@@ -4,7 +4,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Overview
 
-Discord Music Bot - A .NET 10 application that plays music in Discord voice channels from YouTube, SoundCloud, Spotify (playlist metadata only), and radio streams. Ships with a React dashboard for stats and radio-source management. Designed to run on Linux via Docker; native voice dependencies (libdave, libsodium, libopus) make local Windows runs impractical.
+Discord Music Bot - A .NET 10 application that plays music in Discord voice channels from YouTube, SoundCloud, Spotify (playlist metadata only), and radio streams. Supports multiple servers concurrently: each guild gets its own queue, player loop, voice connection, and FFmpeg process, while statistics and the blacklist are shared globally. Ships with a React dashboard for stats and radio-source management. Designed to run on Linux via Docker; native voice dependencies (libdave, libsodium, libopus) make local Windows runs impractical.
 
 ## Build & Run Commands
 
@@ -47,18 +47,18 @@ Tests live in `src/Tests/` (xUnit + NSubstitute; integration tests use Testconta
 
 - **Domain** (`src/Domain/`) - Entities (`Song`, `User`, `PlayHistory`, `RadioSource`), event handler interfaces (`IEventHandler<T>`, `IAsyncEventHandler<T>`), and enums.
 - **Application** (`src/Application/`) - Business services (`SpotifyService`, `JokeService`, `QuoteService`, `HttpRequestService`), DTOs, config binding helpers, the in-process event dispatcher plus `AddEventing` registration (`Application.Eventing`), and the `GlobalStore` singleton.
-- **Infrastructure** (`src/Infrastructure/`) - NetCord commands and interactions, audio pipeline (`MusicPlayerBackgroundService`, `AudioPlayerService`, `FfmpegProcessService`, `MusicQueueService`), `PlayerHandler` (thin Skip/Stop event adapter), YouTube/SoundCloud stream services, EF Core `DiscordBotContext` with compiled models, and radio/user/blacklist/statistics services.
-- **Tests** (`src/Tests/`) - xUnit test project: `Unit/` (queue, player background service, eventing) and `Integration/` (blacklist/statistics/user services against Testcontainers PostgreSQL).
+- **Infrastructure** (`src/Infrastructure/`) - NetCord commands and interactions, audio pipeline (`GuildPlayerManager`, `GuildPlayer`, `AudioPlayerService`, `FfmpegProcessService`, `MusicQueueService`), `PlayerHandler` (thin guild-scoped Skip/Stop event adapter), YouTube/SoundCloud stream services, EF Core `DiscordBotContext` with compiled models, and radio/user/blacklist/statistics services.
+- **Tests** (`src/Tests/`) - xUnit test project: `Unit/` (queue, guild player, guild player manager, eventing) and `Integration/` (blacklist/statistics/user services against Testcontainers PostgreSQL).
 - **UI** (`src/UI/`)
   - `Api/` - ASP.NET Core minimal-API endpoints (see `ControllerExtensions.cs`) with JWT bearer auth. Login checks against `JwtSettings:InternalPassword` (no user password hashing).
   - `App/` - React 19 + TypeScript SPA. Build output writes into `src/Worker/wwwroot/`, which is served by the Worker as static files with SPA fallback to `index.html`.
-- **Worker** (`src/Worker/`) - Composition root. Program.cs builds a `WebApplication` that hosts the NetCord Discord gateway (registered via `AddDiscordGateway`), the ASP.NET Core web API, and the `MusicPlayerBackgroundService` hosted service in one process on port 5000.
+- **Worker** (`src/Worker/`) - Composition root. Program.cs builds a `WebApplication` that hosts the NetCord Discord gateway (registered via `AddDiscordGateway`), the ASP.NET Core web API, and the `GuildPlayerManager` hosted service in one process on port 5000.
 
 ### Key Patterns
 
-**Event system**: Custom in-process dispatcher (`IEventDispatcher`, `IAsyncEventDispatcher`) plus a `HandlerRegistry`. `Application.Eventing.EventingServiceCollectionExtensions.AddEventing(assemblies...)` scans supplied assemblies for `IEventHandler<T>` / `IAsyncEventHandler<T>` implementations and registers them as scoped. When adding a new event handler, ensure its assembly is passed to `AddEventing` in `DependencyInjection.cs` (currently `Application.AssemblyMarker` and `Infrastructure.Services.AssemblyMarker`). Only `EventType.Skip` / `EventType.Stop` are dispatched today (handled by `PlayerHandler`, which forwards to `IMusicPlayerController`); `EventType.Play` is not dispatched anymore because enqueueing wakes the player's channel consumer directly.
+**Event system**: Custom in-process dispatcher (`IEventDispatcher`, `IAsyncEventDispatcher`) plus a `HandlerRegistry`. `Application.Eventing.EventingServiceCollectionExtensions.AddEventing(assemblies...)` scans supplied assemblies for `IEventHandler<T>` / `IAsyncEventHandler<T>` implementations and registers them as scoped. When adding a new event handler, ensure its assembly is passed to `AddEventing` in `DependencyInjection.cs` (currently `Application.AssemblyMarker` and `Infrastructure.Services.AssemblyMarker`). Only `EventType.Skip` / `EventType.Stop` are dispatched today; both carry a `GuildId` and are handled by `PlayerHandler`, which forwards to `IGuildMusicService`. `EventType.Play` is not dispatched anymore because enqueueing wakes the guild's channel consumer directly.
 
-**Queue service pattern**: `MusicQueueService` (singleton) pairs a lock-protected list with an unbounded `System.Threading.Channels` signal channel, following the Microsoft queue-service guidance. `MusicPlayerBackgroundService` (a `BackgroundService`, also registered as `IMusicPlayerController`) is the single consumer: it dequeues a `PlayRequest` into the `NowPlaying` slot, awaits `AudioPlayerService.PlayTrackAsync` (retrying failed tracks up to 3 times), and disconnects from voice when the queue runs empty. Skip/Stop cancel the per-track linked `CancellationTokenSource`.
+**Per-guild players**: `GuildPlayerManager` (a `BackgroundService`, registered as `IGuildMusicService`) owns one `GuildPlayer` per guild, created lazily on the first enqueue for that guild via a component factory (wired in `Worker/DependencyInjection.cs`). Each `GuildPlayer` owns its own `MusicQueueService` (a lock-protected list paired with an unbounded `System.Threading.Channels` signal channel, per the Microsoft queue-service guidance), its own `AudioPlayerService` (voice client) and `FfmpegProcessService` instance, and a consumer loop: it dequeues a `PlayRequest` into the `NowPlaying` slot, awaits `AudioPlayerService.PlayTrackAsync` (retrying failed tracks up to 3 times), and disconnects from that guild's voice channel when its queue runs empty. Skip/Stop cancel the guild's per-track linked `CancellationTokenSource`; commands address a guild through `IGuildMusicService` with `Context.Guild.Id`. None of `MusicQueueService`, `AudioPlayerService`, or `FfmpegProcessService` are DI-registered anymore - the manager constructs them per guild.
 
 **Keyed services**: Multiple implementations of `IStreamService` and `IRandomService` are registered by name and resolved with `[FromKeyedServices(nameof(...))]`:
 
@@ -70,9 +70,10 @@ services.AddKeyedScoped<IRandomService, QuoteService>(nameof(QuoteService));
 ```
 
 **Discord commands** (`src/Infrastructure/Commands/`):
+
 - `PlayCommand` (in `MusicPlayCommands.cs`) - `/play music` and radio subcommands
-- `MusicActionCommands` - pause, skip, stop, volume
-- `AdminCommands` - admin-only actions
+- `MusicActionCommands` - stop, skip, playlist, rewind, statistics
+- `AdminCommands` - admin-only actions (blacklist management)
 - `MiscCommands` - help, joke, motivate
 
 Commands and the `NetCordInteraction` component module are wired in `Worker.DependencyInjection.AddWebApplication`.
@@ -85,7 +86,7 @@ PostgreSQL + EF Core 10. Context: `Infrastructure/Data/DiscordBotContext.cs`. Us
 
 ### Audio Pipeline
 
-A play interaction enqueues a `PlayRequest` into `MusicQueueService`; the channel signal wakes `MusicPlayerBackgroundService`, which calls `AudioPlayerService.PlayTrackAsync`. That method joins the voice channel if needed, resolves the stream URL (`YoutubeExplode` / `YoutubeDLSharp` via `yt-dlp` at runtime, or a radio source URL when the selection is a Guid), logs the play via `IStatisticsService` (radio plays are logged with the station name as the title), spawns FFmpeg through `FfmpegProcessService` (`Ffmpeg:Path` config, default `/usr/bin/ffmpeg`), copies FFmpeg stdout into a NetCord `OpusEncodeStream`, then awaits process exit and maps the exit code to a `TrackPlayResult` (`Completed`/`Failed`/`Skipped`/`NotInVoiceChannel`). There are no C# events in this pipeline; user-facing messages flow through `PlayRequest.Callbacks` and failures are retried by the background service.
+A play interaction enqueues a `PlayRequest` via `IGuildMusicService` into the guild's `MusicQueueService`; the channel signal wakes that guild's `GuildPlayer` loop, which calls `AudioPlayerService.PlayTrackAsync`. That method joins the voice channel if needed, resolves the stream URL (`YoutubeExplode` / `YoutubeDLSharp` via `yt-dlp` at runtime, or a radio source URL when the selection is a Guid), logs the play via `IStatisticsService` (radio plays are logged with the station name as the title), spawns FFmpeg through `FfmpegProcessService` (`Ffmpeg:Path` config, default `/usr/bin/ffmpeg`), copies FFmpeg stdout into a NetCord `OpusEncodeStream`, then awaits process exit and maps the exit code to a `TrackPlayResult` (`Completed`/`Failed`/`Skipped`/`NotInVoiceChannel`). There are no C# events in this pipeline; user-facing messages flow through `PlayRequest.Callbacks` and failures are retried by the guild's player loop.
 
 ### Native Dependencies (installed in the Docker image)
 

README.md

@@ -1,6 +1,6 @@
 # Discord Music Bot
 
-A .NET 10 Discord bot for music playback, supporting various audio sources and radio streams. Includes a React-based web dashboard.
+A .NET 10 Discord bot for music playback, supporting YouTube, SoundCloud, Spotify (playlist metadata), and radio streams. Supports multiple servers concurrently - each server gets its own queue, player, and voice connection. Includes a React-based web dashboard for statistics and radio-source management.
 
 **Note:** This application is designed to run on Linux via Docker. A Dockerfile and docker-compose setup are provided.
 
@@ -16,6 +16,21 @@ A .NET 10 Discord bot for music playback, supporting various audio sources and r
    docker-compose -f deployment/docker-compose.yml up --build
    ```
 
+## Development
+
+```bash
+# Build the whole solution (requires Bun for the frontend build)
+dotnet build discord-project.slnx
+
+# Run all tests (integration tests need a local Docker daemon for Testcontainers)
+dotnet test src/Tests/Tests.csproj
+
+# Unit tests only (no Docker required)
+dotnet test src/Tests/Tests.csproj --filter "FullyQualifiedName~Tests.Unit"
+```
+
+Tests run automatically in CI (`.github/workflows/ci.yml`) on pushes and pull requests to `master`; pushes to `master` are deployed via `.github/workflows/release.yml`.
+
 ## Technologies Used
 
 ### Backend
@@ -24,11 +39,13 @@ A .NET 10 Discord bot for music playback, supporting various audio sources and r
 - [Entity Framework Core](https://learn.microsoft.com/en-us/ef/core/) + [PostgreSQL](https://www.postgresql.org)
 - [YoutubeExplode](https://github.com/Tyrrrz/YoutubeExplode) / [YoutubeDLSharp](https://github.com/Bluegrams/YoutubeDLSharp) + [yt-dlp](https://github.com/yt-dlp/yt-dlp)
 - [SoundCloudExplode](https://github.com/jerry08/SoundCloudExplode)
-- [NAudio](https://github.com/naudio/NAudio) / [FFmpeg](https://ffmpeg.org) - audio processing
-- [libopus](https://opus-codec.org) / [libsodium](https://doc.libsodium.org) / [libdave](https://github.com/discord/libdave) - voice encryption and encoding
+- [Spotify Web API](https://developer.spotify.com/documentation/web-api) - playlist metadata
+- [FFmpeg](https://ffmpeg.org) - audio processing
+- [libopus](https://opus-codec.org) / [libsodium](https://doc.libsodium.org) / [libdave](https://github.com/discord/libdave) - voice encoding and encryption
+- [xUnit](https://xunit.net) + [NSubstitute](https://nsubstitute.github.io) + [Testcontainers](https://dotnet.testcontainers.org) - testing
 
 ### Frontend
 - [React 19](https://react.dev) with TypeScript
 - [TanStack Router](https://tanstack.com/router) / [TanStack Query](https://tanstack.com/query)
 - [Recharts](https://recharts.org)
-- [Vite](https://vite.dev) + [Bun](https://bun.sh)
+- [Vite](https://vite.dev) + [Bun](https://bun.sh)

src/Application/Interfaces/Services/IGuildMusicService.cs

@@ -0,0 +1,46 @@
+using Application.DTOs;
+
+namespace Application.Interfaces.Services;
+
+/// <summary>
+/// Guild-scoped facade over the per-guild music players. Commands and interactions
+/// address a specific guild's queue and playback through this interface; players are
+/// created lazily on the first enqueue for a guild.
+/// </summary>
+public interface IGuildMusicService
+{
+    void Enqueue<T>(ulong guildId, PlayRequest<T> request);
+
+    /// <summary>
+    /// The request currently being played in the guild, or null when the guild has no
+    /// player or nothing is playing.
+    /// </summary>
+    PlayRequest? GetNowPlaying(ulong guildId);
+
+    /// <summary>
+    /// Snapshot of the guild's queue: the currently playing request first (if any),
+    /// then pending ones. Empty when the guild has no player.
+    /// </summary>
+    PlayRequest[] GetAllRequests(ulong guildId);
+
+    /// <summary>
+    /// Number of pending requests in the guild (excludes the currently playing one).
+    /// </summary>
+    int GetQueueCount(ulong guildId);
+
+    /// <summary>
+    /// Re-queues the guild's currently playing request at the front so it plays again.
+    /// </summary>
+    void Rewind(ulong guildId);
+
+    /// <summary>
+    /// Cancels the guild's current track. No-op when the guild has no player.
+    /// </summary>
+    void Skip(ulong guildId);
+
+    /// <summary>
+    /// Clears the guild's queue and cancels its current track. No-op when the guild
+    /// has no player.
+    /// </summary>
+    void Stop(ulong guildId);
+}

src/Domain/Common/Constants.cs

@@ -17,8 +17,8 @@ public class EventType
 {
     public record Play : IEvent;
     public record PlayListPlay : IEvent;
-    public record Stop : IEvent;
-    public record Skip : IEvent;
+    public record Stop(ulong GuildId) : IEvent;
+    public record Skip(ulong GuildId) : IEvent;
 }
 
 public enum AudioSource

src/Infrastructure/Commands/AdminCommands.cs

@@ -17,13 +17,19 @@ namespace Infrastructure.Commands;
 public class AdminCommands(
     [FromKeyedServices(nameof(YoutubeService))]
     IStreamService youtubeService,
-    IMusicQueueService queue,
+    IGuildMusicService guildMusicService,
     IServiceProvider serviceProvider) : ApplicationCommandModule<ApplicationCommandContext>
 {
     [SubSlashCommand("blacklist", "Blacklist the currently playing song")]
     public async Task BlacklistAsync()
     {
-        var song = queue.NowPlaying;
+        if (Context.Guild is null)
+        {
+            await RespondAsync(InteractionCallback.Message("This command can only be used in a server."));
+            return;
+        }
+
+        var song = guildMusicService.GetNowPlaying(Context.Guild.Id);
         if (song is null)
         {
             await RespondAsync(InteractionCallback.Message(
@@ -61,7 +67,7 @@ await RespondAsync(InteractionCallback.Message(
 
         // Skip the blacklisted track; the player disconnects on its own when the queue is empty.
         var eventDispatcher = scope.ServiceProvider.GetRequiredService<IEventDispatcher>();
-        eventDispatcher.Dispatch(new EventType.Skip());
+        eventDispatcher.Dispatch(new EventType.Skip(Context.Guild.Id));
     }
 
     [SubSlashCommand("unblacklist", "Remove a song from the blacklist")]

src/Infrastructure/Commands/MusicActionCommands.cs

@@ -10,7 +10,7 @@
 
 namespace Infrastructure.Commands;
 
-public class MusicActionCommands(IScopeExecutor executor, IMusicQueueService queue)
+public class MusicActionCommands(IScopeExecutor executor, IGuildMusicService guildMusicService)
     : ApplicationCommandModule<ApplicationCommandContext>
 {
     [SlashCommand("stop", "Stop playing and clear the queue")]
@@ -21,7 +21,7 @@ public async Task Stop()
             return;
         }
 
-        DispatchEvent(new EventType.Stop());
+        DispatchEvent(new EventType.Stop(Context.Guild!.Id));
         var message =
             CommandUtils.CreateMessage<InteractionMessageProperties>("Stopping playback and clearing the queue.");
         await RespondAsync(InteractionCallback.Message(message));
@@ -35,7 +35,7 @@ public async Task Skip()
             return;
         }
 
-        DispatchEvent(new EventType.Skip());
+        DispatchEvent(new EventType.Skip(Context.Guild!.Id));
         var message = CommandUtils.CreateMessage<InteractionMessageProperties>("Skipping the current track.");
         await RespondAsync(InteractionCallback.Message(message));
     }
@@ -48,7 +48,7 @@ public async Task Playlist()
             return;
         }
 
-        var requests = queue.GetAllRequests();
+        var requests = guildMusicService.GetAllRequests(Context.Guild!.Id);
         if (requests.Length == 0)
             await RespondAsync(InteractionCallback.Message("No songs in queue."));
         else
@@ -87,14 +87,14 @@ public async Task Rewind()
         }
 
         InteractionMessageProperties message;
-        if(queue.NowPlaying is null)
+        if (guildMusicService.GetNowPlaying(Context.Guild!.Id) is null)
         {
             message = CommandUtils.CreateMessage<InteractionMessageProperties>("No songs in queue.");
             await RespondAsync(InteractionCallback.Message(message));
             return;
         }
 
-        queue.Rewind();
+        guildMusicService.Rewind(Context.Guild.Id);
         message = CommandUtils.CreateMessage<InteractionMessageProperties>("Rewinding the current track.");
         await RespondAsync(InteractionCallback.Message(message));
     }

src/Infrastructure/Interaction/NetCordInteraction.cs

@@ -13,7 +13,7 @@ namespace Infrastructure.Interaction;
 
 public class NetCordInteraction(
     ILogger<NetCordInteraction> logger,
-    IMusicQueueService queueService,
+    IGuildMusicService guildMusicService,
     IBlacklistService blacklistService,
     YoutubeClient youtubeClient,
     [FromKeyedServices(nameof(YoutubeService))] IStreamService youtubeService) : ComponentInteractionModule<StringMenuInteractionContext>
@@ -53,7 +53,7 @@ public async Task<string> Play()
             Context = Context,
             Callbacks = async callbackMessage => await RespondAsyncCallback(callbackMessage),
         };
-        queueService.Enqueue(playRequest);
+        guildMusicService.Enqueue(Context.Guild!.Id, playRequest);
 
         return message;
     }
@@ -91,7 +91,7 @@ public async Task<string> PlayPlaylist()
                 VideoTitle = video.Title,
                 VideoUrl = video.Url
             };
-            queueService.Enqueue(playRequest);
+            guildMusicService.Enqueue(Context.Guild!.Id, playRequest);
             added++;
         }