# Services — index

External-facing logic: YouTube API, persistence. See
[`schema.md`](../schema.md) for the memory-map conventions.

| File | Purpose |
|------|---------|
| `YouTubeAuthService.cs` | OAuth2 via Google: loopback callback (`http://localhost:8765/oauth2/callback`), token exchange, refresh, channel fetch. Constructor takes optional `HttpClient` + `sessionChanged` callback (test seam + save hook); session persists via `Helpers/TokenStore` (DPAPI); `ClearSession()` signs out (called by `MainViewModel.StopStream` on End Livestream) |
| `YouTubeStreamService.cs` | Broadcast/stream management via the v3 API (`enableAutoStart/Stop`). **Not yet switched to the `variable` reusable stream** |
| `YouTubeChatService.cs` | Polls `liveChat/messages`, raises `MessageReceived`; `IDisposable` |
| `LayoutStore.cs` | SQLite persistence (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; assets stored as BLOBs keyed by SHA-256 content hash; save/open layout files; schema `user_version` 4 (`Source.ClipShape`/`IsMirrored` via `ALTER TABLE` for pre-v2 DBs; v3 = singleton `Webcam` + per-scene `WebcamSceneConfig`, migrated idempotently **without backfill** — the stale `Source.DeviceId` column remains but is no longer read/written; v4 = `WebcamSceneConfig.RectWidth`/`RectHeight`, the pre-Round rect for the round-to-rect restore) |
| `VideoFrame.cs` | Normalized CPU frame seam (`Width`/`Height`/tightly-packed BGRA `byte[]`) — the only pixel type the rest of the app knows about; future capture sources (screen, background-removed webcam) feed the same seam |
| `CameraDeviceInfo.cs` | `(Id, DisplayName)` for a physical capture device |
| `ICameraEnumerator.cs` | `GetCamerasAsync()` — seam so the picker/`CameraManager` never touch WinRT (tests inject fakes) |
| `ICameraFrameSource.cs` | `StartAsync`/`StopAsync`/`FrameAvailable(VideoFrame)` — seam for a running capture source |
| `MediaCaptureCameraEnumerator.cs` | WinRT enumeration via `DeviceInformation.FindAllAsync(DeviceClass.VideoCapture)` |
| `MediaCaptureFrameSource.cs` | CPU-first MediaCapture source (`MemoryPreference = Cpu`, BGRA8 via `CreateFrameReaderAsync`); frames arrive on a worker thread |
| `CameraManager.cs` | Webcam capture ownership: refcounted by `DeviceId`, one shared `WriteableBitmap` per camera, dispatcher-coalesced ~render-rate UI updates (latest-frame drop); `PreviewBitmapChanged`/`CameraFailed` events. `ReleaseAsync` decrements a ref (stops at zero); `ReleaseAllAsync` force-drops every ref + stops the source (webcam swap / layout reload) |

Related: constructed in [`ViewModels/MainViewModel.cs`](../ViewModels/MainViewModel.cs)
(no DI container yet). Models in [`Models/index.md`](../Models/index.md).
OAuth credentials live in [`Helpers/OAuthCredentials.cs`](../Helpers/OAuthCredentials.cs).
