# CLAUDE.md - DeepDrftPublic.Client

Guidance for working in the DeepDrftPublic.Client project (the Blazor WebAssembly assembly).

See the root `CLAUDE.md` for full architecture overview. This file covers what is specific to this project.

## One-line purpose

All interactive UI for the site. Blazor WebAssembly. Pages, controls, the streaming audio player stack, theme/dark-mode plumbing, HTTP clients for both backends.

## Actual structure

- `Pages/`: Routable components. `Home.razor` (hero/about), `SessionDetail.razor` (session detail — hero-dominant overlay composition rendered via `<ReleaseHeroOverlay>`: large background hero image with darkening gradient shim, cover thumbnail + title + play button overlaid near the hero's bottom, genre/date/share overlaid at the top; uses `MudContainer MaxWidth="Large"`; **does not compose `ReleaseDetailScaffold`** — `PlayTrack` is wired directly in its own `@code` block; mounts `<WaveformVisualizer>` ambient engine + `<WaveformVisualizerControlPopover>` directly; renders `<ReleaseDescription>` below the hero for the release's description blurb), `MixDetail.razor` (mix detail — composes `ReleaseDetailScaffold` with `TopRightAction` lava-lamp `<WaveformVisualizerControlPopover>`; hero+meta rendered via `<ReleaseHeroOverlay Class="mix-hero">` in the scaffold's `Hero` slot with `ShowHeader="false"` suppressing the duplicate masthead; square ~600px cover-as-background with metadata overlaid; full-bleed `<WaveformVisualizer>` is the mode-A centerpiece mounted by the page directly; renders `<ReleaseDescription>` below the hero for the release's description blurb), `CutDetail.razor` (album detail — composes `ReleaseDetailScaffold` with the `Ambient` slot carrying `<WaveformVisualizer>` + `<WaveformVisualizerControlPopover>` for mode-B ambient layer; renders `<ReleaseDescription>` below the hero for the release's description blurb; each track row carries a per-track `<SharePopover EntryKey="@track.EntryKey" />` aligned far-right as the last flex child of `.cut-detail-track-row`), `FramePlayer.razor` (embeddable iframe player at `/FramePlayer`, uses `EmbedLayout`; two mutually-exclusive modes via query params: `TrackEntryKey` stages a single track as before; `ReleaseEntryKey` resolves the release's ordered tracks via `FramePlayerViewModel`, stages track 0 via `PlayerService.StageTrack`, and arms the queue via `Queue.Arm` — no JS interop in either path, so both run safely during prerender; the first play gesture in `AudioPlayerBar` routes through `Queue.Start()` which streams the current track and clears the armed state; release embeds expose queue skip-prev/next navigation in the player bar while single-track embeds show none; track-title links open in a new tab so the iframe keeps playing). **No demo pages** (`Counter.razor`, `Weather.razor` do not exist).
- `Layout/`: `MainLayout.razor` (root layout, wraps in `AudioPlayerProvider`, hosts theme switcher), `DeepDrftMenu.razor` (branded menu bar), `NavMenu.razor` (nav list), `Pages.cs` (centralised nav index — `MenuPages` for header, `AllPages` for exhaustive list).
- `Controls/`: Reusable components.
  - `TrackCard.razor`: Individual track display (image, name, artist, album, genre, release date). Play/pause icon controlled via `IsPaused` parameter.
  - `TracksGallery.razor`: Responsive grid of `TrackCard` items (MudBlazor `MudGrid` with breakpoints). Fully controlled by parent; derives active-track state from cascaded player service.
  - `AppNavLink.razor`: Nav link with active-page highlight.
  - `AudioPlayerProvider.razor`: Cascading host for `IStreamingPlayerService`. Everything inside it gets the player via `[CascadingParameter]`.
  - `StreamNowButton.razor`: Reusable streaming-trigger button. Fetches a random track, warms the AudioContext (Safari gesture requirement), and starts streaming via `IStreamingPlayerService`. Accepts `ButtonClass` and `ButtonLabel` for distinct visual presentations; `OnStreamStarted` EventCallback for post-stream side effects (e.g., mobile menu close).
  - `AudioPlayerBar.razor`: Dock UI at the bottom (play/pause/seek/volume).
  - `AudioPlayerBar/PlayerControls.razor`: Play/pause/stop buttons in the transport zone. Renders via `<PlayStateIcon>`. In embedded (`Fixed`) mode, skip-previous and skip-next render when `!Fixed || HasPrevious || HasNext` — so a release embed (which has a queue) shows forward/back navigation while a single-track embed (no queue) hides them; the Stop button is hidden in all embed contexts (`!Fixed` only).
  - `AudioPlayerBar/TrackMetaLabel.razor`: Now-playing track-title + artist row. Takes `[Parameter] bool Fixed` (passed from `AudioPlayerBar.razor`). When `Fixed` (embedded iframe), the track-title anchor renders with `target="_blank" rel="noopener noreferrer"` so clicking it opens the release detail page in a new tab; the docked (non-embedded) player keeps same-tab nav. When no release is attached the title renders unlinked in both modes.
  - `AudioPlayerBar/PlayStateIcon.razor`: Icon button encapsulating service subscription + transport-state icon selection. Injects `IPlayerService`, subscribes to `StateChanged`, calls `PlaybackIcons.Resolve()` to determine icon and active state.
  - `AudioPlayerBar/LevelMeterFab.razor`: Floating-action button replacing the static FAB in the minimized dock. Renders a continuous vertical fill inside the music-note silhouette that tracks live audio level (0–100%), with fixed three-zone gradient (green 0–60%, yellow 60–85%, orange 85–100%). Note silhouette always visible at 25% opacity; idle when paused/stopped. Reuses spectrum-callback infrastructure.
  - `SpectrumVisualizer.razor`: Bar-graph spectrum display, driven by `getSpectrumData` JS callback.
  - `ReleaseHeroOverlay.razor`: Shared presentational overlay shell consumed by both `SessionDetail` and `MixDetail`. Renders a background-image hero region with genre/date/share overlaid at the top and title/artist/play at the bottom. Parameters: `HeroImageKey`, `PlaceholderIcon`, `CoverThumbKey` (optional cover thumb in bottom row), `Title`, `Artist`, `Genre`, `ReleaseDate`, `ShareContent` (slot), `PlayContent` (slot), `Class` (per-page aspect/sizing override). Owns no player logic or data fetch; each consuming page passes its own play and share slots. Overlay shell is plain `<div>`s; background-image surface is a `<div class="release-hero-img">` (no `MudPaper`).
  - `ReleaseDescription.razor`: Shared presentational blurb block for release detail pages. Renders a header row (mono uppercase eyebrow label "Notes" in `.deepdrft-release-description-label` + thin horizontal divider in `.deepdrft-release-description-rule`, inside `.deepdrft-release-description-header`) above the release's short `Description` paragraph (`.deepdrft-release-description-text`, display-serif weight 300), all wrapped in `.deepdrft-release-description`, placed just below the hero/header. The header row mirrors the home page's `.section-label`/`.divider-line` motif. Purely presentational — owns no data fetch or player wiring. A null/whitespace `Description` renders nothing at all (no block, no divider, no whitespace artifact; the guard lives here so every consumer gets it for free). Parameter: `Description` (`string?`).
  - `WaveformVisualizer.razor`: The single WebGL2 lava-lamp visualizer engine. Hosts the waveform of whatever track is currently playing/selected. Three hosting modes: mode A (Mix detail — full-bleed centerpiece), mode B (Cut/Session detail — ambient layer behind hero+content via `ReleaseDetailScaffold`'s `Ambient` slot), mode C (NowPlaying hero panel — full-bleed background for the home hero's right side, mounted by `NowPlaying.razor` inside `.np-visualizer-bg`). `[Parameter] bool Fill` switches from fixed-viewport positioning to container-relative sizing (CSS-only; the renderer is identical in both modes). The bridge resolves the current track's `EntryKey` and re-fetches the high-res datum on track change. Subscribes to `WaveformVisualizerControlState.Changed` and pushes each updated dial to the WebGL module via JS interop. Follows the live playing track (keys on host `TrackId` match OR shared host `ReleaseEntryKey`).
  - `WaveformVisualizerControls.razor`: The waveform visualizer control panel (content hosted by `WaveformVisualizerControlPopover`). Phase 15 re-layout: a deterministic **three-row sectioned layout** encoding the visualizer's two subsystems. Row 1 (MODE, always visible): two iconographic lamp toggles (lava on/off, waveform on/off) left-aligned + collisions knob (conditional — only when both subsystems on) + color knob pinned far-right. Row 2 (LAVA, visible only when `LavaEnabled`): "LAVA:" section label + Gravity / Heat / FluidAmount / FluidViscosity knobs. Row 3 (WAVE, visible only when `WaveformEnabled`): "WAVE:" section label + scroll-speed `MudSlider` (not a knob) + width knob pinned far-right. Total: two lamp toggles, seven `RadialKnob`s, one `MudSlider`. Colour principle: lamp toggles / knob arcs / slider are green (`Color.Primary` — interactive); section labels / knob caption icons are light (static). Each control has a playful `MudTooltip`. `[Parameter] bool PanelChrome` scopes panel chrome (NowPlayingCard look — square corners, lighter-navy, thin border) to the popover mount; chrome classes live in the global `deepdrft-styles.css` (CSS isolation cannot reach portaled overlay content). `[Parameter] bool Visible` gates the rows via `@if` while the container holds reserved min-height. Owns no JS interop: mutates the injected `WaveformVisualizerControlState` and raises `Changed`. No control is a seek surface (read-only contract).
  - `WaveformVisualizerControlPopover.razor`: Pairs the lava-lamp icon button with `WaveformVisualizerControls` as a **screen-centered tinted modal** (Phase 15). The primitive is `MudOverlay` (`DarkBackground="true"`, `Modal="true"`) — **not** `MudPopover`; `AnchorOrigin`/`TransformOrigin` parameters do not exist (a centered modal has no anchor). Clicking the lava-lamp icon opens the overlay; clicking the scrim closes it (knob-drag-safe: `RadialKnob`'s `position:fixed` capture div sits above the scrim during a drag, so releasing outside the panel never fires the close handler). The panel stops click propagation so an inside click is not a dismissal. `[Parameter] Size IconSize` controls the trigger-icon size (default `Large`). This is the unit every host places — one icon anywhere gives the full control panel centered on screen, regardless of where the icon sits. Placed identically on Mix, Cut, Session, and the NowPlaying hero panel (full parity; in NowPlaying it sits in `.np-visualizer-controls` at the panel's top-right corner, not inside `NowPlayingCard`).
  - `WaveformZoomMapping.cs`: Maps the `WaveformVisualizerControlState.Resolution` fraction to an integer zoom level for the WebGL renderer.
  - `NowPlayingCard.razor`: Home-page text panel showing the currently playing track (label, title, sub-line). Renders label/"Now Playing" dot, track name, and artist·release sub-line from the cascaded `IStreamingPlayerService`. Subscribes to `IPlayerService.StateChanged` in `OnParametersSet` (reference-guarded, idempotent) and unsubscribes on dispose to re-render on track/state change. No visualizer or popover; those moved to `NowPlaying.razor`.
  - `NowPlayingStats.razor`: Home hero stat row. Three cards: Studio Cuts (total Cut-medium track count + zero-suppressed per-`ReleaseType` Cut release breakdown), Mixes (`MixReleaseCount` labelled "Sets" + `hh:mm` total mix runtime via `RuntimeFormat`), and Plays (static "XXX / Plays (Coming Soon)" odometer placeholder). Fetches `HomeStatsDto` via `IStatsDataService` on init; bridges the prerender fetch across the WASM seam with `PersistentComponentState` (persists only on a successful load, matching the medium-browse bridge pattern). Implements `IDisposable` to release the `PersistingComponentStateSubscription`.
  - `NowPlaying.razor`: Owns the home hero's right-side panel (`.now-playing-panel` — the outer wrapper formerly called `.hero-right` in `Home.razor`). Mounts `<WaveformVisualizer Fill="true">` as a full-bleed background inside `.np-visualizer-bg`, `<WaveformVisualizerControlPopover>` in `.np-visualizer-controls` (top-right corner), the three pulsing `.circle-deco` rings, and the content layer (hosts `<NowPlayingCard>` + `<NowPlayingStats>`). `Home.razor`'s `MudItem` renders `<NowPlaying />` directly with no wrapper. Subscribes to `IPlayerService.StateChanged` in `OnParametersSet` (reference-guarded, idempotent) and unsubscribes on dispose — needed because the player cascade is `IsFixed` (the provider's own re-render does not reach `NowPlaying`), so the subscription is the only way to re-render and re-propagate `ReleaseEntryKey`/`TrackId`/`TrackEntryKey` into `<WaveformVisualizer>` when the playing track changes.
  - `ReleaseDetailScaffold.razor`: Shared scaffold for release detail pages. Gained an optional `Ambient` `RenderFragment` slot (Phase 12) — a full-bleed layer rendered behind the main content. Absent slot = no regression. Cut mounts `<WaveformVisualizer>` + `<WaveformVisualizerControlPopover>` here; Mix uses its own full-bleed mount outside the scaffold.
  - `SharePopover.razor`: Share affordance serving both track and release surfaces from one clipboard/popover-chrome source. **Track mode** (`EntryKey` set): copies the track's canonical URL and offers an iframe embed snippet pointing at `FramePlayer?TrackEntryKey=…`. **Release mode** (`ReleaseEntryKey` + `ReleaseMedium` set): copies the release's canonical detail URL (via `ReleaseRoutes.DetailHref`) and offers an iframe embed snippet pointing at `FramePlayer?ReleaseEntryKey=…`, which queues and auto-advances through the release's tracks on first play. Both modes offer the embed affordance — release mode no longer suppresses it. The iframe snippet is built by `EmbedSnippetBuilder`. A transient "Copied!" confirmation resets after a short delay.
- `Helpers/`: Utilities and mapper functions.
  - `PlaybackIcons.cs`: Static `Resolve(isPlaying, isPaused, trackId, currentTrackId)` method — the sole glyph-mapping source for transport icons across all surfaces. Returns `(Icon, IsActive, IsPaused)` tuple.
  - `RuntimeFormat.cs`: Static `ToHoursMinutes(double totalSeconds)` helper. Formats a seconds value as `h:mm` (hours not zero-padded, minutes always two digits). Negative / non-finite inputs return `"0:00"`. Used by `NowPlayingStats` for the mix runtime figure.
  - `EmbedSnippetBuilder.cs`: Static helper that builds the iframe embed snippet the share popover copies. `ForTrack(baseUri, trackEntryKey)` → `<iframe src="…FramePlayer?TrackEntryKey=…">` and `ForRelease(baseUri, releaseEntryKey)` → `<iframe src="…FramePlayer?ReleaseEntryKey=…">`. iframe chrome (dimensions, border-radius, autoplay permission) is identical across both targets and defined once here.
- `Services/`: Audio player + dark-mode services.
  - `IPlayerService` / `IStreamingPlayerService`: Contracts exposed to UI.
  - `AudioPlayerService`: Abstract base (lifecycle, initialise, select track, play/pause/stop/seek/volume).
  - `StreamingAudioPlayerService`: Production implementation. Chunked stream from `TrackMediaClient`, adaptive 16–64 KB buffer, early-playback, **seek-beyond-buffer** via offset request to the content API.
  - `AudioInteropService`: JS interop wrapper over `window.DeepDrftAudio`. Manages `DotNetObjectReference` lifetimes for progress, end-of-playback, spectrum callbacks.
  - Dark-mode services: `DarkModeServiceBase` (cookie name constant), `DarkModeCookieService` (JS cookie read/write).
  - `WaveformVisualizerControlState`: Scoped session-persistent holder for the visualizer's **eight** continuous control positions plus **two subsystem on/off toggles** (Phase 15): `ScrollSpeed`, `GradientRotationSpeed`, `LavaGravity`, `LavaHeat`, `FluidAmount` (wax count/volume), `FluidViscosity` (cohesion — the second half of the Phase 10 "bubbles" split; `BlobDensity` is gone), `CollisionStrength`, `WaveformWidth`, `LavaEnabled` (bool, default `true`), `WaveformEnabled` (bool, default `true`). Each has a matching `Default*` const. `Changed` event is the decoupling seam — controls mutate state + raise `Changed`; the bridge (`WaveformVisualizer`) subscribes and pushes the affected uniform or subsystem-enable. Scoped DI so state survives SPA nav within a session and resets on fresh page load.
  - `PlayTracker`: Per-session play-session tracker (Phase 16 wave 16.1). Opens on playback start, advances a high-water position on each progress tick (from `StreamingAudioPlayerService` — not the HTTP layer, so seek-beyond-buffer re-fetches are the same play), closes on track-switch / stop / organic-end / page-unload. Engagement floor: ≥3 s OR ≥5% of duration. Three-bucket classification (`partial`/`sampled`/`complete`). Emits at most one event per session via `IPlayEventSink`. No player or JS dependency — testable against a fake sink.
  - `ShareTracker`: Per-session share tracker (Phase 16 wave 16.1). Called by `SharePopover` after a successful clipboard write; applies a 60-second per-(target, channel) debounce. Sends via `BeaconInterop`. Scoped so debounce memory resets on fresh page load.
  - `BeaconInterop`: `navigator.sendBeacon` JS interop wrapper (Phase 16 wave 16.1). Fires JSON payloads to `api/event/{play,share}` fire-and-forget. Also wires a page-unload handler that flushes any pending play event when the page is torn down.
  - `IQueueService` / `QueueService`: Ordered playback orchestrator above the single-slot player. `PlayRelease(tracks, startIndex)` replaces the queue and starts streaming; `Next`/`Previous` advance or step back; `Enqueue`/`EnqueueRange` append without interrupting the current track; `Clear` empties the queue. **Armed-idle state** added to support prerender-safe release embeds: `Arm(tracks)` loads the track list at index 0 with no JS interop (safe during prerender); `IsArmed` signals the armed-but-not-streaming state; `Start()` begins streaming the current track and clears `IsArmed`, leaving the list and position intact so auto-advance carries on. `AudioPlayerBar` reads `IsArmed` to route the first play gesture through `Start()` instead of streaming the staged track alone. `QueueChanged` event fires on all list/position changes; cascaded via `AudioPlayerProvider`.
- `Clients/`: HTTP API clients (both target DeepDrftAPI).
  - `TrackClient`: SQL metadata API. Uses named `IHttpClientFactory` client `"DeepDrft.API"`. Sends `page` param (not `pageNumber`). Deserializes response as bare `PagedResult<TrackDto>` (not wrapped in ApiResultDto envelope).
  - `TrackMediaClient`: Content API. Uses named `IHttpClientFactory` client `"DeepDrft.Content"`. Methods like `GetAudioStreamAsync(trackId, byteOffset?)` → `Stream` with optional Range header support for seek-beyond-buffer.
  - `StatsClient`: Home stats API. Uses named `IHttpClientFactory` client `"DeepDrft.API"`. Single method `GetHomeStats()` → `ApiResult<HomeStatsDto>` (calls `GET api/stats/home`; response is a bare DTO, no `ApiResultDto` envelope). Registered scoped; consumed via `IStatsDataService`.
- `Services/ITrackDataService`: Contract used by the visualizer bridge and other consumers. Includes `GetTrackWaveform(entryKey)` → high-res `WaveformProfileDto` (calls `GET api/track/{entryKey}/waveform/high-res`); used by `WaveformVisualizer` to re-fetch the datum on track change.
- `Services/IStatsDataService` / `StatsClientDataService`: Home-stats read abstraction. `IStatsDataService.GetHomeStats()` → `ApiResult<HomeStatsDto>`. `StatsClientDataService` is the single implementation (delegates to `StatsClient`); registered scoped. Components inject `IStatsDataService` so they do not branch on render mode — mirrors `IReleaseDataService`.
- `ViewModels/`: Component state.
  - `TracksViewModel`: Scoped. Holds current page, page size, sort column, descending flag. `SetPage(pageNumber)` calls `TrackClient.GetPageAsync` and updates. Registered in `Startup.ConfigureDomainServices`.
  - `TrackDetailViewModel`: Scoped. Holds loaded track, loading flag, not-found flag. `Load(entryKey)` fetches via `ITrackDataService` and resets all flags per call (prevents cross-navigation bleed). Registered in `Startup.ConfigureDomainServices`.
  - `FramePlayerViewModel`: Scoped. Resolves the ordered track list for a release embed (`FramePlayer?ReleaseEntryKey=…`). `Load(releaseEntryKey)` calls `IReleaseDataService.GetByEntryKey` → `release.Id` → `ITrackDataService.GetPage(sortColumn:"TrackNumber", releaseId:…)`, mirroring `CutDetailViewModel.Load` exactly so an embedded release queues the same ordered list the Cut detail page plays. Owns no playback or staging — `FramePlayer.razor` uses the loaded `Tracks` to stage and arm. Registered scoped in `Startup.ConfigureDomainServices`.
- `Common/`: Shared utilities.
  - `DarkModeSettings.cs`: `[PersistentState]`-annotated class (single source of truth for dark mode in the client). Registered scoped.
  - `ReleaseRoutes.cs`: Static helper. `DetailHref(long id, ReleaseMedium)` returns the canonical public detail route for a release; consumed by Archive, AlbumsView, player bar, and TrackRedirect (11.B).
- `Program.cs`: WASM entry point. Calls `Startup.ConfigureApiHttpClient`, `ConfigureContentServices`, `ConfigureDomainServices`.
- `_Imports.razor`: Global using statements and component imports.

## Two HTTP clients pattern

Both clients are configured in `Startup.cs` (static methods called from **both** server and WASM `Program.cs`):

- `TrackClient` uses `"DeepDrft.API"` (base address from `appsettings.json` `ApiUrls:SqlApi`, points to DeepDrftAPI). Fetches paginated metadata.
- `TrackMediaClient` uses `"DeepDrft.Content"` (base address from `appsettings.json` `ApiUrls:ContentApi`, points to DeepDrftAPI). Streams audio bytes, optionally with offset.

Both are configured with JSON serializer settings (case-insensitive property matching). The dual-client pattern keeps concerns separated: one for structured data, one for binary streaming. Both target DeepDrftAPI (they may share the same host URL in production).

## Audio player stack (deepest part of the codebase)

### Contracts
- `IPlayerService`: Initialize, SelectTrack, Play, Pause, Stop, Seek, SetVolume. Sync interface. Owns `EventCallback? OnStateChanged` (single, provider-owned) and `event Action? StateChanged` (multicast, for cascade consumers).
- `IStreamingPlayerService`: Extends above. SelectTrackStreaming(track) starts the chunked stream flow.

### Implementation
- `AudioPlayerService` (abstract base): Lifecycle. Stores current track, playback state, volume. `SelectTrack` throws `NotSupportedException` (buffered path is dead); derived classes override `SelectTrackStreaming`.
- `StreamingAudioPlayerService` (production): Constructor takes `TrackMediaClient`, `AudioInteropService`, logger. `SelectTrackStreaming`:
  1. Calls `TrackMediaClient.GetAudioStreamAsync(trackId)`, which returns a response object including `ContentType` (e.g., `audio/wav`, `audio/mpeg`, `audio/flac`).
  2. `StreamingAudioPlayerService.StreamAudioAsync` reads chunks (16–64 KB adaptive), pushes each via `AudioInteropService.ProcessStreamingChunkAsync(contentType, chunk)` (JS interop call with format hint).
  3. TypeScript `StreamDecoder` is format-agnostic; delegates format-specific header parsing and chunked decoding to the appropriate `IFormatDecoder` implementation (e.g., `WavFormatDecoder` for WAV, TBD MP3/FLAC decoders for other formats). Decoder parses header (first chunk), decodes subsequent chunks to `AudioBuffer`s.
  4. `PlaybackScheduler` schedules buffers on Web Audio `AudioContext`.
  5. Playback starts as soon as a configurable min buffer count is queued.
  6. **Seek beyond buffer**: if seek target is past the decoded range, `Seek(position)` calls `TrackMediaClient.GetAudioStreamAsync(trackId, byteOffset)` with a file-absolute byte offset. Client sends `Range: bytes={offset}-`; server responds 206 with raw bytes (same format as original file); decoder retains the parsed header and feeds the continuation directly into the decode pipeline.

### Interop bridge
- `AudioInteropService.CreatePlayerAsync` polls `DeepDrftAudio.isReady()` before proceeding; `index.ts` sets `ready = true` after attaching the API to `window`. This guards against slow WASM boot / cache misses.
- `AudioInteropService.ProcessStreamingChunkAsync(contentType, chunk)` calls JS `window.DeepDrftAudio.processStreamingChunk(contentType, chunk)` and awaits the Promise. The `contentType` parameter is passed through to the format-decoder factory.
- `AudioInteropService` also manages callback registrations for progress (fired by `PlaybackScheduler`), end-of-playback (fired by `PlaybackScheduler`), and spectrum data (fired by `SpectrumAnalyzer`). Each callback is a `DotNetObjectReference` to a delegate.

### Format decoders (TypeScript)
New modules in `DeepDrftPublic/Interop/audio/`:

- `IFormatDecoder.ts`: Interface. Defines contract for format-specific decoders: `parseHeader(chunk, offset)` → header metadata; `decodeChunk(chunk, offset)` → `AudioBuffer`; `getAlignedSegmentSize(chunk, offset, rawData?)` → frame-aligned segment boundary (optional `rawData` parameter for format-specific frame-boundary scanning).
- `WavFormatDecoder.ts`: Concrete WAV implementation (active). Parses RIFF/WAVE structure, fmt and data chunks. All WAV-specific byte-parsing logic lives here. Exported as the default WAV decoder.
- `Mp3FormatDecoder.ts`: Concrete MP3 implementation (implemented, not yet wired). Implements `IFormatDecoder` for MP3: ID3v2 skip, MPEG Layer III frame-sync + header decode (MPEG1/2/2.5), Xing/Info/VBRI VBR-header detection (frame count + 100-entry TOC for seek), CBR frame-aligned segment sizing, VBR TOC-interpolation seek (`calculateByteOffset`), zero-copy `wrapSegment` (raw MP3 frames are self-contained). CBR sub-frame tail guard prevents over-read.
- `FlacFormatDecoder.ts`: Concrete FLAC implementation (implemented, not yet wired). Implements `IFormatDecoder` for FLAC: scans all metadata blocks (STREAMINFO mandatory, SEEKTABLE optional), extracts 20-bit sample rate / 3-bit channels / 5-bit bitsPerSample / 36-bit total-samples from bit-packed STREAMINFO, builds 38-byte synthetic STREAMINFO block for per-segment wrapping, binary-search SEEKTABLE for seek. `wrapSegment` prepends `fLaC + STREAMINFO` to each audio segment so `decodeAudioData` sees a valid FLAC stream. `getAlignedSegmentSize` scans backward through peek bytes for the `0xFF/(0xF8|0xF9)` FLAC frame sync so each segment ends on a real frame boundary.

`StreamDecoder.ts` remains the orchestrator — it accepts the first chunk, selects the right format decoder via factory (based on `contentType`), peeks candidate bytes before calling `getAlignedSegmentSize` (non-destructive read), passes them as `rawData`, and uses zero-copy `subarray` for the actual segment. It delegates all format-specific work to the decoder and chains subsequent chunks through the same decoder instance. `Mp3FormatDecoder` and `FlacFormatDecoder` are implemented modules but not yet wired into `AudioPlayer.createFormatDecoder` factory (Wave 3 pending).

### Component integration
- `AudioPlayerProvider.razor` is the cascading host. It injects `IStreamingPlayerService` (resolved to `StreamingAudioPlayerService` in DI), stores it in a cascade with `IsFixed="true"`, and keeps it alive across navigation.
- `AudioPlayerBar.razor` is the dock UI. It cascades the player, binds buttons to `Play()` / `Pause()` / `Seek()` / `SetVolume()`, and displays current time / duration / progress bar. Minimize-state mutations (`Expand`, `ToggleMinimized`, `Close`) all route through a private `SetMinimized(bool value)` mutator, which guards no-ops, fires the `OnMinimized` callback, and calls `StateHasChanged()`. Subscribes to `IPlayerService.StateChanged` in `OnParametersSet` (reference-guarded, idempotent) and unsubscribes on dispose to re-render itself when the cascade updates.
- `SpectrumVisualizer.razor` calls `AudioInteropService.GetSpectrumData()` on a timer, receives bar heights, renders via MudBlazor `MudChart` or custom canvas.
- `TracksView.razor` injects `TracksViewModel` + cascaded `IStreamingPlayerService`. `PlayTrack(track)` calls `PlayerService.SelectTrackStreaming(track)`. Subscribes to `IPlayerService.StateChanged` in `OnParametersSet` and calls `StateHasChanged()` unconditionally on any state change, ensuring the gallery correctly reflects play/pause/track-change transitions. Active-track state is derived from `PlayerService.CurrentTrack` and `PlayerService.IsPlaying` (no local `_selectedTrack` field).

## Dark-mode plumbing

- `DarkModeSettings` (`Common/`): `[PersistentState]`-annotated class with `IsDarkMode` property. Registered scoped in `Startup.ConfigureDomainServices`. Single source of truth in the client.
- `DarkModeServiceBase`: Holds the cookie name constant (`"darkMode"`).
- `DarkModeCookieService`: Reads/writes the cookie via JS (`document.cookie` interop). Calls `DarkModeSettings.IsDarkMode = value` when the cookie changes or user toggles the button.
- Server-side `DarkModeService` (in `DeepDrftPublic`, **not here**): Reads the cookie during prerender, seeds the `DarkModeSettings` instance, rounds it through `PersistentComponentState` to the client.
- `MainLayout.razor`: Wraps entire layout in `CascadingValue` of `DarkModeSettings`, so all children see the current dark-mode state. The dark-mode toggle button (hand-rolled lit/unlit gas-lamp icon from `DeepDrftShared.Client/Common/DDIcons.cs`) calls `DarkModeCookieService.ToggleDarkModeAsync()`.

The flow ensures the first paint uses the correct theme (no flash), and toggling the button persists the setting to a 365-day cookie.

## MVVM convention

Component state lives in ViewModels (registered scoped in DI). Components render and dispatch only.

- `TracksViewModel`: Holds page number, page size, sort column, descending flag. `SetPage(pageNumber)` is the command. `TracksView.razor` injects it and calls `SetPage`.
- New VMs go in `ViewModels/` and register in `Startup.ConfigureDomainServices`.

## Theming convention

- Bespoke `PaletteLight` / `PaletteDark` defined inline in `MainLayout.razor` (MudBlazor theme objects).
- CSS classes prefixed `deepdrft-` live in `DeepDrftPublic/wwwroot/styles/deepdrft-styles.css` (shared across server and client).
- Custom SVG icons: `DeepDrftShared.Client/Common/DDIcons.cs` (hand-rolled gas-lamp, lava-lamp, etc. — shared across public and CMS surfaces).

## Development commands

```bash
# The client runs as part of the DeepDrftPublic host:
dotnet run --project DeepDrftPublic

# Watch during development (rebuilds WASM as you change .cs/.razor/.ts files):
dotnet watch run --project DeepDrftPublic

# Build just the client (for verification):
dotnet build DeepDrftPublic.Client

# Run client-specific tests (if any; currently none exist):
dotnet test DeepDrftTests/
```

## Configuration

- `Program.cs`: Entry point. Calls `Startup.ConfigureApiHttpClient` (registers named clients), `ConfigureContentServices` (same), `ConfigureDomainServices` (registers services like `TracksViewModel`, `DarkModeSettings`, `AudioPlayerService`).
- Both `Startup` methods are static and called from **both** the server `DeepDrftPublic/Program.cs` and the client `Program.cs`, ensuring prerender and runtime DI are identical.
- No `appsettings.json` in the WASM assembly — config comes from the server `appsettings.json` via HTTP or is hardcoded.

## Important patterns

- **Cascading parameters**: `AudioPlayerProvider` cascades `IStreamingPlayerService`. All children (including `MainLayout` and pages) access it via `[CascadingParameter] IStreamingPlayerService Player { get; set; }`.
- **Result types**: Clients return `ApiResult<T>` from NetBlocks. UI checks `Success` before using `Value`.
- **Async/await**: All operations are async.
- **Stream consumption**: `TrackMediaClient.GetAudioStreamAsync` returns a `Stream` (not fully buffered). `StreamingAudioPlayerService` reads it in chunks to avoid memory pressure on large files.
- **Detail pages under InteractiveAuto must load in `OnParametersSetAsync`, not `OnInitializedAsync`**: Blazor reuses a scoped component instance across same-template navigations (e.g. `/mixes/5` → `/mixes/8`), firing `OnParametersSet`/`OnParametersSetAsync` rather than re-running `OnInitialized`. If load logic is in `OnInitialized` only, the ViewModel retains the prior track and Play will stream the wrong item. Capture the route parameter (id/key) synchronously at the top of `OnParametersSetAsync` before any await — after an await the route state may have advanced. Guard `PersistentComponentState` restores on id/key equality to prevent cross-item bleed when the prerender and WASM-boot passes disagree on which item is current.

When working with this project, maintain the separation between presentation (Razor components) and logic (ViewModels/Clients), follow the established audio player architecture, and respect the dark-mode round-trip (cookie → DarkModeSettings → PersistentComponentState → client).