# TASK 43 — Native events & alerts (the "go" unit: chat parity + six animation alert box)

> Catalog: [`TASKS.md`](../TASKS.md). Status: ✅ **SHIPPED 2026-09-24** — creator said
> **"go"** on the combined work unit (native-chat parity + native alert box). See
> [`ai.md`](../ai.md) → "Native events & alerts" for the architecture.

## Provenance (recorded per the feature-provenance rule)

- **2026-09-23, the creator asked** — "Could you use native YouTube events instead of
  StreamElements?" (the app was designed to feed an external StreamElements alert box).
  Research (websearch + the liveChat/messages + streamList docs, URLs in the commit
  message) established the API facts below; the creator then ruled on product shape.
- **Decisions the creator made in conversation (asked ONCE, then held):**
  1. **No menus / no polls** — "I've asked you before to not use menus/polls." Decisions
     are asked on the open floor once and then executed.
  2. **Events = ONE animated alert box** (OBS alert-box pattern), a designated area on
     the canvas where celebration animations play. NOT a list pane, NOT per-source.
  3. **Six monetization events → SIX UNIQUE animations** — "not cookie-cutter": each of
     Super Chat, Super Sticker, New Member (newSponsor), Member Gift, Gift Received,
     Member Milestone gets its own distinct gesture, palette and layout. Each animation
     is a free branded product-placement ad in the stream (the brand line is drawn into
     every card) and a celebration of the supporter's investment.
  4. **Free subscribers: NO alert** — "subscriber mention in chat is sufficient."
     YouTube exposes no public event for free subs (API fact); a mention arrives as a
     normal chat row and is deliberately `ChatEventKind.None` → the alert engine never
     fires. The app keeps its opinion: none. (The third-party socket + delta-counter
     folklore was explicitly rejected with it.)
  5. **Viewer count: dropped entirely** — demotivating and weaponizable against the
     creator; not even hidden.
  6. **Native chat replaces the SE URI** — the chat box already exists in-app
     (`SourceType.ChatBox`, fed by real `liveChat/messages` polling). The remaining
     parity gaps closed here: the four previously-undecoded event types displayed as
     **empty rows** in the overlay, and the poll cadence was a hardcoded 2s instead of
     the server's `pollingIntervalMillis`.

## API facts (researched + cited in commit)

- Native event feed = the **same** `liveChat/messages` endpoint already polled.
  `streamList` is a *connection semantics* description of that endpoint, not a separate
  call: response carries `pollingIntervalMillis`; reconnect with `nextPageToken` on that
  cadence, never faster (YouTube rejects rapid polling). The code now re-arms the
  one-shot poll on the server's number (clamped 1000–6000ms), and `maxResults=2000`.
  Cite: https://developers.google.com/youtube/v3/live/docs/liveChatMessages/streamList
- Six `snippet.type` event kinds exist: `superChatEvent`, `superStickerEvent`,
  `newSponsorEvent`, `membershipGiftingEvent`, `giftMembershipReceivedEvent`,
  `memberMilestoneChatEvent`. Free subscriptions emit **nothing** — no API event, no
  delta, no count (the "newSponsorEvent counts" folklore is wrong for public subs).
- `videos.list → liveStreamingDetails.concurrentViewers` exists but was **vetoed** by
  the creator (decision 4 above).

## Product model (as shipped)

- **`SourceType.AlertBox`** ("Stream Alerts") — a one-per-layout celebration zone,
  mirroring the chat layer's gate (`CanAddAlerts` = no AlertBox exists in any scene;
  `AddSource` refuses a second). Defaults 620×430 → 680×200. Draggable, previews like a
  source, idle = fully transparent (nothing on stream until an event actually fires).
- **Playback:** events from the chat feed enqueue one-at-a-time on a 33ms UI
  dispatcher tick, play their own animation (4–5s each), then drain; back-to-back floods
  cap the queue at 10 and drop the tail, never stalling playback. The clock is exposed
  as `Advance(double)` so tests drive playback deterministically with no timer.
- **The six animations** (`Services/AlertRenderer.cs`), phases enter[0–0.16] /
  hold[0.16–0.8] / exit[0.8–1]:
  | Kind | Gesture | Palette |
  |---|---|---|
  | SuperChat | slide-up + gold amount count-up + shine sweep | green `#0d3b2b→#14532d` |
  | SuperSticker | scale-pop overshoot, tilted sticker chip, bob | purple `#4a044e→#7e22ce` |
  | NewMember | drop-in + white flash band + gold level chip | violet `#2e1065→#5b21b6` |
  | MemberGift | slide-left + gift-chip fan `×N` | amber `#422006→#a16207` |
  | GiftReceived | confetti burst scale-in | green→purple `#14532d→#4c1d95` |
  | MemberMilestone | rise-up + tenure growth bar | orange `#431407→#c2410c` |
- Every card draws **"made with LlamaCasty!"** bottom-right — each broadcast of an event
  is in-video product placement (creator decision: "it's a free ad each time").

## Chat parity (half 1 of the unit)

- `YouTubeChatService` rewritten around the real cadence + all six event parses:
  `ParsePage(string)` (internal static seam) → `ChatPage(Messages, NextPageToken,
  PollIntervalMs)`; fields landed on `ChatMessage`: `Kind` (`ChatEventKind`),
  `SuperChatDisplayString`, `SuperStickerDescription`, `GiftNewMembersCount`,
  `GifterName`, `MilestoneMonths` (best-effort `(\d+) months` regex from the milestone
  chat text). The four formerly-empty event types now parse as real rows AND drive
  animations. `InjectSimulatedMessage` (TASK 41) preserved.

## Test (Good Dog — ONE integration test per change)

`ytLive.Tests/AlertLayerTests.cs` (RealApp STA host, real WPF raster) — `AlertLayerTests`:
1. **Parse:** a mocked 7-item feed → all six kinds classified, `None` for plain chat,
   `pollingIntervalMillis`/`nextPageToken` honored, fields verified (incl. the
   formerly-empty `3 memberships` / `gifted you a membership` rows).
2. **Playback:** subscriber-mention (`None`) enqueues nothing; the six events play
   through the queue with non-null, non-blank, *moving* frames; every event's mid-hold
   frame is **pairwise distinct from every other** (six unique animations, pinned);
   playback drains to transparent/null.

## Files (declared scope)

- `Models/YouTube.cs` (ChatEventKind + fields), `Models/Source.cs` (SourceType.AlertBox
  + IsDraggable/Kind/DisplaySource)
- `Services/YouTubeChatService.cs` (cadence + six-event ParsePage seam)
- `Services/TestSessionViewModel.cs` (sims tagged: member→NewMember, superchat→SuperChat)
- **NEW** `Services/AlertRenderer.cs`, `Services/AlertOverlayLayer.cs`
- `ViewModels/MainViewModel.cs`, `ViewModels/MainViewModel.Chat.cs`,
  `ViewModels/MainViewModel.Sources.cs` (wiring: `_alertLayer`, render resolver,
  `CanAddAlerts`, menu name, shakedown `LoadLayout`, dispose)
- `Controls/LeftPanel.xaml` (Add → Stream Alerts menu item)
- **NEW** `ytLive.Tests/AlertLayerTests.cs`
- Docs: `ai.md`, `TASKS.md`, this file, `Services/index.md`, `ViewModels/index.md`,
  `Models/index.md`, `TASKS/task-03-capture-pipeline.md`, `HANDOFF.md`

## Gate

Clean build 0 warnings (Windows dotnet host); full suite **316/317** — the one failure
`LayerReorderPersistenceTests.RealMouseDrag…` repros on the CLEAN tree (proved via
`git stash`; it is a real-mouse-drag test that no-ops when a game/fullscreen window
steals the mouse — HANDOFF-documented environmental class). Scope check green.

## Open follow-ups (NOT this unit)

- TASK 3 item 17 (Alerts) is DONE via native events; **item 20 stays open** — the
  RewardEvent SQLite persistence + session-report rollup + `superChatEvents.list`
  backfill were scoped as the capture foundation and remain queued (the shipped alert
  path parses events directly into `ChatMessage`, which is what the report reads).
- TASK 3 item 16 (Text source) still open.
- Creator report still open: "I still cannot post a chat message in the TEST tab" —
  not yet diagnosed; the TEST drawer's Mock Chat Input posts via a real insert.