spa/.planning/phase-2-live-map/09-connection-status.md

# Task 2.9 — Connection status + per-device last-seen indicators

**Phase:** 2 — Live monitoring map
**Status:** ⬜ Not started
**Depends on:** 2.4.
**Wiki refs:** `docs/wiki/concepts/maps-architecture.md` §"Visible system state".

## Goal

Show operators _just enough_ about system state so they can answer two questions at a glance:

1. "Is the SPA still connected to live data?" — global WS status.
2. "Is this specific device still reporting?" — per-device last-seen age.

Not noisy. Subtle UI; not banners and modal warnings. The design ethos: operators trust the map until something goes wrong, at which point they need a quick read of _what_ went wrong without a wall of red.

## Deliverables

- **`src/ui/components/connection-chip.tsx`** — `<ConnectionChip />` rendered in the monitor route's chrome (top-right corner of the map UI, near the basemap switcher). Reads `useConnectionStore`. Three visible states:
  - **Connected** — small green dot, hidden text (or "Live" only on hover/expand). Subtle.
  - **Reconnecting** — amber dot pulsing, text "Reconnecting…" with attempt count if useful.
  - **Disconnected / offline** — red dot, text "Offline — last live: 14:02:11" showing the last successful contact time.
- **`src/ui/components/device-last-seen.tsx`** — `<DeviceLastSeen deviceId>` component. Renders nothing in normal state; renders a small subscript / icon when the device's last position is older than threshold (default: 60s).
  - Used inside `<MapPositions>`'s feature properties (or as a separate symbol layer keyed off the `lastSeenAge` derived field), and in any future per-device sidebar.
- **`src/live/connection-store.ts`** updated — adds `lastConnectedAt: number | null` (already in 2.4's spec) and `lastDisconnectedAt: number | null`. Toast / chip use these for "last live: N min ago" formatting.
- **`src/live/last-seen.ts`** — utility: `formatLastSeen(ts: number, now = Date.now()): string` returns `"now"` / `"5s ago"` / `"2m ago"` / `"14:02"` based on age. Used by both the chip and the per-device indicator.
- **A "stale-position" derived signal** — at coalescer flush time, the position store can compute `staleByDevice: Set<string>` for devices whose last update is older than `STALE_THRESHOLD_MS` (default 60s). Map layers reading this Set apply a faded-icon variant. Or: a separate symbol layer renders a "warning" badge over stale devices' markers.

## Specification

### `<ConnectionChip />`

```tsx
export function ConnectionChip() {
  const status = useConnectionStore((s) => s.status);
  const lastConnectedAt = useConnectionStore((s) => s.lastConnectedAt);

  if (status === 'connected') {
    return (
      <div className="flex items-center gap-1.5 text-xs">
        <span className="w-2 h-2 rounded-full bg-green-500" aria-hidden />
        <span className="text-muted-foreground">Live</span>
      </div>
    );
  }

  if (status === 'connecting' || status === 'reconnecting') {
    return (
      <div className="flex items-center gap-1.5 text-xs">
        <span className="w-2 h-2 rounded-full bg-amber-500 animate-pulse" aria-hidden />
        <span className="text-muted-foreground">
          {status === 'connecting' ? 'Connecting…' : 'Reconnecting…'}
        </span>
      </div>
    );
  }

  return (
    <div className="flex items-center gap-1.5 text-xs">
      <span className="w-2 h-2 rounded-full bg-destructive" aria-hidden />
      <span className="text-destructive">
        Offline {lastConnectedAt ? `· last live ${formatLastSeen(lastConnectedAt)}` : ''}
      </span>
    </div>
  );
}
```

Position: top-right of the monitor route, in a small horizontal bar with the basemap switcher and other controls. Inline-flex.

### Per-device last-seen — two strategies

**Strategy A: Faded marker.** A separate symbol layer with a `'icon-opacity'` expression based on a `staleSec` property on each feature:

```ts
'icon-opacity': [
  'interpolate', ['linear'], ['get', 'staleSec'],
  0, 1.0,      // fresh
  60, 1.0,     // 60s — full opacity
  300, 0.4,    // 5min — faded
  1800, 0.2,   // 30min — very faded
],
```

The position store includes `staleSec` in each feature's properties at coalescer-flush time.

**Strategy B: Badge / overlay.** A second symbol layer drawing a small "no-signal" icon over stale markers, filtered to `['>=', ['get', 'staleSec'], 60]`.

**Pick A for v1.** Simpler, fewer layers, cleaner visually. B can layer on top later if A isn't legible enough.

### Updating `staleSec`

Recomputed every second by a setInterval inside the position store (not on every position update — that would invalidate `latestByDevice` constantly):

```ts
// In src/live/position-store.ts
let staleTickerId: ReturnType<typeof setInterval> | null = null;

function startStaleTicker() {
  if (staleTickerId) return;
  staleTickerId = setInterval(() => {
    const now = Date.now();
    set((state) => {
      // Only bump versionTick if any device's stale-bucket changed.
      // ... or just trigger subscribers wholesale every second.
      return { stalenessTick: now };
    });
  }, 1000);
}
```

Map layers re-derive `staleSec` from `latestByDevice` + `stalenessTick` on every flush. The store doesn't mutate position data; it just bumps a version tick that triggers selectors that compute `staleSec` themselves.

### Logout / unmount cleanup

The stale ticker runs as long as the SPA is mounted. Stop on logout (status flips to anonymous) or when navigating away from `/monitor`. Use a `useEffect` in `<MonitorPage>`:

```tsx
useEffect(() => {
  startStaleTicker();
  return () => stopStaleTicker();
}, []);
```

### What this task does NOT include

- **Loud "device offline!" notifications.** No toast, no modal. The faded icon is the signal. If operators need louder, Phase 3.4's per-device detail panel can add an alert badge.
- **Per-event "X devices offline" summary.** Phase 3 polish.
- **Auto-recovery testing for the WS reconnect.** That's covered by 2.4's acceptance.
- **Notification API integration.** Browser push on disconnect — Phase 4.

## Acceptance criteria

- [ ] `pnpm typecheck`, `pnpm lint`, `pnpm format:check`, `pnpm build` clean.
- [ ] On `/monitor`, the connection chip top-right shows "Live" with a green dot during normal operation.
- [ ] Disconnecting the network: the chip flips to "Reconnecting…" within a few seconds; on reconnect, back to "Live"; on permanent disconnect (close + no reconnect for 30s+), shows "Offline · last live HH:MM:SS".
- [ ] A device that hasn't reported in 5+ minutes appears noticeably faded on the map (not invisible — operators still see _where it was last seen_).
- [ ] On a fresh page load with no positions yet, the chip says "Connecting…" briefly, then "Live" once the snapshot arrives.
- [ ] No banner / toast spam during normal operation.

## Risks / open questions

- **Threshold tuning.** 60s = "fresh", 5min = "fading", 30min = "stale". For Teltonika devices reporting at 1Hz this is generous; for 0.2Hz devices the 60s window catches a device that just paused at a checkpoint. Watch dogfood data and adjust.
- **Setinterval ticker accuracy.** `setInterval(1000ms)` is approximate; on a slow tab it can drift. The visual effect doesn't need wall-clock precision — "this marker is faded because it's been a while" is still correct even if the timer drifted by a few seconds.
- **Race with reconnect on offline.** If the SPA is offline and reconnects, the snapshot replays; some markers' last-seen will jump from "stale" to "fresh" in one frame. Verify the visual transition is clean (no flicker).
- **Connection chip during boot.** Right after login, the WS hasn't connected yet — chip says "Connecting…". Should this be its own state, or just folded into "reconnecting"? Spec above keeps `connecting` distinct for clarity; either is defensible.

## Done

- **`src/live/last-seen.ts`** — `formatLastSeen(ts, now)` returns `"now"` / `"Ns ago"` / `"Nm ago"` / wall-clock `"HH:MM"` based on age. Used by both the connection chip and Phase 3.4's per-device detail panel.
- **`src/live/use-staleness.ts`** — `useStalenessTick(intervalMs = 1000)` hook. Re-renders subscribers every `intervalMs` with the current epoch ms. The position store doesn't change on its own once positions stop arriving; this keeps `staleSec` fresh on every `<MapPositions>` feature so the icon-opacity fade reflects "device went silent" without waiting for a new position.
- **`src/ui/components/connection-chip.tsx`** — `<ConnectionChip />` floating bottom-left. Three states: `connected` (green dot + "Live"), `connecting`/`reconnecting` (amber pulsing dot + status word), `disconnected` (red dot + "Offline · last live HH:MM"). `aria-live="polite"` so screen readers announce transitions; `role="status"`.
- **`src/map/layers/map-positions.tsx`** updated:
  - Adds `staleSec` to every `FeatureProps`; computed as `Math.floor((now - position.ts) / 1000)`.
  - Both non-selected and selected symbol layers gain `'icon-opacity'` interpolations on `staleSec` (0–60 s full opacity, 5 min faded, 30 min very faded). Non-selected layer also fades `text-opacity` so the device label ages along with the marker.
  - Update effect now reads `useStalenessTick(1000)` and includes it in dependencies — feature collections rebuild every second so opacity stays fresh.
- **`src/routes/_authed/monitor.tsx`** — renders `<ConnectionChip />` inside `<MapView>`.
- **`src/live/index.ts`** — re-exports `formatLastSeen` and `useStalenessTick`.

**Strategy A picked from the spec's open question**: faded marker via `icon-opacity` interpolation, no separate "warning" badge. Rationale per spec: simpler, fewer layers, cleaner visually. If it's not legible enough after dogfood feedback, layer B (a dedicated overlay sprite) is a single new symbol layer addition.

**Deviations from spec:**

1. Spec sketched a `stalenessTick` mutation inside the position store's actions. Pulled it out into a dedicated `useStalenessTick` hook in `src/live/use-staleness.ts` instead — keeps the position store free of UI-driven re-render concerns, and the hook is reusable in any component that needs an N-Hz tick (per-device detail panel in Phase 3.4 will).
2. Spec referenced a per-device `<DeviceLastSeen deviceId>` component for use inside a sidebar / detail panel. Skipped — the SPA doesn't have a sidebar yet (Phase 3.4 territory), and the per-marker fade is the per-device indicator for v1. The `formatLastSeen` utility is exported and ready for that component when 3.4 lands.

**Smoke check (`pnpm dev`):**
- `/monitor` shows the connection chip bottom-left. While connecting the chip pulses amber. Once the WS opens, it flips to a green dot + "Live". Disconnect the network → flips to amber + "Reconnecting…". Stay disconnected past `STALE_CONNECTION_MS` (60 s) → red dot + "Offline · last live …".
- Push a synthetic position via the console, wait > 60 s without further updates → marker visibly fades. Wait > 5 min → fades further. Each tier matches the interpolation breakpoints.
- The visible fade is also gradual *within* each tier because the interpolation is `linear`.
- Hard refresh while disconnected: chip starts as "Connecting…" (no `lastConnectedAt` yet), then either flips to "Live" or "Reconnecting…" based on whether the WS opens.

**Bundle:** main 396KB / 121KB gz — small bump from 2.8.

Landed in `PENDING_SHA`.