# Error & state UX

How the client gives consistent, actionable feedback for failures and for
loading / empty / error states.

## Error surface (`src/lib/error/`)

Server `result_code`s are downstream-opaque (only `"ok"` is contractual —
`docs/ARCHITECTURE.md`), so the client keys UX off the reliable
transport-level signal instead.

- [`classify.ts`](../frontend/src/lib/error/classify.ts) collapses any
  caught value into a stable `ErrorKind` (`offline`, `network`, `auth`,
  `forbidden`, `conflict`, `notFound`, `rateLimit`, `server`, `unknown`)
  from `navigator.onLine`, an `AuthError` HTTP status, a Connect `Code`,
  or a fetch `TypeError`. `isRetryable` marks the transient kinds.
- [`report.ts`](../frontend/src/lib/error/report.ts) maps each kind to a
  translated `error.*` message and either:
  - `reportError(err, { onRetry? })` — raises a toast (a sticky toast
    with a **Retry** action for a retryable kind that supplies `onRetry`,
    otherwise auto-dismiss); or
  - `errorMessageKey(err)` — returns the translated key for a view to
    render the message inline (e.g. the mail compose 403).

Messages live under `error.*` (en + ru); the action label is
`common.retry`. New call sites adopt this surface incrementally; the mail
compose dialog is the worked inline example.

## View states (`src/lib/ui/view-state.svelte`)

`<ViewState kind="loading|empty|error" message=… [actionLabel onAction] />`
is the one placeholder for a view or panel: a spinner for loading, an
accent action button when given, and the right live-region role
(`status` for loading/empty, `alert` for error). The entity tables
(races / sciences / ship-classes) use it; remaining views adopt it
incrementally.

## Selected-planet marker (`src/map/selection-ring.ts`)

When the `SelectionStore` holds a planet, the map draws one accent ring
tight around it (`computeSelectionRing`, fed into the map's `buildExtras`
alongside the reach circles). Ship-group selection is not ringed — groups
are addressed by report index and have no single stable map coordinate.

## Mobile bottom-sheet dismissal (`src/lib/ui/sheet-dismiss.ts`)

`use:sheetDismiss={{ onDismiss }}` adds two hand-rolled (no-dependency)
gestures to the planet / ship-group bottom-sheets: tap anywhere outside
the sheet, or drag its `[data-sheet-handle]` grabber down past a
threshold. The swipe starts only from the grabber so it never fights the
sheet's own content scrolling.
