# Frontend

Svelte 5 SPA bundled with esbuild and styled with Tailwind CSS 4.

## Structure

- Entry point: `src/index.ts`, main component: `src/App.svelte`.
- `src/lib/` — utilities, stores, actions, API layer.
- `src/widgets/` — reusable UI components (Button, Input, Form, etc.).
- `src/css/` — global styles and Tailwind imports.
- Keep route components in a `src/routes/` folder when needed.

## Routing

This project uses a **custom SPA router** (NOT SvelteKit, NOT file-based routing). Pages are CMS content entries loaded dynamically by URL path.

- `lib/store.ts` proxies `history.pushState`/`replaceState` → updates `$location` store.
- `App.svelte` reacts to `$location.path` → calls `getCachedEntries("content", { lang, path })` → renders blocks.
- `lib/navigation.ts` provides `spaNavigate(url)` for programmatic navigation and `use:spaLink` action for `<a>` elements.
- URL structure: `/{lang}/{path}` (e.g. `/de/ueber-uns`, `/en/about`).
- Root `/` auto-redirects to `/{browserLanguage}/`.
- **For full details see the `frontend-architecture` skill.**

## Conventions

- PascalCase component names; export props at the top of `<script>` tag.
- Keep code and comments in English.
- SSR safety: guard browser-only code with `typeof window !== "undefined"`.
- API behavior: PUT responses return only changed fields; filter by id uses `_id`; API requests reject non-2xx with `{ response, data }` and error payload in `error.data.error`.

## Tailwind CSS

- Always use canonical Tailwind utility classes instead of arbitrary values when a standard equivalent exists (e.g. `h-16.5` not `h-[66px]`, `min-h-3` not `min-h-[12px]`).
- Only use arbitrary values (`[...]`) when no standard utility covers the needed value.

## i18n

- `svelte-i18n` is configured in `src/lib/i18n/index.ts` with lazy loading for locale files.
- Locale files live in `src/lib/i18n/locales/{lang}.json`.
- URL-based language routing: `/{lang}/...` (e.g. `/de/`, `/en/about`).
- Language utilities in `src/lib/i18n.ts`: `extractLanguageFromPath()`, `localizedPath()`, `getLanguageSwitchUrl()`.
- Use `$_("key")` from `svelte-i18n` for translations in components.

## Related tests

- When developing frontend features: extend or create corresponding E2E tests in `tests/e2e/`.
- After frontend changes, run only the affected E2E tests: `npx playwright test tests/e2e/filename.spec.ts` or `-g "test name"`.
- When tests fail, clarify whether the frontend or the test needs adjustment — coordinate with the user.
