Musify/web-player/CLAUDE.md

Musify: web-player

Musify's public web app (web-player/ folder). For design and UI recipes, use the musify-web skill.

Stack

SvelteKit 2 (adapter-node), Svelte 5 runes, Tailwind 4, TypeScript strict, Zitadel OIDC auth (openid-client + jose).

There's no svelte.config.js (config is inline in vite.config.ts) and no tailwind.config.js (config lives in src/routes/layout.css).

Commands

npm run dev          # dev server (port 5173)
npm run build
npm run check         # svelte-check, must exit 0 errors before closing a change
npm run format         # prettier --write .
npm run test            # vitest run (pure functions, mappers, form parsers)
npm run lint            # prettier --check . && eslint . && npm run lint:tokens && npm run test
npm run lint:tokens      # scripts/check-tokens.mjs, the design system guardrail (see below)

Rules

• No comments in code unless essential.
• npm run lint and npm run check must exit clean before closing a change.
• Imports: always $lib/..., never ../ (ESLint enforces it). Non-null assertions are forbidden too.
• Always Svelte 5 runes: $props() with interface Props, $state, $derived, $effect. No export let or $:. {#each} always keyed.
• Server only code goes under $lib/server/, and it's never imported from client code.
• SSR data comes through load in +page.server.ts/+layout.server.ts and lands in the data prop.
• Links to +server.ts endpoints (/auth/login, /auth/logout) carry data-sveltekit-reload.
• Reuse design system tokens and recipes before writing new CSS. If something repeats, extract it to $lib/components/ui/.

Folder structure

• src/lib/types.ts holds the domain types (Track, Album, Playlist, Mix, Paged<T>). Pages and the player only ever see these, never raw API DTOs.
• src/lib/player/ is the player: player.svelte.ts (state and orchestration), queue.ts (pure queue operations), stream.ts, mediaSession.ts, progressClock.ts, listenTracker.ts, liked.svelte.ts, and actions.ts (playAllOrToggle, playShuffled, isQueueCurrent).
• src/lib/state/ holds reactive rune state: panels.svelte.ts (queue panel, create playlist modal), history.svelte.ts (previous page for BackLink), menu.svelte.ts (createMenu<T>()), pagedList.svelte.ts (createPagedList), dialog.svelte.ts, and scroll.ts. Nothing in state/ imports from components/.
• src/lib/theme/ holds the theme: accent.svelte.ts (accent hue per track and the hue fade), mode.svelte.ts, palette.ts, tokens.ts.
• src/lib/data/ holds client side domain helpers: albums, genres, recentlyPlayed, search.
• src/lib/utils/ holds generic utilities: format.ts, collections.ts, hrefs.ts (search, genre and cover URLs), menuPosition.ts, storage.ts, transitions.ts.
• src/lib/validation.ts holds the form limits (LIMITS) shared by client forms and server parsers.
• src/lib/server/ is server only code (see below).
• src/lib/components/layout/ holds the app chrome: Sidebar, TopBar, TabsBar, MobileHeader, and navLinks.ts.
• src/lib/components/player/ holds the player UI: PlayerBar, PlayerDock, Queue, TrackInfo, TransportControls.
• src/lib/components/ui/ holds the design system components, split into five categories:
  • primitives/ for generic controls with no music domain knowledge (Button, Input, Chip, Slider, and so on).
  • overlay/ for anything that floats above the content (Modal, ContextMenu, TrackContextMenu, AlbumContextMenu, AccountMenu, and so on).
  • media/ for music domain display components (Artwork, TrackList, MediaCard, PlayButton, PlayAllButton, and so on).
  • forms/ for composite entity forms (AlbumForm, PlaylistForm, CoverForm, ImageDropzone).
  • layout/ for page level scaffolding (Page, PageHeader, SectionHeading). This is different from components/layout/ above, which is the global app chrome.
• Everything the user sees after signing in lives under src/routes/(app)/, including Home ((app)/+page.svelte). Auth routes live under src/routes/auth/: +page.svelte is the login screen, and login/, logout/, callback/ are the OIDC endpoints. The public user profile route is src/routes/(app)/user/[id]/, and its followers/following lists share one route, user/[id]/[list=followList]/ (matcher in src/params/followList.ts).

Naming conventions and glossary

• Variant maps are module level constants in upper case (SIZE, VARIANT).
• Errors: destructure as const { data, error } = ... and name the caught value err in catch (err).
• Play handlers: playFrom(index) and playAll(). Form actions: create, edit, delete, addTrack, removeTrack.
• UI copy: "Playlist" (never "Lista"), "Mezcla" (never "Mix"), "Modo claro". Total durations always go through fmtDurationLong.

Styles

The design system lives in src/routes/layout.css (@theme tokens plus @utility recipes) and in src/lib/theme/ (theme.css for the static neutrals, tokens.ts for the dynamic tokens that depend on the user's hue). scripts/check-tokens.mjs (run as npm run lint:tokens, part of lint) fails on a stock radius, an h-N w-N pair, fractional quarter spacing, a literal hex/rgba(), or an arbitrary -[…] value outside its whitelist, so check that script before adding one.

• Radii: always rounded-tag/thumb/control/art/art-lg/panel/panel-lg (or rounded-full for pills and circles). Never rounded-sm/md/lg/xl/2xl/3xl or a bare rounded.
• Square sizes: use size-* instead of repeating h-N w-N (icons: size-icon-xs/sm/md/lg/xl; covers: size-cover-xs through size-cover-hero).
• Typography: use the recipes text-display-1/2/3/4, text-eyebrow, text-body, with tracking through tracking-display/tracking-eyebrow rather than a loose tracking-[…].
• Spacing: stick to the Tailwind scale in .5 steps and avoid quarters like .25/.75, unless the semantic token calls for it (for example mb-4.5 in SectionHeading).
• Colors: always use --mf-*/text-*/bg-*/border-* from theme.css/tokens.ts. Never a literal hex or rgba() inside a .svelte file; those literals only belong in theme.css/tokens.ts as the source of truth.
• Inline style="…" and arbitrary -[…] values: only the ones whitelisted in scripts/check-tokens.mjs (the stagger variable --i, tile hue, menu position, progress width, text-[clamp(…)], leading-[…] on login's display type, grid-cols-[auto_1fr], max-h-[85dvh], my-/py-[Ndvh] for vertical centering, transition-[filter] on genre tiles, and bg-[image:var(--mf-*)]). Everything else should become a token.
• Reach for these base components before creating a new one: Artwork, Avatar, ListRow, MediaIdentity, TrackList, MediaCard, PageHeader, ContextMenu, ConfirmDialog, PlayButton, Slider, Logo, Chip, SegmentedControl, CoverForm.
• Icon stroke: one global rule (svg.lucide { stroke-width: 1.5 } in layout.css) sets the stroke for every icon. Never pass strokeWidth to an icon, since any CSS rule overrides the SVG attribute and it would do nothing. For a different stroke on one icon, use a Tailwind stroke-* utility.

App shell

The shell in src/routes/+layout.svelte is a fixed h-dvh frame: Sidebar | (content column over PlayerDock) | Queue. Only the content column (app-scroll) scrolls, so nothing ever passes under the dock and the chrome can stay transparent over app-backdrop. Because the window never scrolls, scroll reset/restore on navigation is handled by restoreScroll() in $lib/state/navigation.svelte.ts; don't use window.scrollTo/scrollY.

Motion

Every animation follows one scale of three durations and one easing curve, all defined in theme.css. Fast (--mf-motion-fast, 150ms) is for hover, focus and press feedback: color, opacity and small scale changes. Plain transition or transition-colors already uses it because it is the Tailwind default, so never write duration-150. Base (--mf-motion-base, 200ms) is for things that appear on top of the page or move inside a control: modals, menus, the queue panel, animate-pop, animate-fade and the segmented control thumb. Slow (--mf-motion-slow, 300ms) is for content entering the page and larger movement: animate-enter, cover zoom on hover.

Entrances and movement always use --mf-ease (ease-snappy in Tailwind, expoOut in Svelte transitions), which feels immediate because most of the motion happens at the start. Color transitions keep the Tailwind default curve. Overlays must feel instant: the modal backdrop uses transition:fade={{ duration: 200 }} and the panel uses a local pop transition (opacity + scale + translateY, expoOut, 200ms) mirroring animate-pop's keyframes — both directives so the modal fades and pops on close too, not just on open, and the whole thing settles in 200ms. Staggered lists use --i with 40ms steps capped at ten items.

The only exceptions are looping indicators (equalizer bars, pulse, spin, sheen) and the accent hue crossfade in +layout.svelte (a random 2 to 4 seconds per song change), which is ambient and meant to be slow. Do not add new durations or curves; if something needs a different feel, pick the closest step of the scale. prefers-reduced-motion disables everything globally in layout.css.

Auth

hooks.server.ts validates the encrypted session cookie (mf_session), refreshes the access_token, and fills locals.user and locals.accessToken. To protect a route, check locals.user in its load and redirect to /auth?returnTo=…. When talking to the backend, send locals.accessToken as a Bearer token to API_BASE_URL.

Environment variables live in .env (see .env.example): ZITADEL_*, AUTH_REDIRECT_URI, AUTH_POST_LOGOUT_URI, SESSION_SECRET, API_BASE_URL.

Backend API

Typed client via openapi-fetch over the Musify.Api OpenAPI spec. Inside a server load or action use the helpers in $lib/server/api.ts:

const api = apiFor(event); // or apiFor({ fetch, locals }); adds the bearer token when there is a session
const { data, error } = await api.GET('/tracks');

It returns { data, error } (ErrorOr style) and never throws except on network errors. The types live in src/lib/api/schema.d.ts and get regenerated with npm run gen:api (this needs the dev API running at API_BASE_URL, which only exposes /openapi/v1.json in Development).

Server helpers:

• mappers.ts (toTrack, toAlbum, toPlaylist, toMix, toPage, ...) turn DTOs into the domain types. Every load and /api endpoint that returns tracks, albums or playlists goes through them, so Number() conversions never reach the client.
• authedAction(handler) wraps a form action: it returns 401 without a token, reads the form and hands { api, form, params, locals, url } to the handler. Use formString/formFile to read fields, failOnError(result, message) to turn an API error into a fail(...), and requireData(result, message) when you also need the response data narrowed.
• forms/ holds the form parsers (parseAlbumForm, parsePlaylistForm, parseTrackUploadForm); they validate with LIMITS from $lib/validation. uploadOptionalCover handles the optional cover upload.
• genres.ts caches the genre list; playbackConfig.ts caches the anonymous listening setting.
• Page sizes come from $lib/config; do not hardcode them.