Mode
Guest mode
A visitor without a Supabase session keeps using eventmap:favorites and eventmap:favorite-events in localStorage.
Supabase Cloud Favorites
EventMap now switches favorites by auth state: guests keep browser persistence, authenticated users use the Supabase favorites table.
Mode
User mode
An authenticated user reads and writes public.favorites through the browser client and RLS-scoped policies.
Mode
Copy migration
On first sign in, cached local EventCardData snapshots are copied to Supabase. The local cache stays in place as guest fallback.
Hook boundary
useFavoritesCloud
The hook reads the current Supabase user in the browser after hydration. If there is no configured client or no user session, it delegates to the existing localStorage favorites hook.
guest localStorage → login → copy snapshots → cloud favoritesCRUD
SELECT
useFavoritesCloud loads event_id and event_snapshot from public.favorites. RLS limits the result to the current auth.uid().
CRUD
INSERT
Saving an event inserts user_id, event_id and event_snapshot. No upsert is used because this lesson has no UPDATE policy.
CRUD
DELETE
Removing a favorite deletes the matching user_id and event_id row, then the UI updates optimistically.
Boundary
Product page
/favorites stays a normal EventMap page. It shows events, empty state and a link back to search.
Boundary
Client island
FavoriteButton remains the small client island inside server-rendered event cards.
Boundary
Demo Lab
SQL, RLS and CRUD explanations stay here instead of leaking into product UI.