Marketplace Controller + State

Notifier owning the entire paged + filtered list. ProductListState carries loading flags, products, pagination cursor (offset, hasMore), every filter dimension, and the available-filter set computed from page 0.

1. build() schedules a Future.microtask(refresh) so the initial fetch fires on first watch.
2. _fetchProducts respects offset and limit=20; the response is concatenated with previous pages.
3. Sort orders 'price_asc' / 'price_desc' are applied client-side; everything else is server-side (passed as `order=` param).
4. Available filters (Category, Colors, Size) are extracted from page 0 results via _extractFilters and cached.
5. toggleCategory / toggleTag / toggleVariantOption flip an item in the corresponding list, then refresh.

• Medusa's variants[options][value] only accepts a single value — the controller sends the first selected option to the API and filters the rest client-side.
• Filter-error auto-recovery: if a filtered fetch throws and any filter is active, all filters reset, warningMessage is set, and refresh fires unfiltered.
• copyWith does not allow clearing warningMessage; clearWarning rebuilds the state explicitly with warningMessage: null.
• Local price sort is applied on top of paged results — the order across page boundaries is unstable when more items load.
• toggleVariantOption can't enforce per-group single-select (Color vs Size) without group knowledge — the UI must pre-process to send 'one Color + one Size'.

• lib/src/features/shared/marketplace/controllers/marketplace_controller.dart:13 // ProductListState
• lib/src/features/shared/marketplace/controllers/marketplace_controller.dart:116 // MarketplaceController
• lib/src/features/shared/marketplace/controllers/marketplace_controller.dart:145 // _fetchProducts
• lib/src/features/shared/marketplace/controllers/marketplace_controller.dart:282 // clearWarning hack
• lib/src/features/shared/marketplace/controllers/marketplace_controller.dart:432 // _extractFilters

The 100+ lines of inline comments inside ProductListState.copyWith document a real frustration with warningMessage clearing — read those before refactoring.