ARCH-001 Phase 24: shrink Admin CurrencyController/LanguageController

[KrzysztofPajak]

Type: refactor

Issue

ARCH-001 (see repo memory) previously surveyed Currency/Language as a "config-shaped, lower-priority" candidate distinct from every other completed phase: Store's CurrencyController/LanguageController implement a genuinely different feature (per-store currency/language assignment + default picker) than Admin's full CRUD editor, so there is no real cross-host duplication to remove with the usual IAdminDataScope<TEntity> pattern.

Fresh read of both Admin controllers found a smaller, real opportunity instead: business-rule validation and setting+cache-clear orchestration was living directly in the controllers even though both already inject a shared ICurrencyViewModelService/ILanguageViewModelService (Grand.Web.AdminShared) that was the natural home for it.

Solution

Moved into the already-injected view-model services, no new abstractions:

• MarkAsPrimaryExchangeRateCurrency/MarkAsPrimaryStoreCurrency: setting-save + cache-clear now live in CurrencyViewModelService. Removes CurrencyController's private ClearCache() helper and its now-unused ICacheBase dependency.
• Edit(POST)'s "last published currency/language" guard and Delete's "can't delete primary / last published" guards are extracted as separate service methods per entity (ValidateCurrencyUnpublish/ValidateCurrencyDelete, ValidateLanguageUnpublish/ValidateLanguageDelete) — deliberately not merged into one shared method, since Edit's guard is also conditioned on !model.Published while Delete's is not; merging would have re-derived a similar-looking but wrong condition (a mistake this initiative has hit before on other phases).

No behavior change for callers — same messages, same redirects.

One disclosed side effect: Delete's primary/exchange-currency rejection no longer round-trips through a thrown GrandException, so it no longer triggers BaseController.Error(Exception)'s LogException call for this expected, validation-only outcome. This aligns with .ai/standards/csharp-style.md's "prefer result objects over exceptions for expected business failures" and removes ERROR-level log noise for a routine user action, but is a real (intentional) behavior delta worth a second pair of eyes.

Store's CurrencyController/LanguageController are untouched — out of scope, as explained above.

Breaking changes

None. Public HTTP surface, messages, and redirects are unchanged. ICurrencyViewModelService/ILanguageViewModelService gained new methods (additive); no existing interface members changed signature.

Testing

1. dotnet build GrandNode.sln — 0 errors, 0 new warnings.
2. New unit tests added (no prior coverage existed for either controller/service): src/Tests/Grand.Web.Admin.Tests/Services/CurrencyViewModelServiceTests.cs, LanguageViewModelServiceTests.cs — happy path + every extracted guard condition (primary currency, exchange-rate currency, last-published, still-published short-circuit).
3. dotnet test src/Tests/Grand.Web.Admin.Tests/Grand.Web.Admin.Tests.csproj — 1347/1347 green (includes the 14 new tests).
4. Live smoke test run against a real Kestrel instance on the shared dev DB, via curl-based crafted antiforgery-tokened requests (browser automation was unavailable this session, per the established fallback from TaxCategory/Shipping phases). All 6 extracted methods verified, both success and failure branches:
   • MarkAsPrimaryExchangeRateCurrency/MarkAsPrimaryStoreCurrency: set Euro as primary (both flags), grid reflected it immediately (setting + cache-clear both took effect), reverted to US Dollar.
   • ValidateCurrencyDelete: blocked deleting the primary store currency ("The primary store currency can't be deleted.") and the primary exchange-rate currency ("The primary exchange rate currency can't be deleted.") — exact resource strings, entities confirmed untouched. Success path also verified: created and cleanly deleted a throwaway currency.
   • ValidateCurrencyUnpublish: unpublishing a non-last currency succeeded; unpublishing the resulting last-published currency was correctly blocked ("At least one published currency is required."), with the entity's Published state confirmed unchanged (rejected, not partially applied).
   • ValidateLanguageDelete/ValidateLanguageUnpublish: this dev DB has exactly one language (English) — verified the most important edge case directly, both Delete and Edit(POST) unpublish blocked on the sole published language, same resource string as Currency's. Success path verified via a throwaway second language (create → unpublish English while throwaway stays published → succeeds → delete throwaway → succeeds).
   • All test data reverted to original values by the end (both currency primaries, Euro/English published state, English's flag image). One harmless, disclosed drift left in place: Euro's DisplayLocale changed from "" to null after a test round-trip — a pre-existing, unrelated Mongo/mapping quirk (not touched by this change), functionally identical in the UI (both render as "Select locale" unselected).
   • No cross-tenant/access-control surface exists in this change (Admin-only, no Store/Vendor consolidation), so this live test exercised business-rule correctness and cache/setting round-tripping rather than tenant isolation.

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