Feature: Updating Product Service to handle multiple locales, fetching the correct locale, or, the default locale as fallback

src/Localization/Services/LanguageCache.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace Modules\Core\Localization\Services;
+
+use Illuminate\Support\Collection;
+use Illuminate\Support\Facades\Cache;
+use Lunar\Models\Language;
+
+/**
+ * Cached read layer over Lunar's `languages` table — the single source both
+ * Modules\Core\Localization\LocaleMiddleware (request-time locale resolution) and
+ * any other locale-aware code (e.g. Modules\Core\Catalog\ProductService) read
+ * from, so the language list is fetched once per cache lifetime rather than once
+ * per caller. Cached forever, invalidated via forget() by
+ * Modules\Core\Localization\Listeners\FlushLanguageCache on
+ * LanguageCreated/LanguageUpdated/LanguageDeleted.
+ */
+class LanguageCache
+{
+    private const CACHE_KEY = 'core.localization.languages';
+
+    public function all(): Collection
+    {
+        return Cache::rememberForever(
+            self::CACHE_KEY,
+            fn () => Language::query()->get(['id', 'code', 'name', 'default']),
+        );
+    }
+
+    /**
+     * The store's default language code (e.g. 'el') - the fixed fallback other
+     * locale-aware code should use, as opposed to config('app.locale') which
+     * App::setLocale() mutates per request and so can't serve as a stable
+     * fallback.
+     */
+    public function defaultLocale(): ?string
+    {
+        return $this->all()->firstWhere('default', true)?->code;
+    }
+
+    /**
+     * Every configured store locale code (e.g. ['el', 'en']) - for code that needs
+     * to enumerate all locales a TranslatedText attribute was indexed under (see
+     * Modules\Core\Catalog\ProductService::withLocalizedFields()), rather than
+     * hardcoding locale codes.
+     *
+     * @return array<int, string>
+     */
+    public function availableLocales(): array
+    {
+        return $this->all()->pluck('code')->all();
+    }
+
+    public function forget(): void
+    {
+        Cache::forget(self::CACHE_KEY);
+    }
+}