stock check, variants in cart, variant buttons in product page

app/Http/Controllers/Checkout/CartController.php

@@ -3,8 +3,11 @@
 namespace App\Http\Controllers\Checkout;
 
 use App\Http\Controllers\Controller;
+use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
 use Illuminate\View\View;
+use Lunar\Exceptions\Carts\CartException;
+use Lunar\Models\CartLine;
 use Lunar\Models\ProductVariant;
 use Modules\Core\Cart\Exceptions\InvalidCouponException;
 use Modules\Core\Cart\Services\CartService;
@@ -22,7 +25,18 @@ public function __construct(
         private readonly CartService $cart,
     ) {}
 
-    public function add(string $locale, Request $request): View
+    /**
+     * CartException here is Lunar's own add_to_cart validation pipeline
+     * (CartLineQuantity/CartLineStock) rejecting the line — most commonly
+     * "not enough stock at this quantity" for a tracked (purchasable =
+     * in_stock) variant. Its own message is an untranslated, hardcoded
+     * English string not meant for storefront display, so this returns our
+     * own translated one instead rather than passing it through — a
+     * storefront.* key rather than checkout.*, since this is a catalog/stock
+     * concern the storefront owns, not something specific to the portable
+     * checkout module.
+     */
+    public function add(string $locale, Request $request): View|JsonResponse
     {
         $data = $request->validate([
             'purchasable_id' => ['required', 'integer'],
@@ -31,24 +45,49 @@ public function add(string $locale, Request $request): View
 
         $variant = ProductVariant::findOrFail($data['purchasable_id']);
 
-        $this->cart->addLine($variant, $data['quantity'] ?? 1);
+        try {
+            $this->cart->addLine($variant, $data['quantity'] ?? 1);
+        } catch (CartException) {
+            return $this->stockError($variant);
+        }
 
         return view('checkout::partials.cart-body');
     }
 
-    public function updateLine(string $locale, Request $request, int $line): View
+    public function updateLine(string $locale, Request $request, int $line): View|JsonResponse
     {
         $quantity = (int) $request->validate([
             'quantity' => ['required', 'integer', 'min:0'],
         ])['quantity'];
 
-        $quantity === 0
-            ? $this->cart->removeLine($line)
-            : $this->cart->updateLine($line, $quantity);
+        try {
+            $quantity === 0
+                ? $this->cart->removeLine($line)
+                : $this->cart->updateLine($line, $quantity);
+        } catch (CartException) {
+            $variant = CartLine::find($line)?->purchasable;
+
+            return $this->stockError($variant instanceof ProductVariant ? $variant : null);
+        }
 
         return view('checkout::partials.cart-body');
     }
 
+    /**
+     * getTotalInventory() is the same number canBeFulfilledAtQuantity()
+     * checked against (stock, for a tracked in_stock variant) — telling the
+     * shopper how many are actually left beats a generic "not enough stock"
+     * they'd otherwise have to guess around by trial and error.
+     */
+    private function stockError(?ProductVariant $variant): JsonResponse
+    {
+        $available = $variant?->getTotalInventory() ?? 0;
+
+        return response()->json([
+            'error' => trans_choice('storefront.product.add_to_cart_failed', $available, ['count' => $available]),
+        ], 422);
+    }
+
     public function remove(string $locale, int $line): View
     {
         $this->cart->removeLine($line);