first upload all files

Modules/Cart/Http/Middleware/CheckProductIsInStock.php

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+<?php
+
+namespace Modules\Cart\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Modules\Cart\Facades\Cart;
+use Modules\Product\Entities\Product;
+use Modules\FlashSale\Entities\FlashSale;
+
+class CheckProductIsInStock
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param \Illuminate\Http\Request $request
+     * @param \Closure $next
+     * @return mixed
+     */
+    public function handle(Request $request, Closure $next)
+    {
+        $product = Product::withName()
+            ->addSelect('id', 'in_stock', 'manage_stock', 'qty')
+            ->where('id', $this->getProductId($request))
+            ->firstOrFail();
+
+        if ($product->isOutOfStock()) {
+            abort(400, trans('cart::messages.out_of_stock'));
+        }
+
+        if (! $this->hasFlashSaleStock($product, $request)) {
+            abort(400, trans('cart::messages.not_have_enough_quantity_in_stock', [
+                'stock' => FlashSale::remainingQty($product),
+            ]));
+        }
+
+        if (! $this->hasStock($product, $request)) {
+            abort(400, trans('cart::messages.not_have_enough_quantity_in_stock', [
+                'stock' => $product->qty,
+            ]));
+        }
+
+        return $next($request);
+    }
+
+    private function getProductId(Request $request)
+    {
+        if ($request->routeIs('cart.items.store')) {
+            return $request->product_id;
+        }
+
+        $cartItem = $this->getCartItemForUpdateRequest($request);
+
+        if (! is_null($cartItem)) {
+            return $cartItem->product->id;
+        }
+    }
+
+    private function getCartItemForUpdateRequest(Request $request)
+    {
+        return Cart::items()->get($request->route()->parameter('cartItemId'));
+    }
+
+    private function hasFlashSaleStock(Product $product, Request $request)
+    {
+        if (! FlashSale::contains($product)) {
+            return true;
+        }
+
+        $remainingQty = FlashSale::remainingQty($product);
+        $addedCartQty = Cart::addedQty($product->id);
+
+        // Exclude current cart item quantity from the total added cart quantity
+        // So, that current quantity is not added with the updated quantity.
+        $addedCartQty -= $this->currentCartItemQuantity($request);
+
+        return ($remainingQty - $addedCartQty) >= $request->qty;
+    }
+
+    private function hasStock(Product $product, Request $request)
+    {
+        if (! $product->manage_stock) {
+            return true;
+        }
+
+        $addedCartQty = Cart::addedQty($product->id);
+
+        // Exclude current cart item quantity from the total added cart quantity
+        // So, that current quantity is not added with the updated quantity.
+        $addedCartQty -= $this->currentCartItemQuantity($request);
+
+        return ($product->qty - $addedCartQty) >= $request->qty;
+    }
+
+    private function currentCartItemQuantity(Request $request)
+    {
+        if ($request->routeIs('cart.items.update')) {
+            return $this->getCartItemForUpdateRequest($request)->qty;
+        }
+
+        return 0;
+    }
+}