first upload all files

Modules/Cart/Http/Middleware/CheckCartStock.php

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+<?php
+
+namespace Modules\Cart\Http\Middleware;
+
+use Closure;
+use Exception;
+use Modules\Cart\CartItem;
+use Illuminate\Http\Request;
+use Modules\Cart\Facades\Cart;
+use Modules\FlashSale\Entities\FlashSale;
+
+class CheckCartStock
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param \Illuminate\Http\Request $request
+     * @param \Closure $next
+     * @return mixed
+     */
+    public function handle(Request $request, Closure $next)
+    {
+        try {
+            Cart::items()->each(function (CartItem $cartItem) {
+                $cartItem->refreshStock();
+
+                $this->checkQuantity($cartItem);
+            });
+        } catch (Exception $e) {
+            return redirect()->route('cart.index')->with('error', $e->getMessage());
+        }
+
+        return $next($request);
+    }
+
+    private function checkQuantity(CartItem $cartItem)
+    {
+        if ($cartItem->product->isOutOfStock()) {
+            throw new Exception(trans('cart::messages.one_or_more_product_is_out_of_stock'));
+        }
+
+        if (! $this->hasFlashSaleStock($cartItem)) {
+            throw new Exception(trans('cart::messages.one_or_more_product_doesn\'t_have_enough_stock'));
+        }
+
+        if (! $this->hasStock($cartItem)) {
+            throw new Exception(trans('cart::messages.one_or_more_product_doesn\'t_have_enough_stock'));
+        }
+    }
+
+    private function hasFlashSaleStock(CartItem $cartItem)
+    {
+        if (! FlashSale::contains($cartItem->product)) {
+            return true;
+        }
+
+        $remainingQty = FlashSale::remainingQty($cartItem->product);
+        $addedCartQty = Cart::addedQty($cartItem->product->id);
+
+        return ($remainingQty - $addedCartQty) >= 0;
+    }
+
+    private function hasStock(CartItem $cartItem)
+    {
+        if (! $cartItem->product->manage_stock) {
+            return true;
+        }
+
+        $addedCartQty = Cart::addedQty($cartItem->product->id);
+
+        return ($cartItem->product->qty - $addedCartQty) >= 0;
+    }
+}