Laravel 8 Advanced Shopping Cart, Sub Total, Grand Total, Calculate Dynamic Freight Rate Price, Add , Remove, Clear, Remove Selected

ShoppingCartController.php

<?php

namespace App\Http\Controllers;

use App\Models\FreightRate;
use App\Models\ShoppingCart;
use App\Models\ShoppingSession;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use App\Classes\Page;
use App\Models\Product;
use Illuminate\Support\Facades\Auth;
use Illuminate\View\View;

class ShoppingCartController extends Controller
{
    // add product to cart
    public function add(Request $request): JsonResponse | RedirectResponse
    {
        $user = $request->user();
        $product = Product::find($request->input('product_id'));
        if ($user->shoppingSession === null) {
            $freightRatePrice = FreightRate::where('rate', '=', $product->freight_rate)->pluck('price')->first();
            // Starting new shopping session
            $shoppingSession = $user
                ->shoppingSession()
                ->create([
                    'sub_total' => $product->price * $request->input('quantity'),
                    'grand_total' => ($product->price * $request->input('quantity')) + $freightRatePrice,
                    'shipping_pay' => $freightRatePrice * $request->input('quantity')
                ]);
            // Add first product to shopping session
            $shoppingSession
                ->shoppingCart()
                ->create([
                    'product_id' => $request->input('product_id'),
                    'quantity' => $request->input('quantity'),
                    'freight_rate' => $product->freight_rate
                ]);
        } else {
            // If you have a previous shopping session
            $shoppingSession = $user->shoppingSession->first();
            $existingCartItem = ShoppingCart::where('shopping_session_id', $shoppingSession->id)
                ->where('product_id', $request->input('product_id'))
                ->first();
            // If this product is already in the shopping cart, increase the quantity.
            if ($existingCartItem !== null) {
                $existingCartItem->update([
                    'quantity' => $existingCartItem->quantity + $request->input('quantity'),
                ]);
            } else {
                // If the product is added to the cart for the first time
                $shoppingSession
                    ->shoppingCart()
                    ->create([
                        'product_id' => $request->input('product_id'),
                        'quantity' => $request->input('quantity'),
                        'freight_rate' => $product->freight_rate
                    ]);
            }
            $shipping_pay = $this->calculateShippingPay($shoppingSession);
            $shoppingSession
                ->update([
                    'sub_total' => $shoppingSession->sub_total + ($product->price * $request->input('quantity')),
                    'grand_total' => $shoppingSession->sub_total + ($product->price * $request->input('quantity')) + $shipping_pay,
                    'shipping_pay' => $shipping_pay
            ]);
        }
        return response()->json([
            'message' => 'Ürün sepetinize eklendi.'
        ]);
    }
    // remove product from cart
    public function remove(Request $request): JsonResponse
    {
        $user = $request->user();
        $product = Product::find($request->input('product_id'));
        $shoppingSession = $user->shoppingSession->first();

        $existingCartItem = ShoppingCart::where('shopping_session_id', $shoppingSession->id)
            ->where('product_id', $request->input('product_id'))
            ->first();

        // ürünü sil
        if ($existingCartItem->quantity === 1) {
            $existingCartItem->delete();
        } else {
            $existingCartItem->update([
                'quantity' => $existingCartItem->quantity - $request->input('quantity')
            ]);
        }
        // sessionu sil
        if ($shoppingSession->shoppingCart->isEmpty()) {
            $shoppingSession->delete();
        } else {
            $shipping_pay = $this->calculateShippingPay($shoppingSession);
            $shoppingSession->update([
                'sub_total' => $shoppingSession->sub_total - ($product->price * $request->input('quantity')),
                'grand_total' => $shoppingSession->sub_total - ($product->price * $request->input('quantity')) + $shipping_pay,
                'shipping_pay' => $shipping_pay
            ]);
        }

        return response()->json([
            'message' => 'Ürün sepetinizden çıkarıldı.'
        ]);
    }
    // calculator
    public function calculateShippingPay(ShoppingSession $shoppingSession): float
    {
        $rateSum = 0;
        foreach ($shoppingSession->shoppingCart as $item) {
            $rateSum += ($item->quantity * $item->freight_rate);
        }

        if ($rateSum >= 30) {
            return 0;
        } else {
            $shippingPay = FreightRate::where('rate', $rateSum)->first();
        }
        return $shippingPay->price;
    }
    // remove all selected product in cart
    public function removeProduct(Request $request): JsonResponse
    {
        $user = $request->user();
        $product = Product::find($request->input('product_id'));
        $shoppingSession = $user->shoppingSession->first();
        $existingCartItem = ShoppingCart::where('shopping_session_id', $shoppingSession->id)
            ->where('product_id', $request->input('product_id'))
            ->first();

        if ($shoppingSession->shoppingCart->isEmpty()) {
            $shoppingSession->delete();
        } else {
            $shipping_pay = $this->calculateShippingPay($shoppingSession);
            $shoppingSession->update([
                'sub_total' => $shoppingSession->sub_total - ($product->price * $existingCartItem->quantity),
                'grand_total' => $shoppingSession->sub_total - ($product->price * $existingCartItem->quantity) + $shipping_pay,
                'shipping_pay' => $shipping_pay
            ]);
        }
        $existingCartItem->delete();
        return response()->json([
            'message' => 'Ürün sepetinizden çıkarıldı.'
        ]);
    }
    // empty shopping cart, delete shopping session.
    public function clear(Request $request): JsonResponse
    {
        $user = $request->user();

        $user->shoppingSession()
            ->first()
            ->delete();

        return response()->json([
            'message' => 'Sepetiniz temizlendi.'
        ]);
    }
    // page: shopping cart
    public function sepetim(): View
    {
        $page = new Page;
        $page->title = 'Sepetim';
        $page->description = 'Sepetim';
        $shoppingSession = Auth::user()->shoppingSession;
        return view('pages.shopping-cart', compact('page', 'shoppingSession'));
    }
}