adding a cart

app/Http/Controllers/CartController.php

@@ -0,0 +1,78 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Http\Requests\StoreCartRequest;
+use App\Http\Requests\UpdateCartRequest;
+use App\Models\Cart;
+use App\Models\Product;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+class CartController extends Controller
+{
+    public function store(StoreCartRequest $request): JsonResponse
+    {
+        $cart = $this->resolveCart();
+
+        $existing = $cart->products()->wherePivot('product_id', $request->product_id)->first();
+
+        if ($existing) {
+            $cart->products()->updateExistingPivot($request->product_id, [
+                'quantity' => $existing->pivot->quantity + 1,
+            ]);
+        } else {
+            $cart->products()->attach($request->product_id, ['quantity' => 1]);
+        }
+
+        return response()->json($this->cartItems($cart));
+    }
+
+    public function update(UpdateCartRequest $request, Product $product): JsonResponse
+    {
+        $cart = $this->resolveCart();
+
+        $cart->products()->updateExistingPivot($product->id, [
+            'quantity' => $request->quantity,
+        ]);
+
+        return response()->json($this->cartItems($cart));
+    }
+
+    public function destroy(Request $request, Product $product): JsonResponse
+    {
+        $cart = $this->resolveCart();
+
+        $cart->products()->detach($product->id);
+
+        return response()->json($this->cartItems($cart));
+    }
+
+    private function resolveCart(): Cart
+    {
+        $cartId = session('cart_id');
+
+        if ($cartId) {
+            $cart = Cart::find($cartId);
+            if ($cart) {
+                return $cart;
+            }
+        }
+
+        $cart = Cart::create(['user_id' => request()->user()?->id]);
+        session(['cart_id' => $cart->id]);
+
+        return $cart;
+    }
+
+    /**
+     * @return array<int, array{product_id: int, quantity: int}>
+     */
+    private function cartItems(Cart $cart): array
+    {
+        return $cart->products()->get()->map(fn ($p) => [
+            'product_id' => $p->id,
+            'quantity' => $p->pivot->quantity,
+        ])->all();
+    }
+}

app/Http/Requests/StoreCartRequest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Http\Requests;
+
+use Illuminate\Contracts\Validation\ValidationRule;
+use Illuminate\Foundation\Http\FormRequest;
+
+class StoreCartRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /**
+     * @return array<string, ValidationRule|array<mixed>|string>
+     */
+    public function rules(): array
+    {
+        return [
+            'product_id' => ['required', 'integer', 'exists:products,id'],
+        ];
+    }
+}

app/Http/Requests/UpdateCartRequest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Http\Requests;
+
+use Illuminate\Contracts\Validation\ValidationRule;
+use Illuminate\Foundation\Http\FormRequest;
+
+class UpdateCartRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /**
+     * @return array<string, ValidationRule|array<mixed>|string>
+     */
+    public function rules(): array
+    {
+        return [
+            'quantity' => ['required', 'integer', 'min:1'],
+        ];
+    }
+}