feat(orders): add order service and insufficient stock exception

src/Services/InsufficientStockException.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Bazaar\Services;
+
+final class InsufficientStockException extends \RuntimeException
+{
+    public function __construct(public readonly string $productName)
+    {
+        parent::__construct('Insufficient stock for ' . $productName);
+    }
+}

src/Services/OrderService.php

@@ -0,0 +1,162 @@
+<?php
+
+namespace Bazaar\Services;
+
+use Bazaar\Core\Config;
+use Bazaar\Core\Database;
+use Bazaar\Mail\Mailer;
+use Bazaar\Mail\NullMailer;
+use Bazaar\Mail\OrderMailer;
+use Bazaar\Repositories\CouponRepository;
+use Bazaar\Repositories\OrderRepository;
+use Bazaar\Repositories\ProductRepository;
+use Bazaar\Repositories\UserRepository;
+use Bazaar\Repositories\VariantRepository;
+
+final class OrderService
+{
+    private VariantRepository $variants;
+    private CouponRepository $coupons;
+    private UserRepository $users;
+    private OrderMailer $orderMailer;
+
+    public function __construct(
+        private readonly Database $db,
+        private readonly OrderRepository $orders,
+        private readonly ProductRepository $products,
+        ?VariantRepository $variants = null,
+        ?CouponRepository $coupons = null,
+        ?Mailer $mailer = null
+    ) {
+        $this->variants = $variants ?? new VariantRepository($db);
+        $this->coupons = $coupons ?? new CouponRepository($db);
+        $this->users = new UserRepository($db);
+        $this->orderMailer = new OrderMailer($mailer ?? new NullMailer(), (string) Config::get('CURRENCY', 'usd'));
+    }
+
+    public function createFromCart(int $userId, Cart $cart, string $currency, ?array $discount = null): int
+    {
+        $lines = $cart->lines();
+        if ($lines === []) {
+            throw new \RuntimeException('Cannot create an order from an empty cart');
+        }
+
+        foreach ($lines as $line) {
+            if ($line['quantity'] > $line['availableStock']) {
+                throw new InsufficientStockException($line['name']);
+            }
+        }
+
+        $subtotal = 0;
+        foreach ($lines as $line) {
+            $subtotal += $line['lineTotalCents'];
+        }
+        $discountCents = $discount !== null ? min((int) $discount['discountCents'], $subtotal) : 0;
+        $couponCode = $discount !== null ? ($discount['couponCode'] ?? null) : null;
+        $total = $subtotal - $discountCents;
+
+        return $this->db->transaction(function () use ($userId, $total, $currency, $discountCents, $couponCode, $lines): int {
+            $orderId = $this->orders->create($userId, $total, $currency, $discountCents, $couponCode);
+            foreach ($lines as $line) {
+                $this->orders->addItem(
+                    $orderId,
+                    $line['productId'],
+                    $line['name'],
+                    $line['unitPriceCents'],
+                    $line['quantity'],
+                    $line['variantId'],
+                    $line['variantLabel']
+                );
+            }
+            return $orderId;
+        });
+    }
+
+    public function markPaid(int $orderId, ?string $stripeSessionId = null): void
+    {
+        $order = $this->orders->find($orderId);
+        if ($order === null || $order['status'] !== 'pending') {
+            return;
+        }
+
+        $items = $this->orders->items($orderId);
+        foreach ($items as $orderItem) {
+            $available = $this->availableStock($orderItem);
+            if ($available < (int) $orderItem['quantity']) {
+                throw new InsufficientStockException($orderItem['productName']);
+            }
+        }
+
+        $this->db->transaction(function () use ($orderId, $items, $stripeSessionId): void {
+            foreach ($items as $orderItem) {
+                $this->decrementStock($orderItem);
+            }
+            $this->orders->setStatus($orderId, 'paid', 'paidAt', $stripeSessionId);
+        });
+
+        $this->redeemCoupon($order['couponCode'] ?? null);
+        $this->notify($orderId, 'confirmation');
+    }
+
+    public function markFulfilled(int $orderId): void
+    {
+        $order = $this->orders->find($orderId);
+        if ($order === null) {
+            throw new \RuntimeException('Order not found');
+        }
+        if ($order['status'] !== 'paid') {
+            throw new \RuntimeException('Only paid orders can be fulfilled');
+        }
+        $this->orders->setStatus($orderId, 'fulfilled', 'fulfilledAt');
+        $this->notify($orderId, 'status');
+    }
+
+    public function attachStripeSession(int $orderId, string $sessionId): void
+    {
+        $this->orders->setStatus($orderId, 'pending', null, $sessionId);
+    }
+
+    private function availableStock(array $orderItem): int
+    {
+        if ($orderItem['variantId'] !== null) {
+            $variant = $this->variants->find((int) $orderItem['variantId']);
+            return $variant === null ? 0 : (int) $variant['stockQuantity'];
+        }
+        $product = $this->products->find((int) $orderItem['productId']);
+        return $product === null ? 0 : (int) $product['stockQuantity'];
+    }
+
+    private function decrementStock(array $orderItem): void
+    {
+        if ($orderItem['variantId'] !== null) {
+            $this->variants->decrementStock((int) $orderItem['variantId'], (int) $orderItem['quantity']);
+            return;
+        }
+        $this->products->decrementStock((int) $orderItem['productId'], (int) $orderItem['quantity']);
+    }
+
+    private function redeemCoupon(?string $couponCode): void
+    {
+        if ($couponCode === null || $couponCode === '') {
+            return;
+        }
+        $coupon = $this->coupons->findByCode($couponCode);
+        if ($coupon !== null) {
+            $this->coupons->recordRedemption((int) $coupon['id']);
+        }
+    }
+
+    private function notify(int $orderId, string $kind): void
+    {
+        $order = $this->orders->find($orderId);
+        $user = $this->users->findById((int) $order['userId']);
+        if ($user === null) {
+            return;
+        }
+        if ($kind === 'confirmation') {
+            $this->orderMailer->orderConfirmation($user['email'], $order, $this->orders->items($orderId));
+            return;
+        }
+        $this->orderMailer->statusUpdate($user['email'], $order);
+    }
+}