// Module de haut niveau (logique métier)
class OrderService
{
    private MySQLOrderRepository $repo;
    private SmtpMailer $mailer;
    private StripePaymentGateway $gateway;

    public function __construct()
    {
        // Dépendances créées en dur — impossible à tester ou remplacer
        $this->repo    = new MySQLOrderRepository();
        $this->mailer  = new SmtpMailer('smtp.mailtrap.io');
        $this->gateway = new StripePaymentGateway('sk_live_...');
    }

    public function placeOrder(Order $order): void
    {
        $this->gateway->charge($order);
        $this->repo->save($order);
        $this->mailer->send($order);
    }
    // Problèmes :
    // • Changer MySQL → PostgreSQL = modifier OrderService
    // • Changer Stripe → PayPal    = modifier OrderService
    // • Tests unitaires impossibles (appels réels à SMTP, Stripe, MySQL)
}

// Abstractions définies par la logique métier
interface OrderRepositoryInterface
{
    public function save(Order $order): void;
    public function findById(int $id): ?Order;
}

interface MailerInterface
{
    public function send(string $to, string $subject, string $body): void;
}

interface PaymentGatewayInterface
{
    public function charge(Order $order): PaymentResult;
}

// Module de haut niveau — dépend uniquement des interfaces
class OrderService
{
    public function __construct(
        private readonly OrderRepositoryInterface  $repository,
        private readonly MailerInterface           $mailer,
        private readonly PaymentGatewayInterface   $gateway
    ) {}

    public function placeOrder(Order $order): void
    {
        $result = $this->gateway->charge($order);
        $this->repository->save($order);
        $this->mailer->send(
            $order->getCustomerEmail(),
            'Commande confirmée',
            '...'
        );
    }
}

// Implémentations concrètes (modules de bas niveau)
class MySQLOrderRepository implements OrderRepositoryInterface
{
    public function save(Order $order): void  { /* ... */ }
    public function findById(int $id): ?Order { /* ... */ }
}

class StripePaymentGateway implements PaymentGatewayInterface
{
    public function charge(Order $order): PaymentResult { /* ... */ }
}

// Pour les tests : implémentations mock — SANS modifier OrderService
class InMemoryOrderRepository implements OrderRepositoryInterface
{
    private array $store = [];
    public function save(Order $order): void  { $this->store[] = $order; }
    public function findById(int $id): ?Order { return $this->store[$id] ?? null; }
}

# Le conteneur lit ce fichier et injecte les bonnes implémentations
services:
    App\Repository\OrderRepositoryInterface:
        alias: App\Repository\MySQLOrderRepository

    # En environnement de test, on utilise une autre implémentation
    # App\Repository\OrderRepositoryInterface:
    #     alias: App\Repository\InMemoryOrderRepository