michaelschiemer/examples/default-implementation-usage.php

<?php

declare(strict_types=1);

/**
 * DefaultImplementation Attribute - Real-World Usage Examples
 *
 * This file demonstrates practical usage of the #[DefaultImplementation] attribute
 * in a typical application structure.
 */

namespace App\Examples\DefaultImplementation;

use App\Framework\DI\Attributes\DefaultImplementation;

// =============================================================================
// Example 1: Repository Pattern
// =============================================================================

interface UserRepository
{
    public function findById(string $id): ?User;
    public function findAll(): array;
    public function save(User $user): void;
}

/**
 * Database implementation of UserRepository
 * Automatically registered as default implementation
 */
#[DefaultImplementation(UserRepository::class)]
final readonly class DatabaseUserRepository implements UserRepository
{
    public function __construct(
        private DatabaseConnection $db
    ) {}

    public function findById(string $id): ?User
    {
        // Database query implementation
        return null; // Simplified
    }

    public function findAll(): array
    {
        return []; // Simplified
    }

    public function save(User $user): void
    {
        // Database insert/update implementation
    }
}

// =============================================================================
// Example 2: Service Layer
// =============================================================================

interface NotificationService
{
    public function send(string $recipient, string $message): void;
}

/**
 * Email-based notification service
 * Auto-detects NotificationService interface
 */
#[DefaultImplementation]  // No explicit interface - auto-detect
final readonly class EmailNotificationService implements NotificationService
{
    public function __construct(
        private MailerService $mailer
    ) {}

    public function send(string $recipient, string $message): void
    {
        $this->mailer->sendMail($recipient, 'Notification', $message);
    }
}

// =============================================================================
// Example 3: Infrastructure Adapters
// =============================================================================

interface CacheAdapter
{
    public function get(string $key): mixed;
    public function set(string $key, mixed $value, int $ttl = 3600): void;
    public function delete(string $key): void;
}

/**
 * Redis cache adapter
 * Automatically becomes the default cache implementation
 */
#[DefaultImplementation(CacheAdapter::class)]
final readonly class RedisCacheAdapter implements CacheAdapter
{
    public function __construct(
        private RedisConnection $redis
    ) {}

    public function get(string $key): mixed
    {
        return $this->redis->get($key);
    }

    public function set(string $key, mixed $value, int $ttl = 3600): void
    {
        $this->redis->setex($key, $ttl, $value);
    }

    public function delete(string $key): void
    {
        $this->redis->del($key);
    }
}

// =============================================================================
// Example 4: HTTP Client Abstraction
// =============================================================================

interface HttpClient
{
    public function get(string $url, array $headers = []): HttpResponse;
    public function post(string $url, array $data, array $headers = []): HttpResponse;
}

/**
 * Guzzle-based HTTP client
 * Auto-detects HttpClient interface
 */
#[DefaultImplementation]
final readonly class GuzzleHttpClient implements HttpClient
{
    public function __construct(
        private \GuzzleHttp\Client $guzzle
    ) {}

    public function get(string $url, array $headers = []): HttpResponse
    {
        $response = $this->guzzle->get($url, ['headers' => $headers]);
        return new HttpResponse($response->getStatusCode(), (string) $response->getBody());
    }

    public function post(string $url, array $data, array $headers = []): HttpResponse
    {
        $response = $this->guzzle->post($url, [
            'headers' => $headers,
            'json' => $data
        ]);
        return new HttpResponse($response->getStatusCode(), (string) $response->getBody());
    }
}

// =============================================================================
// Example 5: Multiple Interfaces (Auto-detect First)
// =============================================================================

interface EventLogger
{
    public function logEvent(string $event, array $context): void;
}

interface Flushable
{
    public function flush(): void;
}

/**
 * File-based event logger with flush capability
 * Auto-detects EventLogger (first interface)
 */
#[DefaultImplementation]  // Binds to EventLogger, not Flushable
final readonly class FileEventLogger implements EventLogger, Flushable
{
    public function __construct(
        private string $logFilePath
    ) {}

    public function logEvent(string $event, array $context): void
    {
        file_put_contents(
            $this->logFilePath,
            json_encode(['event' => $event, 'context' => $context]) . "\n",
            FILE_APPEND
        );
    }

    public function flush(): void
    {
        file_put_contents($this->logFilePath, '');
    }
}

// =============================================================================
// Example 6: Using Default Implementations
// =============================================================================

/**
 * Service that depends on default implementations
 */
final readonly class UserService
{
    public function __construct(
        private UserRepository $userRepository,         // DatabaseUserRepository injected
        private NotificationService $notifications,     // EmailNotificationService injected
        private CacheAdapter $cache                     // RedisCacheAdapter injected
    ) {}

    public function registerUser(string $email, string $name): void
    {
        // Check cache first
        $cachedUser = $this->cache->get("user:$email");
        if ($cachedUser !== null) {
            return; // User already registered
        }

        // Create and save user
        $user = new User($email, $name);
        $this->userRepository->save($user);

        // Cache the user
        $this->cache->set("user:$email", $user, 3600);

        // Send notification
        $this->notifications->send($email, "Welcome to our platform, $name!");
    }
}

// =============================================================================
// Example 7: Advanced - Combining with Initializers
// =============================================================================

interface PaymentGateway
{
    public function charge(int $amountInCents, string $token): PaymentResult;
}

/**
 * Stripe payment gateway
 * Requires complex initialization via Initializer
 */
#[DefaultImplementation(PaymentGateway::class)]
final readonly class StripePaymentGateway implements PaymentGateway
{
    public function __construct(
        private StripeApiClient $stripeClient
    ) {}

    public function charge(int $amountInCents, string $token): PaymentResult
    {
        return $this->stripeClient->createCharge($amountInCents, $token);
    }
}

/**
 * Initializer for StripeApiClient
 * Runs after DefaultImplementation registration
 */
final readonly class StripeInitializer
{
    #[\App\Framework\DI\Initializer]
    public function initializeStripeClient(): StripeApiClient
    {
        $apiKey = $_ENV['STRIPE_SECRET_KEY'] ?? throw new \RuntimeException('Missing Stripe API key');

        return new StripeApiClient($apiKey, [
            'api_version' => '2023-10-16',
            'timeout' => 30
        ]);
    }
}

// =============================================================================
// Usage in Application
// =============================================================================

/**
 * The container automatically resolves all dependencies:
 *
 * $container->get(UserService::class)
 *   -> UserRepository (DatabaseUserRepository)
 *   -> NotificationService (EmailNotificationService)
 *   -> CacheAdapter (RedisCacheAdapter)
 *
 * All instances are singletons - same instance returned on subsequent calls
 */

// =============================================================================
// Stub Classes (for example completeness)
// =============================================================================

class User
{
    public function __construct(
        public string $email,
        public string $name
    ) {}
}

class DatabaseConnection {}
class MailerService
{
    public function sendMail(string $to, string $subject, string $body): void {}
}
class RedisConnection
{
    public function get(string $key): mixed { return null; }
    public function setex(string $key, int $ttl, mixed $value): void {}
    public function del(string $key): void {}
}
class HttpResponse
{
    public function __construct(
        public int $statusCode,
        public string $body
    ) {}
}
class StripeApiClient
{
    public function __construct(string $apiKey, array $options) {}
    public function createCharge(int $amount, string $token): PaymentResult
    {
        return new PaymentResult(true, 'ch_123');
    }
}
class PaymentResult
{
    public function __construct(
        public bool $success,
        public string $transactionId
    ) {}
}