Adapter Pattern

// ─── EXAMPLE 1 ──────────────────────────────────────────────────────────────
// WHAT WE ARE IMPLEMENTING:
// A generic notification system integrating a legacy third-party SMS API.
//
// WHERE THE PATTERN FITS IN:
// TwilioAdapter is the Adapter. It implements the target client interface
// NotificationChannel and wraps the Adaptee TwilioService.
// ────────────────────────────────────────────────────────────────────────────
// --- Target interface (what the client expects) ---
interface NotificationChannel {
    boolean send(String recipient, String message);
}

// --- Adaptee (incompatible third-party library) ---
class TwilioService {
    public String dispatchSms(String phoneNumber, String text) {
        System.out.println("  [Twilio] Dispatching to " + phoneNumber + ": " + text);
        return "msg_" + System.currentTimeMillis();
    }
}

// --- Adapter ---
class TwilioAdapter implements NotificationChannel {
    private final TwilioService twilioService;

    public TwilioAdapter(TwilioService twilioService) {
        this.twilioService = twilioService;
    }

    public boolean send(String recipient, String message) {
        String msgId = twilioService.dispatchSms(recipient, message);
        return msgId != null;
    }
}

// --- Client ---
class NotificationService {
    private final NotificationChannel channel;

    public NotificationService(NotificationChannel channel) {
        this.channel = channel;
    }

    public void alert(String recipient, String message) {
        if (channel.send(recipient, message)) {
            System.out.println("  Alert sent successfully to " + recipient);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        NotificationChannel adapter = new TwilioAdapter(new TwilioService());
        NotificationService service = new NotificationService(adapter);
        service.alert("+1234567890", "System is down!");
    }
}