using System;

using System.Threading.Tasks;

public interface INotifier

{

    Task SendReminder(string message, string recipient);

    Task SendExpirationWarning(DateTime expiration, string recipient);

}

​

public class EmailNotifier : INotifier

{

    public async Task SendReminder(string message, string recipient)

    {

        // send a reminder email

        Console.WriteLine("Sending reminder email");

    }

    public async Task SendExpirationWarning(DateTime expiration, string recipient)

    {

        // send a reminder email

        Console.WriteLine("Sending warning email");

    }

}

​

public class TextNotifier : INotifier

{

    public async Task SendReminder(string message, string recipient)

    {

        // send a reminder email

        Console.WriteLine("Sending reminder text");

    }

    public async Task SendExpirationWarning(DateTime expiration, string recipient)

    {

        // send a reminder email

        Console.WriteLine("Sending warning text");

    }

}

​

public class NotificationService {

    private readonly INotifier emailNotifier;

    private readonly INotifier textNotifier;

    public NotificationService()

    {

        // normally from DI

        emailNotifier = new EmailNotifier();

        textNotifier = new TextNotifier();

    }

    // *** code for saving/getting notification preferences via DB/cache etc

    private string GetPreference(string notificationType) {

        return notificationType switch {

            "reminder" => "text",

            "warning" => "email",

            _ => null,

        };

    }

​

    // *** 20 more variations of these methods, each with different parameters

    // ***

    // *** QUESTION 1: is there a better way to pass the parameters

    // *** through to the correct INotifier than the ternary

    // ***

    // *** QUESTION 2: is there a way to write all of the methods

    // *** as a single method despite the variations on parameters

    public async Task SendReminder(string message, string recipient)

    {

        var userPref = GetPreference("reminder");

​

        await (

            userPref == "text" ?

                textNotifier.SendReminder(message, recipient)

                : emailNotifier.SendReminder(message, recipient)

        );

    }

​

    public async Task SendExpirationWarning(DateTime expiration, string recipient)

    {

        var userPref = GetPreference("warning");

​

        await (

            userPref == "text" ?

                textNotifier.SendExpirationWarning(expiration, recipient)

                : emailNotifier.SendExpirationWarning(expiration, recipient)

        );

    }

    // etc

}

​

public class Program

{

    public static async Task Main()

    {

        var notifier = new NotificationService();

        await notifier.SendReminder("foo", "bar");

        await notifier.SendExpirationWarning(new DateTime(2025, 10, 20), "bar");

    }

}

​

​

​