using System;

using System.IO;

using System.Threading.Tasks;

​

public interface ILogger

{

    void LogToConsole(string message);

    Task LogToFileAsync(string message);

}

​

public class Constants

{

    public static string DateTimeFormat_yyyyMMdd="yyyy-MM-dd";

}

​

public class FileLogger : ILogger

{

    public void LogToConsole(string message)

    {

        Console.WriteLine(message);

    }

​

    public async Task LogToFileAsync(string message)

    {

        string filename = $"logfile_{DateTime.Now.ToString(Constants.DateTimeFormat_yyyyMMdd)}.log";

        await File.AppendAllTextAsync(filename, message + Environment.NewLine);

    }

}

​

public class Calculator<T> where T : struct, IConvertible

{

    private readonly T _startValue;

    private readonly ILogger _logger;

​

    public Calculator(T startValue, ILogger logger)

    {

        _startValue = startValue;

        _logger = logger;

    }

​

    public int DoCalculation(object arg1, T arg2)

    {

        try

        {

            if (arg1 is not IConvertible convertibleArg1)

                throw new ArgumentException("arg1 must be convertible to int.");

​

            int firstValue = convertibleArg1.ToInt32(null);

            int secondValue = Convert.ToInt32(arg2);

            int startValue = Convert.ToInt32(_startValue);

​

            if (startValue == 0)

                throw new DivideByZeroException("Start value must not be zero.");

​

            return firstValue + secondValue/startValue;

        }

        catch(Exception ex)

        {

            LogToConsole(ex.Message);

            throw ex;

        }

    }

​

    public int HigherOrderCalculation(Func<int, int, int> operation, int x, int y)

    {

        return operation(x, y);

    }

​

    public void LogToConsole(string message)

    {

        _logger.LogToConsole(message);

    }

​

    public Task LogToFileAsync(string message)

    {

        return _logger.LogToFileAsync(message);

    }

}

public class Program

{

    public async static Task Main()

    {

            ILogger _logger = new FileLogger();

            Calculator<double> _calculator = new Calculator<double>(1.5d, _logger);

​

            _calculator.LogToConsole("Hello world");

            await _calculator.LogToFileAsync("Hello world");

​

            var result1 = _calculator.DoCalculation(1, 2.0);

            var result2 = _calculator.HigherOrderCalculation((x, y) => x + y, 3, 4);

    }

}