using System;

using System.IO;

using System.Threading.Tasks;

​

public class Foo<T>

{

    private readonly T _startValue;

​

    public Foo(T startValue)

    {

        _startValue = startValue ?? throw new ArgumentNullException(nameof(startValue), "Start value cannot be null.");

    }

​

    // Perform the calculation safely with input validation

    public int DoCalc(object arg1, T arg2)

    {

        // Validate arg1 type

        if (arg1 is not int)

        {

            throw new ArgumentException("arg1 must be an integer.");

        }

​

        // Ensure T is convertible to int for safety

        if (arg2 is not IConvertible)

        {

            throw new ArgumentException("arg2 must be convertible to an integer.");

        }

​

        int result = (int)arg1 + Convert.ToInt32(arg2) / Convert.ToInt32(_startValue);

        return result;

    }

​

    // Higher-order calculation with input validation

    public static int HigherOrderCalculation(Func<int, int, int> func, int one, int two)

    {

        if (func == null)

        {

            throw new ArgumentNullException(nameof(func), "Function cannot be null.");

        }

​

        return func(one, two);

    }

​

    // Log message to the console

    public void LogToConsole(string message)

    {

        if (string.IsNullOrEmpty(message))

        {

            throw new ArgumentException("Message cannot be null or empty.", nameof(message));

        }

​

        Console.WriteLine(message);

    }

​

    // Log message to a file asynchronously with proper validation

    public async Task LogToFileAsync(string message)

    {

        if (string.IsNullOrEmpty(message))

        {

            throw new ArgumentException("Message cannot be null or empty.", nameof(message));

        }

​

        string fileName = $"logfile{DateTime.Now:yyyy-MM-dd}.log";

        await File.AppendAllTextAsync(fileName, $"{message}{Environment.NewLine}");

    }

}

​

class Program

{

    static async Task Main(string[] args)

    {

        // Create an instance of Foo

        var foo = new Foo<double>(1.5d);

​

        // Log to console

        foo.LogToConsole("Hello World!");

​

        // Log to file asynchronously

        await foo.LogToFileAsync("Hello World!");

​

        // Perform calculations

        var result1 = foo.DoCalc(1, 2.0); // Example for non-static method

        Console.WriteLine($"DoCalc Result: {result1}");

​

        // Perform higher-order calculation

        var result2 = Foo<double>.HigherOrderCalculation((x, y) => x + y, 3, 4);

        Console.WriteLine($"HigherOrderCalculation Result: {result2}");

    }

}

​