using System;

​

/*

Strategy pattern applied

​

    We want modularity and extensibility,

    so we can easily add or remove some other

    variation of the taxes and do not affect 

    any changing of existing code by doing that.

*/

​

public class Program

{

    public static void Main()

    {

        int taxAmount = 0;  

        TaxCalculator taxCal = new TaxCalculator();

        /*

            We can play here more with security of input (only number is allowed)

            but I believe it is not a point of this task

        */

        Console.WriteLine("Enter your gross salary:");

        int grossSalary = Convert.ToInt32(Console.ReadLine());  

        taxCal.Calculate(new IncomeTax());

        taxAmount += taxCal.getTaxAmountFrom(grossSalary);

​

        taxCal.Calculate(new SocialTax());

        taxAmount += taxCal.getTaxAmountFrom(grossSalary);

        Console.WriteLine("Your net salary is:");

        Console.WriteLine(grossSalary - taxAmount + " IDR");

    }

}

​

//Always good to have some constants extracted

public static class TaxStatement

{

    public const int noTax = 0;

    public const int minAmountForCalculation = 1000;

    public const int maxSocialAmountForCalculation = 3000;

}

​

public static class Percentage

{

    public const double ten = 0.10;

    public const double fifteen = 0.15;

}

​

public interface ITax

{

    int Calculate(int amount);

}

​

public class IncomeTax : ITax

{   

    public int Calculate(int grossAmount)

    {

        if (grossAmount > TaxStatement.minAmountForCalculation) 

        {

            int taxableAmount = grossAmount - TaxStatement.minAmountForCalculation;

            return (int)(taxableAmount * Percentage.ten);       

        }

        return TaxStatement.noTax;

    }

}

​

public class SocialTax : ITax

{

    public int Calculate(int grossAmount)

    {

        if (grossAmount > TaxStatement.minAmountForCalculation) 

        {       

            int taxableAmount = grossAmount;

​

            //I hope I understood the way of calculation base, based on given example

            if (grossAmount > TaxStatement.maxSocialAmountForCalculation) 

            {

                taxableAmount = TaxStatement.maxSocialAmountForCalculation - TaxStatement.minAmountForCalculation;

            }

​

            return (int)(taxableAmount * Percentage.fifteen);

        }

        return TaxStatement.noTax;

    }

}

​

public class TaxCalculator 

{

    private ITax tax;

    public void Calculate(ITax tax) 

    {

        this.tax = tax;     

    }

    public int getTaxAmountFrom(int grossAmount)

    {

        return tax.Calculate(grossAmount);

    }

}