using System;

using System.Globalization;

​

public class Program

{

    /*

    Complete the function below which takes a dollar value and writes it out in

    words. It's not a trick question but has a few logic details to work out.

    We're interested in:

    * How you solve a problem

    * Clean, concise code, which communicates your ideas clearly

    * Good understanding of unit testing

​

    Some tests are given below, but they aren't complete. Consider other cases and

    how you might handle them.

​

    There isn't any time limit but it shouldn't take more than a couple of hours,

    and if you are really stuck please get in touch for a hint. We work in a team

    in the real world so sensible questions wont be considered a failure!

    */

​

​

​

    /// <summary>

    /// Write out a dollar value in words. Handles values less than $1,000, and

    /// up to two decimal places.

    /// </summary>

    static string DollarsToWords(decimal value)

    {

        if (value < 0)

        {

            value = Math.Abs(value);

        }

        if (value == 0) return "zero dollars";

        string word;

        var valStr = value.ToString(CultureInfo.InvariantCulture);

        var splitOnDecimalVal = valStr.Split(new[] {'.'});

        if (splitOnDecimalVal.Length == 2)

        {

            var dollarAmtString = ConvertDollarAmountToWords(Convert.ToInt32(splitOnDecimalVal[0]), true);

            var centAmtString = ConvertCentAmountToWords(Convert.ToInt32(splitOnDecimalVal[1]));

            if (!string.IsNullOrWhiteSpace(dollarAmtString))

            {

                word = $"{dollarAmtString}".Trim();

                word = AppendAndIfNeeded(centAmtString, word);

                word += $" {centAmtString}";

            }

            else

            {

                word = $"{centAmtString}";

            }

        }

        else

        {

            var centAmtString = ConvertCentAmountToWords(Convert.ToInt32(splitOnDecimalVal[0]));

            word = centAmtString;

        }

​

        return word.Trim().ToLowerInvariant();

    }

​

    private static string ConvertCentAmountToWords(int value)

    {

        if (value <= 0) return string.Empty;

        var word = GetEquivalentWordForInt(value);

        return $"{word} {(value == 1 ? "cent" : "cents")}";

    }

    private static string ConvertDollarAmountToWords(int value, bool hasDecimals)

    {

        if (value <= 0 && hasDecimals) return string.Empty;

        var word = GetEquivalentWordForInt(value);

        return $"{word} {(value == 1 ? "dollar" : "dollars")}";

    }

    private static string GetEquivalentWordForInt(int value)

    {

        var word = string.Empty;

        string tens;

        string hundreds;

        var tensVal = value % 100;

​

        //Check to see if the last see is less than twenty

        if (tensVal < 20)

        {

            tens = ConvertIntToWords(tensVal.ToString());

            var hundredVal = value / 100;

            hundreds = ConvertIntToWords(hundredVal.ToString());

            if (!string.IsNullOrWhiteSpace(hundreds))

            {

                word += $"{hundreds} hundred";

            }

            if (!string.IsNullOrWhiteSpace(tens))

            {

                word = AppendAndIfNeeded(tens, word);

                word += $" {tens}";

            }

        }

        else

        {

            var onesVal = tensVal % 10;

            var tenVal = tensVal / 10;

            var hundredVal = (value / 100);

​

            hundreds = ConvertIntToWords(hundredVal.ToString());

            tens = ConvertTensToWords(tenVal.ToString());

            var ones = ConvertIntToWords(onesVal.ToString());

            if (!string.IsNullOrWhiteSpace(hundreds))

            {

                word += $"{hundreds} hundred";

            }

            if (!string.IsNullOrWhiteSpace(tens))

            {

                word = AppendAndIfNeeded(tens, word);

                word += $" {tens}";

            }

​

            if (!string.IsNullOrWhiteSpace(ones))

            {

                if (string.IsNullOrWhiteSpace(tens))

                {

                    word = AppendAndIfNeeded(hundreds, word);

                }

​

                word += $" {ones}";

            }

        }

​

        return word.Trim();

    }

​

    public static string AppendAndIfNeeded(string s, string toBeModified)

    {

        if (!string.IsNullOrEmpty(s))

        {

            if (!string.IsNullOrEmpty(toBeModified))

            {

                toBeModified = $"{toBeModified} and";

            }

        }

​

        return toBeModified;

    }

​

    private static string ConvertTensToWords(string c)

    {

        var word = string.Empty;

        switch (c)

        {

            case "2":

                word = "Twenty";

                break;

            case "3":

                word = "Thirty";

                break;

            case "4":

                word = "Forty";

                break;

            case "5":

                word = "Fifty";

                break;

            case "6":

                word = "Sixty";

                break;

            case "7":

                word = "Seventy";

                break;

            case "8":

                word = "Eighty";

                break;

            case "9":

                word = "Ninety";

                break;

        }

        return word;

    }

    private static string ConvertIntToWords(string c)

    {

        var word = string.Empty;

        switch (c)

        {

            case "1":

                word = "One";

                break;

            case "2":

                word = "Two";

                break;

            case "3":

                word = "Three";

                break;

            case "4":

                word = "Four";

                break;

            case "5":

                word = "Five";

                break;

            case "6":

                word = "Six";

                break;

            case "7":

                word = "Seven";

                break;

            case "8":

                word = "Eight";

                break;

            case "9":

                word = "Nine";

                break;

            case "10":

                word = "Ten";

                break;

            case "11":

                word = "Eleven";

                break;

            case "12":

                word = "Twelve";

                break;

            case "13":

                word = "Thirteen";

                break;

            case "14":

                word = "Fourteen";

                break;

            case "15":

                word = "Fifteen";

                break;

            case "16":

                word = "Sixteen";

                break;

            case "17":

                word = "Seventeen";

                break;

            case "18":

                word = "Eighteen";

                break;

            case "19":

                word = "Ninteen";

                break;

        }

​

        return word;

    }

​

    public static void Main()

    {

        Test(0, "zero dollars");

        Test(0.12m, "twelve cents");

        Test(10.55m, "ten dollars and fifty five cents");

        Test(120, "one hundred and twenty cents");

        Test(-120, "one hundred and twenty cents");

        Test(999.99m, "nine hundred and ninety nine dollars and ninety nine cents");

        Test(999, "nine hundred and ninety nine cents");

        Test(100.50m, "one hundred dollars and fifty cents");

        Test(101.50m, "one hundred and one dollars and fifty cents");

        Test(1.00m, "one dollar");

        Test(1.05m, "one dollar and five cents");

        Test(1.01m, "one dollar and one cent");

        Test(500.00m, "five hundred dollars");

        Test(110.10m, "one hundred and ten dollars and ten cents");

        Test(0.02m, "two cents");

        Test(0.01m, "one cent");

​

    }

​

​

    static void Test(decimal number, string expected)

    {

        var actual = DollarsToWords(number);

​

        if (actual == expected)

        {

            Console.WriteLine($"{number}: PASS");

            return;

        }

​

        Console.WriteLine($"{number}: FAIL");

        Console.WriteLine($"  Expected: {expected}");

        Console.WriteLine($"  Actual:   {actual}");

        Console.WriteLine();

    }

}