using System;

using System.Linq;

using System.Text.RegularExpressions;

​

/// <summary>

/// Translate English text in to Pig Latin. Based on the rules outlined on Wikipedia:

/// https://en.wikipedia.org/wiki/Pig_Latin

/// 

/// Press "Run" above, then check the output in the pane below to see if all the tests

//  pass and the program is correct.

/// </summary>

public class Program

{

    /// <summary>

    /// Unit tests. Add new tests to this list to check for new cases not

    /// covered by existing code.

    /// </summary>

    public static void Main()

    {

        // Words beginning with one consonant

        Test("pig", "igpay");

        Test("latin", "atinlay");

        Test("banana", "ananabay");

        // Words beginning with two consonants

        Test("smile", "ilesmay");

        Test("string", "ingstray");

​

        // Words beginning with vowels

        Test("angel", "angelway");

        Test("astronomer", "astronomerway");

        // Sensible treatment of capital letters

        Test("Pig", "Igpay");

        Test("SHOUT", "OUTSHAY");

        // Multiple words

        Test("flying pigs", "ingflyay igspay");

        Test("Hello World", "Ellohay Orldway");

        Test("This is a test.", "Isthay isway away esttay.");

        // single letters

        Test("p", "pay");

        Test("i", "iway");

        Test("g", "gay");

        // Nonsense

        Test(string.Empty, string.Empty);

        Test(null, null);

        // Non-english-word input

        Test("12345", "12345");

        Test("!@#$%", "!@#$%");

        Test("ㄱㄴㄷ", "ㄱㄴㄷ");

​

        Results();

    }

    /// <summary>

    /// Implementation. Make code changes here to make the tests pass.

    /// </summary>

    static string EnglishToPigLatin(string english)

    {

        var wordPattern = new Regex(@"\w+");

        return wordPattern.Replace(english, new MatchEvaluator(match =>

        {

            var word = match.Value;

            return CopyCapitalization(word, ConvertEnglishToPigLatin(word));

        }));

    }

    static string ConvertEnglishToPigLatin(string english)

    {

        if (english.Length == 0) {

            return string.Empty;

        }

        if (IsVowel(english[0])) {

            return english + "way";

        }

        var firstConsCount = english.TakeWhile(IsConsonant).Count();

        if (firstConsCount > 1) {

            return english.Substring(firstConsCount) + english.Substring(0, firstConsCount) + "ay";

        } else {

            return english.Substring(1) + english[0] + "ay";

        }

    }

    static string CopyCapitalization(string source, string text)

    {

        if (string.IsNullOrEmpty(text)) {

            return text;

        }

        if (source.All(Char.IsUpper)) {

            return text.ToUpper();

        }

        if (Char.IsUpper(source[0])) {

            return text.Substring(0, 1).ToUpper() + text.Substring(1).ToLower();

        }

        return text;

    }

    static bool IsVowel(char c) => "aeiou".Contains(c, StringComparison.InvariantCultureIgnoreCase);

    static bool IsConsonant(char c) => !IsVowel(c);

    /*

     * What follows is a very short testing framework. You can ignore everything below here

     * if you want to, or add to it if you want better output from the tests above.

     */

    static int pass, fail;

​

    static void Test(string input, string expected)

    {

        Console.WriteLine("Test: " + input);

        string actual;

        try {

            actual = EnglishToPigLatin(input);

            if (actual == expected)

            {

                pass++;

                Console.WriteLine("PASS.\n");

                return;

            }

        } catch(Exception e) {

            actual = "Exception: " + e.Message;

        }

        fail++;

        Console.WriteLine("FAIL:");

        Console.WriteLine("    Expected: " + expected);

        Console.WriteLine("    Actual  : " + actual);

        Console.WriteLine();

    }

    static void Results()

    {

        Console.WriteLine($"{pass} / {pass + fail} tests passed.\n");

        Console.WriteLine(fail == 0 ? "SUCCESS!" : "FAILURE!");

    }

}

​