using System;

using System.Linq;

using System.Text;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        string[] subdomains = new[] { "customer1", "222", "blah", "longsubdomain", "longersubdomainstill" };

        int[] randomIndex = new[] { 0, 5, 10, 20, 12 }; // Random number 0 to 31 which serves as a randomly picked

                                                        // index within the length of an md5 string

        foreach (var index in randomIndex)

        {

            Console.WriteLine("index: " + index);

            foreach (var subdomain in subdomains)

            {

                Console.WriteLine(subdomain);

                Console.WriteLine("\tiscanary:" + IsCanaryUI(subdomain, index));

            }

            Console.WriteLine("-------");

        }

    }

    private static bool IsCanaryUI(string customerId, int index)

    {

        // if customer opts in - return true;

        // Load percentage from /assets/workspace/canary.json

        // ie { 'percentage' : 10 }

        var currentCanaryPercent = 38;

        // if (100) return true;

        // Calculate for this request based on percentage

        var customerMd5 = GetMd5(customerId);

        var targetKey = customerMd5[index];

        var hexKey = Convert.ToInt32("0x"+targetKey, 16);

        Console.WriteLine("\tmd5: " + customerMd5);

        Console.WriteLine("\ttarget: " + targetKey);

        Console.WriteLine("\thexkey: " + hexKey);

        var customerOptInPercent = Math.Floor(hexKey * 6.25); // There are 16 possible values 0-9a-f

                                                              // 100 / 16 = 6.25, so each value represent ~6%

                        // If we didn't want anyone to get the code at 0%, we could use

                        // Math.Floor(hexKey * 6.25) + 1 (so the minimum opt in threshold is > 0

        Console.WriteLine("\tcustomerPercent:" + customerOptInPercent);

        return customerOptInPercent < currentCanaryPercent;

    }

    private static string GetMd5(string customerId)

    {

        var hash = new StringBuilder();

        var md5provider = new MD5CryptoServiceProvider();

        byte[] bytes = md5provider.ComputeHash(new UTF8Encoding().GetBytes(customerId));

        for (int i = 0; i < bytes.Length; i++)

        {

            hash.Append(bytes[i].ToString("x2"));

        }

        return hash.ToString();

    }

}