using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Atlantis_Mask
{
    class Program
    {
        static void Main(string[] args)
        {


        }

        /// <summary>
        /// Formats a full address of a user in a certain mask format as in the following list where m = masktype % 10 and fulladdress = nick!~user@some.host.com
        /// <list type="bullet">
        ///     <item>
        ///         <term>0</term>
        ///         <description>No nick: *!user@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>1</term>
        ///         <description>No nick or identd marker (~): *!*user@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>2</term>
        ///         <description>No nick or identd: *!*@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>3</term>
        ///         <description>No nick or identd marker, no first host token: *!*user@*.host.com (or *!*user@host if host contains no '.')</description>
        ///     </item>
        ///     <item>
        ///         <term>4</term>
        ///         <description>No nick or identd: *!*@*.host.com (or *!*@host if host contains no '.')</description>
        ///     </item>
        ///     <item>
        ///         <term>5</term>
        ///         <description>No change: nick!~user@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>6</term>
        ///         <description>No identd marker (~): nick!*user@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>7</term>
        ///         <description>No identd: nick!*@some.host.com</description>
        ///     </item>
        ///     <item>
        ///         <term>8</term>
        ///         <description>No identd marker (~) or first host token: nick!*user@*.host.com (or nick!*user@host if host contains no '.')</description>
        ///     </item>
        ///     <item>
        ///         <term>9</term>
        ///         <description>No identd or first host token: nick!*@*.host.com (or nick!*@host if host contains no '.')</description>
        ///     </item>
        /// </list>
        /// </summary>
        /// <param name="fulladdress"></param>
        /// <param name="masktype"></param>
        /// <returns></returns>
        public static string Mask(string fulladdress, int masktype)
        {
            string nick = ClipAddress(fulladdress, AddressPart.NICK);
            string identd = ClipAddress(fulladdress, AddressPart.IDENTD);
            string host = ClipAddress(fulladdress, AddressPart.HOST);
            int m = masktype % 10;
            switch (m)
            {
                case 0: // *!user@some.host.com
                    return String.Format("*!{0}@{1}", identd, host);
                case 1: //  *!*user@some.host.com
                    if (identd[0] == '~') // If starts with marker, clip marker
                        identd = identd.Substring(1);
                    else if (identd[0] == '*')
                        return String.Format("*!{0}@{1}", identd, host);
                    return String.Format("*!*{0}@{1}", identd, host);
                case 2: // *!*@some.host.com
                    return String.Format("*!*@{0}", host);
                case 3: // *!*user@*.host.com
                    string[] hosttokens = host.Split('.');
                    if (hosttokens.Length > 1)
                        host = "*." + String.Join(".", hosttokens, 1, hosttokens.Length - 1);
                    return Mask(String.Format("{0}!{1}@{2}",nick,identd,host), 1);

                case 4: //*!*@*.host.com
                     hosttokens = host.Split('.');
                    if (hosttokens.Length > 1)
                        host = "*." + String.Join(".", hosttokens, 1, hosttokens.Length - 1);
                    return Mask(String.Format("*!*@{0}", host), 2);

                case 5: // No change
                    return fulladdress;

                case 6:  // nick!*user@some.host.com
                    if (identd[0] == '~') // If starts with marker, clip marker
                        identd = identd.Substring(1);
                    else if (identd[0] == '*')
                        return String.Format("{2}!{0}@{1}", identd, host, nick);
                    return String.Format("{2}!*{0}@{1}", identd, host, nick);
                case 7: // nick!*@some.host.com
                    return String.Format("{0}!*@{1}", nick, host);
                case 8: // nick!*user@*.host.com
                     hosttokens = host.Split('.');
                    if (hosttokens.Length > 1)
                        host = "*." + String.Join(".", hosttokens, 1, hosttokens.Length - 1);
                    string identdMasked = Mask(fulladdress, 6);
                    return identdMasked.Substring(0,identdMasked.IndexOf('@') +1) + host ;
                case 9: // nick!*@*.host.com
                    string hostMasked = Mask(fulladdress, 8);
                    return String.Format("{0}!*@{1}", nick, hostMasked.Substring(hostMasked.IndexOf('@') +1));

                default:
                    return "A";
                    throw new Exception("Logic fault. Impossible.");
            }
        }
        /// <summary>
        /// Returns the specified portion of a full address in format nick!user@host. Throws MalformedAddressException if address is malformed.;
        /// </summary>
        ///
        /// <param name="fulladdress"></param>
        /// <param name="part"></param>
        /// <returns></returns>
        public static string ClipAddress(string fulladdress, AddressPart part)
        {
            int index1 = fulladdress.IndexOf('!');
            int index2 = fulladdress.IndexOf('@');
            if (index1 > index2)
                throw new MalformedAddressException(fulladdress, "'!' is located after '@'");
            else if (index1+1 == fulladdress.Length || index2+1 == fulladdress.Length)
                throw new MalformedAddressException(fulladdress, "No identd or host body");
            else if (index1 == 0)
                throw new MalformedAddressException(fulladdress, "No nick body");

            string identd = fulladdress.Substring(index1 + 1, index2 - index1 - 1);
            if (identd[0] == '~' && identd.Length == 1)
                throw new MalformedAddressException(fulladdress, "Identd contains only the identd marker (~) and is therefore invalid");


            switch (part)
            {
                case AddressPart.HOST:
                    return fulladdress.Substring(index2+1);
                case AddressPart.IDENTD:
                    return identd;
                case AddressPart.NICK:
                    return fulladdress.Substring(0, index1);
                default:
                    throw new Exception("Error in ClipAddress: AddressPart enumeration not handled.");

            }
        }
    }
    public class MalformedAddressException : Exception
    {
        public MalformedAddressException(string address, string reasonForMalformity)
            : base("\"" + address + "\" is not a valid address: " + reasonForMalformity)
        {

        }
    }
    public enum AddressPart { NICK, IDENTD, HOST }
}