HostName.cs

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

namespace Hosts;

public class HostName
{
	private static IdnMapping IdnMapping = new IdnMapping();

	public string Ascii { get; protected set; }
	public string Unicode { get; protected set; }
	public bool Idn { get; protected set; }

	public HostName(string host)
	{
		if (host == null) { throw new ArgumentNullException(); }

		try
		{
			host = host.ToLower();
			if (Uri.CheckHostName(host) != UriHostNameType.Dns) { throw new Exception(); }
			if (host.StartsWith("xn--") || host.Contains(".xn--"))
			{
				Unicode = IdnMapping.GetUnicode(host);
				Ascii = IdnMapping.GetAscii(Unicode);
			}
			else
			{
				Ascii = IdnMapping.GetAscii(host);
				Unicode = IdnMapping.GetUnicode(Ascii);
			}
			Idn = Ascii != Unicode;
		}
		catch (Exception e)
		{
			throw new FormatException($"Invalid host '{host}'.", e);
		}
	}

	public static HostName TryCreate(string host)
	{
		try	{ return new HostName(host); }
		catch { return null; }
	}

	public static implicit operator HostName(string host)
	{
		return new HostName(host);
	}

	public static implicit operator string(HostName host)
	{
		return host.ToString();
	}

	public override string ToString()
	{
		return Idn ? Unicode : Ascii;
	}

	public string ToString(bool idn)
	{
		return idn ? Unicode : Ascii;
	}

	public override int GetHashCode()
	{
		return ToString().GetHashCode();
	}

	public bool Equals(HostName host)
	{
		if ((object)host == null) { return false; }
		return host.Unicode == this.Unicode;
	}

	public bool Equals(string host)
	{
		return Equals(HostName.TryCreate(host));
	}

	public override bool Equals(object obj)
	{
		if (obj == null) { return false; }
		if (obj is string) { return Equals((string)obj); }
		if (obj is HostName) { return Equals((HostName)obj); }
		return false;
	}

	public static bool operator ==(HostName hn1, HostName hn2)
	{
		return Object.ReferenceEquals(hn1, hn2) || hn1.Equals(hn2);
	}

	public static bool operator !=(HostName hn1, HostName hn2)
	{
		return !(Object.ReferenceEquals(hn1, hn2) || hn1.Equals(hn2));
	}
}