using System.Collections.Generic;

namespace AMWD.Common.Comparer
{
	/// <summary>
	/// Defines a method to compare two domain strings.
	/// </summary>
	public class DomainComparer : IComparer<string>
	{
		/// <summary>
		/// Compares two domain strings and returns a value indicating
		/// whether one is less than, equal to, or greater than the other.
		/// </summary>
		/// <param name="x">The first domain string.</param>
		/// <param name="y">The second domain string.</param>
		/// <returns>
		/// A signed integer that indicates the relative values of x and y, as shown in the following table:
		/// <list type="table">
		///   <listheader>
		///     <term>Value</term>
		///     <description>Meaning</description>
		///   </listheader>
		///   <item>
		///     <term>Less than zero</term>
		///     <description>x is less than y</description>
		///   </item>
		///   <item>
		///     <term>Zero</term>
		///     <description>x equals y</description>
		///   </item>
		///   <item>
		///     <term>Greater than zero</term>
		///     <description>x is greater than y</description>
		///   </item>
		/// </list>
		/// </returns>
		public int Compare(string x, string y)
		{
			string[] left = x.Split('.');
			string[] right = y.Split('.');

			int result = left.Length.CompareTo(right.Length);
			if (result != 0)
				return result;

			// Compare from TLD to subdomain with string comparison
			for (int i = left.Length - 1; i >= 0; i--)
			{
				result = left[i].CompareTo(right[i]);
				if (result != 0)
					return result;
			}

			return 0;
		}
	}
}