using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace AMWD.Common.Comparer
{
	/// <summary>
	/// Defines a method to compare two <see cref="Version"/> strings.
	/// </summary>
#if NET8_0_OR_GREATER
	public partial class VersionStringComparer : IComparer<string>
	{
		private readonly Regex _versionRegex = VersionRegex();
#else

	public class VersionStringComparer : IComparer<string>
	{
		private readonly Regex _versionRegex = new("([0-9.]+)");
#endif

		/// <summary>
		/// Compares two <see cref="Version"/> strings and returns a value indicating
		/// whether one is less than, equal to, or greater than the other.
		/// </summary>
		/// <param name="x">The first version string.</param>
		/// <param name="y">The second version 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>-1</term>
		///     <description>x is less than y</description>
		///   </item>
		///   <item>
		///     <term>0</term>
		///     <description>x equals y</description>
		///   </item>
		///   <item>
		///     <term>1</term>
		///     <description>x is greater than y</description>
		///   </item>
		/// </list>
		/// </returns>
		public int Compare(string x, string y)
		{
			if (string.IsNullOrWhiteSpace(x) && string.IsNullOrWhiteSpace(y))
				return 0;

			if (string.IsNullOrWhiteSpace(x))
				return -1;

			if (string.IsNullOrWhiteSpace(y))
				return 1;

			string xMainVersion = _versionRegex.Match(x).Groups[1].Value;
			string yMainVersion = _versionRegex.Match(y).Groups[1].Value;

			string xAppendix = x.ReplaceStart(xMainVersion, "");
			string yAppendix = y.ReplaceStart(yMainVersion, "");

			if (xMainVersion.IndexOf('.') < 0)
				xMainVersion += ".0";

			if (yMainVersion.IndexOf('.') < 0)
				yMainVersion += ".0";

			var xVersion = Version.Parse(xMainVersion);
			var yVersion = Version.Parse(yMainVersion);

			int versionResult = xVersion.CompareTo(yVersion);
			if (versionResult != 0)
				return versionResult;

			return xAppendix.CompareTo(yAppendix);
		}

#if NET8_0_OR_GREATER
		[GeneratedRegex("([0-9.]+)")]
		private static partial Regex VersionRegex();
#endif
	}
}