using System.IO;

// TODO: Split into separate library
namespace NaturalSort
{
    public static class NaturalComparerUtil
    {
        public static int CompareNumeric(string s1, string s2)
        {
            // Save the orginal strings, for later comparison
            string s1orig = s1;
            string s2orig = s2;

            // We want to normalize the strings, so we set both to lower case
            s1 = s1.ToLowerInvariant();
            s2 = s2.ToLowerInvariant();

            // If the strings are the same exactly, return
            if (s1 == s2)
                return s1orig.CompareTo(s2orig);

            // If one is null, then say that's less than
            if (s1 == null)
                return -1;
            if (s2 == null)
                return 1;

            // Now split into path parts after converting AltDirSeparator to DirSeparator
            s1 = s1.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
            s2 = s2.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
            string[] s1parts = s1.Split(Path.DirectorySeparatorChar);
            string[] s2parts = s2.Split(Path.DirectorySeparatorChar);

            // Then compare each part in turn
            for (int j = 0; j < s1parts.Length && j < s2parts.Length; j++)
            {
                int compared = CompareNumericPart(s1parts[j], s2parts[j]);
                if (compared != 0)
                    return compared;
            }

            // If we got out here, then it looped through at least one of the strings
            if (s1parts.Length > s2parts.Length)
                return 1;
            if (s1parts.Length < s2parts.Length)
                return -1;

            return s1orig.CompareTo(s2orig);
        }

        private static int CompareNumericPart(string s1, string s2)
        {
            // Otherwise, loop through until we have an answer
            for (int i = 0; i < s1.Length && i < s2.Length; i++)
            {
                int s1c = s1[i];
                int s2c = s2[i];

                // If the characters are the same, continue
                if (s1c == s2c)
                    continue;

                // If they're different, check which one was larger
                if (s1c > s2c)
                    return 1;
                if (s1c < s2c)
                    return -1;
            }

            // If we got out here, then it looped through at least one of the strings
            if (s1.Length > s2.Length)
                return 1;
            if (s1.Length < s2.Length)
                return -1;

            return 0;
        }
    }
}