Split command line into file name and arguments

/// <summary>
/// Splits the file name if it contains an executable AND an argument.
/// </summary>
private static void checkSplitFileName( ref string fileName, ref string arguments )
{
    if ( !string.IsNullOrEmpty( fileName ) )
    {
        if ( fileName.IndexOf( @"http://" ) == 0 ||
            fileName.IndexOf( @"https://" ) == 0 ||
            fileName.IndexOf( @"ftp://" ) == 0 ||
            fileName.IndexOf( @"file://" ) == 0 )
        {
            // URLs not supported, skip.
            return;
        }
        if ( File.Exists( fileName ) )
        {
            // Already a full path, do nothing.
            return;
        }
        else if ( Directory.Exists( fileName ) )
        {
            // Already a full path, do nothing.
            return;
        }
        else
        {
            // Remember.
            string originalFileName = fileName;

            if ( !string.IsNullOrEmpty( fileName ) )
            {
                fileName = fileName.Trim();
            }

            if ( !string.IsNullOrEmpty( arguments ) )
            {
                arguments = arguments.Trim();
            }

            // --

            if ( string.IsNullOrEmpty( arguments ) &&
                !string.IsNullOrEmpty( fileName ) && fileName.Length > 2 )
            {
                if ( fileName.StartsWith( @"""" ) )
                {
                    int pos = fileName.IndexOf( @"""", 1 );

                    if ( pos > 0 && fileName.Length > pos + 1 )
                    {
                        arguments = fileName.Substring( pos + 1 ).Trim();
                        fileName = fileName.Substring( 0, pos + 1 ).Trim();
                    }
                }
                else
                {
                    int pos = fileName.IndexOf( @" " );
                    if ( pos > 0 && fileName.Length > pos + 1 )
                    {
                        arguments = fileName.Substring( pos + 1 ).Trim();
                        fileName = fileName.Substring( 0, pos + 1 ).Trim();
                    }
                }
            }

            // --
            // Possibly revert back.

            if ( !string.IsNullOrEmpty( fileName ) )
            {
                string s = fileName.Trim( '"' );
                if ( !File.Exists( s ) && !Directory.Exists( s ) )
                {
                    fileName = originalFileName;
                }
            }
        }
    }
}