namespace ZetaProducer.RuntimeBusinessLogic.Rendering.Helper
{
    using AngleSharp.Dom;
    using AngleSharp.Parser.Html;
    using System.Linq;
    using System.Net;
    using System.Text.RegularExpressions;

    public static class Texturizer
    {
        /// <summary>
        /// Angelehnt an die WordPress-Funktion "wptexturize".
        /// https://developer.wordpress.org/reference/functions/wptexturize
        /// https://codex.wordpress.org/Function_Reference/wptexturize
        /// Ersetzt bestimmte Zeichen.
        /// 
        /// Ist aber noch lange nicht so umfangreich wie die WordPress-Funktion.
        /// 
        /// Quelltext zu "wptexturize":
        /// https://github.com/WordPress/WordPress/blob/master/wp-includes/formatting.php#L51
        /// </summary>
        public static string Texturize(string text)
        {
            if (string.IsNullOrWhiteSpace(text)) return text;

            var parser = new HtmlParser();
            var document = parser.Parse(text);

            var it = document.CreateNodeIterator(document);

            INode node;
            var didFindBody = false;

            while ((node = it.Next()) != null)
            {
                if ((didFindBody || node.NodeName.ToLowerInvariant() == @"body") && !NoTexturizeTags.Contains(node.NodeName.ToLower()))
                {
                    didFindBody = true;

                    var before = node.NodeValue; // TODO: Ist 'NodeValue' die korrekte Property?
                    if (!string.IsNullOrEmpty(before))
                    {
                        var after = processOneNode(before);

                        if (after != before) node.NodeValue = after; // TODO: Ist 'NodeValue' die korrekte Property?
                    }
                }
            }

            return document.DocumentElement.GetElementsByTagName(@"body").First().InnerHtml;
        }

        private static string processOneNode(string content)
        {
            var result = content;

            result = Regex.Replace(result, @"(^|\s+)-(\s+|$)", $@"$1{EmDash}$2", RegexOptions.Singleline);
            result = Regex.Replace(result, @"(^|\b)\.\.\.(\b|$)", $@"$1{Ellipsis}$2", RegexOptions.Singleline);
            result = Regex.Replace(result, @"(^|\s+)""(\w+)", $@"$1{OpeningDoubleQuote}$2", RegexOptions.Singleline);
            result = Regex.Replace(result, @"(\w+)""(\s+|$|[!.,;])", $@"$1{ClosingDoubleQuote}$2", RegexOptions.Singleline);
            result = Regex.Replace(result, @"(^|\s+)'(\w+)", $@"$1{OpeningSingleQuote}$2", RegexOptions.Singleline);
            result = Regex.Replace(result, @"(\w+)'(\s+|$)", $@"$1{ClosingSingleQuote}$2", RegexOptions.Singleline);

            // TODO: Noch mehr (alle?) Regeln von WordPress übernehmen.

            // https://github.com/AngleSharp/AngleSharp/issues/361#issuecomment-230155588
            var c = WebUtility.HtmlDecode(result);

            return c;
        }

        private static readonly string[] NoTexturizeTags =
        {
            @"pre",
            @"code",
            @"kbd",
            @"style",
            @"script",
            @"tt"
        };

        private const string OpeningDoubleQuote = @"&bdquo;";
        private const string ClosingDoubleQuote = @"&ldquo;";
        private const string Apostrophe = @"&apos;";
        private const string OpeningSingleQuote = @"&sbquo;";
        private const string ClosingSingleQuote = @"&lsquo;";
        private const string EmDash = @"&mdash;";
        private const string EnDash = @"&ndash;";
        private const string Ellipsis = @"&hellip;";
    }
}