using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading;
using System.Xml.Linq;
using NzbDrone.Core.Indexers;
using NzbDrone.Core.Parser.Model;

namespace NzbDrone.Core.IndexerSearch
{
    public class NewznabResults
    {
        private static readonly XNamespace _AtomNs = "http://www.w3.org/2005/Atom";
        private static readonly XNamespace _TorznabNs = "http://torznab.com/schemas/2015/feed";
        private static readonly XNamespace _NewznabNs = "http://www.newznab.com/DTD/2010/feeds/attributes/";

        // filters control characters but allows only properly-formed surrogate sequences
        // https://stackoverflow.com/a/961504
        private static readonly Regex _InvalidXmlChars = new Regex(
            @"(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|[\x00-\x08\x0B\x0C\x0E-\x1F\x7F-\x9F\uFEFF\uFFFE\uFFFF]",
            RegexOptions.Compiled);

        public List<ReleaseInfo> Releases { get; set; }

        private static string RemoveInvalidXMLChars(string text)
        {
            if (text == null)
            {
                return null;
            }

            return _InvalidXmlChars.Replace(text, "");
        }

        private static string XmlDateFormat(DateTime dt)
        {
            Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");

            //Sat, 14 Mar 2015 17:10:42 -0400
            return $"{dt:ddd, dd MMM yyyy HH:mm:ss} " + $"{dt:zzz}".Replace(":", "");
        }

        private static XElement GetNabElement(string name, object value, DownloadProtocol protocol)
        {
            if (value == null)
            {
                return null;
            }

            var feedNamespace = protocol == DownloadProtocol.Torrent ? _TorznabNs : _NewznabNs;

            return new XElement(feedNamespace + "attr", new XAttribute("name", name), new XAttribute("value", value));
        }

        public string ToXml(DownloadProtocol protocol)
        {
            // IMPORTANT: We can't use Uri.ToString(), because it generates URLs without URL encode (links with unicode
            // characters are broken). We must use Uri.AbsoluteUri instead that handles encoding correctly
            var xdoc = new XDocument(
                new XDeclaration("1.0", "UTF-8", null),
                new XElement("rss",
                    new XAttribute("version", "1.0"),
                    new XAttribute(XNamespace.Xmlns + "atom", _AtomNs.NamespaceName),
                    protocol == DownloadProtocol.Torrent ?
                        new XAttribute(XNamespace.Xmlns + "torznab", _TorznabNs.NamespaceName) :
                        new XAttribute(XNamespace.Xmlns + "newznab", _NewznabNs.NamespaceName),
                    new XElement("channel",
                        new XElement(_AtomNs + "link",
                            new XAttribute("rel", "self"),
                            new XAttribute("type", "application/rss+xml")),
                        new XElement("title", "Prowlarr"),
                        from r in Releases
                        let t = (r as TorrentInfo) ?? new TorrentInfo()
                        select new XElement("item",
                            new XElement("title", RemoveInvalidXMLChars(r.Title)),
                            new XElement("guid", r.Guid),  // GUID and (Link or Magnet) are mandatory
                            new XElement("prowlarrindexer", new XAttribute("id", r.IndexerId), r.Indexer),
                            r.InfoUrl == null ? null : new XElement("comments", r.InfoUrl),
                            r.PublishDate == DateTime.MinValue ? new XElement("pubDate", XmlDateFormat(DateTime.Now)) : new XElement("pubDate", XmlDateFormat(r.PublishDate)),
                            new XElement("size", r.Size),
                            r.Categories == null ? null : from c in r.Categories select new XElement("category", c.Id),
                            new XElement(
                                "enclosure",
                                new XAttribute("url", r.DownloadUrl ?? t.MagnetUrl ?? string.Empty),
                                r.Size == null ? null : new XAttribute("length", r.Size),
                                new XAttribute("type", protocol == DownloadProtocol.Torrent ? "application/x-bittorrent" : "application/x-nzb")),
                            r.Categories == null ? null : from c in r.Categories select GetNabElement("category", c.Id, protocol),
                            r.IndexerFlags == null ? null : from f in r.IndexerFlags select GetNabElement("tag", f.Name, protocol),
                            GetNabElement("rageid", r.TvRageId, protocol),
                            GetNabElement("thetvdb", r.TvdbId, protocol),
                            GetNabElement("imdb", r.ImdbId.ToString("D7"), protocol),
                            GetNabElement("tmdb", r.TmdbId, protocol),
                            GetNabElement("seeders", t.Seeders, protocol),
                            GetNabElement("files", r.Files, protocol),
                            GetNabElement("grabs", r.Grabs, protocol),
                            GetNabElement("peers", t.Peers, protocol),
                            GetNabElement("infohash", RemoveInvalidXMLChars(r.Guid), protocol),
                            GetNabElement("minimumratio", t.MinimumRatio, protocol),
                            GetNabElement("minimumseedtime", t.MinimumSeedTime, protocol),
                            GetNabElement("downloadvolumefactor", t.DownloadVolumeFactor, protocol),
                            GetNabElement("uploadvolumefactor", t.UploadVolumeFactor, protocol),
                            GetNabElement("coverurl", r.PosterUrl, protocol)))));

            return xdoc.Declaration + Environment.NewLine + xdoc;
        }
    }
}