using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Xml;
using System.Net;

namespace AppLimit.NetSparkle
{
    public class NetSparkleAppCast
    {
        private NetSparkleConfiguration _config;
        private String _castUrl;

        private const String itemNode = "item";
        private const String descriptionNode = "description";
        private const String enclosureNode = "enclosure";
        private const String releaseNotesLinkNode = "sparkle:releaseNotesLink";
        private const String versionAttribute = "sparkle:version";
        private const String dasSignature = "sparkle:dsaSignature";
        private const String urlAttribute = "url";

        public NetSparkleAppCast(String castUrl, NetSparkleConfiguration config)
        {
            _config     = config;
            _castUrl    = castUrl;
        }

        public NetSparkleAppCastItem GetLatestVersion()
        {
            NetSparkleAppCastItem latestVersion = null;
          
            // build a http web request stream
            var request = WebRequest.Create(_castUrl);
            
            // request the cast and build the stream
            using(var response = request.GetResponse())
            using(var inputstream = response.GetResponseStream())
            using (var reader = new XmlTextReader(inputstream))
            {
                NetSparkleAppCastItem currentItem = null;

                while (reader.Read())
                {
                    if (reader.NodeType == XmlNodeType.Element)
                    {
                        switch (reader.Name)
                        {
                            case itemNode:
                                {
                                    currentItem = new NetSparkleAppCastItem();
                                    break;
                                }
                                /*
                                                    case descriptionNode:
                                                        {
                                                            if (currentItem != null)
                                                            {
                                                                currentItem.Summary = reader.ReadElementContentAsString();
                                                            }
                                                            break;
                                                        }
                            */
                            case releaseNotesLinkNode:
                                {
                                    currentItem.ReleaseNotesLink = reader.ReadString();
                                    currentItem.ReleaseNotesLink = currentItem.ReleaseNotesLink.Trim('\n');
                                    break;
                                }
                            case enclosureNode:
                                {
                                    currentItem.Version = reader.GetAttribute(versionAttribute);

                                    var downloadLink = reader.GetAttribute(urlAttribute);
                                    downloadLink = Environment.Is64BitOperatingSystem
                                                       ? downloadLink.Replace(".x86.", ".x64.")
                                                       : downloadLink.Replace(".x64.", ".x86.");
                                    currentItem.DownloadLink = downloadLink;
                                    currentItem.DSASignature = reader.GetAttribute(dasSignature);

                                    break;
                                }
                        }
                    }
                    else if (reader.NodeType == XmlNodeType.EndElement)
                    {
                        switch (reader.Name)
                        {
                            case itemNode:
                                {
                                    if (latestVersion == null)
                                        latestVersion = currentItem;
                                    else if (currentItem.CompareTo(latestVersion) > 0)
                                    {
                                        latestVersion = currentItem;
                                    }
                                    break;
                                }
                        }
                    }
                }
            }
            // add some other attributes
            if (latestVersion != null)
            {
                latestVersion.AppName = _config.ApplicationName;
                latestVersion.AppVersionInstalled = _config.InstalledVersion;
            }
            // go ahead
            return latestVersion;
        }
            
    }
}