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 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
            WebRequest request = HttpWebRequest.Create(_castUrl);

            // request the cast and build the stream
            WebResponse response = request.GetResponse();

            Stream inputstream = response.GetResponseStream();

            NetSparkleAppCastItem currentItem = null;

            XmlTextReader reader = new XmlTextReader(inputstream);
            while(reader.Read())
            {
                if ( reader.NodeType == XmlNodeType.Element)
                {
                    switch(reader.Name)
                    {
                        case itemNode:
                            {
                                currentItem = new NetSparkleAppCastItem();
                                break;
                            }
                        case releaseNotesLinkNode:
                            {
                                currentItem.ReleaseNotesLink = reader.ReadString();
                                currentItem.ReleaseNotesLink = currentItem.ReleaseNotesLink.Trim('\n');
                                break;
                            }                            
                        case enclosureNode:
                            {
                                currentItem.Version = reader.GetAttribute(versionAttribute);
                                currentItem.DownloadLink = reader.GetAttribute(urlAttribute);
                                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
            latestVersion.AppName = _config.ApplicationName;
            latestVersion.AppVersionInstalled = _config.InstalledVersion;
            
            // go ahead
            return latestVersion;
        }
            
    }
}