/Growl Extras/Feed Monitor/GrowlExtras.FeedMonitor/_source/Rss10FeedFormatter.cs

using System;

using System.Collections.ObjectModel;

using System.Xml;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel.Syndication;



namespace GrowlExtras.FeedMonitor

{

    public class Rss10FeedFormatter : SyndicationFeedFormatter

    {

        #region Constructors

        public Rss10FeedFormatter() { }



        public Rss10FeedFormatter(SyndicationFeed feed) : base(feed) { }

        #endregion



        #region Properties

        public override string Version

        {

            get { return "Rss10"; }

        }



        public virtual string RdfNamespaceUri

        {

            get { return "http://www.w3.org/1999/02/22-rdf-syntax-ns#"; }

        }



        public virtual string NamespaceUri

        {

            get { return "http://purl.org/rss/1.0/"; }

        }

        #endregion



        #region Methods

        #region Read XML Methods

        public override bool CanRead(System.Xml.XmlReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException("reader");



            return reader.IsStartElement("RDF", this.RdfNamespaceUri);

        }



        protected override SyndicationFeed CreateFeedInstance()

        {

            return new SyndicationFeed();

        }



        public override void ReadFrom(System.Xml.XmlReader reader)

        {

            if (!this.CanRead(reader))

                throw new XmlException("Unknown RSS 1.0 feed format.");



            this.ReadFeed(reader);

        }



        private void ReadFeed(XmlReader reader)

        {

            this.SetFeed(this.CreateFeedInstance());

            this.ReadXml(reader, base.Feed);

        }



        protected virtual void ReadXml(XmlReader reader, SyndicationFeed result)

        {

            if (result == null)

                throw new ArgumentNullException("result");

            else if (reader == null)

                throw new ArgumentNullException("reader");



            reader.ReadStartElement();              // Read in <RDF>

            reader.ReadStartElement("channel");     // Read in <channel>

            while (reader.IsStartElement())         // Process <channel> children

            {

                if (reader.IsStartElement("title"))

                    result.Title = new TextSyndicationContent(reader.ReadElementString());

                else if (reader.IsStartElement("link"))

                    result.Links.Add(new SyndicationLink(new Uri(reader.ReadElementString())));

                else if (reader.IsStartElement("description"))

                    result.Description = new TextSyndicationContent(reader.ReadElementString());

                else

                    reader.Skip();

            }

            reader.ReadEndElement();                // Read in </channel>



            while (reader.IsStartElement())

            {

                if (reader.IsStartElement("item"))

                {

                    result.Items = this.ReadItems(reader, result);



                    break;

                }

                else

                    reader.Skip();

            }

        }



        protected virtual IEnumerable<SyndicationItem> ReadItems(XmlReader reader, SyndicationFeed feed)

        {

            if (feed == null)

                throw new ArgumentNullException("feed");

            else if (reader == null)

                throw new ArgumentNullException("reader");



            Collection<SyndicationItem> items = new Collection<SyndicationItem>();

            while (reader.IsStartElement("item"))

            {

                items.Add(this.ReadItem(reader, feed));

            }



            return items;

        }



        protected virtual SyndicationItem ReadItem(XmlReader reader, SyndicationFeed feed)

        {

            if (feed == null)

                throw new ArgumentNullException("feed");

            else if (reader == null)

                throw new ArgumentNullException("reader");



            SyndicationItem result = new SyndicationItem();

            this.ReadItemFrom(reader, result);



            return result;

        }



        protected virtual void ReadItemFrom(XmlReader reader, SyndicationItem result)

        {

            if (result == null)

                throw new ArgumentNullException("result");

            else if (reader == null)

                throw new ArgumentNullException("reader");



            reader.ReadStartElement();

            while (reader.IsStartElement())

            {

                if (reader.IsStartElement("title"))

                    result.Title = new TextSyndicationContent(reader.ReadElementString());

                else if (reader.IsStartElement("link"))

                    result.Links.Add(new SyndicationLink(new Uri(reader.ReadElementString())));

                else if (reader.IsStartElement("description"))

                    result.Summary = new TextSyndicationContent(reader.ReadElementString());

                else

                    reader.Skip();

            }

            reader.ReadEndElement();

        }

        #endregion



        #region Write XML Methods

        public override void WriteTo(System.Xml.XmlWriter writer)

        {

            if (writer == null)

                throw new ArgumentNullException("writer");



            writer.WriteStartElement("rdf", "RDF", this.RdfNamespaceUri);      // Write <RDF>

            writer.WriteAttributeString("xmlns", this.NamespaceUri);

            this.WriteFeed(writer);

            writer.WriteEndElement();

        }



        protected virtual void WriteFeed(XmlWriter writer)

        {

            if (writer == null)

                throw new ArgumentNullException("writer");

            if (base.Feed == null)

                throw new InvalidOperationException("Feed formatter does not have a feed.");



            string alternateLink = string.Empty, selfLink = string.Empty;

            foreach (SyndicationLink lnk in base.Feed.Links)

            {

                if (alternateLink.Length == 0 && lnk.RelationshipType == "alternate")

                    alternateLink = lnk.Uri.IsAbsoluteUri ? lnk.Uri.AbsoluteUri : lnk.Uri.ToString();

                else if (selfLink.Length == 0 && lnk.RelationshipType == "self")

                    selfLink = lnk.Uri.IsAbsoluteUri ? lnk.Uri.AbsoluteUri : lnk.Uri.ToString();

            }



            if (selfLink.Length == 0 && alternateLink.Length > 0)

                selfLink = alternateLink;

            else if (alternateLink.Length == 0 && selfLink.Length > 0)

                alternateLink = selfLink;





            writer.WriteStartElement("channel");     // Write <channel>

            writer.WriteAttributeString("about", this.RdfNamespaceUri, selfLink);



            if (base.Feed.Title == null || string.IsNullOrEmpty(base.Feed.Title.Text))

                throw new ArgumentException("Feed title required for RSS 1.0 feeds.");

            writer.WriteElementString("title", base.Feed.Title.Text);       // Write <title>





            if (alternateLink.Length == 0)

                throw new ArgumentException("Feed link required for RSS 1.0 feeds.");

            writer.WriteElementString("link", alternateLink);       // Write <link>





            if (base.Feed.Description == null || string.IsNullOrEmpty(base.Feed.Description.Text))

                throw new ArgumentException("Feed title required for RSS 1.0 feeds.");

            writer.WriteElementString("description", base.Feed.Description.Text);       // Write <description>





            writer.WriteStartElement("items");              // Write <items>

            writer.WriteStartElement("Seq", this.RdfNamespaceUri);

            foreach (SyndicationItem item in base.Feed.Items)

            {

                string itemAlternateLink = GetAlternateLinkForItem(item);



                writer.WriteStartElement("li", this.RdfNamespaceUri);

                writer.WriteAttributeString("resource", this.RdfNamespaceUri, itemAlternateLink);

                writer.WriteEndElement();

            }

            writer.WriteEndElement();

            writer.WriteEndElement();



            writer.WriteEndElement();       // Write </channel>



            // Write the <item> elements

            this.WriteItems(writer, base.Feed.Items);

        }



        protected virtual void WriteItems(XmlWriter writer, IEnumerable<SyndicationItem> items)

        {

            if (writer == null)

                throw new ArgumentNullException("writer");



            if (items != null)

                foreach (SyndicationItem item in items)

                    this.WriteItem(writer, item);

        }



        protected virtual void WriteItem(XmlWriter writer, SyndicationItem item)

        {

            if (writer == null)

                throw new ArgumentNullException("writer");



            string alternateLink = GetAlternateLinkForItem(item);



            writer.WriteStartElement("item");           // Write <item>

            writer.WriteAttributeString("about", this.RdfNamespaceUri, alternateLink);

            this.WriteItemContents(writer, item);

            writer.WriteEndElement();

        }



        protected virtual void WriteItemContents(XmlWriter writer, SyndicationItem item)

        {

            if (writer == null)

                throw new ArgumentNullException("writer");



            if (item.Title == null || string.IsNullOrEmpty(item.Title.Text))

                throw new ArgumentException("Feed title required for RSS 1.0 feeds.");

            writer.WriteElementString("title", item.Title.Text);       // Write <title>





            string alternateLink = GetAlternateLinkForItem(item);

            if (string.IsNullOrEmpty(alternateLink))

                throw new ArgumentException("Feed link required for RSS 1.0 feeds.");

            writer.WriteElementString("link", alternateLink);       // Write <link>





            if (base.Feed.Description != null && string.IsNullOrEmpty(item.Summary.Text) == false)

                writer.WriteElementString("description", item.Summary.Text);       // Write the optional <description>

        }



        private string GetAlternateLinkForItem(SyndicationItem item)

        {

            foreach (SyndicationLink lnk in item.Links)

                if (lnk.RelationshipType == "alternate")

                    return lnk.Uri.IsAbsoluteUri ? lnk.Uri.AbsoluteUri : lnk.Uri.ToString();



            // If we reach here, return an empty string

            return string.Empty;

        }

        #endregion

        #endregion

    }

}