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/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: CMNext
* Package: Content.Publishing.Blog.Admin
* File: FeedGenerator.cs
*
* CMNext is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* CMNext is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see https://www.gnu.org/licenses/.
*/
using System;
using System.Xml;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using VNLib.Utils.IO;
using VNLib.Plugins;
using Content.Publishing.Blog.Admin.Model;
namespace Content.Publishing.Blog.Admin
{
internal sealed class FeedGenerator : IRssFeedGenerator
{
const int defaultMaxItems = 20;
const string ITUNES_XML_ATTR = "http://www.itunes.com/dtds/podcast-1.0.dtd";
const string CONTENT_XML_ATTR = "http://purl.org/rss/1.0/modules/content/";
public FeedGenerator(PluginBase pbase)
{ }
public void BuildFeed(IChannelContext context, IEnumerable<PostMeta> posts, VnMemoryStream output)
{
_ = context.Feed ?? throw new ArgumentNullException(nameof(context.Feed));
//Build the feed
using XmlWriter writer = XmlWriter.Create(output, new XmlWriterSettings
{
Encoding = Encoding.UTF8,
Indent = true,
IndentChars = " ",
NewLineChars = "\n",
NewLineHandling = NewLineHandling.Entitize,
NewLineOnAttributes = false,
CloseOutput = false,
NamespaceHandling = NamespaceHandling.OmitDuplicates,
});
string currentTime = DateTime.UtcNow.ToString("R");
//Write the feed
writer.WriteStartDocument();
writer.WriteStartElement("rss");
writer.WriteAttributeString("version", "2.0");
writer.WriteAttributeString("xmlns", "itunes", null, ITUNES_XML_ATTR);
writer.WriteAttributeString("xmlns", "content", null, CONTENT_XML_ATTR);
//Channel element
writer.WriteStartElement("channel");
writer.WriteElementString("title", context.BlogName);
writer.WriteElementString("link", context.Feed.PublihUrl);
//Description/summary
writer.WriteElementString("description", context.Feed.Description);
writer.WriteElementString("itunes", "summary", null, context.Feed.Description);
writer.WriteElementString("itunes", "author", null, context.Feed.Author);
//Itunes owner tag
writer.WriteStartElement("itunes", "owner", null);
writer.WriteElementString("itunes", "email", null, context.Feed.WebMaster);
writer.WriteElementString("itunes", "name", null, context.Feed.Author);
writer.WriteEndElement();
//Write extended properties
if (context.Feed.ExtendedProperties != null)
{
foreach (ExtendedProperty prop in context.Feed.ExtendedProperties)
{
PrintExtendedProps(prop, writer);
}
}
//Author
writer.WriteElementString("itunes", "author", null, context.Feed.Author);
//Itunes image url
if (context.Feed.ImageUrl != null)
{
WriteImageTag(writer, context.Feed.ImageUrl);
}
writer.WriteElementString("language", "en-us");
writer.WriteElementString("pubDate", currentTime);
writer.WriteElementString("lastBuildDate", currentTime);
int maxItems = context.Feed.MaxItems ?? defaultMaxItems;
//Take only the latest max items
posts = posts.OrderByDescending(static p => p.Date).Take(maxItems);
//Write the posts as items but sort in order of their pub date
foreach (PostMeta post in posts)
{
writer.WriteStartElement("item");
writer.WriteElementString("title", post.Title);
writer.WriteElementString("itunes","title", null, post.Title);
writer.WriteElementString("link", $"{context.Feed.PublihUrl}/{post.Id}");
writer.WriteElementString("itunes", "author", null, post.Author);
//Description is just the post summary
writer.WriteElementString("description", post.Summary);
writer.WriteElementString("itunes", "summary", null, post.Summary);
//Time as iso string from unix seconds timestamp
string pubDate = DateTimeOffset.FromUnixTimeSeconds(post.Date).ToString("R");
writer.WriteElementString("pubDate", pubDate);
writer.WriteElementString("published", pubDate);
if (post.Image != null)
{
WriteImageTag(writer, post.Image);
}
//Add extended properties as itunes tags
if (post.ExtendedProperties != null)
{
//Recursivley add extended properties
foreach (ExtendedProperty prop in post.ExtendedProperties)
{
PrintExtendedProps(prop, writer);
}
}
//Set post id as the guid
writer.WriteElementString("guid", post.Id);
writer.WriteEndElement();
}
//End the feed
writer.WriteEndElement();
writer.WriteEndElement();
writer.WriteEndDocument();
}
private static void PrintExtendedProps(ExtendedProperty? prop, XmlWriter writer)
{
if (prop?.Name == null)
{
return;
}
//Open the element
writer.WriteStartElement(prop.NameSpace, prop.Name, null);
//Write the attributes
if (prop.Attributes != null)
{
foreach (KeyValuePair<string, string> attr in prop.Attributes)
{
writer.WriteAttributeString(attr.Key, attr.Value);
}
}
//nested child elements before closing
if (prop.Children != null)
{
foreach (ExtendedProperty child in prop.Children)
{
PrintExtendedProps(child, writer);
}
}
else
{
//Write the value
writer.WriteString(prop.Value);
}
//Close the element
writer.WriteEndElement();
}
private static void WriteImageTag(XmlWriter writer, string imageUrl)
{
writer.WriteStartElement("itunes", "image",null);
writer.WriteAttributeString("href", imageUrl);
writer.WriteEndElement();
}
}
}
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