Implemented simple rss support

Wave/Controllers/RssController.cs

@@ -0,0 +1,83 @@
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.ServiceModel.Syndication;
+using System.Xml;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Routing;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Options;
+using Microsoft.Net.Http.Headers;
+using Wave.Data;
+using Wave.Data.Migrations.postgres;
+
+namespace Wave.Controllers;
+
+
+[ApiController]
+[Route("/[controller]")]
+public class RssController(IOptions<Customization> customizations, ApplicationDbContext context) : ControllerBase {
+	private ApplicationDbContext Context { get; } = context;
+	private IOptions<Customization> Customizations { get; } = customizations;
+
+	[HttpGet("rss.xml", Name = "RssFeed")]
+	[Produces("application/rss+xml")]
+	[ResponseCache(Duration = 60*15, Location = ResponseCacheLocation.Any)]
+	public async Task<IActionResult> GetRssFeedAsync() {
+		return Ok(await CreateFeedAll("RssFeed"));
+	}
+	[HttpGet("atom.xml", Name = "AtomFeed")]
+	[Produces("application/atom+xml")]
+	[ResponseCache(Duration = 60*15, Location = ResponseCacheLocation.Any)]
+	public async Task<IActionResult> GetAtomFeedAsync() {
+		return Ok(await CreateFeedAll("AtomFeed"));
+	}
+	
+	private async Task<SyndicationFeed> CreateFeedAll(string? routeName) {
+		var query = Context.Set<Article>()
+			.Include(a => a.Author).
+			Include(a => a.Categories)
+			.OrderByDescending(a => a.PublishDate)
+			.Take(15);
+		
+		var articles = await query.ToListAsync();
+		var date = query.Max(a => a.PublishDate);
+
+		return CreateFeedAsync(articles, date, routeName);
+	}
+
+	private SyndicationFeed CreateFeedAsync(IEnumerable<Article> articles, DateTimeOffset date, string? routeName) {
+		string appName = Customizations.Value.AppName;
+		var host = new Uri($"{Request.Scheme}://{Request.Host}{Request.PathBase}", UriKind.Absolute);
+		var link = new Uri(Url.RouteUrl(routeName, null, Request.Scheme, host.Host) ?? host.AbsoluteUri);
+
+		return new SyndicationFeed(appName, "Feed on " + appName, link, articles
+			.Select(article => {
+				var item = new SyndicationItem(
+					article.Title,
+					new TextSyndicationContent(article.BodyHtml, TextSyndicationContentKind.Html),
+					new Uri(host,
+						$"/{article.PublishDate.Year}/{article.PublishDate.Month:D2}/{article.PublishDate.Day:D2}/{Uri.EscapeDataString(article.Title.ToLowerInvariant()).Replace("-", "+").Replace("%20", "-")}"),
+					new Uri(host, "article/" + article.Id).AbsoluteUri,
+					article.PublishDate) {
+					Authors = {
+						new SyndicationPerson { Name = article.Author.FullName }
+					},
+					LastUpdatedTime = article.LastModified ?? article.PublishDate,
+					PublishDate = article.PublishDate
+				};
+
+				foreach (var category in article.Categories.OrderBy(c => c.Color)) {
+					item.Categories.Add(new SyndicationCategory(category.Name));
+				}
+				return item;
+			})
+			.ToList()) {
+				TimeToLive = TimeSpan.FromMinutes(15),
+				LastUpdatedTime = date,
+				Generator = "Wave",
+				Links = {
+					new SyndicationLink(link) { RelationshipType = "self" }
+				}
+		};
+	}
+}

Wave/Program.cs

@@ -15,6 +15,7 @@
 using Wave.Components.Account;
 using Wave.Data;
 using Wave.Services;
+using Wave.Utilities;
 
 var builder = WebApplication.CreateBuilder(args);
 builder.Configuration
@@ -26,7 +27,9 @@
     .AddEnvironmentVariables("WAVE_");
 
 builder.Services.AddRazorComponents().AddInteractiveServerComponents();
-builder.Services.AddControllers();
+builder.Services.AddControllers(options => {
+    options.OutputFormatters.Add(new SyndicationFeedFormatter());
+});
 
 #region Data Protection & Redis
 

Wave/Utilities/SyndicationFeedFormatter.cs

@@ -0,0 +1,46 @@
+using System.ServiceModel.Syndication;
+using System.Text;
+using System.Xml;
+using Microsoft.AspNetCore.Mvc.Formatters;
+using Microsoft.Net.Http.Headers;
+
+namespace Wave.Utilities;
+
+public class SyndicationFeedFormatter : TextOutputFormatter {
+
+	public SyndicationFeedFormatter() {
+		SupportedMediaTypes.Add(MediaTypeHeaderValue.Parse("application/rss+xml"));
+		SupportedMediaTypes.Add(MediaTypeHeaderValue.Parse("application/atom+xml"));
+		
+		SupportedEncodings.Add(Encoding.UTF8);
+	}
+
+	protected override bool CanWriteType(Type? type)
+		=> typeof(SyndicationFeed).IsAssignableFrom(type);
+
+	public override async Task WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding) {
+		var httpContext = context.HttpContext;
+		httpContext.Response.Headers.ContentDisposition = "inline";
+
+		var feed = context.Object as SyndicationFeed;
+		
+		await using var stringWriter = new StringWriter();
+		await using var rssWriter = XmlWriter.Create(stringWriter, new XmlWriterSettings {
+			Async = true
+		});
+		System.ServiceModel.Syndication.SyndicationFeedFormatter formatter;
+		if (context.ContentType.Value?.StartsWith("application/rss+xml") is true) {
+			formatter = new Rss20FeedFormatter(feed) {
+				SerializeExtensionsAsAtom = false
+			};
+		} else if (context.ContentType.Value?.StartsWith("application/atom+xml") is true) {
+			formatter = new Atom10FeedFormatter(feed);
+		} else {
+			throw new FormatException($"The format {context.ContentType.Value} is not supported.");
+		}
+		formatter.WriteTo(rssWriter);
+		rssWriter.Close();
+
+		await httpContext.Response.WriteAsync(stringWriter.ToString(), selectedEncoding);
+	}
+}

Wave/Wave.csproj

@@ -26,6 +26,7 @@
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.19.6" />
     <PackageReference Include="NetEscapades.Configuration.Yaml" Version="3.1.0" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="8.0.0" />
+    <PackageReference Include="System.ServiceModel.Syndication" Version="8.0.0" />
     <PackageReference Include="Tomlyn.Extensions.Configuration" Version="1.0.5" />
   </ItemGroup>