Absolutify urls before generating feeds

PolyFeed/FeedBuilder.cs

@@ -67,6 +67,9 @@ namespace PolyFeed
 
 			HtmlNode document = html.DocumentNode;
 
+			document.AbsolutifyUris(new Uri(source.Feed.Url));
+
+
 			await Console.Error.WriteLineAsync("[Builder/Html] Generating feed content");
 
 			// Add the title

PolyFeed/Helpers/HtmlHelpers.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Threading;
+using System.Threading.Tasks;
 using Fizzler.Systems.HtmlAgilityPack;
 using HtmlAgilityPack;
 
@@ -30,5 +32,33 @@ namespace PolyFeed.Helpers
 
 			return selectedNode.Attributes[settings.Attribute].Value;
 		}
+
+		/// <summary>
+		/// Searches for and converts all the links that are children of the current 
+		/// <see cref="HtmlNode" /> to absolute URIs.
+		/// </summary>
+		/// <param name="rootNode">The root node to search from.</param>
+		/// <param name="baseUri">The base URI to use for conversion.</param>
+		/// <returns>The number of nodes updated.</returns>
+		public static int AbsolutifyUris(this HtmlNode rootNode, Uri baseUri)
+		{
+			int nodesUpdated = 0;
+			Parallel.ForEach(rootNode.QuerySelectorAll("a, img"), (HtmlNode node) => {
+				string attributeName = null;
+				if (node.Attributes["href"] != null) attributeName = "href";
+				if (node.Attributes["src"] != null) attributeName = "src";
+
+				if (node.Attributes[attributeName] == null)
+					return;
+
+				node.Attributes[attributeName].Value = new Uri(
+					baseUri,
+					node.Attributes[attributeName].Value
+				).ToString();
+
+				Interlocked.Increment(ref nodesUpdated);
+			});
+			return nodesUpdated;
+		}
 	}
 }