various updates

Web/Helpers/HtmlHelper.cs

@@ -0,0 +1,57 @@
+using HtmlAgilityPack;
+
+namespace FileFlows.Web.Helpers;
+
+/// <summary>
+/// HTML Helper
+/// </summary>
+public class HtmlHelper
+{
+    
+    /// <summary>
+    /// Converts all relative URLs in the provided HTML content to absolute URLs based on the given base URL.
+    /// This method processes the href attribute of <a> tags and the src and content attributes of <img> tags.
+    /// </summary>
+    /// <param name="htmlContent">The HTML content containing relative URLs.</param>
+    /// <param name="baseUrl">The base URL to convert relative URLs to absolute URLs.</param>
+    /// <returns>The HTML content with all relative URLs converted to absolute URLs.</returns>
+    /// <exception cref="UriFormatException">Thrown when the base URL is not in a valid format.</exception>
+    public static string ConvertRelativeUrlsToAbsolute(string htmlContent, string baseUrl)
+    {
+        var htmlDoc = new HtmlDocument();
+        htmlDoc.LoadHtml(htmlContent);
+
+        var uri = new Uri(baseUrl);
+
+        // Convert relative URLs in <a> tags (href attribute)
+        foreach (var link in htmlDoc.DocumentNode.SelectNodes("//a[@href]"))
+        {
+            var hrefValue = link.GetAttributeValue("href", string.Empty);
+            if (Uri.TryCreate(hrefValue, UriKind.Relative, out var relativeUri))
+            {
+                var absoluteUri = new Uri(uri, relativeUri);
+                link.SetAttributeValue("href", absoluteUri.ToString());
+            }
+        }
+
+        // Convert relative URLs in <img> tags (src and content attributes)
+        foreach (var img in htmlDoc.DocumentNode.SelectNodes("//img[@src or @content]"))
+        {
+            var srcValue = img.GetAttributeValue("src", string.Empty);
+            if (Uri.TryCreate(srcValue, UriKind.Relative, out var relativeSrcUri))
+            {
+                var absoluteSrcUri = new Uri(uri, relativeSrcUri);
+                img.SetAttributeValue("src", absoluteSrcUri.ToString());
+            }
+
+            var contentValue = img.GetAttributeValue("content", string.Empty);
+            if (Uri.TryCreate(contentValue, UriKind.Relative, out var relativeContentUri))
+            {
+                var absoluteContentUri = new Uri(uri, relativeContentUri);
+                img.SetAttributeValue("content", absoluteContentUri.ToString());
+            }
+        }
+
+        return htmlDoc.DocumentNode.OuterHtml;
+    }
+}