feat: replace external links in description and comments to confirm before leaving

src/invidious/comments/links_util.cr

@@ -73,4 +73,30 @@ module Invidious::Comments
 
     return html.to_xml(options: XML::SaveOptions::NO_DECL)
   end
+
+  def replace_external_links(html)
+    # Check if the document is empty
+    # Prevents edge-case bug with Reddit comments, see issue #3115
+    if html.nil? || html.empty?
+      return html
+    end
+
+    html = XML.parse_html(html)
+
+    html.xpath_nodes(%q(//a)).each do |anchor|
+      url = URI.parse(anchor["href"])
+
+      if !url.host.nil? && !url.host.not_nil!.ends_with?("youtube.com") && !url.host.not_nil!.ends_with?("youtu.be")
+        confirm_leave = "/confirm_leave?link=#{URI.encode_path(url.to_s)}"
+        anchor["href"] = confirm_leave
+      end
+    end
+
+    html = html.xpath_node(%q(//body)).not_nil!
+    if node = html.xpath_node(%q(./p))
+      html = node
+    end
+
+    return html.to_xml(options: XML::SaveOptions::NO_DECL)
+  end
 end

src/invidious/comments/youtube.cr

@@ -303,6 +303,7 @@ module Invidious::Comments
     if format == "html"
       response = JSON.parse(response)
       content_html = Frontend::Comments.template_youtube(response, locale, thin_mode)
+      content_html = Comments.replace_external_links(content_html)
       response = JSON.build do |json|
         json.object do
           json.field "contentHtml", content_html

src/invidious/videos/parser.cr

@@ -316,6 +316,9 @@ def parse_video_info(video_id : String, player_response : Hash(String, JSON::Any
 
   description_html = parse_description(video_secondary_renderer.try &.dig?("attributedDescription"), video_id)
 
+  # use comments link_utils to replace external links with the confirmation page
+  description_html = Invidious::Comments.replace_external_links(description_html)
+
   # Video metadata
 
   metadata = video_secondary_renderer