DEV: Extract out html cleanup so it can be used on other types of cooked content (#31385)

`PrettyText.cook` does two things: 1️⃣ convert raw to cooked, 2️⃣
partial sanitisation.

This commit splits the 2️⃣ up so that it can be applied to other cooked
content.

lib/pretty_text.rb

@@ -295,25 +295,13 @@ module PrettyText
       JS
   end
 
-  def self.cook(text, opts = {})
+  def self.cook(raw, opts = {})
     options = opts.dup
-    working_text = text.dup
+    working_text = raw.dup
 
-    sanitized = markdown(working_text, options)
+    html = markdown(working_text, options)
 
-    doc = Nokogiri::HTML5.fragment(sanitized)
-
-    add_nofollow = !options[:omit_nofollow] && SiteSetting.add_rel_nofollow_to_user_content
-    add_rel_attributes_to_user_content(doc, add_nofollow)
-    strip_hidden_unicode_bidirectional_characters(doc)
-    sanitize_hotlinked_media(doc)
-    add_video_placeholder_image(doc)
-
-    add_mentions(doc, user_id: opts[:user_id]) if SiteSetting.enable_mentions
-
-    scrubber = Loofah::Scrubber.new { |node| node.remove if node.name == "script" }
-    loofah_fragment = Loofah.html5_fragment(doc.to_html)
-    loofah_fragment.scrub!(scrubber).to_html
+    cleanup(html, opts)
   end
 
   def self.strip_hidden_unicode_bidirectional_characters(doc)
@@ -692,6 +680,22 @@ module PrettyText
     rval
   end
 
+  def self.cleanup(html, opts = {})
+    doc = Nokogiri::HTML5.fragment(html)
+
+    add_nofollow = !opts[:omit_nofollow] && SiteSetting.add_rel_nofollow_to_user_content
+    add_rel_attributes_to_user_content(doc, add_nofollow)
+    strip_hidden_unicode_bidirectional_characters(doc)
+    sanitize_hotlinked_media(doc)
+    add_video_placeholder_image(doc)
+
+    add_mentions(doc, user_id: opts[:user_id]) if SiteSetting.enable_mentions
+
+    scrubber = Loofah::Scrubber.new { |node| node.remove if node.name == "script" }
+    loofah_fragment = Loofah.html5_fragment(doc.to_html)
+    loofah_fragment.scrub!(scrubber).to_html
+  end
+
   private
 
   USER_TYPE = "user"

spec/lib/pretty_text_spec.rb

@@ -731,6 +731,26 @@ RSpec.describe PrettyText do
       expect(cooked).to eq(html.strip)
     end
 
+    it "strips out unicode bidirectional (bidi) override characters and replaces with a highlighted span" do
+      cooked = <<~HTML
+        <p>X</p>
+        <pre><code class="lang-auto">var isAdmin = false;
+        \u202E
+        </code></pre>
+      HTML
+      cleaned = PrettyText.cleanup(cooked)
+      hidden_bidi_title = I18n.t("post.hidden_bidi_character")
+
+      html = <<~HTML
+        <p>X</p>
+        <pre><code class="lang-auto">var isAdmin = false;
+        <span class="bidi-warning" title="#{hidden_bidi_title}">&lt;U+202E&gt;</span>
+        </code></pre>
+      HTML
+
+      expect(cleaned.strip).to eq(html.strip)
+    end
+
     it "fuzzes all possible dangerous unicode bidirectional (bidi) override characters, making sure they are replaced" do
       bad_bidi = [
         "\u202A",
@@ -2389,6 +2409,9 @@ HTML
   it "should strip SCRIPT" do
     expect(PrettyText.cook("<script>alert(42)</script>")).to eq ""
     expect(PrettyText.cook("<div><script>alert(42)</script></div>")).to eq "<div></div>"
+
+    expect(PrettyText.cleanup("<script>alert(42)</script>")).to eq ""
+    expect(PrettyText.cleanup("<div><script>alert(42)</script></div>")).to eq "<div></div>"
   end
 
   it "strips script regardless of sanitize" do