Refactor formatter (#17828)

* Refactor formatter

* Move custom emoji pre-rendering logic to view helpers

* Move more methods out of Formatter

* Fix code style issues

* Remove Formatter

* Add inline poll options to RSS feeds

* Remove unused helper method

* Fix code style issues

* Various fixes and improvements

* Fix test

spec/lib/html_aware_formatter.rb

@@ -0,0 +1,44 @@
+require 'rails_helper'
+
+RSpec.describe HtmlAwareFormatter do
+  describe '#to_s' do
+    subject { described_class.new(text, local).to_s }
+
+    context 'when local' do
+      let(:local) { true }
+      let(:text) { 'Foo bar' }
+
+      it 'returns formatted text' do
+        is_expected.to eq '<p>Foo bar</p>'
+      end
+    end
+
+    context 'when remote' do
+      let(:local) { false }
+
+      context 'given plain text' do
+        let(:text) { 'Beep boop' }
+
+        it 'keeps the plain text' do
+          is_expected.to include 'Beep boop'
+        end
+      end
+
+      context 'given text containing script tags' do
+        let(:text) { '<script>alert("Hello")</script>' }
+
+        it 'strips the scripts' do
+          is_expected.to_not include '<script>alert("Hello")</script>'
+        end
+      end
+
+      context 'given text containing malicious classes' do
+        let(:text) { '<span class="mention  status__content__spoiler-link">Show more</span>' }
+
+        it 'strips the malicious classes' do
+          is_expected.to_not include 'status__content__spoiler-link'
+        end
+      end
+    end
+  end
+end