Add image method to get first image from rich text

lib/rich_text.rb

@@ -49,6 +49,10 @@ module RichText
         (spammy_phrases * 40)
     end
 
+    def image
+      nil
+    end
+
     protected
 
     def simple_format(text)
@@ -80,12 +84,33 @@ module RichText
 
   class Markdown < Base
     def to_html
-      linkify(sanitize(Kramdown::Document.new(self).to_html), :all)
+      linkify(sanitize(document.to_html), :all)
     end
 
     def to_text
       to_s
     end
+
+    def image
+      return @image if defined? @image
+
+      @image = first_image_element(document.root)&.attr&.[]("src")
+    end
+
+    private
+
+    def document
+      @document ||= Kramdown::Document.new(self)
+    end
+
+    def first_image_element(element)
+      return element if element.type == :img
+
+      element.children.find do |child|
+        nested_image = first_image_element(child)
+        break nested_image if nested_image
+      end
+    end
   end
 
   class Text < Base

test/lib/rich_text_test.rb

@@ -250,6 +250,31 @@ class RichTextTest < ActiveSupport::TestCase
     assert_equal 141, r.spam_score.round
   end
 
+  def test_text_no_image
+    r = RichText.new("text", "foo https://example.com/ bar")
+    assert_nil r.image
+  end
+
+  def test_html_no_image
+    r = RichText.new("html", "foo <a href='https://example.com/'>bar</a> baz")
+    assert_nil r.image
+  end
+
+  def test_markdown_no_image
+    r = RichText.new("markdown", "foo [bar](https://example.com/) baz")
+    assert_nil r.image
+  end
+
+  def test_markdown_image
+    r = RichText.new("markdown", "foo ![bar](https://example.com/image.jpg) baz")
+    assert_equal "https://example.com/image.jpg", r.image
+  end
+
+  def test_markdown_first_image
+    r = RichText.new("markdown", "foo ![bar1](https://example.com/image1.jpg) baz\nfoo ![bar2](https://example.com/image2.jpg) baz")
+    assert_equal "https://example.com/image1.jpg", r.image
+  end
+
   private
 
   def assert_html(richtext, &block)