1 files changed, 81 insertions, 0 deletions
diff --git a/actiontext/lib/action_text/plain_text_conversion.rb b/actiontext/lib/action_text/plain_text_conversion.rb
new file mode 100644
index 0000000000..0eb4e2e7da
--- /dev/null
+++ b/actiontext/lib/action_text/plain_text_conversion.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module ActionText
+  module PlainTextConversion
+    extend self
+
+    def node_to_plain_text(node)
+      remove_trailing_newlines(plain_text_for_node(node))
+    end
+
+    private
+      def plain_text_for_node(node, index = 0)
+        if respond_to?(plain_text_method_for_node(node), true)
+          send(plain_text_method_for_node(node), node, index)
+        else
+          plain_text_for_node_children(node)
+        end
+      end
+
+      def plain_text_for_node_children(node)
+        node.children.each_with_index.map do |child, index|
+          plain_text_for_node(child, index)
+        end.compact.join("")
+      end
+
+      def plain_text_method_for_node(node)
+        :"plain_text_for_#{node.name}_node"
+      end
+
+      def plain_text_for_block(node, index = 0)
+        "#{remove_trailing_newlines(plain_text_for_node_children(node))}\n\n"
+      end
+
+      %i[ h1 p ul ol ].each do |element|
+        alias_method :"plain_text_for_#{element}_node", :plain_text_for_block
+      end
+
+      def plain_text_for_br_node(node, index)
+        "\n"
+      end
+
+      def plain_text_for_text_node(node, index)
+        remove_trailing_newlines(node.text)
+      end
+
+      def plain_text_for_div_node(node, index)
+        "#{remove_trailing_newlines(plain_text_for_node_children(node))}\n"
+      end
+
+      def plain_text_for_figcaption_node(node, index)
+        "[#{remove_trailing_newlines(plain_text_for_node_children(node))}]"
+      end
+
+      def plain_text_for_blockquote_node(node, index)
+        text = plain_text_for_block(node)
+        text.sub(/\A(\s*)(.+?)(\s*)\Z/m, '\1“\2”\3')
+      end
+
+      def plain_text_for_li_node(node, index)
+        bullet = bullet_for_li_node(node, index)
+        text = remove_trailing_newlines(plain_text_for_node_children(node))
+        "#{bullet} #{text}\n"
+      end
+
+      def remove_trailing_newlines(text)
+        text.chomp("")
+      end
+
+      def bullet_for_li_node(node, index)
+        if list_node_name_for_li_node(node) == "ol"
+          "#{index + 1}."
+        else
+          "•"
+        end
+      end
+
+      def list_node_name_for_li_node(node)
+        node.ancestors.lazy.map(&:name).grep(/^[uo]l$/).first
+      end
+  end
+end