From https://once.com/writebook

lib/rails_ext/action_text_has_markdown.rb

@@ -0,0 +1,40 @@
+module ActionText
+  module HasMarkdown
+    extend ActiveSupport::Concern
+
+    class_methods do
+      def has_markdown(name, strict_loading: strict_loading_by_default)
+        class_eval <<-CODE, __FILE__, __LINE__ + 1
+          def #{name}
+            markdown_#{name} || build_markdown_#{name}
+          end
+
+          def #{name}?
+            markdown_#{name}.present?
+          end
+
+          def #{name}=(content)
+            self.#{name}.content = content
+          end
+        CODE
+
+        has_one :"markdown_#{name}", -> { where(name: name) },
+          class_name: "ActionText::Markdown", as: :record, inverse_of: :record, autosave: true, dependent: :destroy,
+          strict_loading: strict_loading
+
+        scope :"with_markdown_#{name}", -> { includes("markdown_#{name}") }
+        scope :"with_markdown_#{name}_and_embeds", -> { includes("markdown_#{name}": { embeds_attachments: :blob }) }
+      end
+    end
+
+    def safe_markdown_attribute(name)
+      if self.class.reflect_on_association("markdown_#{name}")&.klass == ActionText::Markdown
+        public_send(name)
+      end
+    end
+  end
+end
+
+ActiveSupport.on_load :active_record do
+  include ActionText::HasMarkdown
+end

lib/rails_ext/action_text_markdown.rb

@@ -0,0 +1,42 @@
+module ActionText
+  class Markdown < Record
+    DEFAULT_RENDERER_OPTIONS = {
+      filter_html: false
+    }
+
+    DEFAULT_MARKDOWN_EXTENSIONS = {
+      autolink: true,
+      highlight: true,
+      no_intra_emphasis: true,
+      fenced_code_blocks: true,
+      lax_spacing: true,
+      strikethrough: true,
+      tables: true
+    }
+
+    mattr_accessor :renderer, default: Redcarpet::Markdown.new(
+      Redcarpet::Render::HTML.new(DEFAULT_RENDERER_OPTIONS), DEFAULT_MARKDOWN_EXTENSIONS)
+
+    belongs_to :record, polymorphic: true, touch: true
+
+    def to_html
+      (renderer.try(:call) || renderer).render(content).html_safe
+    end
+  end
+end
+
+module ActionText::Markdown::Uploads
+  extend ActiveSupport::Concern
+
+  included do
+    has_many_attached :uploads, dependent: :destroy
+  end
+end
+
+ActiveSupport.on_load :active_storage_attachment do
+  class ActionText::Markdown
+    include ActionText::Markdown::Uploads
+  end
+end
+
+ActiveSupport.run_load_hooks :action_text_markdown, ActionText::Markdown

lib/rails_ext/action_text_tag_helper.rb

@@ -0,0 +1,39 @@
+module ActionText
+  module TagHelper
+    def markdown_area(record, name, value: nil, **options)
+      field_name = "#{record.class.model_name.param_key}[#{name}]"
+      value = record.safe_markdown_attribute(name).content.to_s if value.nil?
+
+      data = options.delete(:data) || {}
+      data.reverse_merge! \
+        uploads_url: action_text_markdown_uploads_url(record_gid: record.to_signed_global_id.to_s, attribute_name: name, format: "json")
+
+      tag.house_md value, name: field_name, data: data, **options
+    end
+
+    def house_toolbar(**options, &block)
+      tag.house_md_toolbar(**options, &block)
+    end
+
+    def house_toolbar_button(action, **options, &block)
+      tag.button title: action.to_s.humanize, data: { "house-md-action": action }, **options, &block
+    end
+
+    def house_toolbar_file_upload_button(name: "upload", title: "Upload File", **options, &block)
+      tag.label title: title, **options do
+        safe_join [
+          file_field_tag(name, data: { "house-md-toolbar-file-picker": true }, style: "display: none;"),
+          capture(&block)
+        ]
+      end
+    end
+  end
+end
+
+module ActionView::Helpers
+  class FormBuilder
+    def markdown_area(method, **options)
+      @template.markdown_area(@object, method, **options)
+    end
+  end
+end

lib/rails_ext/active_storage_sluggable.rb

@@ -0,0 +1,32 @@
+module ActiveStorage::Sluggable
+  extend ActiveSupport::Concern
+
+  included do
+    before_create :set_slug
+  end
+
+  def slug_url(host: ActiveStorage::Current.host)
+    Rails.application.routes.url_helpers.action_text_markdown_upload_url(slug, host: host)
+  end
+
+  private
+    def set_slug
+      self.slug = "#{slug_basename}-#{SecureRandom.alphanumeric(6)}.#{slug_extension}"
+    end
+
+    def slug_basename
+      File.basename(slug_filename, ".*").parameterize
+    end
+
+    def slug_extension
+      File.extname(slug_filename).delete(".").parameterize
+    end
+
+    def slug_filename
+      slug.presence || filename.to_s
+    end
+end
+
+ActiveSupport.on_load :active_storage_attachment do
+  ActiveStorage::Attachment.include ActiveStorage::Sluggable
+end