Import Action Text

24 files changed, 1075 insertions, 0 deletions

diff --git a/actiontext/lib/action_text.rb b/actiontext/lib/action_text.rb
new file mode 100644
index 0000000000..0dd6318f89
--- /dev/null
+++ b/actiontext/lib/action_text.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require "active_support"
+require "active_support/rails"
+
+require "nokogiri"
+
+module ActionText
+  extend ActiveSupport::Autoload
+
+  autoload :Attachable
+  autoload :AttachmentGallery
+  autoload :Attachment
+  autoload :Attribute
+  autoload :Content
+  autoload :Fragment
+  autoload :HtmlConversion
+  autoload :PlainTextConversion
+  autoload :Serialization
+  autoload :TrixAttachment
+
+  module Attachables
+    extend ActiveSupport::Autoload
+
+    autoload :ContentAttachment
+    autoload :MissingAttachable
+    autoload :RemoteImage
+  end
+
+  module Attachments
+    extend ActiveSupport::Autoload
+
+    autoload :Caching
+    autoload :Minification
+    autoload :TrixConversion
+  end
+end
diff --git a/actiontext/lib/action_text/attachable.rb b/actiontext/lib/action_text/attachable.rb
new file mode 100644
index 0000000000..38cd24aa8d
--- /dev/null
+++ b/actiontext/lib/action_text/attachable.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachable
+    extend ActiveSupport::Concern
+
+    LOCATOR_NAME = "attachable"
+
+    class << self
+      def from_node(node)
+        if attachable = attachable_from_sgid(node["sgid"])
+          attachable
+        elsif attachable = ActionText::Attachables::ContentAttachment.from_node(node)
+          attachable
+        elsif attachable = ActionText::Attachables::RemoteImage.from_node(node)
+          attachable
+        else
+          ActionText::Attachables::MissingAttachable
+        end
+      end
+
+      def from_attachable_sgid(sgid, options = {})
+        method = sgid.is_a?(Array) ? :locate_many_signed : :locate_signed
+        record = GlobalID::Locator.public_send(method, sgid, options.merge(for: LOCATOR_NAME))
+        record || raise(ActiveRecord::RecordNotFound)
+      end
+
+      private
+        def attachable_from_sgid(sgid)
+          from_attachable_sgid(sgid)
+        rescue ActiveRecord::RecordNotFound
+          nil
+        end
+    end
+
+    class_methods do
+      def from_attachable_sgid(sgid)
+        ActionText::Attachable.from_attachable_sgid(sgid, only: self)
+      end
+    end
+
+    def attachable_sgid
+      to_sgid(expires_in: nil, for: LOCATOR_NAME).to_s
+    end
+
+    def attachable_content_type
+      try(:content_type) || "application/octet-stream"
+    end
+
+    def attachable_filename
+      filename.to_s if respond_to?(:filename)
+    end
+
+    def attachable_filesize
+      try(:byte_size) || try(:filesize)
+    end
+
+    def attachable_metadata
+      try(:metadata) || {}
+    end
+
+    def previewable_attachable?
+      false
+    end
+
+    def as_json(*)
+      super.merge(attachable_sgid: attachable_sgid)
+    end
+
+    def to_rich_text_attributes(attributes = {})
+      attributes.dup.tap do |attrs|
+        attrs[:sgid] = attachable_sgid
+        attrs[:content_type] = attachable_content_type
+        attrs[:previewable] = true if previewable_attachable?
+        attrs[:filename] = attachable_filename
+        attrs[:filesize] = attachable_filesize
+        attrs[:width] = attachable_metadata[:width]
+        attrs[:height] = attachable_metadata[:height]
+      end.compact
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachables/content_attachment.rb b/actiontext/lib/action_text/attachables/content_attachment.rb
new file mode 100644
index 0000000000..804f74713f
--- /dev/null
+++ b/actiontext/lib/action_text/attachables/content_attachment.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachables
+    class ContentAttachment
+      include ActiveModel::Model
+
+      def self.from_node(node)
+        if node["content-type"]
+          if matches = node["content-type"].match(/vnd\.rubyonrails\.(.+)\.html/)
+            attachment = new(name: matches[1])
+            attachment if attachment.valid?
+          end
+        end
+      end
+
+      attr_accessor :name
+      validates_inclusion_of :name, in: %w( horizontal-rule )
+
+      def attachable_plain_text_representation(caption)
+        case name
+        when "horizontal-rule"
+          " ┄ "
+        else
+          " "
+        end
+      end
+
+      def to_partial_path
+        "action_text/attachables/content_attachment"
+      end
+
+      def to_trix_content_attachment_partial_path
+        "action_text/attachables/content_attachments/#{name.underscore}"
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachables/missing_attachable.rb b/actiontext/lib/action_text/attachables/missing_attachable.rb
new file mode 100644
index 0000000000..2f3bd40563
--- /dev/null
+++ b/actiontext/lib/action_text/attachables/missing_attachable.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachables
+    module MissingAttachable
+      extend ActiveModel::Naming
+
+      def self.to_partial_path
+        "action_text/attachables/missing_attachable"
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachables/remote_image.rb b/actiontext/lib/action_text/attachables/remote_image.rb
new file mode 100644
index 0000000000..650b11862b
--- /dev/null
+++ b/actiontext/lib/action_text/attachables/remote_image.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachables
+    class RemoteImage
+      extend ActiveModel::Naming
+
+      class << self
+        def from_node(node)
+          if node["url"] && content_type_is_image?(node["content-type"])
+            new(attributes_from_node(node))
+          end
+        end
+
+        private
+          def content_type_is_image?(content_type)
+            content_type.to_s =~ /^image(\/.+|$)/
+          end
+
+          def attributes_from_node(node)
+            { url: node["url"],
+              content_type: node["content-type"],
+              width: node["width"],
+              height: node["height"] }
+          end
+      end
+
+      attr_reader :url, :content_type, :width, :height
+
+      def initialize(attributes = {})
+        @url = attributes[:url]
+        @content_type = attributes[:content_type]
+        @width = attributes[:width]
+        @height = attributes[:height]
+      end
+
+      def attachable_plain_text_representation(caption)
+        "[#{caption || "Image"}]"
+      end
+
+      def to_partial_path
+        "action_text/attachables/remote_image"
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachment.rb b/actiontext/lib/action_text/attachment.rb
new file mode 100644
index 0000000000..e90a3e7d48
--- /dev/null
+++ b/actiontext/lib/action_text/attachment.rb
@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+module ActionText
+  class Attachment
+    include Attachments::TrixConversion, Attachments::Minification, Attachments::Caching
+
+    TAG_NAME = "action-text-attachment"
+    SELECTOR = TAG_NAME
+    ATTRIBUTES = %w( sgid content-type url href filename filesize width height previewable presentation caption )
+
+    class << self
+      def fragment_by_canonicalizing_attachments(content)
+        fragment_by_minifying_attachments(fragment_by_converting_trix_attachments(content))
+      end
+
+      def from_node(node, attachable = nil)
+        new(node, attachable || ActionText::Attachable.from_node(node))
+      end
+
+      def from_attachables(attachables)
+        Array(attachables).map { |attachable| from_attachable(attachable) }.compact
+      end
+
+      def from_attachable(attachable, attributes = {})
+        if node = node_from_attributes(attachable.to_rich_text_attributes(attributes))
+          new(node, attachable)
+        end
+      end
+
+      def from_attributes(attributes, attachable = nil)
+        if node = node_from_attributes(attributes)
+          from_node(node, attachable)
+        end
+      end
+
+      private
+        def node_from_attributes(attributes)
+          if attributes = process_attributes(attributes).presence
+            ActionText::HtmlConversion.create_element(TAG_NAME, attributes)
+          end
+        end
+
+        def process_attributes(attributes)
+          attributes.transform_keys { |key| key.to_s.underscore.dasherize }.slice(*ATTRIBUTES)
+        end
+    end
+
+    attr_reader :node, :attachable
+
+    delegate :to_param, to: :attachable
+    delegate_missing_to :attachable
+
+    def initialize(node, attachable)
+      @node = node
+      @attachable = attachable
+    end
+
+    def caption
+      node_attributes["caption"].presence
+    end
+
+    def full_attributes
+      node_attributes.merge(attachable_attributes).merge(sgid_attributes)
+    end
+
+    def with_full_attributes
+      self.class.from_attributes(full_attributes, attachable)
+    end
+
+    def to_plain_text
+      if respond_to?(:attachable_plain_text_representation)
+        attachable_plain_text_representation(caption)
+      else
+        caption.to_s
+      end
+    end
+
+    def to_html
+      HtmlConversion.node_to_html(node)
+    end
+
+    def to_s
+      to_html
+    end
+
+    def inspect
+      "#<#{self.class.name} attachable=#{attachable.inspect}>"
+    end
+
+    private
+      def node_attributes
+        @node_attributes ||= ATTRIBUTES.map { |name| [ name.underscore, node[name] ] }.to_h.compact
+      end
+
+      def attachable_attributes
+        @attachable_attributes ||= (attachable.try(:to_rich_text_attributes) || {}).stringify_keys
+      end
+
+      def sgid_attributes
+        @sgid_attributes ||= node_attributes.slice("sgid").presence || attachable_attributes.slice("sgid")
+      end
+  end
+end
diff --git a/actiontext/lib/action_text/attachment_gallery.rb b/actiontext/lib/action_text/attachment_gallery.rb
new file mode 100644
index 0000000000..45afbff058
--- /dev/null
+++ b/actiontext/lib/action_text/attachment_gallery.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module ActionText
+  class AttachmentGallery
+    include ActiveModel::Model
+
+    class << self
+      def fragment_by_canonicalizing_attachment_galleries(content)
+        fragment_by_replacing_attachment_gallery_nodes(content) do |node|
+          "<#{TAG_NAME}>#{node.inner_html}</#{TAG_NAME}>"
+        end
+      end
+
+      def fragment_by_replacing_attachment_gallery_nodes(content)
+        Fragment.wrap(content).update do |source|
+          find_attachment_gallery_nodes(source).each do |node|
+            node.replace(yield(node).to_s)
+          end
+        end
+      end
+
+      def find_attachment_gallery_nodes(content)
+        Fragment.wrap(content).find_all(SELECTOR).select do |node|
+          node.children.all? do |child|
+            if child.text?
+              child.text =~ /\A(\n|\ )*\z/
+            else
+              child.matches? ATTACHMENT_SELECTOR
+            end
+          end
+        end
+      end
+
+      def from_node(node)
+        new(node)
+      end
+    end
+
+    attr_reader :node
+
+    def initialize(node)
+      @node = node
+    end
+
+    def attachments
+      @attachments ||= node.css(ATTACHMENT_SELECTOR).map do |node|
+        ActionText::Attachment.from_node(node).with_full_attributes
+      end
+    end
+
+    def size
+      attachments.size
+    end
+
+    def inspect
+      "#<#{self.class.name} size=#{size.inspect}>"
+    end
+
+    TAG_NAME = "div"
+    ATTACHMENT_SELECTOR = "#{ActionText::Attachment::SELECTOR}[presentation=gallery]"
+    SELECTOR = "#{TAG_NAME}:has(#{ATTACHMENT_SELECTOR} + #{ATTACHMENT_SELECTOR})"
+
+    private_constant :TAG_NAME, :ATTACHMENT_SELECTOR, :SELECTOR
+  end
+end
diff --git a/actiontext/lib/action_text/attachments/caching.rb b/actiontext/lib/action_text/attachments/caching.rb
new file mode 100644
index 0000000000..7c727bfc26
--- /dev/null
+++ b/actiontext/lib/action_text/attachments/caching.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachments
+    module Caching
+      def cache_key(*args)
+        [self.class.name, cache_digest, *attachable.cache_key(*args)].join("/")
+      end
+
+      private
+        def cache_digest
+          Digest::SHA256.hexdigest(node.to_s)
+        end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachments/minification.rb b/actiontext/lib/action_text/attachments/minification.rb
new file mode 100644
index 0000000000..edc8f876d6
--- /dev/null
+++ b/actiontext/lib/action_text/attachments/minification.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachments
+    module Minification
+      extend ActiveSupport::Concern
+
+      class_methods do
+        def fragment_by_minifying_attachments(content)
+          Fragment.wrap(content).replace(ActionText::Attachment::SELECTOR) do |node|
+            node.tap { |n| n.inner_html = "" }
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attachments/trix_conversion.rb b/actiontext/lib/action_text/attachments/trix_conversion.rb
new file mode 100644
index 0000000000..24937d6c22
--- /dev/null
+++ b/actiontext/lib/action_text/attachments/trix_conversion.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attachments
+    module TrixConversion
+      extend ActiveSupport::Concern
+
+      class_methods do
+        def fragment_by_converting_trix_attachments(content)
+          Fragment.wrap(content).replace(TrixAttachment::SELECTOR) do |node|
+            from_trix_attachment(TrixAttachment.new(node))
+          end
+        end
+
+        def from_trix_attachment(trix_attachment)
+          from_attributes(trix_attachment.attributes)
+        end
+      end
+
+      def to_trix_attachment(content = trix_attachment_content)
+        attributes = full_attributes.dup
+        attributes["content"] = content if content
+        TrixAttachment.from_attributes(attributes)
+      end
+
+      private
+        def trix_attachment_content
+          if partial_path = attachable.try(:to_trix_content_attachment_partial_path)
+            ActionText::Content.renderer.render(partial: partial_path, object: self, as: model_name.element)
+          end
+        end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/attribute.rb b/actiontext/lib/action_text/attribute.rb
new file mode 100644
index 0000000000..f226dd21bd
--- /dev/null
+++ b/actiontext/lib/action_text/attribute.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Attribute
+    extend ActiveSupport::Concern
+
+    class_methods do
+      # Provides access to a dependent RichText model that holds the body and attachments for a single named rich text attribute.
+      # This dependent attribute is lazily instantiated and will be auto-saved when it's been changed. Example:
+      #
+      #   class Message < ActiveRecord::Base
+      #     has_rich_text :content
+      #   end
+      #
+      #   message = Message.create!(content: "<h1>Funny times!</h1>")
+      #   message.content.to_s # => "<h1>Funny times!</h1>"
+      #   message.content.to_plain_text # => "Funny times!"
+      #
+      # The dependent RichText model will also automatically process attachments links as sent via the Trix-powered editor.
+      # These attachments are associated with the RichText model using Active Storage.
+      #
+      # If you wish to preload the dependent RichText model, you can use the named scope:
+      #
+      #   Message.all.with_rich_text_content # Avoids N+1 queries when you just want the body, not the attachments.
+      #   Message.all.with_rich_text_content_and_embeds # Avoids N+1 queries when you just want the body and attachments.
+      def has_rich_text(name)
+        class_eval <<-CODE, __FILE__, __LINE__ + 1
+          def #{name}
+            self.rich_text_#{name} ||= ActionText::RichText.new(name: "#{name}", record: self)
+          end
+
+          def #{name}=(body)
+            self.#{name}.body = body
+          end
+        CODE
+
+        has_one :"rich_text_#{name}", -> { where(name: name) }, class_name: "ActionText::RichText", as: :record, inverse_of: :record, dependent: :destroy
+
+        scope :"with_rich_text_#{name}", -> { includes("rich_text_#{name}") }
+        scope :"with_rich_text_#{name}_and_embeds", -> { includes("rich_text_#{name}": { embeds_attachments: :blob }) }
+
+        after_save do
+          public_send(name).save if public_send(name).changed?
+        end
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/content.rb b/actiontext/lib/action_text/content.rb
new file mode 100644
index 0000000000..16bc6fe031
--- /dev/null
+++ b/actiontext/lib/action_text/content.rb
@@ -0,0 +1,132 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/module/attribute_accessors_per_thread"
+
+module ActionText
+  class Content
+    include Serialization
+
+    thread_cattr_accessor :renderer
+
+    attr_reader :fragment
+
+    delegate :blank?, :empty?, :html_safe, :present?, to: :to_html # Delegating to to_html to avoid including the layout
+
+    class << self
+      def fragment_by_canonicalizing_content(content)
+        fragment = ActionText::Attachment.fragment_by_canonicalizing_attachments(content)
+        fragment = ActionText::AttachmentGallery.fragment_by_canonicalizing_attachment_galleries(fragment)
+        fragment
+      end
+    end
+
+    def initialize(content = nil, options = {})
+      options.with_defaults! canonicalize: true
+
+      if options[:canonicalize]
+        @fragment = self.class.fragment_by_canonicalizing_content(content)
+      else
+        @fragment = ActionText::Fragment.wrap(content)
+      end
+    end
+
+    def links
+      @links ||= fragment.find_all("a[href]").map { |a| a["href"] }.uniq
+    end
+
+    def attachments
+      @attachments ||= attachment_nodes.map do |node|
+        attachment_for_node(node)
+      end
+    end
+
+    def attachment_galleries
+      @attachment_galleries ||= attachment_gallery_nodes.map do |node|
+        attachment_gallery_for_node(node)
+      end
+    end
+
+    def gallery_attachments
+      @gallery_attachments ||= attachment_galleries.flat_map(&:attachments)
+    end
+
+    def attachables
+      @attachables ||= attachment_nodes.map do |node|
+        ActionText::Attachable.from_node(node)
+      end
+    end
+
+    def append_attachables(attachables)
+      attachments = ActionText::Attachment.from_attachables(attachables)
+      self.class.new([self.to_s.presence, *attachments].compact.join("\n"))
+    end
+
+    def render_attachments(**options, &block)
+      content = fragment.replace(ActionText::Attachment::SELECTOR) do |node|
+        block.call(attachment_for_node(node, **options))
+      end
+      self.class.new(content, canonicalize: false)
+    end
+
+    def render_attachment_galleries(&block)
+      content = ActionText::AttachmentGallery.fragment_by_replacing_attachment_gallery_nodes(fragment) do |node|
+        block.call(attachment_gallery_for_node(node))
+      end
+      self.class.new(content, canonicalize: false)
+    end
+
+    def to_plain_text
+      render_attachments(with_full_attributes: false, &:to_plain_text).fragment.to_plain_text
+    end
+
+    def to_trix_html
+      render_attachments(&:to_trix_attachment).to_html
+    end
+
+    def to_html
+      fragment.to_html
+    end
+
+    def to_rendered_html_with_layout
+      renderer.render(partial: "action_text/content/layout", locals: { content: self })
+    end
+
+    def to_s
+      to_rendered_html_with_layout
+    end
+
+    def as_json(*)
+      to_html
+    end
+
+    def inspect
+      "#<#{self.class.name} #{to_s.truncate(25).inspect}>"
+    end
+
+    def ==(other)
+      if other.is_a?(self.class)
+        to_s == other.to_s
+      end
+    end
+
+    private
+      def attachment_nodes
+        @attachment_nodes ||= fragment.find_all(ActionText::Attachment::SELECTOR)
+      end
+
+      def attachment_gallery_nodes
+        @attachment_gallery_nodes ||= ActionText::AttachmentGallery.find_attachment_gallery_nodes(fragment)
+      end
+
+      def attachment_for_node(node, with_full_attributes: true)
+        attachment = ActionText::Attachment.from_node(node)
+        with_full_attributes ? attachment.with_full_attributes : attachment
+      end
+
+      def attachment_gallery_for_node(node)
+        ActionText::AttachmentGallery.from_node(node)
+      end
+  end
+end
+
+ActiveSupport.run_load_hooks :action_text_content, ActionText::Content
diff --git a/actiontext/lib/action_text/engine.rb b/actiontext/lib/action_text/engine.rb
new file mode 100644
index 0000000000..01222f077b
--- /dev/null
+++ b/actiontext/lib/action_text/engine.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "rails"
+require "action_controller/railtie"
+require "active_record/railtie"
+require "active_storage/engine"
+
+require "action_text"
+
+module ActionText
+  class Engine < Rails::Engine
+    isolate_namespace ActionText
+    config.eager_load_namespaces << ActionText
+
+    initializer "action_text.attribute" do
+      ActiveSupport.on_load(:active_record) do
+        include ActionText::Attribute
+      end
+    end
+
+    initializer "action_text.attachable" do
+      ActiveSupport.on_load(:active_storage_blob) do
+        include ActionText::Attachable
+
+        def previewable_attachable?
+          representable?
+        end
+      end
+    end
+
+    initializer "action_text.helper" do
+      ActiveSupport.on_load(:action_controller_base) do
+        helper ActionText::Engine.helpers
+      end
+    end
+
+    initializer "action_text.renderer" do
+      ActiveSupport.on_load(:action_text_content) do
+        self.renderer ||= ApplicationController.renderer
+      end
+
+      ActiveSupport.on_load(:action_controller_base) do
+        before_action { ActionText::Content.renderer = ActionText::Content.renderer.new(request.env) }
+      end
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/fragment.rb b/actiontext/lib/action_text/fragment.rb
new file mode 100644
index 0000000000..af276b2b26
--- /dev/null
+++ b/actiontext/lib/action_text/fragment.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module ActionText
+  class Fragment
+    class << self
+      def wrap(fragment_or_html)
+        case fragment_or_html
+        when self
+          fragment_or_html
+        when Nokogiri::HTML::DocumentFragment
+          new(fragment_or_html)
+        else
+          from_html(fragment_or_html)
+        end
+      end
+
+      def from_html(html)
+        new(ActionText::HtmlConversion.fragment_for_html(html.to_s.strip))
+      end
+    end
+
+    attr_reader :source
+
+    def initialize(source)
+      @source = source
+    end
+
+    def find_all(selector)
+      source.css(selector)
+    end
+
+    def update
+      yield source = self.source.clone
+      self.class.new(source)
+    end
+
+    def replace(selector)
+      update do |source|
+        source.css(selector).each do |node|
+          node.replace(yield(node).to_s)
+        end
+      end
+    end
+
+    def to_plain_text
+      @plain_text ||= PlainTextConversion.node_to_plain_text(source)
+    end
+
+    def to_html
+      @html ||= HtmlConversion.node_to_html(source)
+    end
+
+    def to_s
+      to_html
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/gem_version.rb b/actiontext/lib/action_text/gem_version.rb
new file mode 100644
index 0000000000..5a640de5c8
--- /dev/null
+++ b/actiontext/lib/action_text/gem_version.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ActionText
+  # Returns the currently-loaded version of Action Text as a <tt>Gem::Version</tt>.
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 6
+    MINOR = 0
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end
diff --git a/actiontext/lib/action_text/html_conversion.rb b/actiontext/lib/action_text/html_conversion.rb
new file mode 100644
index 0000000000..1e1062ea3f
--- /dev/null
+++ b/actiontext/lib/action_text/html_conversion.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActionText
+  module HtmlConversion
+    extend self
+
+    def node_to_html(node)
+      node.to_html(save_with: Nokogiri::XML::Node::SaveOptions::AS_HTML)
+    end
+
+    def fragment_for_html(html)
+      document.fragment(html)
+    end
+
+    def create_element(tag_name, attributes = {})
+      document.create_element(tag_name, attributes)
+    end
+
+    private
+      def document
+        Nokogiri::HTML::Document.new.tap { |doc| doc.encoding = "UTF-8" }
+      end
+  end
+end
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
diff --git a/actiontext/lib/action_text/serialization.rb b/actiontext/lib/action_text/serialization.rb
new file mode 100644
index 0000000000..8ecf8c9157
--- /dev/null
+++ b/actiontext/lib/action_text/serialization.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module ActionText
+  module Serialization
+    extend ActiveSupport::Concern
+
+    class_methods do
+      def load(content)
+        new(content) if content
+      end
+
+      def dump(content)
+        case content
+        when nil
+          nil
+        when self
+          content.to_html
+        else
+          new(content).to_html
+        end
+      end
+    end
+
+    # Marshal compatibility
+
+    class_methods do
+      alias_method :_load, :load
+    end
+
+    def _dump(*)
+      self.class.dump(self)
+    end
+  end
+end
diff --git a/actiontext/lib/action_text/trix_attachment.rb b/actiontext/lib/action_text/trix_attachment.rb
new file mode 100644
index 0000000000..c16c1c090d
--- /dev/null
+++ b/actiontext/lib/action_text/trix_attachment.rb
@@ -0,0 +1,92 @@
+# frozen_string_literal: true
+
+module ActionText
+  class TrixAttachment
+    TAG_NAME = "figure"
+    SELECTOR = "[data-trix-attachment]"
+
+    COMPOSED_ATTRIBUTES = %w( caption presentation )
+    ATTRIBUTES = %w( sgid contentType url href filename filesize width height previewable content ) + COMPOSED_ATTRIBUTES
+    ATTRIBUTE_TYPES = {
+      "previewable" => ->(value) { value.to_s == "true" },
+      "filesize"    => ->(value) { Integer(value.to_s) rescue value },
+      "width"       => ->(value) { Integer(value.to_s) rescue nil },
+      "height"      => ->(value) { Integer(value.to_s) rescue nil },
+      :default      => ->(value) { value.to_s }
+    }
+
+    class << self
+      def from_attributes(attributes)
+        attributes = process_attributes(attributes)
+
+        trix_attachment_attributes = attributes.except(*COMPOSED_ATTRIBUTES)
+        trix_attributes = attributes.slice(*COMPOSED_ATTRIBUTES)
+
+        node = ActionText::HtmlConversion.create_element(TAG_NAME)
+        node["data-trix-attachment"] = JSON.generate(trix_attachment_attributes)
+        node["data-trix-attributes"] = JSON.generate(trix_attributes) if trix_attributes.any?
+
+        new(node)
+      end
+
+      private
+        def process_attributes(attributes)
+          typecast_attribute_values(transform_attribute_keys(attributes))
+        end
+
+        def transform_attribute_keys(attributes)
+          attributes.transform_keys { |key| key.to_s.underscore.camelize(:lower) }
+        end
+
+        def typecast_attribute_values(attributes)
+          attributes.map do |key, value|
+            typecast = ATTRIBUTE_TYPES[key] || ATTRIBUTE_TYPES[:default]
+            [key, typecast.call(value)]
+          end.to_h
+        end
+    end
+
+    attr_reader :node
+
+    def initialize(node)
+      @node = node
+    end
+
+    def attributes
+      @attributes ||= attachment_attributes.merge(composed_attributes).slice(*ATTRIBUTES)
+    end
+
+    def to_html
+      ActionText::HtmlConversion.node_to_html(node)
+    end
+
+    def to_s
+      to_html
+    end
+
+    private
+      def attachment_attributes
+        read_json_object_attribute("data-trix-attachment")
+      end
+
+      def composed_attributes
+        read_json_object_attribute("data-trix-attributes")
+      end
+
+      def read_json_object_attribute(name)
+        read_json_attribute(name) || {}
+      end
+
+      def read_json_attribute(name)
+        if value = node[name]
+          begin
+            JSON.parse(value)
+          rescue => e
+            Rails.logger.error "[#{self.class.name}] Couldn't parse JSON #{value} from NODE #{node.inspect}"
+            Rails.logger.error "[#{self.class.name}] Failed with #{e.class}: #{e.backtrace}"
+            nil
+          end
+        end
+      end
+  end
+end
diff --git a/actiontext/lib/action_text/version.rb b/actiontext/lib/action_text/version.rb
new file mode 100644
index 0000000000..ed72859fa4
--- /dev/null
+++ b/actiontext/lib/action_text/version.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require_relative "gem_version"
+
+module ActionText
+  # Returns the currently-loaded version of Action Text as a <tt>Gem::Version</tt>.
+  def self.version
+    gem_version
+  end
+end
diff --git a/actiontext/lib/tasks/actiontext.rake b/actiontext/lib/tasks/actiontext.rake
new file mode 100644
index 0000000000..4f90e4930c
--- /dev/null
+++ b/actiontext/lib/tasks/actiontext.rake
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+namespace :action_text do
+  # Prevent migration installation task from showing up twice.
+  Rake::Task["install:migrations"].clear_comments
+
+  desc "Copy over the migration, stylesheet, and JavaScript files"
+  task install: %w( environment run_installer copy_migrations )
+
+  task :run_installer do
+    installer_template = File.expand_path("../templates/installer.rb", __dir__)
+    system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{installer_template}"
+  end
+
+  task :copy_migrations do
+    Rake::Task["active_storage:install:migrations"].invoke
+    Rake::Task["railties:install:migrations"].reenable # Otherwise you can't run 2 migration copy tasks in one invocation
+    Rake::Task["action_text:install:migrations"].invoke
+  end
+end
diff --git a/actiontext/lib/templates/actiontext.scss b/actiontext/lib/templates/actiontext.scss
new file mode 100644
index 0000000000..7cb26e74ac
--- /dev/null
+++ b/actiontext/lib/templates/actiontext.scss
@@ -0,0 +1,36 @@
+//
+// Provides a drop-in pointer for the default Trix stylesheet that will format the toolbar and
+// the trix-editor content (whether displayed or under editing). Feel free to incorporate this
+// inclusion directly in any other asset bundle and remove this file.
+//
+//= require trix/dist/trix
+
+// We need to override trix.css’s image gallery styles to accommodate the
+// <action-text-attachment> element we wrap around attachments. Otherwise,
+// images in galleries will be squished by the max-width: 33%; rule.
+.trix-content {
+  .attachment-gallery {
+    > action-text-attachment,
+    > .attachment {
+      flex: 1 0 33%;
+      padding: 0 0.5em;
+      max-width: 33%;
+    }
+
+    &.attachment-gallery--2,
+    &.attachment-gallery--4 {
+      > action-text-attachment,
+      > .attachment {
+        flex-basis: 50%;
+        max-width: 50%;
+      }
+    }
+  }
+
+  action-text-attachment {
+    .attachment {
+      padding: 0 !important;
+      max-width: 100% !important;
+    }
+  }
+}
diff --git a/actiontext/lib/templates/fixtures.yml b/actiontext/lib/templates/fixtures.yml
new file mode 100644
index 0000000000..8b371ea604
--- /dev/null
+++ b/actiontext/lib/templates/fixtures.yml
@@ -0,0 +1,4 @@
+# one:
+#   record: name_of_fixture (ClassOfFixture)
+#   name: content
+#   body: <p>In a <i>million</i> stars!</p>
diff --git a/actiontext/lib/templates/installer.rb b/actiontext/lib/templates/installer.rb
new file mode 100644
index 0000000000..ee5a5af75b
--- /dev/null
+++ b/actiontext/lib/templates/installer.rb
@@ -0,0 +1,22 @@
+say "Copying actiontext.scss to app/assets/stylesheets"
+copy_file "#{__dir__}/actiontext.scss", "app/assets/stylesheets/actiontext.scss"
+
+say "Copying fixtures to test/fixtures/action_text/rich_texts.yml"
+copy_file "#{__dir__}/fixtures.yml", "test/fixtures/action_text/rich_texts.yml"
+
+say "Copying blob rendering partial to app/views/active_storage/blobs/_blob.html.erb"
+copy_file "#{__dir__}/../../app/views/active_storage/blobs/_blob.html.erb",
+  "app/views/active_storage/blobs/_blob.html.erb"
+
+# FIXME: Replace with release version on release
+say "Installing JavaScript dependency"
+run "yarn add https://github.com/rails/actiontext"
+
+APPLICATION_PACK_PATH = "app/javascript/packs/application.js"
+
+if File.exists?(APPLICATION_PACK_PATH) && File.read(APPLICATION_PACK_PATH) !~ /import "actiontext"/
+  say "Adding import to default JavaScript pack"
+  append_to_file APPLICATION_PACK_PATH, <<-EOS
+import "actiontext"
+EOS
+end