notebook/app/services/content_formatter_service.rb

class ContentFormatterService < Service
  extend ActionView::Helpers::UrlHelper # link_to, *_url, *_path
  extend ActionView::Helpers::TagHelper # content_tag (used by link_to under the hood)
  extend ActionView::Context            # content_tag

  include Rails.application.routes.url_helpers
  default_url_options[:host] = 'localhost' # todo We should figure out how to remove this #codesmell

  # Token format is [[character-35]] or [[location-1]] etc, with the format:
  # [[<page_type>-<page_id>]].
  # todo page slugs could be cool for this? I dunno. We probably don't want to use a
  # field like name that can change ([[bob]]) or have an ambiguous link.
  TOKEN_REGEX = /\[\[([^\-]+)\-([^\]]+)\]\]/

  # Only allow linking to content type classes
  # todo: we shouldn't have to map name here, but apparently rails is having a little difficulty
  # https://s3.amazonaws.com/raw.paste.esk.io/Llb%2F64DJHK?versionId=19Lb_TtukDbo1J_IoCpkr.d.pwpW_vmH
  VALID_LINK_CLASSES = Rails.application.config.content_types[:all].map(&:name)
  def self.show(text:, viewing_user: User.new)
    # We want to evaluate markdown first, because the markdown engine also happens
    # to strip out HTML tags. So: markdown, _then_ insert content links.
    formatted_text = markdown.render(text || '').html_safe
    substitute_content_links(formatted_text, viewing_user).html_safe
  end

  private

  def self.markdown
    # Returns a shared markdown rendering engine; use self.markdown.render(text)
    Rails.application.config.markdown
  end

  def self.substitute_content_links(text, viewing_user)
    tokens_to_replace(text).each do |token|
      text.gsub!(token[:matched_string], replacement_for_token(token, viewing_user))
    end
    text
  end

  def self.tokens_to_replace(text)
    text.scan(TOKEN_REGEX).map do |klass, id|
      {
        content_type:   klass,
        content_id:     id,
        matched_string: "[[#{klass}-#{id}]]"
      }
    end
  end

  def self.replacement_for_token(token, viewing_user)
    return unknown_link_template(token) unless token.key?(:content_type) && token.key?(:content_id)
    begin
      content_class = token[:content_type].titleize.constantize
    rescue
      return unknown_link_template(token)
    end
    return unknown_link_template(token) unless VALID_LINK_CLASSES.include?(content_class.name)

    content_id    = token[:content_id].to_i
    content_model = content_class.find_by(id: content_id)
    return unknown_link_template(token) unless content_model.present?

    if content_model.readable_by?(viewing_user)
      link_template(content_model)
    else
      private_link_template(content_model)
    end
  end

  def self.link_template(content_model)
    inline_template(content_model.class) { link_to(content_model.name, link_for(content_model), class: "content_link #{content_model.class.name.downcase}-link") }
  end

  def self.private_link_template(content_model)
    inline_template(content_model.class) { link_to(content_model.name, link_for(content_model), class: 'grey-text content_link disabled') }
  end

  def self.unknown_link_template(attempted_key)
    attempted_key[:matched_string]
  end

  #todo maybe just move this to a partial?
  def self.chip_template(class_model=nil)
    content_tag(:span, class: 'chip') do
      body = ''
      if class_model
        body += content_tag(:span, class: class_model ? "#{class_model.color}-text" : '') do
          # todo tooltip the class icon
          content_tag(:i, class: 'material-icons left', style: 'position: relative; top: 3px;') do
            class_model.icon
          end
        end
      end
      body += yield
      body.html_safe
    end
  end

  def self.inline_template(class_model=nil)
    content_tag(:span, class: 'inline-link') do
      content_tag(:span, class: class_model ? "#{class_model.color}-text" : '') do
        yield
      end
    end
  end

  # This is a hack until I figure out how to include polymorphic paths in a service model.
  #todo remove this
  def self.link_for(content_model)
    [
      Rails.env.production? ? 'https://' : 'http://',
      Rails.env.production? ? 'www.notebook.ai' : 'localhost:3000', # Rails.application.routes.default_url_options[:host]?
      '/plan/',
      content_model.class.name.downcase.pluralize,
      '/',
      content_model.id
    ].join
  end
end