styled_templates.rb

styled_templates.rb

# <%= style_for_this_template do %>
#   width: 128px;
#   .caption {
#     font-size: 12px;
#     text-align: center;
#   }
# <% end %>
# <div class="<%= css_class_for_this_template %>">
#   <div class="title">Hello!</div>
# </div>
module StyledTemplatesHelper
  def css_class_selector_for_this_template
    ".#{css_class_for_this_template}"
  end

  def css_class_for_this_template
    raise "@current_template is not set, so we can't intuit the wrapping class name for this block" unless @current_template.present?

    # Rails computes the method name the template will be compiled into. This method name changes with changes to the template
    # source, and includes the digest-like details and all the other useful bits.
    compiled_template_method_name = @current_template.method_name
    # We will use the virtual path as the base for our CSS class
    template_virtual_path = @current_template.virtual_path
    _css_class_name = template_virtual_path.gsub(/(\/|_)/, "-") + "-" + Digest::SHA1.hexdigest(compiled_template_method_name)[0..3]
  end

  def style_for_this_template(css_source_or_nil = nil)
    if !block_given? && style_source.blank?
      raise "You need to either pass the CSS code as the first argument or render it from the passed block"
    end
    css_class_name = css_class_for_this_template
    @styles_already_output ||= Set.new
    return if @styles_already_output.include?(css_class_name)

    # https://thepugautomatic.com/2013/06/helpers/
    capture do
      concat("<style>\n".html_safe)
      concat("\n.#{css_class_name} {\n")
      concat((block_given? ? yield : css_source_or_nil) + "\n")
      concat("\n}\n")
      concat("</style>\n".html_safe)
    end.tap do
      @styles_already_output << css_class_name
    end
  end
end