module BootstrapComponentsHelpers
  module AccordionHelper
    def accordion opts = {}
      opts[:accordion_id] ||= 'accordion'
      builder = AccordionBuilder.new opts, self
      content_tag :div, :class => 'accordion', :id => opts[:accordion_id] do
        yield builder
      end
    end

    class AccordionBuilder

      attr_reader :parent
      delegate :capture, :to => :parent

      def initialize opts, parent
        @first = true
        @parent = parent
        @opts = opts
      end

      def pane title, &block
        b = Builder::XmlMarkup.new
        b.div :class => 'accordion-group' do
          b.div :class => 'accordion-heading' do
            b.a title, :class => 'accordion-toggle', :'data-toggle' => 'collapse',
            :'data-parent' => "##{@opts[:accordion_id]}", :href => "##{title.parameterize}_pane"
          end
          css_class =  (@first && @opts[:open]) ? 'in' : ''
          @first = false
          b.div :class => "accordion-body collapse #{css_class}", :id => "#{title.parameterize}_pane" do
            b.div :class => 'accordion-inner' do
              b << capture(&block)
            end
          end
        end.html_safe
      end
    end
  end
end

ActionView::Base.send :include, BootstrapComponentsHelpers::AccordionHelper