grammar Block
  rule document
     block* {
      def content
        elements.map{ |element| element.content}
      end
    }
  end

  rule block
     block_header block_text? {
      def content
        elements.map{ |element| element.respond_to?(:content) ? element.content : nil}.compact
      end
    }
  end

  rule block_header
     block_start block_type block_id? parent_id? attribute_list? [\n]*  {
      def content
        elements.map{ |element| element.respond_to?(:content) ? element.content : nil}.compact
      end
    }
  end

  rule block_start
    ":" {
      def content
        nil
      end
    }
  end

  rule block_text
    (!(block_header) .)+ {
      def content
        text_value
      end
    }
  end
 
  rule block_type
    ( paragraph / feed / preformatted / list / header / blockquote ) {
      def content
        [:block_type, text_value.to_sym ]
      end
    }
  end
 
  rule paragraph
    "paragraph" { def content; text_value; end }
  end

  rule header
    ( header_one / header_two / header_three / header_four / header_five / header_six ) { def content; text_value; end }
  end

  rule header_one
    "header_one" { def content; text_value; end }
  end

  rule header_two
    "header_two" { def content; text_value; end }
  end

  rule header_three
    "header_three" { def content; text_value; end }
  end

  rule header_four
    "header_four" { def content; text_value; end }
  end

  rule header_five
    "header_five" { def content; text_value; end }
  end

  rule header_six
    "header_six" { def content; text_value; end }
  end

  rule blockquote
    "blockquote" { def content; text_value; end }
  end

  rule feed
    "feed" { def content; text_value; end }
  end

  rule preformatted
    "preformatted" { def content; text_value; end }
  end

  rule list
    "list" { def content; text_value; end }
  end

  rule block_id
    " "+ [a-z\-_]+ {
      def content
        [:block_id, text_value.strip]
      end
    }
  end

  rule parent_id
    block_id {
      def content
        [:parent_id, text_value.strip]
      end
    }
  end

  rule name
    [A-Za-z0-9]+ {
      def content
        text_value
      end
    }
  end

  rule attribute_list
    attribute* {
      def content
        attributes = elements.map{ |element| element.content }
        attributes.unshift :attribute_list
      end
    }
  end
 
  rule attribute
    [\s]+ name "=" attribute_value {
      def content
        [elements[1].content.to_sym, elements[3].content]
      end
    }
  end
 
  rule attribute_value
    [a-z\-_]+ {
      def content
        text_value
      end
    }
  end

  #rule beginning_of_line
  #   {
  #    def content
  #      nil
  #    end
  #  }
  #end
end