class Asciidoctor::AbstractBlock

def assign_index(section)
  section.index = @next_section_index
  @next_section_index += 1
  if section.sectname == 'appendix'
    appendix_number = @document.counter 'appendix-number', 'A'
    section.number = appendix_number if section.numbered
    if (caption = @document.attr 'appendix-caption', '') != ''
      section.caption = %(#{caption} #{appendix_number}: )
    else
      section.caption = %(#{appendix_number}. )
    end
  elsif section.numbered
    # chapters in a book doctype should be sequential even when divided into parts
    if (section.level == 1 || (section.level == 0 && section.special)) && @document.doctype == 'book'
      section.number = @document.counter('chapter-number', 1)
    else
      section.number = @next_section_number
      @next_section_number += 1
    end
  end
end