class PageTocFilter

# File lib/page-toc-filter.rb, line 5
def call
  doc.search('p').each do |node|
    content = node.to_html
    next unless content == '<p>{:toc}</p>'
    html = page_toc_filter(doc)
    node.replace(html)
  end

  doc
end

# File lib/page-toc-filter.rb, line 16
def page_toc_filter(doc)
  levels = doc.search(context[:toc_levels] || 'h2')
  return '' if levels.empty?

  toc = %(<ul id="markdown-toc">\n)
  last_level = nil
  depth = 1

  levels.each do |node|
    current_level = node.name.match(/h(\d)/)[1]

    text = node.text
    id = node.child['id']

    link = %(<a href="##{id}" id="markdown-toc-#{id}">#{text}</a>)

    if last_level.nil?
      toc << %(<li>#{link})
    elsif current_level == last_level
      toc << %(</li>\n<li>#{link})
    elsif current_level > last_level
      depth += 1
      toc << %(\n<ul><li>#{link})
    elsif current_level < last_level
      depth -= 1
      toc << %(</li></ul>\n<li>#{link})
    end

    last_level = current_level
  end

  if depth < 0
    raise ArgumentError, 'Your headings are not in sequential order. It seems that a lower heading level (like an h4) is being defined before a higher heading level (like an h1).'
  end

  toc << %(</li>\n</ul>) * depth
  toc
end