class RDoc::Markup::ToHtmlSnippet

def accept_heading heading
  @res << "<p>#{to_html heading.text}\n"
  add_paragraph
end

def accept_list_item_end list_item
end

def accept_list_item_start list_item
  @res << list_item_start(list_item, @list.last)
end

def accept_list_start list
  @list << list.type
  @res << html_list_name(list.type, true)
  @in_list_entry.push ''
end

def accept_paragraph paragraph
  para = @in_list_entry.last || "<p>"
  text = paragraph.text @hard_break
  @res << "#{para}#{wrap to_html text}\n"
  add_paragraph
end

def accept_verbatim verbatim
  throw :done if @characters >= @character_limit
  input = verbatim.text.rstrip
  text = truncate input
  text << ' ...' unless text == input
  super RDoc::Markup::Verbatim.new text
  add_paragraph
end

def add_paragraph
  @paragraphs += 1
  throw :done if @paragraphs >= @paragraph_limit
end

def convert content
  catch :done do
    return super
  end
  end_accepting
end

def convert_flow flow
  throw :done if @characters >= @character_limit
  res = []
  @mask = 0
  flow.each do |item|
    case item
    when RDoc::Markup::AttrChanger then
      off_tags res, item
      on_tags  res, item
    when String then
      text = convert_string item
      res << truncate(text)
    when RDoc::Markup::Special then
      text = convert_special item
      res << truncate(text)
    else
      raise "Unknown flow element: #{item.inspect}"
    end
    if @characters >= @character_limit then
      off_tags res, RDoc::Markup::AttrChanger.new(0, @mask)
      break
    end
  end
  res << ' ...' if @characters >= @character_limit
  res.join
end

def gen_url url, text
  if url =~ /^rdoc-label:([^:]*)(?::(.*))?/ then
    type = "link"
  elsif url =~ /([A-Za-z]+):(.*)/ then
    type = $1
  else
    type = "http"
  end
  if (type == "http" or type == "https" or type == "link") and
     url =~ /\.(gif|png|jpg|jpeg|bmp)$/ then
    ''
  else
    text.sub(%r%^#{type}:/*%, '')
  end
end

def handle_special_CROSSREF special
  special.text.sub(/\A\\/, '')
end

def handle_special_HARD_BREAK special
  @characters -= 4
  '<br>'
end

def html_list_name list_type, open_tag
  ''
end

def initialize options, characters = 100, paragraphs = 3, markup = nil
  super options, markup
  @character_limit = characters
  @paragraph_limit = paragraphs
  @characters = 0
  @mask       = 0
  @paragraphs = 0
  @markup.add_special RDoc::CrossReference::CROSSREF_REGEXP, :CROSSREF
end

def list_item_start list_item, list_type
  throw :done if @characters >= @character_limit
  case list_type
  when :BULLET, :LALPHA, :NUMBER, :UALPHA then
    "<p>"
  when :LABEL, :NOTE then
    labels = Array(list_item.label).map do |label|
      to_html label
    end.join ', '
    labels << " &mdash; " unless labels.empty?
    start = "<p>#{labels}"
    @characters += 1 # try to include the label
    start
  else
    raise RDoc::Error, "Invalid list type: #{list_type.inspect}"
  end
end

def off_tags res, item
  @mask ^= item.turn_off
  super
end

def on_tags res, item
  @mask ^= item.turn_on
  super
end

def start_accepting
  super
  @characters = 0
end

def truncate text
  length = text.length
  characters = @characters
  @characters += length
  return text if @characters < @character_limit
  remaining = @character_limit - characters
  text =~ /\A(.{#{remaining},}?)(\s|$)/m # TODO word-break instead of \s?
  $1
end