class Rouge::Formatters::HTMLLineHighlighter

def initialize(delegate, opts = {})
  @delegate = delegate
  @highlight_line_class = opts.fetch(:highlight_line_class, 'hll')
  @highlight_lines = opts[:highlight_lines] || []
end

def stream(tokens)
  token_lines(tokens).with_index(1) do |line_tokens, lineno|
    line = %(#{@delegate.format(line_tokens)}\n)
    line = %(<span class="#{@highlight_line_class}">#{line}</span>) if @highlight_lines.include? lineno
    yield line
  end
end