module CodeRay::Encoders::HTML::Numbering

def self.number! output, mode = :table, options = {}
  return self unless mode
  options = DEFAULT_OPTIONS.merge options
  start = options[:line_number_start]
  unless start.is_a? Integer
    raise ArgumentError, "Invalid value %p for :line_number_start; Integer expected." % start
  end
  
  anchor_prefix = options[:line_number_anchors]
  anchor_prefix = 'line' if anchor_prefix == true
  anchor_prefix = anchor_prefix.to_s[/\w+/] if anchor_prefix
  anchoring =
    if anchor_prefix
      proc do |line|
        line = line.to_s
        anchor = anchor_prefix + line
        "<a href=\"##{anchor}\" name=\"#{anchor}\">#{line}</a>"
      end
    else
      proc { |line| line.to_s }  # :to_s.to_proc in Ruby 1.8.7+
    end
  
  bold_every = options[:bold_every]
  highlight_lines = options[:highlight_lines]
  bolding =
    if bold_every == false && highlight_lines == nil
      anchoring
    elsif highlight_lines.is_a? Enumerable
      highlight_lines = highlight_lines.to_set
      proc do |line|
        if highlight_lines.include? line
          "<strong class=\"highlighted\">#{anchoring[line]}</strong>"  # highlighted line numbers in bold
        else
          anchoring[line]
        end
      end
    elsif bold_every.is_a? Integer
      raise ArgumentError, ":bolding can't be 0." if bold_every == 0
      proc do |line|
        if line % bold_every == 0
          "<strong>#{anchoring[line]}</strong>"  # every bold_every-th number in bold
        else
          anchoring[line]
        end
      end
    else
      raise ArgumentError, 'Invalid value %p for :bolding; false or Integer expected.' % bold_every
    end
  
  line_count = output.count("\n")
  position_of_last_newline = output.rindex(RUBY_VERSION >= '1.9' ? /\n/ : ?\n)
  if position_of_last_newline
    after_last_newline = output[position_of_last_newline + 1 .. -1]
    ends_with_newline = after_last_newline[/\A(?:<\/span>)*\z/]
    line_count += 1 if not ends_with_newline
  end
  
  case mode
  when :inline
    max_width = (start + line_count).to_s.size
    line_number = start
    nesting = []
    output.gsub!(/^.*$\n?/) do |line|
      line.chomp!
      open = nesting.join
      line.scan(%r!<(/)?span[^>]*>?!) do |close,|
        if close
          nesting.pop
        else
          nesting << $&
        end
      end
      close = '</span>' * nesting.size
      
      line_number_text = bolding.call line_number
      indent = ' ' * (max_width - line_number.to_s.size)  # TODO: Optimize (10^x)
      line_number += 1
      "<span class=\"line-numbers\">#{indent}#{line_number_text}</span>#{open}#{line}#{close}\n"
    end
  when :table
    line_numbers = (start ... start + line_count).map(&bolding).join("\n")
    line_numbers << "\n"
    line_numbers_table_template = Output::TABLE.apply('LINE_NUMBERS', line_numbers)
    output.gsub!(/<\/div>\n/, '</div>')
    output.wrap_in! line_numbers_table_template
    output.wrapped_in = :div
  when :list
    raise NotImplementedError, 'The :list option is no longer available. Use :table.'
  else
    raise ArgumentError, 'Unknown value %p for mode: expected one of %p' %
      [mode, [:table, :inline]]
  end
  output
end