class Test::Unit::UI::Console::ColorizedReadableDiffer

def diff_line(from_line, to_line)
  to_operations = []
  mark_operations = []
  from_line, to_line, _operations = line_operations(from_line, to_line)
  no_replace = true
  _operations.each do |tag,|
    if tag == :replace
      no_replace = false
      break
    end
  end
  output_single("?", color("diff-difference-tag"))
  output_single(" ")
  _operations.each do |tag, from_start, from_end, to_start, to_end|
    from_width = compute_width(from_line, from_start, from_end)
    to_width = compute_width(to_line, to_start, to_end)
    case tag
    when :replace
      output_single(from_line[from_start...from_end],
                    color("diff-deleted"))
      if (from_width < to_width)
        output_single(" " * (to_width - from_width))
      end
      to_operations << Proc.new do
        output_single(to_line[to_start...to_end],
                      color("diff-inserted"))
        if (to_width < from_width)
          output_single(" " * (from_width - to_width))
        end
      end
      mark_operations << Proc.new do
        output_single("?" * from_width,
                      color("diff-difference-tag"))
        if (to_width < from_width)
          output_single(" " * (from_width - to_width))
        end
      end
    when :delete
      output_single(from_line[from_start...from_end],
                    color("diff-deleted"))
      unless no_replace
        to_operations << Proc.new {output_single(" " * from_width)}
        mark_operations << Proc.new do
          output_single("-" * from_width,
                        color("diff-deleted"))
        end
      end
    when :insert
      if no_replace
        output_single(to_line[to_start...to_end],
                      color("diff-inserted"))
      else
        output_single(" " * to_width)
        to_operations << Proc.new do
          output_single(to_line[to_start...to_end],
                        color("diff-inserted"))
        end
        mark_operations << Proc.new do
          output_single("+" * to_width,
                        color("diff-inserted"))
        end
      end
    when :equal
      output_single(from_line[from_start...from_end])
      unless no_replace
        to_operations << Proc.new {output_single(" " * to_width)}
        mark_operations << Proc.new {output_single(" " * to_width)}
      end
    else
      raise "unknown tag: #{tag}"
    end
  end
  output("")
  unless to_operations.empty?
    output_single("?", color("diff-difference-tag"))
    output_single(" ")
    to_operations.each do |operation|
      operation.call
    end
    output("")
  end
  unless mark_operations.empty?
    output_single("?", color("diff-difference-tag"))
    output_single(" ")
    mark_operations.each do |operation|
      operation.call
    end
    output("")
  end
end