class Labels

  def initialize argv
    @savefile = '/dev/stdout'
    @files = []
    for arg in argv
      case arg
      when /^-o:?/ then @savefile = $'
      when /^-/ then $stderr.puts "unknown option #{arg}"
      else @files.push arg
      end
    end
    raise "usage: #{$0} input output" if @files.empty?
    @nfstack = []
    @labels = {}
  end

  def marksec level
    if level > @nfstack.size
      raise "heading out of sequence"
    end
    if @nfstack.size > level
      @nfstack = @nfstack[0, level + 1]
    end
    @nfstack[level] = 0 unless @nfstack[level]
    @nfstack[level] += 1
    $stderr.puts "section #{sec_name}" if $VERBOSE
  end

  def sec_name
    @nfstack.join('.')
  end

  def setlabel label
    @labels[label] = sec_name
  end

  def so file
    File.open(file, 'r') {|fp|
      for line in fp
        case line
        when /^\.\s*NH\s+(\d+)/ then
	  marksec($1.to_i - 1)
        when /^\.\s*LB\s+(\w+)/ then
	  setlabel $1
        when /^\.\s*so\s+(\S+)/ then
	  so $1
	end
      end
    }
  rescue Errno::ENOENT
    $stderr.puts "file #{file} not found"
  end

  def save
    File.open(@savefile, 'w') {|fp|
      for label in @labels.keys.sort
	fp.puts ".ds S#{label} #{@labels[label]}"
      end
    }
  end

  def run
    @files.each {|file| so file}
    save   
  end

end

Labels.new(ARGV).run