rotate-files

#!/usr/bin/env ruby
require File.expand_path(File.dirname(__FILE__) + '/shared')
require 'optparse'

class RotateFiles
  def initialize(argv)
    @argv = argv.dup
  end

  def run
    parse_options
    prepare
    create_file
    cleanup
  end

private
  def parse_options
    @max = 50

    parser = OptionParser.new do |opts|
      nl = "\n#{' ' * 37}"
      opts.banner = "Usage: rotate-files <INPUT> <OUTPUT PREFIX> [OUTPUT SUFFIX] [OPTIONS]"
      opts.separator 'Copy INPUT to the path specified by OUTPUT_PREFIX + timestamp + OUTPUT_SUFFIX,'
      opts.separator 'then delete excess files that match the same pattern.'
      opts.separator ''
      opts.separator 'Example: rotate-files backup.tar.gz /backups/backup- .tar.gz'
      opts.separator 'Creates /backups/backup-<TIMESTAMP>.tar.gz, deletes old backup files matching'
      opts.separator 'this pattern.'
      opts.separator ''

      opts.on('--max NUMBER', Integer, "Maximum number of files to keep.#{nl}" \
          "Default: 50") do |val|
        @max = val
      end
      opts.on('--dry-run', "Print what will happen, but do not#{nl}" \
          "actually do it") do
        @dry_run = true
      end
      opts.on('-h', '--help', 'Display this help message') do
        @help = true
      end
    end

    begin
      parser.parse!(@argv)
    rescue OptionParser::ParseError => e
      STDERR.puts "*** ERROR: #{e}"
      abort parser.to_s
    end

    if @help
      puts parser
      exit
    end

    if @argv.size < 2
      puts parser
      abort
    end

    @input = @argv[0]
    @output_prefix = @argv[1]
    @output_suffix = @argv[2]
  end

  def prepare
    now = Time.now.strftime('%Y-%m-%d-%H:%M:%S')
    @output = "#{@output_prefix}#{now}#{@output_suffix}"
    @output_dir = File.dirname(@output)
  end

  def create_file
    puts "Creating #{@output}"
    if @dry_run
      puts 'Dry running, not actually creating that file'
    else
      sh 'cp', @input, @output
    end
  end

  def cleanup
    puts "Cleaning up, keeping only #{@max} most recent files"
    files = sorted_files_eligible_for_cleanup

    # Determine which files to keep
    keep = files[0..@max]
    if !keep.include?(@output)
      keep << @output
    end

    # Determine which files to delete, then do that
    delete = files - keep
    if delete.empty?
      puts 'Nothing to remove'
    else
      delete.each do |path|
        if @dry_run
          puts "Dry running; would have removed #{path}"
        else
          sh 'rm', path
        end
      end
    end
  end

  def sorted_files_eligible_for_cleanup
    files = []
    Dir["#{@output_dir}/*"].each do |path|
      if File.file?(path) && 
           path.start_with?(@output_prefix) &&
           path.end_with?(@output_suffix)
        files << path
      end
    end
    files.sort!
    files.reverse!
    files
  end
end

RotateFiles.new(ARGV).run