#!/usr/bin/ruby
#
# Usage: ftp-backup.rb <directory> <filename>
# Example: ftp-backup.rb /home/jwood/backup/ my_important_file

require 'net/ftp'

NUM_BACKUPS = 7

directory_name = ARGV[0]
file_name = ARGV[1]

server = 'my.server.address'
username = 'jwood'
password = 'secret'
remote_dir = 'backup'

#
# Rename the file to the new name, if it exists
#
def rename_if_exists(ftp, from_filename, to_filename)
  ftp.rename(from_filename, to_filename)
rescue
  # Swallow - who cares
end

#
# Delete the file, if it exists
#
def delete_if_exists(ftp, file_to_delete)
  ftp.delete(file_to_delete)
rescue
  # Swallow - who cares
end

#
# Coordinate the backup
#
Net::FTP.open(server) do |ftp|
  ftp.login(username, password)
  ftp.chdir(remote_dir)

  delete_if_exists(ftp, "#{file_name}.#{NUM_BACKUPS-1}")

  (NUM_BACKUPS-2).downto(1) do |i|
    rename_if_exists(ftp, "#{file_name}.#{i}", "#{file_name}.#{i+1}")
  end

  rename_if_exists(ftp, file_name, "#{file_name}.1")
  ftp.putbinaryfile(directory_name + file_name)
end