require 'pty'
require 'expect'
require 'fileutils'
#
# This class encrypts and decrypts a file using GnuPG.
# Output file will stay in the same directory as input file.
#
# Author:: FUJIWARA Teruyoshi <tf (at) dsl.gr.jp>
# Copyright:: Copyright (c) 2010 FUJIWARA Teruyoshi
# License:: Distributes under the same terms as Ruby
# Date:: July 3, 2010
# Version:: 1.0
#
# == Requirement
# * You need GnuPG installed on your box.
#
# == Note
# This script requires 'pty' and 'expect' modules.
# So be careful of follwoing issues:
# * It won't work on Windows and requires Unix/Cygwin environment.
# * Be careful of locale. It changes message from gpg and may cause trouble with 'expect'.
#
# == See Also
# * http://www.gnupg.org
#
class Crypt
  @@gpg_cmd_encrypt = "/usr/bin/gpg -c"
  @@gpg_cmd_decrypt = "/usr/bin/gpg"
  @@verbose = false
  
  # Encriypt a file using GnuPG.
  # === Arguments
  # [path] a file to be encrypted.
  # [password] password
  # === Return value
  # [true] succeeded
  # [false] failed
  def self.encrypt(path, password)
    ENV["LC_ALL"] = "C"
    unless FileTest.file?(path)
      puts("Error: File not found(#{path}).")
      return false
    end
    
    if FileTest.file?("#{path}.gpg")
      FileUtils.mv("#{path}.gpg", "#{path}.gpg.old", {:force => true})
      puts("#{path}.gpg already exists. Renamed as #{path}.gpg.old")
    end
    
    cmd = "#{@@gpg_cmd_encrypt} \"#{path}\" ; echo done."
    puts(cmd) if @@verbose
    begin
      PTY.spawn(cmd) do |r, w|
        w.sync = true
        puts("enter password...") if @@verbose
        r.expect(/Enter passphrase:/) { w.puts("#{password}\n") }
        puts("re-enter password") if @@verbose
        r.expect(/Repeat passphrase:/) { w.puts("#{password}\n") }
        puts("waiting finish.") if @@verbose
        r.expect(/done/) { puts("done.\n") if @@verbose }
      end
    rescue PTY::ChildExited => e
      puts("GPG process finished.\n") if @@verbose
    end
    
    puts("#{path}.gpg") if @@verbose
    if FileTest.file?("#{path}.gpg")
      puts("Succeeded to encrypt.\n") if @@verbose
      return true
    else
      puts("Failed to encrypt.\n") if @@verbose
      return false
    end
  end
  
  # Decriypt a file Using GnuPG.
  # === Arguments
  # [path] a file to be decrypted. Maybe it has a filename like "*.gpg".
  # [password] password
  # === Return value
  # [true] succeeded
  # [false] failed
  def self.decrypt(path, password)
    ENV["LC_ALL"] = "C"
    unless FileTest.file?(path)
      puts("Error: File not found(#{path}).")
      return false
    end
    
    cmd = "#{@@gpg_cmd_decrypt} \"#{path}\" ; echo done."
    puts(cmd) if @@verbose
    begin
      PTY.spawn(cmd) do |r, w|
        w.sync = true
        puts("enter password...") if @@verbose
        r.expect(/Enter passphrase:/) { w.puts("#{password}\n") }
        puts("waiting finish.") if @@verbose
        r.expect(/done/) { puts("done.\n") if @@verbose }
      end
    rescue PTY::ChildExited => e
      puts("GPG process finished.\n") if @@verbose
    end
    
    if FileTest.file?(path.gsub(/\.gpg$/, ""))
      puts("Succeeded to decrypt.\n") if @@verbose
      return true
    else
      puts("Failed to decrypt.\n") if @@verbose
      return false
    end
  end
end