@gems_installed_list = `sudo gem list`

begin
  @gems_to_install_list = File.open(ARGV.first)
rescue
  puts "usage: ruby sync_gems.rb your_file_with_gems_list"
  exit 1
end

def gem_versions(gem_string)
  if(releases = gem_string.match(/\((.*)\)/)[1])
    releases.split(",").each {|r| r.strip!}
  end
end

def gem_name(gem_string)
  gem_string.match(/(.*)\s\(/)[1]
end

def gem_exist?(name, version)
  @gems_installed_list.each do |gem_string|
    return true if gem_name(gem_string) == name && gem_versions(gem_string).include?(version)
  end
  false
end

# begin

@gems_to_install_list.each do |gem_string|
  gem_versions(gem_string).each do |version|
    name = gem_name(gem_string)
    if !gem_exist?(name, version)
      puts "Installing: #{name} version #{version}"
      puts `sudo gem install #{name} -v=#{version} --no-rdoc --no-ri`
    else
      puts "skipping #{name} version #{version}, because it is already installed"
    end
  end
end